Severe Weather Hits Southeast Colorado

Strong thunderstorms battered portions of the southeast plains the first few weeks of August, with numerous reports of hail, wind and tornadoes reported to the Pueblo weather office.

Monday the 9th Pueblo West Equestrian Easement
The two busiest days of the week, in terms of the number of severe thunderstorms, were Monday the 9th and Tuesday the 10th. Storms began to form across the Eastern Plains early in the afternoon, with the first warnings issued for Baca and Huerfano counties between 2:30 and 3:30 pm.  A Tornado Warning was issued for El Paso county as numerous reports of funnel clouds were called in, and a storm chaser later reported a brief touchdown of a tornado in the vicinity of Calhan from 4:51 pm to 4:45 pm.  Severe weather continued across El Paso county later in the evening, with storms producing hail as large as softballs in Ramah around 7:20 pm, and baseball sized hail reported in Rush around 8:10 pm. The city of Colorado Springs was spared the large hail, but did receive reports of hail up to an inch in diameter.   Next in line for severe storms was Pueblo county, as strong thunderstorms began to rapidly develop along a boundary and ahead of an upper shortwave around 6 pm. A severe thunderstorm warning was issued for Pueblo county at 6:06 pm. By 6:37 pm, several reports of golf ball sized hail were reported from Pueblo West.  

The author was caught in this hailstorm, receiving occasional golf ball sized hail intermixed with copious amounts of near one inch hailstones and very heavy rainfall.  Other thunderstorms developed concurrently along the St. Charles Mesa, bringing reports of 2 inch hail to this area.  A flash flood warning was issued for Pueblo county, as creeks and arroyos ran bankfull, and streets turned into creeks in many areas as the one to two inches of rainfall made its way to drainages.   

Photos Courtesy D. Metze


23 warnings were issued by the Pueblo office this day - 17 severe thunderstorm warnings, 5 tornado warnings, and one flash flood warning. 

Fortunately, no damage has been reported so far from the brief tornado near Calhan, and only funnel clouds have been reported with the other tornado warnings. See the summary local storm report for this event.

Tuesday the 10th
Round two occurred on the 10th, as the strongest in the series of cold fronts made its way across the plains late in the evening. A few warnings were issued early in the day for El Paso and Las Animas counties ahead of the main coldfront. By 7 pm, the front had raced into into El Paso County, bringing with it hail reports of up to 3 inches in diameter, and wind gusts near 70 mph. Colorado Springs Hailstones - approx quarter to golf ball sized Large hail and strong winds continued into Pueblo county, with a brief tornado touchdown reported 10 miles northwest of Onley Springs at 7:45 pm. As the front progressed across the eastern plains, strong winds moved through Baca county after 10 pm, with another public report of a tornado 12 miles southeast of Walsh at 10:38 pm.  25 warnings were issued this day, 5 of which were Tornado Warnings, 2 Flash Flood warnings, and 18 severe thunderstorm warnings.

 "It was by far the busiest 2 days in my 13 years as a NOAA employee. The good news was we knew it was coming a day ahead of time and we were prepared, " said lead forecaster Steve Hodanish, who worked as a radar warning forecaster both days. (See the summary local storm report for this day.)
 
The storms put on quite a show at sunset, as many photos came into the office email of mammatus clouds and thunderstorms as they continued across the plains.  

Colorado Springs Mammatus Colorado Springs Mammatus

Photos Courtesy T. Magnuson, Copyright 2004


Special thanks to all of our spotters who reported in during the severe weather, as well as the hard  work and dedication of Ham radio.


Meteorology

A strong upper level trof was forming over the eastern US for this time period. As a result, strong north to northwest winds in the upper levels of the atmosphere aided in pushing a series of cooler high pressure systems into our area from the north. You can see a representation of this pattern in the figures below. The first chart depicts whats going on higher up in the atmosphere. Notice the northerly wind "barbs" over the Central US, and the strong upper trof (the large "U" shaped feature) over the eastern US.

  RUC analysis 500 milibar height and wind
(Click to Enlarge)


The second chart depicts what is occurring at the surface as high pressure moves into the area from the north - note the southeast to east winds across the Colorado Plains.
RUC surface analysis
(Click to Enlarge)
 
These two wind directions, north to northwest aloft, and east to southeast at the surface, created strong wind shear which is important in the formation of long lived severe thunderstorms.  Another important factor, instability, was also very strong over the area.  Increased instability allows air to rise quickly and aids in the production of severe thunderstorms.  Last but not least, a series of upper level impulses moved across the state in the northwest flow, acting as the "trigger" to start air rising and therefore for strong storms to begin.
 


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