The May 22 2008 Tornado Outbreak

May 22 2008 Tornado Outbreak
Under construction (last updated August 10 2008 0512 UTC)

by

Jonathan D. Finch

and

Dan Bikos

best viewed with 1024 by 768 resolution

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 of Events

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. This 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. This map shows the path of the tornadoes relative to the topographic features. The

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.

Towering cumulus clouds developed southeast of Denver International Airport (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.

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

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. 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 at 1825 UTC. The most damaging part of the tornado path ended northwest of Windsor. Very large hail up to baseball size 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!!

The storm weakened briefly as it moved northwest of Wellington, CO, but then strengthened and accelerated as it passed east of Virginia Dale. This storm produced a 2nd tornado from 1858 UTC to 1935 UTC. There may have been a break in the damage northwest of Howe Lane Rd after 1922 UTC. This Wyoming tornado was accompanied by quarter to golfball sized hail (and apparently larger at the Mitros residence). These pictures were taken by Jeff Mitros. 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. It is unclear whether the tornado that hit Laramie was a 3rd tornado from the same supercell or whether the 2nd tornado continued into Laramie. It is more probable that the tornado shrunk in size just before entering the eastern edge of Laramie. The tornadic storm continued well northwest of Laramie. Radar indicated another possible tornado 7 miles north of Harper, WY at 2017 UTC.

Since I have a strong interest in high elevation severe weather, and since this was a particularly rare and exceptional tornado event on the high terrain, I decided to document the Wyoming part of the tornado outbreak. This was accomplished using the internet white pages along with live maps. 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 after about 5 minutes I found the name Paul Hanselmann on Ramshorn Road. Ramshorn Road was close to the tornado path. So I called Paul Hanselmann. This immediately paid off as his house was unfortunately hit by the tornado. He gave me 2 other names and then those people referred me to others. So information piled up quickly. I want to thank all those who took the time to share information over the phone.

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 road along the state line(elevation 7500 ft) at 1858 UTC (1258 pm MDT). 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 occurred at the residence of Richard Miller. 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 pine trees were downed on the Claire Hoover farm as the tornado passed between the house and a barn. Then the tornado toppled 4 more trees on Belinda Scott's property. A few trees were downed on Wylie Walno's property.

                        Storm relative velocity loop (1845 to 1934 UTC)

                        Reflectivity loop (1845 to 1930 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 8500 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.

Fairly extensive tree damage occurred just northwest of the initial touchdown location as the tornado widened. This is tree damage 3 miles northwest of Harriman in far southeast Albany county (pictures taken by Jack Riske and Jeff Mitros). Peter Hansen reported to me that the tornado downed trees for several miles on his property. Tim Warfield told me that there was extensive tree damage on his land. By 1904 UTC the tornado was over 1/4 mile wide and was climbing up the Laramie Ridge to 8000 ft. Very old pine trees 3 to 4 ft. in diameter were mowed down by the tornado. Tom Nowak, Jim Price and another person were putting fish into Imson Pond in the dense fog with visibilities near 100ft. 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 Road (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 the pond, the tornado hit on Ramshorn Rd. Ted Lewis measured 153 mph winds on his Davis Monitor 2. His house faired fairly well even though huge pines were blown down. A 12 ft. aluminum boat 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.

Melissa Goering (Science Operations Officer at NWS Cheyenne) took these photos of damage near the Hanselmann residence:

pic1 pic2 pic3 pic4 pic5 pic6

After leaving the Hanselmann house, the periphery of the tornado hit the Maher?? residence and the roof had to be replaced. This residence is apparently 1/2 mile north or northwest of the Hanselmann house. Melissa Goering also took pictures in this area:

pic1 pic2

The tornado moved over barren country with few trees from the Maher?? residence to near Vedauwoo Rd, but a few lone trees and other objects such as fences were damaged in a 1/4 to 3/4 mile wide swath all the way northwest to Overlook Rd according to Bob Adams. Jeff Mitros 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. The Gayle Wilson 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 pines 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 Overlook Rd and Laramie where no people live. Bob Adams told me that the continuous path seems to have ended beyond Overlook Rd. I am not sure if it will ever be determined whether the tornado continued all the way to Laramie continuously.

Here are some pictures taken by Jeff Mitros who lives on Vedauwoo Rd. Mitros reported that dense fog with visibilities around 100 ft prevailed all day. These pictures show the extensive damage to the windows of his house caused by very large hail. His Datsun Z-280 was dented by very large hail. Some of the holes in his house windows were the size of baseballs and even softballs. The elevation of the Mitro residence is 8400 ft and is located close to "the summit" of the Laramie Ridge (Laramie Mountains). Mitros also took some pictures of the tornado damage. 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 went out of his way to help document this rare storm.

All the pictures below were taken by Jeff Mitros and Jack Riske:

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

A tree was snapped off and another uprooted near the Jeff Mitros residence.

