The May 22 2008 Tornado Outbreak

May 22 2008 Tornado Outbreak
Under construction (last updated December 24 2008 1115 UTC)

by

Jonathan D. Finch

and

Dan Bikos

best viewed with 1024 by 768 resolution

Jonathan's email

Related items of interest

Historical Tornado Cases for the Cheyenne Warning Area

Detailed Tornado Cases for the Cheyenne Warning Area

Historical Tornado Cases for the Boulder Warning Area

Historical Tornado Cases for the United States

Elevated Mixed Layer

Elevated Heating

Overview

On May 22-23, 2008, a favorable pattern for severe thunderstorms developed across the high plains, front range and eastern slopes of the Rockies. Slow moving meridional troughs have historically provided some of the more notable severe weather events for this region. Examples include April 23 1960 and June 14-17 1965.

Several tornadic storms occurred on May 22, and a few of these produced large, long-lived tornadoes. The most damaging and long-lived storm initiated near the Denver International Airport (DIA) around 1630 UTC (1030 am MDT) and became severe southwest of Hudson, CO around 1705 UTC. The storm continued moving north-northwest along the front range of Colorado through 1830 UTC. Between 1830 and 1845 UTC the storm climbed the high terrain of northern Larimer county and lost some intensity. The storm still may have been marginally severe but very few people live in this area. The storm intensified after 1845 UTC and produced tornadoes from just east of the tri-county border of Larimer, Laramie and Albany counties to Laramie Wyoming and beyond. This Wyoming tornado was accompanied by quarter to golfball sized hail (and apparently much larger at the Mitros residence). These pictures were taken by Jeff Mitros. After a brief weakening, the storm intensified northwest of Bosler, WY and likely produced large hail and another tornado from north of Cooper Lake to 7 miles north of Harper to north of Rock River between 2005 and 2028 UTC. Although severe weather and even tornadoes have occurred on the higher terrain of the Laramie Range, it is very rare for an individual storm to initiate along the urban corridor of Colorado and then move to the northwest over the Laramie Range, through Laramie, and into northwest Albany county, producing high-end severe weather for 3.5 hours along a 140 mile path. This storm moved over highly varying terrain (elevations from 4700 ft to 8700 ft) and even moved into dense fog over the Laramie Range. In fact, golfball to baseball sized hail and larger, along with damaging tornadoes, occurred in the dense fog at elevations from 7500 to 8700 ft. A few hours after the tornado and hail occurred in the Vedauwoo area, thundersnow occurred with 3 to 6" accumulations. The focus of this web site is on this rare and particularly damaging storm.

The severe weather episode was well forecasted by the ECMWF model. This model indicated that a deep, slow moving, meridional trough would approach the high plains on May 22-23. It also predicted a deep trough over New England, with an associated surface front behind this system through the lower midwest into northeast Kansas, southwest Nebraska and eastern Wyoming. The ECMWF did an excellent job with these features well in advance. The 144 hr ECMWF showed a stationary front through northern Kansas and southern Nebraska, with strong upslope flow across western Nebraska and eastern Wyoming. On May 17, I expressed my thoughts about the severe weather pattern. This web page will focus on the Colorado and Wyoming part of the tornado outbreak. Large, wedge tornadoes are uncommon so close to the front range of Colorado. Damaging tornadoes are very rare at 7500 to 8700 ft in southeast Wyoming. An updated map showing the path of tornadoes associated with the main tornadic storm (relative to the topographic features) is here.

In lieu of the clickable imagemap, I have opted to post the path and photos in "Google Maps". This information is readily accessible. A map showing the center of the Harriman-Laramie tornado path and hail swath as well as the Hecla tornado path can be found here.

A tornado watch was issued by the Storm Prediction Center at 1725 UTC (1125 am MDT) for much of northeast Colorado and part of southeast Wyoming.

Storm Initiation near Denver

It is well known that thunderstorms tend to develop along the front range earlier than on the low plains. This is because capping tends to be weaker due to elevated heating, and lower moisture content of the air allows for a rapid warmup to the convective temperature by local noon. Also, the front range of Colorado is above the traditional capping level. But convection began even before local noon on this day.

Towering cumulus clouds developed southeast of DIA around 16 UTC on May 22. The first elevated radar echoes appeared around 1612 UTC near Watkins or just southeast of DIA. These initial echoes were stronger by 1621 UTC. By 1635 UTC, 45 dbz echoes were noted at 23,000 ft about 3 miles northeast of the airport. By 1657 UTC, a 61 dbz echo was located 14 miles north of Denver at 21,000ft. The first echo approaching 50 dbz (48 dbz) on the lowest slice occurred at 1648 UTC. The first 60 dbz echo on the lowest slice was noted 5 miles west-southwest of Hudson at 1652 UTC. By 1701 UTC there was a 62 dbz echo up to 26,000ft and 47 dbz echo up to 32,000ft. The storm was severe at this point. At 1705 UTC, the storm had 63-66 dbz echoes northwest and west of Hudson at the lowest slice. A few calls were made to find out when the storm became severe. I received a report of dime sized hail 4 miles north of Lochbuie or about 7 miles north of DIA. Based on radar, this occurred around 1705 UTC. The hail got larger as the storm moved north-northwest. Large hail left marks on houses 4.5 miles north-northeast of Fort Lupton or 2.5 miles northeast of Ione around 1714 UTC. The first official report of large hail was quarter size at 1719 UTC 3 miles north-northeast of Platteville. This is actually close to where the tornado first touched down only a few minutes later. The Front Range (FTG) WSR-88d radar loops are storm below:

storm relative velocity loop (1718 to 1814 UTC)
reflectivity loop (1635 to 1814 UTC)

reflectivity loop (1430 to 1827 UTC) faster version
reflectivity loop (1430 to 1827 UTC) slower version

The Pueblo radar actually showed the initial development better since the Denver radar was too close.

The Cheyenne radar shows the entire life of the storm from 1612 to 2042 UTC:

reflectivity
storm relative velocity

The Platteville-Windsor-Wellington Tornado

The first tornado report was east of Platteville at 1726 UTC. The tornado was already doing damage by 1726 UTC and was reported to be 1/2 mile wide at 1727 UTC. This tornado was very large (published by the Denver Post) and damaging and continued for 37 miles to northwest of Wellington through 1825 UTC. The most damaging part of the tornado path ended northwest of Windsor. Very large hail up to baseball size or larger occurred along and west of the tornado path. The tornado moved generally to the north-northwest at 35 to 40 mph. The elapsed time between the first 50 dbz echo on the .5 deg slice from the Denver radar and initial tornado damage was 37 minutes!! Here are some pictures of the tornado from "The Denver Channel", KOAA news, channel 9 news and Ted Ullmann. Pictures 7a and 7b were taken in Windsor, CO by Ted Ullmann.

pic1 pic2 pic3 pic4 pic5 pic6 pic7a pic7b pic8 pic9 pic10 pic11 pic12 pic13 pic14

An updated map showing the path of the primary Colorado tornado is here. Apparently, several tornadoes caused damage near the end of the path to the west and northwest of Wellington. Actually a waterspout was seen over Douglas Lake and this tornado caused significant damage along county road 17. This information is still being compiled. The large tornado near Windsor apparently evolved into 2 or more smaller tornadoes north of Fort Collins. These smaller tornadoes continued to about 4 miles west-northwest of Wellington. However, to keep things simple, we will refer to this as 1 tornado.

The storm weakened briefly as it moved into northern Larimer county, but then strengthened and accelerated as it passed east of Virginia Dale.

The Harriman-Vedauwoo-Laramie Tornado


            Brief Overview

This storm produced a 2nd tornado from 1858 UTC to 1923 UTC. There may have been a break in the damage northwest of Howe Lane Rd. between 1923 and 1927 UTC before another (or the same) tornado touched down just southeast of Laramie. There may have also been a break in the path between 1900 and 1901 UTC. I received this picture from the Laramie Fire Department/EMA that was supposedly the Laramie tornado. They said that this picture was taken at the Walmart, but they had no details and couldn't vouch for its authenticity. Large hail as large of baseballs accompanied the storm

The Harriman-Laramie tornado moved to the north-northwest at an average speed of 47 to 50 mph. The heading of the tornado was 320° at the beginning of the path and 330° toward the end. This was an exceptionally fast moving tornado by Wyoming standards. Typically the mid- level (600-300 mb) flow over southeast Wyoming is fairly weak in tornadic situations, hence strong right-movement and slow storm motion (10 to 30 mph). The fast storm motion on May 22 is more typical of the southeastern United States in winter or early spring. The storm accelerated as it climbed closer to the stronger mid level flow. Basically, the storm was closer to the stronger, higher level winds after it climbed to 7500 ft. As previously mentioned, the tornadoes on this day moved to the northwest and north-northwest. This is unusual, but certainly not unprecedented. The Wyoming tornado on April 23, 1960 moved to the north-northwest. The tornado climbed the higher terrain of the Laramie Ridge/Range.

