After calling in the tornado to the Weather Service, I shoot this overexposed picture about 3 minutes after initial touchdown.
WxTorn05a_32 		There is cyclonic circulation to the dust column as well as a downdraft causing the curl on the left edge of the debris.
WxTorn05a_33 		The mesocyclone is quite narrow on this tornado-producing storm as is the updraft.
WxTorn05a_35
The tornadic circulation dissipates for a few minutes as the mesocyclone appears to narrow and intensify.
WxTorn05b_03 		Rain fell on our position so we moved west while a new funnel formed and created this more classical-looking tornado.
WxTorn05b_05 		The tornado continues moving south along the Weld and Morgan County border near the town of Weldona.
WxTorn05b_07
In this position east of the tornado, contrast problems are typical and one needs to bracket - this exposure is 2 f-stops above what the meter dictated but the ground and cloud remain too dark.
WxTorn05b_11 		The tornado has now been on the ground for 15 minutes and is beginning to dissipate.
WxTorn05b_13 		The tornado weakens and we pack up our gear and try to re-position closer to the storm in case it produces another one, however, this storm did not produce any additional tornadoes.
WxTorn05b_15
In the Clouds Photography
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    Weather Gallery (6 Pages)
  1. Cloud basics
  2. Cloud-specifics
  3. Optical Phenomenon
  4. Supercell Thunderstorms
  5. Tornadoes
  6. Lightning


© 2000 Gregory Thompson
All rights reserved

21 July 2000 west of Weldona, Colorado
 For two days prior to 21 July, eastern Colorado was the target for tornadic storms to develop. Storms that occurred on Wed and Thurs did not produce the tornadoes that some expected which may have been due to the lack of sufficient shear since the surface winds were relatively light and variable. At 9 AM Fri, however, I noted easterly winds around 10 to 15 knots at Akron, CO. With this improvement in the data, I decided it was time I chased.  
 
I left work around 2 PM and made arrangements to pick up a pro photographer in Boulder, Allen Birnbach, who wanted to photo a tornado. We went up I25 to CO14 to intercept storms rolling south from the Cheyenne ridge. We watched as a couple of weak cells moved south directly toward us. We thought they would intensify as they moved south but instead they practically evaporated in front of our faces in 10-15 minutes. Then, a new updraft formed in-situ just north of Hwy 14 near Briggsdale and sent anvil streaming over our heads. About this time another updraft formed well southeast of us perhaps near Akron. That one looked great for a time and we decided to move to a middle position on Hwy 52 between Ft. Morgan and Hwy 14 - this gave us the choice to jump east to Akron or stay with the original storm.  
 
WxTorn05a_32 Going south to Ft. Morgan, we noticed the eastern updraft was just pulsing while the western one (Weld County) was getting a nicer base. The base continued to improve so we stuck with it. We thought it was moving SE but in retrospect I think it moved due south. We took Morgan County Rd W west paralleling the Platte River and US34 and a few minutes later a 30 second dust swirl occurred. Precipitation was beginning overhead, east, and northeast but not southeast through northwest. We had 15 knots of easterly winds. A tornado warning was issued on the mesocyclone in front of us (west) and I called the Weather Service in Boulder to tell them we had good eyes on it from 5-10 miles east of it. While on the phone a new dust whirl started, slowly grew and widened and reached half-way to cloud base with no apparent funnel above. The mesocyclone had quite a good shape but we could not discern a funnel, perhaps just a nipple.  
 
WxTorn05b_05 During the next 60 seconds, I stayed on the phone telling the NWS that we had an intensifying tornado (this was 6:02 PM MDT). The tornado continued to lengthen as a dust column connected fully to cloud base and stayed rather constant for 5 or so minutes. Then the dust dispersed some as if the tornado was dying but after a 60-120 second gap, a nice condensation funnel appeared. The funnel extended into the residual dust/debris and stirred things up again with a more concentrated dust column obscuring the condensation funnel. This form lasted until about 6:19 when everything slowly dissipated.  
 
WxClds20a_21 We then drove south on Hwy 52 from Wiggins to get closer to the storm updraft in case it decided to produce another tornado. Instead, the storm was lifting and dying and we watched as mushball hail (many around 1 to 1.5") fell hundreds of feet and smashed onto pavement like a snowball! Snowballs falling from the sky were fun to watch. Rotation was still found in cloud base and we were very close looking nearly straight up. The storm fizzled and merged with another after 6:30 so we broke things off around 7:15 on the Morgan/Adams county border where I shot a series of mammatus photos.