Tree damage Tree Damage Tree Damage

A house belonging to Phil Robinson received holes in south facing windows from large hail. This house is 1 miles west-northwest of the Mitros residence.

A small trailer located southeast of the Mitro residence was thrown 300 to 500 yds.

Jack Riske took these pictures of the Gayle Wilson house.

Fence located southeast of the Wilson residence was scattered.

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

A garage was destroyed west of the Mitros residence.

A house 1/2 mile north of the Gayle Wilson house was damaged on the periphery of the tornado.

This trailer belonging to Phil Robinson Monument road (not far from I-80) exit 329 was flipped (Occurred on the northeastern extremity of the tornado).

John Myers lives on the summit of the Laramie Ridge (elevation 8720 ft). He indicated that the tornado path was continuous from 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
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Pic6

So the only undocumented part of the Harriman-Laramie path is the 4 mile section from Howe Lane to the southeast outskirts of Laramie. Based on a storm motion of 45 to 50 mph, this is only a 5 minute gap. It is possible that the tornado that developed along the Colorado-Wyoming border west-southwest of Harriman was continuous for 31 miles to the northern outskirts of Laramie.

Beam blockage was occurring with the .5° slice from the Cheyenne radar. As the storm moved from 7500ft to 8700 ft, the lowest slice of the 88d was partially beneath the ground. This resulted in lower reflectivity(50-55 dbz) values from Vedauwoo to Laramie when the actual reflectivity values were probably 60-65 dbz. The 1.5° slice supports this notion.

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 damaged
Church damaged
Dance hall damaged
College of Agriculture greenhouse facilities damaged (5 of 18 greenhouses damaged and the hoophouse greenhouse destroyed)
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

The tornadic storm continued to the north-northwest through central and northern Albany county. No tornado damage occurred, but this area is very rural. Given the fog, it is possible that tornadoes went unreported.

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 (600-300mb) 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 7500ft. 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.

A small tornado apparently touched down 3 miles south of I-80 on Harriman Road a little later in the afternoon from another storm. 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 with this storm. 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 log 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.

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.

A storm developed about 40 miles west-southwest of DIA at 1630 UTC. Radar indicates that this storm may have produced large hail several miles northwest or west-northwest of Golden, CO. This storm was right on the edge of the Rockies about 9000 ft.

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 large map with 2 of the 3 Wyoming tornadoes can be found here. This map shows the possible break in damage between Overlook Road and I-80. Another map shows the hail swath and tornado paths. The largest hail was likely southwest of the tornado path as the storm moved from west of Harriman to Ames Monument. However, this area is unpopulated so reports were unavailable. I plotted a damage path using http://maps.live.com and google maps with both Wyoming tornadoes. I also plotted the Windsor, Harriman-Laramie and other tornado paths on a terrain map off of AWIPS. This image is less detailed, but shows the topographic features well. The possible tornado that occurred several miles west of Harriman is not plotted here. Wylie Walno reported to me that there may have been another tornado that destroyed a barn about 4 miles west of his house(or about 5 miles west of Harriman). Interestingly, a severe storm did move along US-287 from west of Virginia Dale to 5-8 miles west of Harriman to just east of Tie Siding. But there is just not enough information thus far about this event to plot a damage path. Although I plotted the primary Wyoming tornado as a continuous path on the satellite image, I have no evidence of tornado damage on the rugged terrain between Overlook Road and the southeast outskirts of Laramie along I-80 (about 3-4 mile stretch). This area is uninhabited and a storm survey on foot would probably be required. Perhaps high resolution satellite data would also help determine if the tornado was continuous to Laramie or whether the Laramie tornado was a different tornado.

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 tornado paths in Wyoming will eventually be plotted on this very detailed map.

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.

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.

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.

A radar loop from 1541 UTC to 1731 UTC shows a boundary sagging south into southern Weld county between 1600 and 1630 UTC. The loop also shows the storm intensifying north of Denver where dewpoints were higher. Surface winds were still light in this area. However, surface winds were much stronger north of the boundary. This loop is actually composed of 2 parts and needs to be corrected. The map scale is different for the 2nd part of the loop.

reflectivity loop (1541 to 1731 UTC)

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 54 and 56F. The storm was 25 minutes away from producing a strong tornado. The storm was about to encounter a surface boundary 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). As previously mentioned, another surface boundary was oriented generally south to north from Parker to east of DIA to near Hudson, 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 along 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. 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 surging northwest and was through Peckham, CO through 1745 UTC. But by 18 UTC the boundary that had been surging northwest was stalling just northwest of Peckham and 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.

The distribution of surface based CAPE (SBCAPE) is very important when assessing the severe storm environment. At 18 UTC, the SBCAPE along the direction of the storm motion was fairly broad along the immediate front range. Note the moderate 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 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		43	43	8.2	91.7	331.4
Red Feather	8214	733		44	44	8.4	90.7	331.4
Harriman,WY	7450	755	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)
Harriman,WY	7450	754	985	47	47	9.3	89.7	333.3
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 Harriman, WY actually has almost the same theta-e as Scandia, KS, even though the temperature/dewpoint are 22F/14F 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 89.7F at Harriman and only 77F at Scandia.