Here is a map showing the center of the Harriman-Laramie tornado path and hail swath.

            Storm Documentation

Since I have a strong interest in high elevation severe weather, and since this was a particularly rare and exceptional tornado and large hail event on the high terrain, I decided to thoroughly document the Wyoming part of the tornado outbreak. But when I first started this task, I had no names to work with. So I ordered a phone book for Cheyenne, WY called the "Country Cowboy". I started with the H's and searched for specific roads that I knew were close to the tornado path, and after about 5 minutes I found the name Paul Hanselmann on Ramshorn Rd. So I called Paul Hanselmann and found that his house was hit by the tornado. He gave me 2 other names and those people referred me to others. So information piled up quickly. I made extensive use of the reverse address search feature in the Dexknows online white pages along with Google Maps to find obscure residences in remote areas such as Pumpkin Vine Rd. and Monument Rd. I was actually about to give up on finding people on Pumpkin Vine Rd. I finally made an effort to search Pumpkin Vine Rd. in Tie Siding, WY and stumbled across the Levinger's residence. Their residence is actually quite a distance from Tie Siding. After considerable effort trying to find residences on Hermosa Rd., I was finally successful. There is actually a National Weather Service cooperative observer there by the name of Francis Magrath. The Magrath's referred me to George Obssuth who also lives on Hermosa Rd. I also had considerable difficulty finding residences on Harriman Rd. I realized after prolonged digging that the name of the road was County Road 102 and not Harriman Rd. Also, the Laramie Fire Department referred me to Jeff Mitros and Jeff was a great source of information.

I want to thank all those who took the time to share information over the phone about the storms, or who provided weather data.

The 1st and strongest Albany county tornado touched down about 0.4 miles east of the intersection of Albany, Larimer and Laramie counties, or about 3/4 mile west of Harriman Rd. along the state line (elevation 7480 ft) at 1858 UTC (1258 pm MDT). The latitude and longitude were about (41.00, 105.27). I used radar to determine the exact times as this is usually the most accurate method. The land along the path of the tornado is barren in most places except for some trees along the creekbeds and near the isolated houses. Therefore, only a few houses were affected by the tornado. Prior to the tornado, dense fog shrouded the eastern slopes of the Laramie mountains, with visibilities almost zero at the residence of Wylie D. Walno II Lt. Col. near the tri-county border. Wylie Walno arrived home just before the storm hit the area. He said that the visibility suddenly jumped from near zero to unlimited as the storm passed to his north. He could see low-hanging clouds pass by. Golfball sized hail also occurred at the Walno residence.

The first signs of tornado damage was at the residence of Richard Miller about 700 ft north of the Colorado-Wyoming border. Two trees on his property were downed and his garage door was bent. Half-dollar sized hail also occurred there. Immediately to the northwest, 20 Ponderosa pines were downed at the Claire Hoover residence (1200 ft north of the state border) as the tornado passed between the house and a barn around 1859 UTC. Then the tornado toppled 4 trees on Belinda Scott's property. A few trees were downed on Wylie Walno's property. So the initial tornado touchdown as along the Colorado-Wyoming border about 1858 UTC. After the tornado left the Hoover residence, trees were downed south of the old Union-Pacific railroad tracks according to Claire Hoover. He will be surveying this area soon.

Here are a few pictures that Claire Hoover took around his property showing tree damage and minor house damage.

trees trees trees trees trees trees trees trees

house house

There may have been a brief break in the tornado path from 1900 to 1901 UTC starting near the old Union Pacific Railroad tracks. No storm documentation was received during this time.

Nancy Levinger (Chemist who lives and works in Fort Collins) took pictures of the tree damage near the family cabin. The damage occurred from 1902 to 1906 UTC at elevations from 7700 to 7900 ft. She provided valuable detail about the tornado path and is still in the process of documenting the tree damage. She took pictures of the downed trees and documented the latitude and longitude of the damage. This information was extremely helpful.

Here are a few of her pictures:

Trees uprooted
Trees snapped off
Trees snapped off and uprooted
Trees snapped off
Trees uprooted and snapped off
Trees uprooted
Trees uprooted
Trees uprooted

Jeff Mitros and Mr. Riske took pictures of tree damage that occurred a few miles northwest of Harriman. I do not know the exact location where these pictures were taken, but my guess is that they were taken along Monument Rd. about 3 to 5 miles northwest of Harriman. A tree was snapped off and another uprooted somewhere southeast of Imson Pond along Monument Rd.

Tree damage occurred on Peter Hansen and Tim Warfield's property for several miles. This damage was between the old Union Pacific Railroad to near Imson Pond.

Very old pine trees 3 to 4 ft in diameter were blown down by the tornado near Imson Pond (7820 ft) around 1908 UTC. Tom Nowak, Jim Price and another person were putting fish into Imson Pond in the dense fog with visibilities near 100 ft. Quarter to ping-pong ball sized hail chased them to their trucks. This is a good thing since they were then hit by the tornado around 1908 UTC. They described a frightening experience. The tornado buffeted their vehicles. One truck contained a 1000 lb fish tank. This truck rocked back and forth by the tornado and most of the windows were smashed out. Another truck was actually lifted off the ground and set back down, with windows knocked out as well. A camper shell was broken off one of the trucks and flung 1/2 mile to the south. Debris was flying everywhere during the tornado including picnic tables. Large trees were downed on both sides of the road near the pond. Tom Nowak took some pictures of the tree damage at Imson Pond and west of Monument Rd. (southeast of Imson Pond). He also took some pictures of the tree damage but apparently these didn't come out so well. He is going back to the tornado damage area to take more pictures of the tree damage. These will be posted when I receive them. Here are a few pictures of his truck that were taken the next day: pic1 pic2 pic3 pic4 pic5 pic6 pic7 pic8 pic9 pic10

After leaving Imson Pond, the tornado moved northwest over open country and destroyed snow fences paralleling the railroad tracks to the north of Ramshorn Rd. (information provided by Ted Lewis). The tornado paralleled Ramshorn Rd. at 8170 ft from 1910 to 1911 UTC. Ted Lewis measured 153 mph winds on his Davis Monitor 2. His house faired fairly well even though trees were blown down. The northern periphery of the tornado hit the Ted Lewis residence on the north side of Ramshorn Rd. Many trees were downed on Ted's property. Ted took this picture of his 12 ft. aluminum boat that was blown 500 yds.

The tornado then hit the Paul Hanselmann house also on Ramshorn Rd. The front half of his roof was blown off, with pieces of it found over 2 miles away. The back part of the roof was heavily damaged. The Hanselmann house was well constructed with concrete-filed styrofoam and was reinforced with steel rebar anchored to the foundation. Trees were downed near the Hanselmann and Lewis residences. Here is a picture of waferboard from the Hanselmann house pushed through tree limbs. All these pictures that were taken near the Hanselmann residence were taken by Melissa Goering of the National Weather Service in Cheyenne. Shown below are additional pictures taken by Melissa Goering.

trees1    trees2    trees3    trees4    trees5    trees6    trees7    trees8    trees9    trees10

house1    house2

misc1    misc2    misc3

Ted Lewis took these pictures of the Hanselmann house.

After leaving the Hanselmann house, the periphery of the tornado hit the Maher residence around 1911 or 1912 UTC and the roof had to be replaced. The pictures shown below were taken by the National Weather Service in Cheyenne. This residence is 1/2 mile north or northwest of the Hanselmann house.

house1    house2    house3    house4    house5    house6    house7

trees1    trees2    trees3    trees4    trees5    trees6    trees7    trees8    trees9    trees10    trees11    trees12    trees13    trees14

trees15    trees16

misc1    misc2    misc3

Some tornado was done to a residence and outbuilding .87 miles southeast of Ames Monument as shown (pictures by Melissa Goering).

