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Lead forecaster at NWS DDC and storm chaser/photographer extraordinaire Mike Umscheid documented a rare Kansas November wedge tornado, in the far southwest corner of the sunflower state yesterday. Wow! Go to: http://www.underthemeso.com/blog/ to see and read more.
The setting was a cold core setup (read paper here), with a 500 mb low attempting to cut-off over eastern Colorado within a strong upper wave lifting northeast (see SPC graphics above). An area of CAPE was over southwest Kansas, just east of the surface low where boundaries intersected (a fairly classic localized setup, see surface map above). The cell Mike chased looked to be pretty close to this key boundary intersection (see radar above), with sunny skies to the south on satellite (not shown), generating a good surface heat axis pointing into the area.
The RUC analysis sounding in the Johnson/Ulysses KS area at 21 UTC (see above), about 20-25 minutes before the tornado, showed good CAPE for a cold core setup (near 700 J/kg), all bunched below roughly 400 mb for a classic small supercell profile. With plenty of really cold air aloft (-10 C at 700 mb!), dew points in the 40s F and temps in the 50s F were all that was needed. Amazing!
A potential cold core setup in South Dakota last week (11/5/08) didn't pan out for tornadoes, as there appeared to be way too many low clouds for needed surface heating and instability near the boundary intersection with that system, unlike the one in southwest Kansas yesterday.
Excellent job, Mike!
- Jon Davies 11/11/08
Hey Jon, Thanks for the case study! I always love the cold core setups and am always looking to chase them and your info is really helpful in tying in all the lose ends when it comes to my forecasts, and you seem to be the only one who studies these cases so thanks for the post!
ReplyDeleteGlad this was helpful, Michael. Thanks for the comments.
ReplyDeleteMike U. also has a set of graphics on his blog from that morning when he was making his forecast.