Wyoming Tornadoes on
June 3 1958
A special case study
Jonathan D. Finch
Historical Tornado Cases for the Boulder Warning Area
Historical Tornado Cases for the Cheyenne Warning Area
Historical Tornado Cases for the United States
April 23 1960 Cheyenne Ridge Tornado
The July 16 1979 Cheyenne Tornado
May 7-8 1965 Front Range Tornado
June 14-17 1965 Front Range Superstorm
High plains and front range topo maps
Overview
There were only 3 reports of severe weather on June
3, 1958. Two tornadoes were reported in Wyoming and
there was 1 rerport of 3/4" hail in Idaho. Both
tornadoes were in open country and did no damage. One tornado
occurred 7 miles east of Gilette at 530 pm and the
other was just west of the Bighorn mountains near Shell at
330 pm. But June 3 1958 featured a classic severe
weather pattern for eastern and northeast Wyoming.
The author believes that a lot more severe weather
occurred than was reported on this day.
The northeast Wyoming severe weather hole
From January 1955 to December 1973, there was a large area in northeast Wyoming with no large hail reports
greater than or equal to 1". This area is greater
than 6000 sq mi and contains the town of Wright and the tiny town
of Bill. During this period, severe weather reports
were not
sought after. Occasionally someone would report this event
by telephone. With almost nothing to hit over
such a large area, significant tornadoes are very rare in this area.
On rare occasions, a small town takes a direct hit
with a strong tornado. This was certainly the case on August
15, 2004 when 2 people were killed in Wright.
Undoubtedly, tornadoes of this magnitude or even stronger have
occurred and hit nothing (rated F0). The
town of Bill is pretty much a ghosttown with a population of only
76.
One undocumented hailstorm and tornado that occurred
in this severe weather hole occurred in June 15, 1965.
about 40 miles north of Douglas. This tornado barely missed
the farm house but destroyed 2 trailer houses. A man
inside of the trailers suffered 2 broken ribs.
Thousands of valuable trees were destroyed by the tornado, some
of which were giant trees that stood for long time.
Giant masses of uprooted and broken, giant trees were all that
remained. This event was documented in the Douglas
Budget but never made it into the official storm databases.
I stumbled across this event after going through one
year of newspaper microfilm.
The event I would like to discuss occurred on June 3
1958. All the ingredients came together for high-end severe
weather on this day. But officially, not much
happened on this day!!
Meteorological Discussion
At 12 UTC June 3 1958, a strong upper jet was located from southern California into Utah and Wyoming. The
exact speeds in this jet are unknown since many of
the soundings were missing at upper levels. But 80 to 100kt
winds were probably common. A deep 500mb low (about 558 dm) was located over northern CA with southwest
flow across the Rockies. A 500mb ridge was
centered over Missouri and eastern Kansas. The 500mb wind
was missing at Grand Junction. However their 550mb
wind was 52 kts. Ahead of a pacific
cold front, a mid level warm plume covered much of
eastern Arizona, eastern Utah, New Mexico, Colorado and
probably southern Wyoming as shown on this 700mb chart. Ahead of the 700mb baroclinic zone in the warm
sector, 500mb temperatures were chilly by early June
standards with -13C at Grand Junction. 850mb dewpoints
were quite high at North Platte and Omaha. There was
an 850mb front between North Platte and Rapid City.
The 21 UTC surface chart showed a pacific cold front charging into western Wyoming. The progression of this
front was pinpointed using surface observations from
Provo, Salt Lake City and Evanston. A warm front was located
north of Riverton, Casper, Cheyenne, North Platte and
Norfolk, but south of Sidney and Douglas. A dryline was
buldging east of Imperial in southwest Nebraska, and a front extending from northern Wyoming into North Dakota.
The warm front moved only stopped advancing after 21
UTC and remained just southwest of Douglas. North of the
front in the Nebraska panhandle, moisture was
surging to the west-west-northwest into eastern Wyoming as shown
in the surface observations at Chadron and Scottsbluff.
The surface observations at Worland indicate CB W-N
at 20 UTC, CB NW at 21 UTC and CB N-E at 22 UTC.
The weather observer at Greybull observed a tornado to the southeast at 2155 UTC. This was probably the same
tornado that occurred near Shell at 2200 UTC. There
was apparently no damage with this tornado. It is possible
that this tornado was occurring southwest of
Greybull as well. But this is wide open country with very few people.
No hail was reported with this storm. There was a
gap in the surface observations between 19 UTC and 2100 UTC.
The surface wind up through 19 UTC was fairly light.
Thunderstorm(s) apparently developed west or northwest of
Worland around 20 UTC and then affected the Greybull
and Shell areas around 22 UTC. The wind at Worland was
light from the north from 20 to 22 UTC. The vertical
wind shear profile was characterized by light winds or light
northerlies at low levels, and fairly strong
southwest mid to high level flow. It has been previoulsly documted by
"" that northerly low level flow is favorable for
getting moisture west of the Big Horns. The surface based CAPE
was estimated using the 21 UTC surface observation
from Worland and the 00 UTC sounding from Lander.
The Lander sounding was immediately upstream from
the storm location at is probably fairly representative of the
mid and high levels over the storm area. Since the
surface pressure was about 862 mb at Worland, I used a recent
sounding from Grand Junction that corresponding had
a surface pressure about 862mb since the elevation of Grand
Junction and Worland are similar. The surface
based CAPE approximation was 2600 j/kg.