Some tornado and hail damage was done to a residence and outbuildings .46 miles south of Ames Monument as shown in these pictures by Melissa Goering.

hail1 hail2 hail3 hail4

debris1 debris2 debris3

house1

buildings

Francis Magrath who lives 1/2 mile west of the intersection of Monument Rd. and Hermosa Rd. reported hail as large as golfballs. A few trees were downed about 1/2 mile northeast of the Magrath's as the tornado passed to the east of their residence. They reported that the visibility was around 100 ft. when the hail was falling.

Some damage was done to the George Obssuth residence (8280 ft) about 1/4 mile due west of the intersection of Monument and Hermosa Rds. (north of Hermosa Rd.) around 1913 or 1914 UTC. He reported that $32,000 damage was done to his deck when support beams were broken. Two isolated, old trees dating back to 1870 were heavily damaged just southeast of his house. A 1000 lb utility trailer was blown 300-400 ft. on his property. South facing windows of his house were blown/knocked in. The largest hail at the Obssuth residence was 2" in diameter. Shards of metal were blown several miles to the northwest. Many small trees were uprooted and sheet metal roofing from the Hanselmann house (1.5 miles to the southeast) was wrapped around wooden poles south of Ames Monument along Monument Rd. (east side of the road) as photographed by George Obssuth. This homestead was damaged south of Ames Monument to the southwest of Monument Rd.

Here are some pics of the trees downed behind the Obssuth residence. The first picture shows Ames Monument in the background and shows just how treeless this area is.

Trees1    Trees2    Trees3    Trees4

The tornado then moved over the Glen Smith residence between Hermosa Rd. and Vedauwoo Rd. His house was partially unroofed and the deck received damage. However, there is a 200 ft. rocky escarpment immediately south of his house and this may have spared his residence major damage. Many trees (100 to 150) were downed on his property and along the dirt road that leads to his house. According to Smith, the trees were downed in a 1/2 mile swath centered near his house. In fact, trees were downed at least as far west as the Von Lunen residence. The roof of the Von Lunen house was lifted and set back down and had to be replaced.

Some tornado and hail damage was done off of exit 329 along Monument Rd. as shown in these pictures by Melissa Goering.

trailer1    trailer2    trailer3    trailer4    trailer5    trailer6

house

This trailer belonging to Phil Robinson Monument Rd. (not far from I-80 exit 329) was flipped. This occurred on the easternmost extremity of the tornado. This picture was taken by Jack Riske. This is the same trailer as shown in the pictures immediately above taken by Melissa Goering.

The tornado then hit the Gil Wilson house and especially the Gayle Wilson house immediately south of Vedauwoo Rd. Jack Riske took these pictures of the Gayle Wilson house. In the first picture, the Gil Wilson house can be seen in the background. The roof of his house was partially torn off. The porch was torn off and the garage lost its roof.

Fence located southeast of the Wilson residence was scattered.

The tornado then moved just west of the house belonging to Russ Rogers. Ten windows of his house were broken by large hail and 2X4's. Thirteen roof panels came off. His S-10 pickup was totaled after being hit by boards. Debris was strewn all over his property. 2X4's were embedded in the ground. Parts of a trailer were scattered for a mile. Many trees were blown down. A 24 ft trailer was overturned and moved 150 ft. Glass from a house window blew into the house and sliced a wall.

Pic1    Pic2    Pic3    Pic4    Pic5    Pic6    Pic7    Pic8    Pic9    Pic10    Pic11    Pic12 Pic13   Pic14   Pic15   Pic16

Jeff Mitros of Vedauwoo Rd. reported to me that most of the extensive tornado damage was confined to a path about 1/4 mile wide. Along this path the tornado climbed in elevation to 8700 ft. Major damage occurred around 1917 UTC on West Vedauwoo road at 8400 ft. Gayle Wilson's house was destroyed by the tornado. 2X4's from her roof were embedded in the ground several feet. She told me this was quite an accomplishment since the ground is so hard (gravel-like) that it is difficult to even dig a shovel into it. She also reported that nails from her roof were embedded the wrong way into fence posts 500 yds. away at another residence. A woman in the Vedauwoo area was injured by flying glass as one of the windows in her house was blown out. All the south facing windows were either knocked out or punched through by hail at the Jeff Mitros residence. Mitros also reported numerous hail dents in vehicles. These dents were mainly on the sides of the vehicles since the wind was so strong. Many of the wooden logs of his log cabin were damaged by hail. Hail also left large holes in the south facing windows of another house on Vedauwoo Rd. Ping-pong to golfball sized hail occurred on Overlook Rd and Howe Lane. The tornado climbed to the summit of the Laramie Ridge (>8700 ft) as it approached Overlook Rd. A grove of Pine trees was downed by the tornado on Overlook Rd. The Harriman-Laramie tornado path was continuous for 18 miles from west of Harriman to north of Overlook Rd, and possibly for 31 miles to north of Laramie. There is a hilly area between Howe Lane and the southeast extremity of Laramie (3 to 4 mile stretch) where no people live and where few trees grow.

Jeff Mitros and Jack Riske took many pictures of the tornado and hail damage. The Jeff Mitros residence suffered damage from wind-driven hail. Mitros reported that dense fog with visibilities around 100 ft. prevailed all day. Some of the holes in his house windows were the size of baseballs and even softballs. The elevation of the Mitros residence is 8400 ft and is located close to "the summit" of the Laramie Range. Three inches of snow fell on Overlook and Vedauwoo roads (Mitros and Myers residences) during the evening of May 22 (after the tornado). Jeff Mitros and Jack Riske helped document this rare storm.

These pictures show the extensive damage to the windows of his house, Datsun Z-280 and other items caused by very large hail. His windows are double paned, single strength, 1/4" glass. The hail did not damage the interior glass. The circular hole in the window on the 2nd floor was 4" in diameter while one of the windows on the lower floor had a hole 4.75" by 4.5". Perhaps there are studies that have determined hail size by the size of holes in glass.

Pic1 Pic2 Pic3 Pic4 Pic5 Pic6 Pic7 Pic8

A Datsun Z-280 received large dents and the passenger window was shattered at the Mitros residence.

Holes in ~ 1/8" plastic sheet at Jeff Mitros residence

The tornado kept moving north-northwest after passing west of the Mitros residence. A house belonging to Phil Robinson received holes in south facing windows from large hail. This house is 1 mile north-northwest of the Mitros residence. The garage was also damaged.

A few small trees were snapped off or uprooted south of the Phil Robinson residence. Metal was also wrapped around a pole.

A small trailer located south or southwest of the Mitros residence was thrown 300 to 500 yds.

A 15 gallon galvanized steel wash tub was wrapped around a fence.

A garage was destroyed and roof was lifted and set back down.

Thundersnow occurred on Vedauwoo Rd. for several hours starting around 630 pm MDT. The highest snow amount measured that evening was 5 to 6". Fairly frequent lightning accompanied the heavy snow according to Ethan Smith. However, residents 2 or 3 miles to the southeast along Hermosa Rd. reported no measurable snow.

John Myers lives on the summit of the Laramie Range (elevation 8720 ft). He indicated that the tornado path was continuous from West Vedauwoo Rd. to Overlook Rd, and northwest to Indian Springs Rd. Myers prepared maps showing the locations of the damage. The tornado just missed his house to the west around 1921 UTC. He reported quarter to golfball sized hail. A "center-ridge skylight" on his property made of "heavy semi-rigid plastic" had a hole about the size of a golfball. Many trees 16" to 30" in diameter were snapped off or uprooted along Dry Gulch (many about 10 ft above the ground). He told me that trees tend to grow on the southern end of the gulches (on the north facing slopes). He also took pictures of trees uprooted or snapped off about 150 yds. southwest of his house. Myers also documented trees down along Indian Springs Rd. He tried to survey the tree damage further north next to Howe Lane (north of the Gilmore Gulch area) but was unsuccessful at getting close since the land is private or government owned. As far as he could see, there was no damage from his vantage point. John Myers went out of his way to help document the storm.

Other pictures taken by Myers include:

Pic1
Pic2
Pic3
Pic4
Pic5
Pic6
Pic7
Pic8

A CoCoRaHS observer 1.3 miles southeast of Laramie reported that 1.5" hail caused car dents.

According to Dave Claypool, a master technician at the College of Agriculture's Plant Science Center, "It got very noisy from the hail and wind. There was a lot of pea sized hail, but there were many big ones mixed in. "We picked up one hailstone that was 1.5" across."

A tornado moved along I-80 between 1928 and 1930 UTC, and then across the far eastern and northeastern part of Laramie between 1931 and 1935 UTC. F1 damage was done to many structures.

