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Late on June
13 and early on June 14, 1965, low level upslope flow pushed moisture onto the front range. Two frontal
boundaries were present by the 22 UTC June 14. The northern front extended from southern Colorado across Oklahoma
and Arkansas. The southern front extended up and down the front range into New Mexico and Texas. Very unstable
conditions existed along the length of the front range with the highest instability further north in Colorado and Wyoming.
The 00z June 15 500mb chart showed a deep trough in the western US with moderate mid level flow as far east as
the front range of Colorado. The 6km flow (close to 400mb at Denver) was 40kts, which is fairly strong by eastern
Colorado standards in mid June. It was fairly cold aloft for mid June with 400mb temperatures from -22 to -24C and
300mb temps from -38C to -40C. 700mb temps were 15C at Albuquerque, +13C at Denver and slightly cooler further
north in Wyoming. Approximate soundings for Douglas, WY and Fort Collins, CO show moderate to high surface based
CAPE from 2500 to 3500 j/kg. Tornadoes occurred 3 to 5 miles west of Loveland and southeast of Douglas, WY.
The surface observation form from Fort Collins makes reference to the the tornado that occurred west of Loveland that
lasted for 15 minutes. The approximate sounding for Fort Collins showed 2800 j/kg surface based CAPE. The capping
inversion was obviously much weaker in the foothills and mountains southwest of Fort Collins where the storm developed.
The storm probably initiated on the edge of the mountains west or southwest of Loveland. Given the sw to wsw mid level
flow, the storm probably moved to the ene or east.
The other upper air charts are 850mb 700mb 200mb
The theta-e was higher at Las Vegas than at Chanute even though the T/TD were 4F/19F higher at Chanute. This is because
15, 1965 , a tornado was observed by a weather research team at Colorado State University. The surface
observation sheet from Fort Collins indicated that a weather research team witnessed a tornado 8 miles west of
Fort Collins at 413 pm.
A major hailstorm occurred in the northern suburbs of
Las Vegas, NM and Sapello, NM with hail up to 3" in diameter.
A tornado occurred 32 miles west of Cheyenne (elev. 8200ft) or about 15 miles southeast of Laramie, tearing up some
timber, but hitting no structures. Another tornado occurred 25 miles west of Cheyenne.
A tornado and baseball sized hail occurred about 40 miles north of Douglas near the Cheyenne river. This tornado
is not listed in any storm databases. The surface observations at Douglas, WY are here. My approximate sounding
for Douglas, WY during the late afternoon shows about 3000 j/kg surface based CAPE. Of course the shear was good
with ese low level winds veering to the south or southwest with increasing speeds. The wet-bulb zero was around 7700ft AGL.
The 19 UTC surface chart showed 2
areas of moist upslope flow--one in New
Mexico and the other in northeast Colorado
back to the front range.
The approximate sounding for Las Vegas, NM for 21 UTC showed 2500 j/kg CAPE, with a freezing level of 8400 ft AGL
and web-bulb zero height of 6000 ft AGL.
were 18F and 13F higher at Tulsa compared to
Las Vegas but the theta-e was slightly higher at Las Vegas. The
T/TD were 9F/12F lower at Denver compared to Ardmore but the theta-e was slightly higher at Ardmore. The potential
temperature at Santa Fe was 111F. This makes up for the lack of moisture(mixing ratio 9.5 g/kg) as the theta-e was higher than
at Tulsa (T/TD of 84F/66F). So even though the mixing ratio was 47% lower at Santa Fe, and the temperature 8F lower
than at Tulsa, the theta-e was actually higher at Santa Fe since the potential temperature was 111F.
Very strong upslope flow on the 16th resulted in very high surface dewpoints along the
front range from Las Vegas, NM
to Pueblo and Colorado Springs. On June 16, 1965 several tornadoes occurred along and west of the urban corridor in
Colorado. On this day, hail to golfball size and greater occurred at Holman, NM (elev. 7800ft) which is 32 miles northwest
of Las Vegas in the foothills of the southern Rockies. Hail to 1.5" fell at Black Lake NM (elev. 8600 ft). I plotted the
20 UTC surface observations on a terrain map as well. The 20 UTC surface map showed strong southeast winds advecting
moisture onto the front range. The T/TD at Colorado Springs(elevation 6180 ft.) were 64F/60F. At Dallas the dewpoint was
70F. But since a 60F dewpoint at COS has the same amount of moisture as a 66F dewpoint at Dallas, the mixing ratio at
Fort Worth was only 16% higher than at COS. The surface temperature at Dallas was 85F compared to 64F at Colorado
Springs. However, the potential temperature was much higher at Colorado Springs--96.9F versus 85.8F. Therefore, the
surface theta-e was higher at COS(351.6K versus 350.8K). The 500mb charts at 12Z and 00Z showed southerly flow up
and down the western high plains. Even though COS and Vichy(VIH) had about the same T/TD, the theta-e was much higher
at COS owing to a MUCH higher potential temperature and somewhat higher mixing ratio. The theta-e at COS was also
higher than at Dodge City, mostly due to the huge difference in potential temperature. Here is an terrain map with a depiction
of the strong upslope on the windward side of Pikes Peak and the training of storms to the N/NNE that lead to 12 to 14" rain
amounts in Larkspur, Palmer Lake and south of Castle Rock. Creeks in the region flooded and caused major flooding in
Denver with $250,000,000 damage.
The approximate sounding for Colorado Springs at 20 UTC shows about 3200 j/kg surface based CAPE.