Storms were exploding north of Casper around the
same time the storms were developing west of Worland. The
surface remarks on the surface observation
sheet from Casper showed "Rapidly Building CB NE" at 20 UTC,
"CB NW-NNW HUGE CB NNE-NE at 21 UTC, CB NNE-NE at 22
UTC, CB NNE at 23 UTC, CB NNE at
00 UTC, CB DSNT NNE at 01 UTC and CB DSNT NNE at 02
UTC. Its is fairly obvious from a glimpse of the
21 UTC surface chart that areas north of Douglas and N/NE of Casper were in prime locations for severe weather.
Lets attempt to estimate the lifted index at
Douglas, WY and northeast of Casper at 21 UTC. The surface
observation at Casper shows completely mixed out
conditions with T/TD of 85F/13F and wind of 21025KT. They
just recently mixed out and winds are howling from
the SW. The low levels are probably not strongly superadiabatic
since the winds are so strong and since they just
recently mixed out after the warm frontal passage. Given that the
dewpoint depression is 72F, the temperature profile
over casper at 21 UTC is probably dry adiabatic from the surface
to 500mb. Let's lift a parcel from the surface to
700mb and then 500mb at 21 UTC to estimate the 700mb and 500mb
temps. This gives 700mb and 500mb temperatures of 15C and -11.3C respectively. The 21 UTC temperature of 85F
at Casper also corresponds to a the maximum
temperature -3 or MaxT-3. But when Casper initially mixed out at 20 UTC
the surface temperature was 83F. Lifting 83F up the
dry adiabat yields 14.6C and -11.9C. To corroborate this finding, let's look
immediately upstream at Rawlins and use the same
procedure. The 19 UTC (local noon) temperature at Rawlins
had leveled off at 75F. In fact the temperature was
75F at both 18 and 19 UTC. The temperature then increased to
77F at 20 UTC and then 79F by 21 UTC. The winds
during this period were gusting from the southwest at 35 to 40KTS.
Using the mixout temperture of 75F and taking this
up the dry adiabat yields 700mb and 500mb temperatures of
14.2C and -12.7C. Using Max-T -3 = 77F yields 14.8C and -12.1C. The bottom line from this exercise is that the
700mb and 500mb temperature at Casper and Rawlins
during the afternoon was 14.2C-15C and -11.3C-12.7C.
Using an average of these values gives -14.6C at
700mb and -12C at 500mb. Using upper level data from surrounding
raobs sites, the most probably thermal profile at
Casper at 21 UTC looks something like this. Now let's construct a
sounding for a location just northeast of Casper and
estimate the surface based CAPE and lifted index. First, Lets
assume that the theta-e at Douglas is representative
of the area north of Douglas and northeast of Casper. This is
probably a fair assumption since the winds were
howling from the southeast at Douglas all afternoon. We will also
assume that the air over Casper and Rawlins moved
northeast and acted as a lid over the moist air to the northeast.
The surface pressure at Douglas was 844mb at 21 UTC.
This was calculated by looking at the 21 UTC station pressure for
Douglas(24.95) and multiplying by 33.86. Since the
surface T/TD at Douglas were 79/58 at 21 UTC, the mixing depth in
the
boundary layer was probably about 4000ft. The
approximate sounding for the area around Douglas and northwest of
Douglas shows about 4300 j/kg of surface based CAPE.
Its is very likely that the surface dewpoints to the northeast and
north of Douglas were 1 to 2F higher while the
potential temperatures were probably about 1 to 2F lower. Maximum
temperatures from cooperative observer locations
were 74F just southwest of Gillette and 75 to the southeast of
Gillete.
The maximum temperature at Moorcraft(4200ft)
was 76F. Areas north of Douglas probably had dewpoints close to
60F and surface temperatures in the mid 70sF in the
afternoon. This would still result in surface based CAPE values
around 4000j/kg.
The vertical wind shear was excellent in the region
north of Douglas. The 500mb, 400mb, 300mb and 200mb charts
indicate speeds of 50kts, 60kts, 70kts and 80kts
from about 220 degrees. Since the surface winds were gusting to
between 33 and 40kts and sustained at 25kts, the
700mb winds were probably from the southwest at 35kts.
The surface winds were from the southeast to
south-southeast at 15 to 20kts.
Two tornadoes were observed about 7 miles east of
Gillete around 530 pm MST (2330 UTC). Storms developing
about 20 miles north of Casper would take about 2.5
hours to move as far northeast as the tornado location by 2330 UTC
assuming a storm motion of 30 mph. So the storm that
produced the tornado east of Gillete at 2330 UTC probably
developed north of Casper around 230 pm MST (2130
UTC). This makes sense recalling the remarks of HUGE CB
NE-NNE on the Casper surface observation sheet at 21
UTC.
I believe that the storms in northeast Wyoming
produced a lot of severe weather between 21 UTC and 01 UTC.
Given the very favorable environment, very large
hail undoubtedly occurred despite the lack of reports. There also
may have been more tornadoes in the wide open areas
to the north of Douglas and northeast of Casper.
Upper air charts:
7-15-79 00 UTC 700 500 250
7-15-79 12 UTC 700 500 250
7-16-79 00 UTC 850 700 500 400 300 250 200
7-16-79 12 UTC 850 700 500 400 300 250 200
7-17-79 00 UTC 850 700 500 400 300 250 200
Surface charts 21 UTC 14 06 UTC 15 09 UTC 15 12 UTC 15 15 UTC 15 18 UTC 15 21 UTC 15 00 UTC 16
03 UTC 16 06 UTC 16 09 UTC 16 12 UTC 16 16 UTC 16 17 UTC 16 18 UTC 16 19 UTC 16
20 UTC 16 21 UTC 16 22 UTC 16