Sunday, September 14, 2008

Tornadoes on 9/12/08 near Kansas City

A somewhat rare September tornado episode occured on Friday 9/12/08 in the Kansas City area. While visually impressive (see photos above near Eudora & Desoto, Kansas), the tornadoes were weak, with damage only in the EF0-EF1 range (the National Weather Service has officially rated the tornadoes near DeSoto, Kansas and Sedalia, Missouri EF0 in intensity).

Shawna and I had a birthday celebration planned in north KC for her son Zach on Friday evening, so we missed alot of the excitement. When picking up Zach from school in Plattsburg, Missouri at mid-afternoon, Shawna and I noticed SE to NW bands of low dark clouds with rapid motion, suggesting strong low-level wind shear. With rain all day and a cool surface air mass north of a boundary to our south (see surface map above), I didn't give the setting much thought until Shawna saw what looked like a wispy funnel that lasted a few seconds under a cloud band in the distance. I looked at some maps online, and began to wonder a bit what might happen. SPC issued a tornado watch around 4:30 pm with tornado reports coming in to the southwest of Kansas City near the boundary, but we were committed to our celebration. Watching TV later at Shawna's parent's house, we saw how large the tornado near DeSoto was, and heard about reports of damage. Thankfully, the tornado warned cells that went over the KC metro area did not produce any damaging tornadoes.

The DeSoto, Kansas tornado was a classic case of a supercell crossing a boundary where wind shear increased rapidly, with easterly surface winds. The surface map above shows the stationary front in the Topeka-Olathe area, and the SPC maps above show the large increase in low-level wind shear (storm-relative helicity or SRH) along and north of the front, with CAPE near and south of the front. The best combination of CAPE-SRH was right along the front just south and southwest of the KC metro area. Deep-layer shear through 6 km above ground (not shown) was also on the order of 40 kts along and north of the front, suggesting good support for tornadic supercells. On radar images above, notice how the DeSoto cell (indicated by white arrow) crossed the boundary moving northeastward, which is about the time it produced a tornado. As this cell moved deeper into the cool surface air north of the front, it stopped producing tornadoes.

The RUC analysis profile at Olathe (OJC, also shown above) is interesting, showing a large veering wind profile in the lowest 1-2 km, and around 900 J/kg of CAPE. While the instability wasn't super-impressive, notice that it was bunched low in the profile, with the "fattest" CAPE roughly 13,000 ft above ground. Most warm-season tornadic thunderstorms average larger CAPE, with the "fattest" CAPE up around 24,000-30,000 ft above ground. With the CAPE in the Olathe profile "squeezed" down fairly low, that suggests more rapid movement of air accelerating upward, like a hot air balloon encountering cold air aloft and moving upward faster. This could help with upward stretching, and combined with the wind shear, might be another factor to help increase potential for a tornado in a "smaller CAPE" environment.

- Jon Davies 9-14-08


goooooood girl said...
This comment has been removed by a blog administrator.
DM said...

Great analysis as always, Jon. I put up some pictures of the supercell that was to the south of the "Eudora" one on my blog (stacked plates) I never saw that boundary while chasing, but I would have never thought that supercell would produce...

On May 22nd/23rd the supercells that fired on the dryline moving towards the WF would constantly produce, even after crossing the boundary as well...I guess 2008 was the boundary cross year!

Tell Shawna hello and I hope you guys are doing well!


LDCT said...

Looks like I missed some crazy stuff while I was chasing Hurricane Ike... I echo what Dick said, GREAT ANALYSIS!!! Justyn told me you said Hi and I just wanted to make sure I said Hi back... I saw that you got married this summer so Congratulation Jon!!! Getting married after a storm chase as to be one of the coolest things I have ever heard of!!! She must be a great lady!

I got back a couple of days ago from Galveston Island... It was a crazy experience and I have to say the island got rocked very hard... There were a few areas that looked similar to Katrina... However, we got very lucky that the eye went directly over us because if Ike would have gone 40 miles west I doubt there would still be a Galveston Island!!! As bad as it was, we got very lucky!

I hope all is well with you buddy and Congrats again on the marriage! Hopefully someday you and your wife can make it down to Starkville for a symposium... We would love to have you, and as always it would be great to see you again! You can't beat the BBQ!!! Talk to you again soon Jon!


111 said...

WoW shares many wow gold of its features with previously launched games. Essentially, you battle with wow gold cheap monsters and traverse the countryside, by yourself or as a buy cheap wow gold team, find challenging tasks, and go on to higher aoc gold levels as you gain skill and experience. In the course of your journey, you will be gaining new powers that are increased as your skill rating goes up. All the same, in terms of its features and quality, that is a ture stroy for this.WoW is far ahead of all other games of the genre the wow power leveling game undoubtedly is in a league of its own and cheapest wow gold playing it is another experience altogether.

Even though WoW is a Cheap Wow Gold rather complicated game, the controls and interface are done in warhammer gold such a way that you don't feel the complexity. A good feature of the game is that it buy wow items does not put off people with lengthy manuals. The instructions bygamer cannot be simpler and the pop up tips can help you start playing the game World Of Warcraft Gold immediately. If on the other hand, you need a detailed manual, the instructions are there for you to access. Buy wow gold in this site,good for you, BUY WOW GOLD.

kissouyin said...

Weekends to peopleig2tmean that they can have a two-day wowgold4europe good rest. For example, people gameusdcan go out to enjoy themselves or get meinwowgoldtogether with relatives and friends to talk with each storeingameother or watch interesting video tapes with the speebiewhole family.
Everyone spends agamegoldweekends in his ownmmoflyway. Within two days,some people can relax themselves by listening to music, reading novels,or watchingogeworld films. Others perhaps are more active by playing basketball,wimming ormmorpgvipdancing. Different people have different gamesavorrelaxations.
I often spend weekends withoggsalemy family or my friends. Sometimes my parents take me on a visit to their old friends. Sometimesgamersell I go to the library to study or borrow some books tommovirtexgain much knowledge. I also go to see various exhibition to broadenrpg tradermy vision. An excursion to seashore or mountain resorts is my favorite way of spending weekends. Weekends are always enjoyable for me.
igxe swagvaultoforu wowgold-usaignmax wowgoldlivebrogame thsaleGoldRockU