I did not document the Laramie segment of the tornado. A quick internet search revealed the following damage:

A truck driver suffered a broken ankle when his truck was overturned on I-80.
Numerous homes, a church and dance hall were damaged.
College of Agriculture greenhouse facilities were damaged (5 of 18 greenhouses damaged and the hoophouse greenhouse destroyed)
A storage shed and wooden pole barn were destroyed near the greenhouses. Huge pieces of the barn were carried 250 yds.
10 large spruce trees were either uprooted of snapped in half at the greenhouse facilities.
Many trees were snapped in half or uprooted at the Jacoby golf course.
A board was driven into a building.

The tornadic storm continued to the north-northwest through central Albany county. No tornado damage occurred, but this area is fairly desolate. It is possible that tornadoes went unreported. Based on radar, large hail undoubtedly occurred as the storm moved to the east and north of Rock River.

It is possible but unlikely that the tornado that touched down along the Colorado state line was continuous to Laramie. As already noted in the discussion above, there were at least 2 and possibly 3 breaks in the tornado path. The first break may been from 1900 to 1901 UTC north of the old Union Pacific Railroad. The 2nd possible break occurred over an undocumented and inaccessible area between 1917 and 1919 UTC. The 3rd possible break occurred between 1922 and 1926 UTC before the storm reached the southeast outskirts of Laramie.

Again, I would like to thank those in southeast Wyoming who helped me complete this investigation. Benjamin Franklin once said:

"Some are weatherwise but most are otherwise."

This may be true for some parts of the country, but after talking to many residents in southeast Wyoming, I can conclude that most are weather-wise and some are otherwise!!


            Radar Loops

The following are radar loops from the Cheyenne WSR-88D. The 3rd loop was extended out in time until 2038 UTC to capture a probable tornado with this storm from north of Cooper Lake to north of Rock Creek.

Storm relative velocity loop (1845 to 1934 UTC)
Reflectivity loop (1845 to 1930 UTC)
Storm relative velocity loop (1900 to 2038 UTC)

Keep in mind that beam blockage was likely occurring with the .5° slice from the Cheyenne radar. As the storm moved from 7500 ft. to 8700 ft., the lowest slice of the Cheyenne radar was partially beneath the ground, resulting in lower reflectivity (50-55 dbz) values from southeast of Vedauwoo to Laramie. The actual reflectivity values were probably 60-65 dbz. The 1.5° slice supports this notion.

The Crystal Lake Reservoir/Hecla Tornado

Unofficially, a small tornado touched down 3 miles south of I-80 on Harriman Rd. a little later in the afternoon from another storm. I was able to document this storm with the help of Walter Ferguson and a few other people. This tornado moved to the north-northwest and downed trees in several locations. Several trees were downed 3 miles south of I-80 on Harriman Rd on the William Prince property. They estimated winds up to 80 mph. Walter Ferguson reported to me that there was lots of tree damage southwest of Hecla along South Crow Creek in sections 2 and 34 of townships 13 and 14. An old cabin was extensively damaged on Crystal Lake Road in section 28 of township 14, with the roof blown across the road. This tornado continued north-northwest. A few trees were downed and shingles were torn off of a house. A heavy camper was turned upside down. This damage occurred about 4 miles east-northeast of Buford. Residents described this event as a mini-tornado. The tornado most likely started between 2115 and 2125 UTC (325 pm MDT) and ended before 2140 UTC. These times were obtained by matching the radar imagery to the locations that received damage. However, the radar signatures were not nearly as clear cut with this storm since the tornado was so small. This storm was not as strong as the Harriman-Laramie storm, but still contained dime sized hail that was blowing horizontally at the William Prince residence. The southern end of the storm was centered just east of Wellington, CO at 2038 UTC, 6 miles east of Harriman at 2108 UTC, 3 miles west of Granite at 2129 UTC and 4 miles west-northwest of Granite at 2137 UTC. The area southeast of Granite is completely devoid of people. It is possible that tornadoes occurred earlier with this storm. The path of this tornado was very close to the path of the April 23, 1960 tornado. It appears that the 1960 tornado path was about 1 to 2 miles west of this tornado, and about 4 to 7 miles east of the Harriman-Laramie tornado. I drew the path of the 1960 tornado in 2000 with the help of Walter Ferguson whose family has resided in the local area for several generations.

Other Severe Storms

According to Wylie Walno II Lt. Col., another tornado apparently destroyed a barn 4 miles west of the tri-county border. Hail accumulated to a foot deep in this area and took 3 days to melt. I am still trying to confirm this tornado, but the area is very sparsely populated. The same storm produced large amounts of hail west of Virginia Dale. This center of the storm was located 5 miles southeast of Virginia Dale at 2012 UTC, from Virginia Dale to 4 miles northwest of Virginia Dale at 2025 UTC, 4.5 miles northwest of Virginia Dale at 2029 UTC (6 to 8 miles west of Harriman) and 1.5 miles east of Tie Siding at 2038 UTC. This possible tornado is not plotted on any of the damage path maps.

Another storm developed near Broomfield, CO at 1752 UTC and produced a tornado southwest and west of Dacona between 1823 and 1832 UTC. 2" hail and 1.5" hail were reported via CoCoRaHS 3 miles east and 2.5 miles northeast of Longmont respectively. This storm temporarily weakened after moving past Longmont. The storm intensified near Masonville and produced golfball sized hail 1 mile east of Buckhorn Mountain. Golfball sized hail dented cars in Poudre Park.

A severe storm developed north of Hardin, CO in Weld county at 2055 UTC. Large hail probably occurred with this storm southeast of Barnesville. This severe storm continued to 3 miles northeast of Purcell at 2135 UTC.

A very brief tornado apparently occurred just west of Interstate 25 (time ??) in southeast Wyoming and caused no damage.

A storm moved into Wyoming from Colorado after 02 UTC and produced a tornado about 13 miles east of Cheyenne at 0233 UTC. A pole barn was destroyed. The Laramie Fire Department and EMA provided me with this picture of the tornado (supposedly from the Hillsdale area). However, they told me that this could also be the Laramie tornado. They didn't have high confidence about where this tornado occurred. This tornado is not shown on the smaller scale maps, but is shown on this larger scale terrain map. A more accurate version of the terrain map showing the updated, main storm track can be found here.

Meteorological Discussion

A deep upper trough was digging into the intermountain west at 00 UTC May 22, 2008. 500mb winds of 100 kts on the back side of this trough were indicative of a deepening system. The 500mb height in the center of the upper low was 550 dm over central UT. The surface chart at 00 UTC showed a surface front stretching from central LA into north TX and then into northeast NM and eastern Colorado. Only marginal moisture was in place across western Kansas with surface dewpoints in the 50-55F range. However, rich moisture in the Red River Valley of southern Oklahoma and north Texas was poised to make a fast return.

The 03, 06, 09 and 12 UTC surface charts show a strong surge of moisture through western Oklahoma, western Kansas and eventually eastern Colorado. By 03 UTC, 60-65F dewpoints were surging through northwest Oklahoma and into the eastern Oklahoma panhandle. In fact by 06
UTC, 55-60F surface dewpoints were already surging into eastern Colorado. By 09 UTC the dewpoint at Limon, CO was up to 58F, with 53-55F dewpoints along the front range of northern Colorado. Limon reported overcast skies at 1800ft, which indicates the low level moisture was at least 1800 ft deep.

This loop of the NAM 00hr to 18hr dewpoint and sea level pressure (SLP) fields valid from 00 UTC May 22 to 18 UTC May 22 shows the moisture racing to the northwest between 00 and 12 UTC. This upslope flow north of the warm front can be easily seen. At 00 UTC the warm front was across southern Oklahoma. The dryline intersected the warm front southwest of Childress. By 12 UTC the warm front was located across far southern Kansas.

By 12 UTC the moist axis was located from southwest Kansas into eastern and northern Colorado and had shifted a little to the northeast since 09 UTC. The 12 UTC 500mb chart indicated strong cooling since 00 UTC. The 500mb temperature was down to -14C at Denver. The pacific cold front had already progressed through Albuquerque as seen on the 700mb chart. The 700 mb temperature was down to -1C at Albuquerque. Mid level cooling had obviously occurred even ahead of the front across the plains and at Denver.

