May 10, 2010


Today looks to be a HUGE day for tornadoes across parts of south-central KS and north-central OK. A very potent shortwave trough will plow through the warm sector with the perfect timing to initiate supercells along the dryline. Seasonably high dew points (65+) are being advected northward and, with strong surface heating and steep mid-level lapse rates, should result in very strong instability along the I-35 corridor and eastward. The wind fields today are going to be outrageous... with a very strong westerly jet streak juxtaposed with a strong southerly low level jet you'll get rotating storms. When that happens in a very unstable and moist environment, like today, you have the perfect ingredients for a tornado outbreak. Hence the HIGH risk just issued from the SPC. The image below is the NAM's output for the Significant Tornado Index for 7pm tomorrow, as you can see it is completely maxed out!

My target is around Enid, OK. Storms should fire around 3pm and will move east rather quickly. The live stream will be up once we hit the road. Tune in for what promises to be a day to remember!

May 6, 2010

Triple Tornado Thursday

Thursday, May 6:
SHORT: I will be leaving Lawrence here soon for Ottawa, KS where I expect initiation in the next couple hours. Very large hail will be likely here in eastern KS, and there is an outside chance at tornadoes. If I do see one, it will be the third Thursday in a row. I will try to get the live stream up, but I've been having difficulties with that since switching to Blackberry and can't guarantee it will be without hiccups. My video of the tornado near Washington, KS and other fun stuff from last Thursday is on the Videos page.

LONG:Well the new Day 1 outted my favorite lesser-known forecast reflectivity model so I don't mind talking about it now... the HRRR has been absolutely stellar this season with predicting initiation (timing AND location). For each of the last 6 hourly runs (up to 18z) it has been initiating convection between 23z and 01z along the nose of the strengthening LLJ in essentially the same location in eastern KS. With +60kts of effective shear, supercells will be the dominant storm mode. The question is whether or not the storms will be able to form south of the warm front and root in the boundary layer, not atop the stable layer north of the warm front. If they do become surface based and then interact with the boundary, there is a good chance of tornadoes in the 7-9pm time frame, given the strong low-level turning. That's a big if, though. As of right now, I don't think the dynamic ascent and surface heating will be enough to break the cap, I think isentropic lift will be needed for that. Regardless, I'm expecting to see a few significant hail reports to the south and southwest of the KC metro area this evening.

Below is a composite map I threw together of the 17z HRRR's output for 7pm. The fcst composite reflectivity shows a nice blob southwest of Lawrence, right on the WF, and other updrafts further south, into the warm sector. The underlay is the sfc CAPE chart, showing +2000 j/kg south of the front. The white line is the 1500 j/kg isoline from the MUCAPE chart (not shown), which indicates ample elevated instability north of the warm front. LINK:

April 28, 2010

It's the most wonderful time of the year...

April 29th Forecast:
The placement of the secondary sfc low is going to be pivotal in whether or not tomorrow is a tornado day. Most of the recent model runs (including the new GFS) have developed it further down the front, in the Panhandles, but the new 0z NAM puts it in wcntrl KS. If this actually happens, it would really help out with low-level convergence, and also (hopefully) slow the forward speed of the cold front which would extend the tornado window.

This initial shortwave over the nrn Plains will pull moisture rapidly northward throughout the day but will also act to slightly veer the LL winds in KS/NE. If the secondary low does develop further north, as the 0z NAM suggests, hodograph shapes in the lowest 1km will be much more favorable for tornadoes before dark from cntrl KS northeastward into wrn IA.

Marginal low-level moisture will be a limiting factor for tornadoes but, regardless, there is going to be some WICKED structure out there somewhere. My initial target will be in southeast NE, but I will adjust west from there if initiation appears likely at the cold front/dryline intersection north of Salina. Storms will be moving east rather quickly so my options will be open if something fires to the west.

April 30th Forecast:
Feel free to call it a geographic bias and stay away, but I'm really liking the ern KS target for Friday. Some precip forecasts (including the 0z NAM) have been clearing the squall line out of this area by late morning, which combined with strong moisture advection will allow for rapid destabilization. Storms would fire first along the surface front in northeast KS into southern IA in late afternoon and then possibly southward, along the dryline as the cap erodes. +80 kts (!) of effective shear along with moderate instability will promote the rapid development of rapidly moving supercells. We've got climatology and synoptics pointing to a big tornado threat over a big area, we'll just have to wait and see how the mesoscale plays out.

Again, the placement of the secondary surface low along the front will dictate the amount of low-level turning and the overall tornado threat. If the track is similar to what the NAM is thinking, it could be a big tornado day in the KC area.