At 19 UTC, two mesonet observations and 1 cooperative observer location recorded hourly temperatures. 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 18 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 the surface based CAPE was 1000-1300 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 surface based CAPE (at least lately), actually did a reasonably good job with CAPE fields, perhaps for the wrong reasons. The fact that this model actually forecasted surface based CAPE values up to 1000 j/kg at 6 to 12 hours could be a result of the model's usual overestimation. The NAM/WRF dramatically underestimated surface based CAPE in southeast Wyoming.

The surface temperature at Buford was slightly lower than I expected (44 F) at 19 and 20 UTC. If this temperature is accurate, then the surface based CAPE was lower at Buford (perhaps 800-900 j/kg). So it is possible that the surface based CAPE was lower after the storm passed Ames Monument (or the 2nd half of the tornado path). However, the temperature at Crow Creek (northwest of Buford at 8600 ft) was 46 F at 19 UTC. Therefore, one of these surface observations is likely in error (probably the Crow Creek observation). So the CAPE approximation for the last half of the tornado path is more problematic. The mixing ratios were lower to the west of the Laramie Mountains. So the surface based CAPE was surely lower as the storm moved through the Laramie area. However given the fast storm motion, the storm didn't have time to weaken much before striking Laramie.

Table 4 and Table 5 show the surface based CAPE values for Harriman, Virginia Dale and Lynch. Table 4 uses the 18 UTC Denver sounding while Table 5 uses the 18 UTC RUC initialization. These are modified using the temperature readings from the 3 stations and assumes saturation (there was dense fog).


Table 4
DEN 18 Z/mesonet/profiler modified	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	1190
Virginia Dale(7ene)	7000	760	48.5	48.5	9.6	88.9	333.7	1217
Lynch	7200	766	48	48	9.5	89.4	333.6	1215


Table 5
RUC 18 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	1260
Harriman updated

It is very difficult to achieve low dewpoint depressions, relatively high theta-e values at low-levels and excellent vertical wind shear at 7500-8500 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 surface based CAPE values still exceeded 1000 j/kg. In typical low plains severe storm situations, 1000 j/kg CAPE would be considered very marginal. When CAPE is marginal, tornadic storms can still occur, especially when LCL and LFC heights are low and considerable surface based CAPE 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. In preparing the soundings, I assumed that the vertical temperature profile was moist adiabatic from the surface through the depth of the moist layer. In this case, the level of free convection would be near the top of the moist layer.

The vertical wind shear profile featured strong shear. The surface wind backed to the northeast by midday at the mesonet locations. However, windspeed is not represented the same way at the mesonet locations. For some hours the wind speed was the same as the wind gust while for other hours they were vastly different. Also, some of the winds measurements were influenced by inflow into the storm. The pre-storm winds were probably about 25-30 kts from the east-northeast or northeast (060° at 30 kts). Wylie Walno reported that the winds was about 20-30 kts. For the winds above the surface we used the Medicine Bow and Platteville profilers as well as the 18 UTC RUC. The wind just above the moist layer (600mb) was about 140° at 55 kts. So there was tremendous shear between the surface and 600mb (1.5 to 1.8 km agl). The 500 mb wind was from 150° at 55 kts while the 400mb wind was from 165 deg at 75 kts. 400 mb is 4.4 to 4.7 km above the surface, so the shear from the surface to 4.5 km was about 80 kts. The 0-3 km shear was about 50kts.

The WYDOT stations and 1 cooperative observer station also helped to assess the shear profile in southeast Wyoming in Table 6. These stations show a backing in the surface wind around 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.


Table 6	14 UTC	15	16	17	18	19	20	21	22
supplemental obs. (dddffggg) in mph
Virginia Dale(7ene) 4SE of tornado at 19 UTC			ese	e	e	ene	e	se
Lynch 7E of tornado at 19 UTC	09024g30	09023g36	03022g37	08023g30	08039g40	06027g51	07051g51	08027g50	09009g22
Buford (7N of tornado at 19 UTC)	07020g30	06027g30	05033g37	07029g41	05038g48	03052g52	08041g57	07052g52	07013g26

These mesonet observations indicate that the surface winds near the primary tornadic storm were between 030° and 060°. 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 VWP, 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.

Hodographs for Harriman, WY at 19 UTC using surface wind of:

Note that these hodographs were made using a surface wind speed of 25kts 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

An updated hodograph for a surface wind of 70° at 35 kts is available.

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 so rare in the immediate lee of the Laramie Mountains. The upslope flow in the May 22 case was "cooler", but 1000+ j/kg surface based CAPE 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, gulf 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.

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.

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 in some states have established roadway surface observations. 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. In fact, WYDOT 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 direction also showed a backing to the east-northeast there. 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).