By 15 UTC, the warm front had progressed into central CO and western Kansas. Rich moisture was in place across the front range of northern CO with 54 and 55F dewpoints at Greeley and Akron respectively. The surface theta-e axis extended from central Kansas into northwest Kansas to Woodrow and Greeley, CO. Strong upslope flow was occurring and rich moisture was being transported into the Laramie Ridge and up the Laramie mountains. A surface dryline was beginning to take shape from the western Panhandles to extreme eastern Colorado.

Between 1500 and 1600 UTC, the east to west frontal boundary over Weld county, CO actually sagged south as a cold front into southern Weld county. By 1600 UTC this boundary was located from Fort Lupton to Hudson. The first part of the radar loop from FTG clearly demonstrates this.

By 16 UTC, 55-56F dewpoints were noted as far west as Kersey and Boulder, CO, or just south and southwest of Greeley. Initial radar echoes began to develop just south of the Denver International Airport by 16 UTC. This area of development was along or just west of a N-S boundary that was probably forced by the terrain. A surface front stretched from Platteville to Hoyt to Woodrow. This front actually pushed southward on the western end between 1600 and 1630 UTC, stalling in southern Weld county. The dewpoints in this initiation area were only in the 40s to near 50F. But higher dewpoints were located just to the north and west. By 1635 UTC, 45 dbz echoes were noted at 23,000 ft about 3 miles northeast of the airport. The front at 1635 UTC stretched across southern Weld county. A terrain related feature (at least that is our current thinking) extended from Parker to east of DIA to near Fort Lupton. As earlier noted, 50 dbz echoes were present on the lowest radar slice from Denver by 1648 UTC. The storm was severe by 1700 UTC just west of Hudson, CO.

The 17 UTC surface chart showed a T/TD of 70F/55F at Greeley, CO. Modifying the 18 UTC Denver sounding with these values yields 2800 j/kg surface based CAPE. This represents the upper limit for surface based, pre-storm CAPE that was available. The moist axis extended all the way northwest to Red Feather Lakes and Crystal Lake, where the T/TD were 43F/43F at both stations. Interestingly, the theta-e values were the same at these stations as Haigler, NE and Concordia, KS. T/TD values of 43F/43F at Crystal Lake and 47F/47F at Harriman at 17 UTC have almost the same theta-e as T/TD values of 72F/61F at Emporia, KS and 74F/61F at Chanute, KS.

At 1701 UTC the storm north of Denver and southwest of Hudson was rapidly becoming severe after encountering dewpoints between 53 and 55F. The storm was 25 minutes away from producing a strong tornado. The storm was about to encounter a surface that stretched ese to wsw from Woodrow to Wiggins and then ene to wsw from Wiggins to north of Brighton. There was a very narrow corridor of higher theta-e surface air immediately north of the front. Sunshine was warming the low levels north of the boundary on the front's western end (east of Greeley to Wiggins to east of Platteville). This elevated heating, along with dewpoints from 54 to 56F, and reasonably cool 500-300mb temperatures, was allowing for moderate surface based CAPE ahead of the storm (particularly in the inflow of the storm). Another surface boundary was oriented generally south to north from Parker to east of DIA to near Hudson at 1700 UTC, and was likely forced by terrain. The storm initially developed along this N-S boundary. Thus far, the storm was located in marginal instability immediately to the west of the N-S boundary, but south of the warm front that stretched from generally west to east. Surface based CAPE values in this region near DIA were about 1500 j/kg. Dry air was actually located east of the storm (south of the boundary) from just east of Hudson to Prospect Valley to Hoyt and southward to the Front Range Airport. The T/TD were 72F/29F at the Front Range Airport (FTG) while the T/TD at DIA were 65F/50F. The wsr-88d is located at FTG. Backed winds and relatively high theta-e low level air existed northwest and north of the storm over southern Weld county. In fact the storm was about to move into a very favorable area for tornadoes. Fairly high dewpoints actually existed north of DIA but south of the boundary. So the storm became severe by 17 UTC even before reaching the warm front. By 1727 UTC when the storm became tornadic, the storm was located just north of the surface boundary. From 1727 to 1745 UTC, the surface boundary surged to the north and northwest immediately behind the storm so that the storm stayed in an ideal location, with high theta-e air and strong east winds immediately on the cool side of the boundary. The 1730 UTC radar image with surface observations overlaid shows strong inflow to the east-northeast of the storm at Greeley and Kersey. Here is the 1740 UTC radar image with the boundaries drawn in. At this time the storm was immediately north of the boundary, with relatively high theta-e inflow into the storm from the east.

This dry surge actually kept pushing northwest and was through Peckham, CO by 1745 UTC. But by 18 UTC the boundary that had been surging northwest had slowed somewhat and was located just northwest of Peckham. The storm was beginning to move further away from the boundary. At 18 UTC the storm was obviously still ingesting high theta-e air from the east. Therefore, the storm managed to stay in a favorable location for tornadoes through 1810 UTC. After 1810 UTC the storm passed south and west of Wellington where surface temperatures were cooler. By 1820 UTC, a tornado was still occurring west of Wellington. The T/TD at Wellington were 55F/54F at 18 UTC and 58F/56F at 19 UTC. Thus, as the storm moved west of Wellington, surface based CAPE was down to roughly 1500 j/kg. There may have been a small inversion near the ground as the storm suddenly moved into cooler air. The storm temporarily weakened. This surface chart and radar overlay for 1830 UTC shows that "cooler air" was indeed surrounding the storm. I use the term cooler here because the storm was still located around 5200 ft elevation and had not started climbing to higher elevations yet. While surface temperatures were from 66 to 70F around Greeley, Peckham and Lucerne (4700-4900 ft), temperatures were only around 55F at Wellington and Briggsdale (5200 ft). So the storm had moved into a potentially much cooler airmass. Although difficult to prove, the storm likely moved into an area with a near-surface temperature inversion.

The previously shown .5° reflectivity loop from FTG (1430 to 1827 UTC) shows how the storm moved relative to the boundaries.

To demonstrate further how the storm moved in relation to the surface boundaries, an 8-frame loop was made in which radar data were overlaid with surface observations every 30 minutes. A few COAGMET surface locations provided data that were unavailable otherwise. For example, the observation near Peckham showed the passage of the warm front from 1730 to 18 UTC. Locations that were hit by the tornado early on (1727 to 18 UTC, actually experienced a sudden windshift to the southeast and pronounced drying as the front passed. Keep in mind that these frames were every 30 minutes and do not show the elevated core that developed near DIA around 1630 UTC. This loop clearly shows that the front sagged south into southern Weld county between 1500 and 16 UTC, then suddenly surged north as the storm crossed the boundary after 17 UTC. This surge was short-lived and by 1830 UTC had slowed its northward movement. So in summary, the storm developed near DIA immediately on the cool side of the N-S boundary, then moved north-northwest and stayed immediately west of the westward moving, N-S boundary through 1700 UTC. At 1701 UTC the storm was still south of the warm front. The storm crossed the warm front (east-west boundary) around 1710 UTC. By 1722 UTC the storm had already developed a hook.

The 8 frames described above can be found below:

1500 1530 1600 1630 1700 1730 1800 1830

The distribution of surface-based CAPE (CAPE_sb) is very important when assessing the severe storm environment. At 18 UTC, the CAPE_sb along the direction of the storm motion was fairly broad along the immediate front range. Note the moderate to high CAPE values (2000-2900 j/kg) from Arvada and Brighton north-northwest to Greeley. So a storm developing near DIA would have more time in the high-theta-e air compared to storms further east on the plains.

A hodograph was constructed by Dan Bikos for the Windsor tornado event. Note that the 0-3 km storm relative helicity was not very large (about 50 m²/s²). However, it is possible that the srh was over 100 m²/s² if the low level winds were 40-45 kts instead of 30 to 35 kts. This is still not very large. However, the 0-3 km and 0-6 km shear values were very large (over 50 kts and near 80 kts respectively). Dan's approximate sounding is shown here.

A satellite loop from 14 UTC to 2030 UTC can be found here.

Now let's turn our attention to Wyoming. As already discussed, the primary Colorado storm weakened a little in northern Larimer county and then intensified before entering Wyoming. By 17 and 18 UTC the surface temperature was 47F at Harriman, WY. Also, since dense fog was occurring, the dewpoint was equal to the temperature. Assuming saturation, what T/TD would be required at sea level to achieve the same theta-e as Harriman, WY? Since the T/TD were 47F/47F at Harriman, a T/TD of 66F/66F would be required at 1000 mb to yield the same theta-e. Why is this? To understand this, let's look at the potential temperature and mixing ratio's for both locations. For Harriman, the potential temperature and mixing ratio were 89F and 9.2 g/kg. At 1000mb, a location with T/TD of 66F/66F would have a potential temperature of 66F and mixing ratio of 13.8 g/kg. Thus, the mixing ratio would be 50% lower at Harriman than at the sea level location. However, the potential temperature would be 23F higher at Harriman. Thus the notion that it was too cool on the Laramie Ridge on May 22, 2008 for severe storms is obviously misguided. In fact, it was warm enough so that the level of free convection was near the ground. This is despite dense fog and actual temperatures from 44 to 48F. Thus, before drawing conclusions about the severe weather environment, one should modify soundings using actual surface observations. Sometimes this requires the use of mesonet data since surface observations are sparse.

Let's compare (Table 1) the theta-e values on the elevated terrain and lower terrain by displaying temperature, dewpoint, mixing ratio, potential temperature and equivalent potential temperatures at 17 UTC. Note that only temperature data were available for Harriman, Lynch, Virginia Dale 7 ENE and Emkay. Dewpoint data actually were available at the remainder of the stations including Estes Park, Crystal Lakes and Red Feather Lakes. However, since dense fog was present at these 4 Wyoming stations through 19 UTC, we will assume that the dewpoints were equal to the temperatures.


Table 1
17 UTC	Elev(ft)	Pres.(mb)	SLP(mb)	T(F)	Td(F)	MR(g/kg)	theta(F)	theta-e(K)
Crystal Lake	8620	724	986	43	43	8.2	92	331.6
Estes Park	7700	745	983	53	46	8.9	98	337.5
Harriman,WY	7450	756	987	47	47	9.2	89	332.5
Lynch,WY	7200	762	987	46	46	8.7	86.7	329.9
Virginia Dale 7 ENE	7000	767	988	47	47	9	86.9	330.8
Emkay,WY	6720	774	989	49	49	9.6	87.6	333.1
Cheyenne	6140	789	987.7	48	47	8.8	83.5	328
Nunn	5650	804	986	51	51	10	83.8	331.8
Wellington	5300	813	985	55	54	11.1	86.3	336.5
Briggsdale S	4838	833	991	55	54	10.8	82.6	333.3
Greeley	4700	835	984	64	55	11.2	91.7	340.2
Akron	4700	839	990	56	56	11.5	82.1	335.1
Goodland	3700	870	990.7	69	60	12.9	90.4	344.5
Saint Francis	3350	881		68	55	10.6	87.4	335.8
Hill City	2600	918	995.5	65	58	11.3	78	332
Concordia	1500	948	1000.5	65	59	11.4	73.1	329
OKC	1230	951	997	81	66	14.6	88.8	348.5
Chanute	1000	967	1001.6	74	61	12	79.1	334.6
Salina	1280	957	999.1	67	59	11.3	73.6	329
Emporia	1170	960	1001.5	72	61	12.1	78.2	334.3

Notice that Lynch, WY actually has the same theta-e as Salina, KS even though the T/Td are 21F/13F higher at Salina. The mixing ratio is 30% higher at Salina, so the potential temperature must compensate to yield similar theta-e values. Indeed, the potential temperature was 86.7F at Lynch and only 73.6F at Salina.

Surface theta-e continued to increase from 17 to 18 to 19 UTC. Tables 2 and 3 show temperature, dewpoint, mixing ratio, potential temperature and equivalent potential temperature values for various sites over the plains. Again, this is done to demonstrate that T/Td values cannot be used without elevation to assess how "juiced up" the surface layer is. In Table 5 the theta-e values between 330K and 335K are highlighted in red. The theta-e values from 330 to 335K are shown in a partially analyzed surface chart for 19 UTC. This terrain map with surface observations for 19 UTC overlain is only partially completed.

Let's compare(Table 2) the theta-e values on the elevated terrain and lower terrain by displaying temperature, dewpoint, mixing ratio, potential temperature and equivalent potential temperatures at 18 UTC.


Table 2
18 UTC	Elev(ft)	Pres.(mb)	SLP(mb)	T(F)	Td(F)	MR(g/kg)	theta(F)	theta-e(K)
Crystal Lakes	8620	723	887	43	43	8.2	91.7	331.4
Red Feather	8214	733	887	44	44	8.4	90.7	331.4
Ames Mon. 2S	8200	735	987	45.5	45	8.7	91.9	333.0
Pumpkin Vine	7700	749	987	46.3	46	9.0	89.4	332.3
Harriman,WY	7450	756	987	47	47	9.2	89.3	332.7
Lynch,WY	7200	761	987	46	46	8.8	87	330.1
Virginia Dale 7 ENE	7000	766	987	48	48	9.4	88.1	332.7
Emkay,WY	6720	773	987	48	48	9.3	86.7	331.5
Cheyenne	6140	788	988.2	49	49	9.5	84.8	330.8
Nunn	5650	803	985	52	52	10.4	85.1	333.7
Greeley	4700	833	983	70	55	11.2	98.4	344.5
Akron	4700	839	989.7	57	56	11.5	83.4	335.9
Goodland	3700	870	990.7	64	59	12.4	85.2	339.7
MCcook	2800	911	996.2	61	56	10.6	75	328
Hill City	2600	918	994.3	73	62	13.1	86.2	342.4
Concordia	1500	948	1000.6	67	59	11.4	75.1	330.3
Imperial	3300	885	995.7	56	54	10.2	74.3	326.3
OKC	1230	951	996.2	86	67	15.1	93.9	353.4
Chanute	1000	967	1001.6	76	64	13.4	81.2	339.9
Topeka	890	972	1004.1	66	59	11.1	70.3	326.4
Salina	1280	957	998.6	73	61	12.1	79.7	335.4
Emporia	1170	960	1001.4	76	63	13.0	82.3	339.5

Notice that Greeley, CO actually has a higher theta-e than Emporia, KS even though the temperature/dewpoint are 6F/8F higher at Emporia. The mixing ratio is 16% higher at Emporia, so the potential temperature must have compensated to yield a higher theta-e at Greeley. Indeed, the potential temperature was 98.4F at Greeley and only 82.3F at Emporia.

Notice that Red Feather Lakes, CO actually has a higher theta-e than Concordia, KS even though the temperature/dewpoint are 23F/15F higher at Concordia. The mixing ratio is 36% higher at Concordia, so the potential temperature must compensate to yield a higher theta-e at Red Feather Lakes. Indeed, the potential temperature was 90.7F at Red Feather Lakes and only 75.1F at Concordia. Severe storms passed just east of Red Feather Lakes in the early afternoon.

Let's compare(Table 3) the theta-e values on the elevated terrain and lower terrain by displaying temperature, dewpoint, mixing ratio, potential temperature and equivalent potential temperatures at 19 UTC.


Table 3
19 UTC	Elev(ft)	Pres.(mb)	SLP(mb)	T(F)	Td(F)	MR(g/kg)	theta(F)	theta-e(K)
Vedauwoo 2S	8200	735	985	45.5	45.0	8.7	91.9	333.0
Lynch,WY	7200	760	985	48	48	9.5	89.4	333.6
Virginia Dale 7 ENE	7000	765	985	48.5	48.5	9.6	88.9	333.7
Emkay,WY	6720	772	986	49	49	9.7	88.2	333.8
Cheyenne	6140	787	987.7	50	49	9.5	86	331.7
Nunn	5650	803	983	52.5	52.5	10.6	85.6	334.6
Wellington	5300	812	983	58	56	11.9	87.9	341.1
Briggsdale N	5039	826	988	56	54	10.0	84.9	335.1
Iliff	3900	865	988	55	54	10.4	76.8	328.5
Sterling	3900	865		59	56	11.2	80.9	333.4
Briggsdale S	4838	831	988	58	55	11.2	86.1	336.8
Akron	4700	839	990	56	55	11.1	82.3	334.1
Goodland	3700	870	990	69	61	13.4	90.4	345.8
Haigler	3291	883		60	56	11	78.8	331.4
OBerlin	2736	911		61	58	11.4	75	330.4
Saint Francis	3350	881		68	57	11.4	87.4	338.1
Hill City	2600	918	994	78	63	13.6	91.3	347.2
Concordia	1500	948	1000	71	61	12.2	79.2	335.3
OKC	1230	951	996	87	67	15.1	94.9	354.1
Chanute	1000	967	1001.5	78	65	13.8	83.2	342.3
Topeka	890	972	1003.7	69	58	10.7	73.3	327.2
Salina	1280	957	998.0	74	62	12.6	80.7	337.3
Fairbury	1500	950	1003.0	61	59	11.4	68.9	326.1
Scandia	1450	949	1001	69	61	12.2	77	333.9

Notice that Vedauwoo, WY actually has almost the same theta-e as Scandia, KS, even though the temperature/dewpoint are 24F/16F higher at Scandia. The mixing ratio is 31% higher at Scandia, so the potential temperature must compensate to yield similar theta-e values. Indeed, the potential temperature was 91.9F at Vedauwoo and only 77F at Scandia.

At 19 UTC, two mesonet observations and 1 cooperative observer location recorded hourly temperatures. These observations were all within 8 miles of each other. The temperature was 47F at Harriman (756 mb), 48.5F at the cooperative observer site 7 miles east-northeast of Virginia Dale (767 mb) and 48F at Lynch (762 mb). These 3 observations lie along the same moist adiabat, as one would expect in moist upslope flow. So I have fairly high confidence in the accuracy of these measurements. Veta Mitchell, the cooperative observer 7 miles east-northeast of Virginia Dale provided me with the hourly temperature measurements for her location. The tornado actually first touched down about 2 miles north-northwest of her house. So the hourly measurements that she collected are very useful in determining surface based CAPE.

An important thing to note is that a 47F dewpoint at Harriman actually has about the same mixing ratio as a 54.5F dewpoint at 1000mb. Of course this assumes that the sea level pressure at Virginia Dale and 1000 mb are similar. If the sea level pressure is higher at the lower elevation then the difference would be greater. Also, even though 47F seems chilly, this temperature at 7500 ft actually lies along the same dry adiabat as 90F at 1000mb.

Since visibilities were near zero before the storm, I am assuming that dewpoints were equal to the temperatures. I constructed approximate soundings for these locations using the 19 UTC RUC initialization and 18 UTC Denver sounding. Of course, the boundary layer had to be modified based on the surface mesonet observations. I modified using the 19 UTC observations since these are just prior to the tornadic storm. The RUC soundings were more representative than the NAM/WRF soundings. The nam soundings were superadiabatic near the surface and dry adiabatic above the surface layer. This is not reasonable. The RUC soundings were closer to moist adiabatic from the surface to above 700mb. The modified 18 UTC RUC soundings yielded similar CAPE values to the modified 18 UTC Denver sounding. I have determined that CAPE_sb was 750 to 850 j/kg near the beginning of the Harriman-Laramie tornado path where surface measurements were available. The theta-e values at the three locations were almost identical. The RUC model, which typically overestimates CAPE_sb (at least lately), actually did a reasonably good job with CAPE_sb fields, perhaps for the wrong reasons. The fact that this model actually forecasted CAPE_sb values up to 1000 j/kg at 6 to 12 hours could be a result of the model's usual overestimation. A look at RUC soundings for May 22 showed a superadiabatic layer near the surface and unreasonably high dewpoints. The starting pressures were also too high. The NAM/WRF underestimated CAPE_sb in southeast Wyoming.

The storm kept moving upslope from southwest of Harriman at 1858 UTC to near Vedauwoo at 1917 UTC. Meteorological towers actually measured the wind and temperature at several locations near the path of the storm. Thus far I have access to the data for two of these towers. One of the towers is located 2 miles west-southwest of Ames Monument at 41', 7.51' latitude and 105', 25.6' longitude with an elevation of 8220 ft. The tornado actually passed east and north of this tower by 2 miles. The average temperature at the tower (near ground level) from 1830 to 1840 UTC was 45.4F. The sustained windspeed was about 30 kts from 80° around 1830 UTC. The wind became variable and subsided after 1840 UTC. The tornadic storm passed to the east and north of the tower, so by 1910 UTC the strongest low-level flow was surely northeast of the tower. Using 44.5F at 735 mb in the Denver 18 UTC and RUC 19 UTC soundings (using starting pressure of 735mb) yields CAPE values from 600 to 750 g/kg. I assumed T=Td since dense fog blanketed the Ames Monument area before and during the storm. The freezing level near Vedauwoo was 3700 ft. I have prepared a new sounding for the area south of Ames Monument since the wind tower data showed a warmer temperature of 45.4F. This sounding, which was modified at the lowest levels from the 19 UTC RUC, shows 800 j/kgCAPE _sb.

Another wind tower located at 41° 2.7' N and 105° 18.36' (elev. 7700 ft) showed winds backing to 70° well ahead of the tornado, then backing even further to between 35° and 55° as the tornado approached from the south. The wind data from this tower showed a 90 mph wind gust at 128 ft as the tornado passed just to the west. The tower reported a nearly constant average temperature from 46.0F to 46.6F leading up to the tornado. This yields about the same theta-e as Harriman, WY (47F/47F at 7450 ft). Note that temperatures changed roughly moist adiabatically with increasing elevation from Harriman to south of Ames Monument. So CAPE values changed little following the storm (650 to 800 j/kg). Another sounding using surface data at the wind tower location will be generated, but the CAPE with this sounding will probably be very similar to the CAPE for the Harriman sounding.

Table 4 and Table 5 show the CAPE_sb values for Harriman and Vedauwoo 2S(Ames Monument 1.6 wsw). Table 4 uses the 18 UTC Denver sounding while Table 5 uses the 19 UTC RUC initialization. These are modified using the temperature readings from the 3 stations and assumes saturation (there was dense fog). Note that the winds in these soundings were derived from KCYS VWP and Base Velocity.


Table 4
DEN 18 Z/mesonet/VWP/Base V	Elev(ft)	Pres.(mb)	T(F)	Td(F)	MR(g/kg)	theta(F)	theta-e(K)	CAPE(j/kg)
Harriman	7450	756	47	47	9.2	89	332.5	858
Vedauwoo 8SE	7700	747	46.4	46	8.9	90.3	332.7	871


Table 5
RUC 19 Z/VWP/mesonet/base vel.	Elev(ft)	Pres.(mb)	T(F)	Td(F)	MR(g/kg)	theta(F)	theta-e(K)	CAPE(j/kg)
Harriman	7450	756	47	47	9.2	89	332.5	843
Vedauwoo 2S	8200	735	45.5	45.0	8.7	91.9	333.0	760
Vedauwoo 8SE	7700	747	46.4	46	8.9	90.3	332.7	714

Here is a sounding for Harriman, WY by Dan Bikos using RAOB.

It is very difficult to achieve low dewpoint depressions, relatively high theta-e values at low-levels and excellent vertical wind shear at 7500-8700 ft on the Laramie Ridge/Mountains. As previously mentioned, the dewpoints were equal to the temperatures along and east of the summit of the Laramie Ridge. But CAPE_sb values still ranged from 600 to 900 j/kg. In typical low plains severe storm situations, these CAPE would be considered very marginal. When CAPE_sb is marginal, tornadic storms can still occur, especially when LCL and LFC heights are low and considerable CAPE_sb exists at low levels. This was indeed the case on May 22 on the Laramie Ridge. In fact, after initially weakening upon moving into cooler air on higher terrain northwest of Wellington, CO, the storm quickly reintensified after encountering dense fog east of Virginia Dale. The LFC (level of free convection) was possibly at the ground as the storm moved from west of Harriman to Overlook Rd since the approximate soundings show no CIN above the surface.

The vertical wind shear profile featured strong shear. The surface wind backed to the northeast by mid-day at the mesonet locations. This backing was corroborated by the wind tower data. Thus we have high confidence that the surface winds were from the east-northeast around 30 kts before the storm approached from the southeast. As the storm approached, winds likely backed to the northeast as shown by the wind tower that was less than 1/2 mile east of the tornado path. For the winds above the surface we used the WSR-88d CYS VWP (VAD wind profile),WSR-88d CYS base velocity as well as the 18 UTC RUC. The wind just above the moist layer (600mb) was about 120° at 70 kts. So there was tremendous shear between the surface and 600mb (1.5 to 1.8 km agl). The 500 mb wind was from 140° at 70 kts while the 400mb wind was from 165 deg at 90 kts. 400 mb is 4.4 to 4.7 km above the surface, so the shear from the surface to 4.5 km was 90 to 100 kts. The 0-3 km and 0-6 km shear values were about 65 and 105 kts respectively.

The MESOWEST stations, 1 cooperative observer station and wind tower data also helped to assess the shear profile in southeast Wyoming in Table 6. These stations show a backing in the surface wind around before 19 UTC. Windspeeds are in miles per hour. The windspeed at Virginia Dale is not given since it was much too low and apparently in error. I currently do not know how these windspeeds and wind gusts were calculated and exactly what time the measurements represent. For example, the 1900 UTC observation could be for the period 1800-1900 UTC.


Mesowest Station	14 UTC	15	16	17	18	19	20	21	22
Lynch (7E of tornado at 19 UTC)	09021g26	09020g31	03019g32	08020g26	08034g35	06023g44	07044g44	08023g44	0908g20
Buford (7N of tornado at 19 UTC)	07017g26	06023g26	05029g32	07025g36	05033g42	03045g45	08036g50	07045g45	07011g23

It is important to note that the RUC and NAM/WRF showed no indication of a northerly wind component. But this has important implications for windshear and storm relative helicity. The low-level storm relative flow was apparently much greater than shown by the models. This shows that added surface observations can help us assess the near storm environment. The Cheyenne metar (further east) showed a slight northerly component at 19 UTC (080°).

Hodographs and a shear analysis were completed by Dan Bikos of CIRA. He varied the surface wind from 040° to 090°. The surface wind speed was 35 kts and storm motion vector 146° at 42 kts. The 0-3 km storm relative helicity(srh) varied from 200 to 682 m²/s²!! 0-1 km srh ranged from 98 to 314 m²/s² depending on surface wind direction. 0-6 km shear ranged from 90 to 110 kts depending on surface wind direction. Storm relative inflow varied from 37 to 56 kts depending on surface wind direction. These have not been finalized and future tweaks are likely. The wind vectors at various levels were obtained from the CYS VAD wind profile, base velocity data from CYS WSR-88D, as well as the various model initializations. However, the models were apparently underestimating windspeeds at most levels by 10 to 20%. Also, the winds were too veered in the models from the surface to 3 km.

Note that these hodographs were made using a surface wind speed of 25 kts and storm motion vector of 150° at 42 kts. New ones will be generated using the updated wind profile.

040 deg
050 deg
060 deg
070 deg
080 deg
090 deg

This shear analysis was made using a surface wind vector of 70° at 35 kts. Again, the table shows the various shear and storm-relative helicity values when the surface wind direction is varied from 40° to 90°. The storm motion vector was 146° at 42 kts.

An updated hodograph for a surface wind vector of 70° at 35 kts and storm motion vector of 146° at 42 kts.

It is clear that srh values depend strongly on the surface wind direction.

One would think that it would be easier to get sufficient CAPE and shear on the high terrain (7000+ ft) in June or July than in April or May. But this is not necessarily the case. Strong synoptic scale systems in spring can have very strong upslope flow associated with them, whereas systems in late spring and summer tend to be weaker, with weaker upslope flow. That said, the upslope flow tends to be cooler in April and May and oftentimes more stable. Upslope flow tends to be located on the cool side of a surface front or north of a developing surface low. Again, these airmasses tend to be too cool in April and much of May. This is why significant tornadoes are rare in the immediate lee of the Laramie Mountains. The upslope flow in the May 22 case was "cooler", but 700-800+ j/kg CAPE_sb values were still achieved. Elevations from 5000-6000 ft do have more severe weather in June and July compared to April and May. But further west on the very high terrain, strong upslope flow is generally required to obtain adequate theta-e values, low dewpoint depressions and high shear that typically accompany tornadic storms. By mid-June, strong upper systems become less common so that very strong upslope flow is rare. In the May 22 case, rich moisture raced northwestward from north Texas and southern Oklahoma into northern Colorado and southeast Wyoming in 9 to 12 hours from 00 to 09 UTC. Then during the day of May 22, a very strong upslope flow developed north of a surface front. Very strong upslope flow is required to keep adequate mixing ratios at the 7000-8000 ft elevations on the eastern slopes of the Laramie mountains. It is also important to understand that it is the potential temperature that is important in achieving higher theta-e values and not the temperature. Even in the presence of only moderately cool 500-300mb temperatures of -13C, -26C and -40C, surface temperatures from 7 to 9C were still sufficient to yield moderately high theta-e values, and hence moderately high CAPE values. When potential temperatures are high, mixing ratios do not have to be very high to achieve sufficiently high theta-e values. By later in June and July, surface temperatures become so warm that cloud bases are typically too high for tornadic storms given the meager mixing ratios typically found at these elevations.

Freezing levels were very low on the elevated terrain of southeast Wyoming and ranged from 3900 ft at 8700 ft AGL to 4600 ft at 8700 ft AGL. Wet-bulb zero heights were of course even lower.

Additional surface charts will be coming soon. Since terrain is so crucial to this meteorological discussion, I like to plot the surface observations on top of the terrain. However, this is a very labor-intensive process, especially since I need to include the mesonet observations.

Lets compare the present event with a tornado event on January 24, 1964. The soundings are similar in that the low levels were nearly saturated and the mid to high level thermal profile was very similar. Surface based CAPE values were also very similar. The marginal CAPE at Birmingham was achieved by high dewpoints despite the cool airmass. The marginal CAPE at Vedauwoo was achieved by high potential temperatures despite modest mixing ratios and cool actual temperatures.


Table 5
	Elev(ft)	Pres.(mb)	T(F)	Td(F)	MR(g/kg)	theta(F)	theta-e(K)	CAPE(j/kg)
Vedauwoo 8 SE	7700	747	46.4	46	8.9	90.3	332.7	714
Montgomery	23	1000	68	66	13.9	68	332.7	738

These two skewt-Log P diagrams show how Harriman, WY (elev 7450 ft) and Montgomery, AL (elev 22 ft) have the same theta-e even though the T/TD are 20F cooler at the high elevation location.

Other Thoughts

Until recently, surface observations were never taken between Cheyenne and Laramie and southward to Fort Collins and Akron (except for Sterling, CO for a few years). This is a shame. Surface observations have always been tied to aviation in the United States, making one wonder what our observation network would be like if we never had airflight. Therefore, instead of surface observations being placed where we need them meteorologically, we have to settle for widely spaced observations in rural areas and densely spaced observations around major airports.

The British surface observation network pre-dates aviation and is superior. A storm in 1859 inspired Robert FitzRoy to establish a surface observation network composed of 15 land stations that were transmitted via telegraph at regular intervals. In fact, the British even maintained a nice surface observation network in south Asia in the 1880s. This surface chart is from 05 UTC April 7, 1888. A storm developed over northern Bangladesh and moved south-southeast, killing 118 people in Dacca and 70 people in the district south of Dacca. Of course, this area now called Bangladesh was part of the British Empire until the late 1940s.

Meanwhile, there has been a big push for improving tornado warnings with better lead time. While the WSR-88d improvements help in this goal, we need more surface observations so we can assess the near-storm environments. Mesoscale models do not suffice. Real time storm chaser reports are great too, but we can't wait until there is a tornado tearing up a neighborhood before issuing a warning. I have chased storms since 1992 and I admit that much of the time I am confused about what storms are doing. Sometimes I don't even know exactly where to look for a tornado. If the tornado is wrapped in rain, storm chasers might not even see the tornado. Also, some storm chasers might wait 5 minutes to call in a tornado, perhaps taking video or still shots first. I can't say I blame them given the high gas prices and the fact that most of these people are not paid. Legitimate storm chasers are often looked down upon and not appreciated anyway.

A few AWOS and mesonet stations have popped up in recent years. This is a good start. Some of these data are of low quality, but certainly much better than nothing. Of course, Ken Crawford established a statewide "Oklahoma Mesonet" in 1994 with over 100 stations. This is a fabulous, high quality network.

The Departments of Transportation have established roadway surface observations and other agencies also maintain surface weather sites. These observations are oftentimes poorly placed and not representative of surrounding areas. The data quality is often not very good. However, when used with caution, these can be very useful.

Other weather observing sites are also scattered around the intermountain west. "Mesowest" surface observations were used in the meteorological part of this page. Why were these observations so useful? Well, in this particular case dense fog was occurring, so only the temperatures were needed to determine theta-e and CAPE values. Also, Lynch and Buford showed winds backing to the northeast or east-northeast around 19 UTC. This helped determine the vertical shear profile and storm-relative helicity. By a stroke of luck, the cooperative observer location 7 miles east-northeast of Virginia Dale happened to be well placed and hourly wind directions from there showed winds from the east-northeast at 19 UTC. Hourly temperatures were also available for this COOP site and these were very helpful in CAPE calculations(corroborated the sfc theta-e calculation for Harriman and Lynch). I was able to access these data by email after contacting the observer (Veta Mitchell) by phone.