Day 1: better than it ought to have been

We caught some neat storms today, and I would submit that it was worth the lack of sleep and driving all day. We essentially got to areas southwest of Omaha and caught a supercell that gave us some hope and wall clouds. At times it looked like it would produce, as it was sucking air in pretty consistently at an estimated 25 knots. And just when we thought it was over, another burst of air ingestion would occur, making it look like it was about to produce. Given the relatively low dewpoints, I suppose we couldn't expect tornadoes, but it's nice to hope.

On the road

We got on the road at a ridiculously early hour, 4 AM. This after I had just come back from a week-long work trip 4 hours before. Apparently we're hardcore. Anyhow, we're targeting, at least initially, Omaha, NE, where modest moisture and good flow should combine to produce some nice storms. There were some bumps along the way, specifically with regard to data, but my wife fixed those problems for us (thanks, sweetie!) and we are no longer running blind. If you want to follow along on Twitter, we're likely to have more up-to-date bite-sized nuggets of observations. Follow me @StormStructure, Hobson @justinhobson85, or Chris @CKStamms.

Chase forecast, May 17 evening version

Sorry, folks, no imagery today. Go look it up for yourself, if you're so inclined. So it appears I may lose the bet I made with Hobson yesterday, and that's just fine. If that happens, it means our chase will have better moisture than has been in the region recently. If storms do go, though, they'll likely be organized, possibly supercells, albeit high-based. I suppose going chasing to work out the kinks will be beneficial. Or perhaps I'm just trying to make myself feel better because I can't go. Saturday looks pretty good, although still somewhat lacking in terms of moisture. But a surface low west of Omaha coupled with the approach of a compact short-wave trough will likely lead to some rather good storms in the Omaha region. Sunday has some storm potential, but I don't know how realistic it is to chase them--they will likely be in the Texas panhandle. The drive from Omaha to Amarillo is on the order of 11 hours. Yeah. Monday is when the return flow really starts to get going. The Gulf is forecast to open up. Finally. Nebraska or Colorado for a northwest flow setup. Tuesday looks like the day before the day in Nebraska. Wednesday--this is still looking like a big day. Back to eastern Nebraska, at least with this run. Thursday looks uncertain, but perhaps Iowa will work out. A few more days of chasing could occur, although I don't trust the models much at this time in the future. That being said, the central plains could see some action in a week and a half.

A new year, a new chase

So I suppose it's about time I blogged here, detailing the travels and travails of this year. This year, we're heading out on a trip that will last up to 10 days (much likely fewer than 10 days) in search of the rotating atmosppheric violence for which so many of us clamour. Okay, after that lame attempt at prose even I'm ready to punch myself in the face. But still. We start out on Saturday. This is out of necessity due to scheduling made well in advance, but it looks like it could end up working for us. Friday (May 18) looks marginal, at best, as although moisture and, as a result, CAPE, are progged to be good over the northern plains and southern Red River Valley (of the north, or "the *real* Red River Valley, as an SPC forecaster friend of mine calls it), the NAM and GFS have been consistently painting dewpoints way higher over the continental US than reality has shown. As it sits right now, as I type this, dewpoints (hereafter called "dews") are struggling to get into the double digits (C) in Kansas. KANSAS! So any return of moisture would have to encompass a) an open Gulf of Mexico and b) a strong low-level jet (LLJ). So to begin, let's look at those: the LLJ and moisture. I present to you the NAM 48-hour forecast of dewpoint and wind at 850 mb and the surface. Note that a) the Gulf seems to be open and b) there are 2 distinct areas of moisture, one in the northern plains and one stretching as far north as Kansas. I posit that the area of moisture as far north as Kansas is the *real* return flow, and won't make it in time for convection to be more robust farther north. I will also admit, though, that I have a bet with Justin right now that the dews won't reach 15°C anywhere in Manitoba on Friday. I hope to win said bet.

Anyhow, to beat the hell out of this dead horse, I think that moisture is overdone, badly, so I doubt there will be any major league severe in the region Friday. Now onto Saturday. The beginning of our chase. I feel almost that I should make a "ta-da" sound, or at least make the Imperial Margarine crown appear. But you won't get it; I'm just that kind of guy. Anyhow, we're looking at departing from Winnipeg and trying to make it to the zone of terror. In this case, it appears the farther south, the better. Keeping in mind the craptacularity of moisture being handled in the NAM, we will cautiously look at the trough/convergence line stretching from the progged low in northwest Ontario to the other one in the northeast Texas panhandle. Flow should be not too bad at midlevels, with winds on the order of 30 to 40 knots from the southwest, juxtaposed (I like that word!) with surface winds out of the south.

The NAM does make a convective signal happen, with showers and thunderstorms between Dodge City and Wichita, KS by 3Z on Sunday morning. Is this real? Beats the hell out of me, but with the prog sounding and wind profile, it sure looks promising.

Here's a problem, though: have you ever tried to drive from Winnipeg to even Kansas City? It takes a few (read: MANY) hours. So that's an unrealistic target. So Saturday may, by necessity, end up being a positioning day for us, all while watching storms go up and nothing we can do about it. We may, however, be able to catch something, say, close to Omaha, where similar instability but not-so-backed winds are progged. That's at least a realistic chance.

The 17/00Z GFS, for what it's worth, produces better conditions farther north than does the NAM. We will see, but it appears we will only be able to chase this stuff, if anything at all. Sunday looks only okay at this point. It appears that the trough causing all the awesomeness on Saturday will move east Sunday, leaving only some places for storms, the best of which appears (at this time) to be northeast Oklahoma. The wind fields, however, aren't forecast to be great--multicell, if maybe marginal supercell. Monday looks like a returning flow day in north Texas (Wichita Falls?) or maybe on the caprock. Tuesday looks pretty good for the western plains, be it Nebraska, the Black Hills or western North Dakota. If I had a better confidence in moisture I would be jumping up and down about this day. The good thing I see is stronger winds on the west side of the upper trough, which leads us to... Wednesday is a damn fine day, if the GFS is to be believed. The *digging trough* (referenced above) will cause lee cyclogenesis out over the plains, and the response should be good. This will be a forecast based on convection, if any, the previous night and its resultant outflow, juxtaposed with the good (50 knot) midlevel flow. After this point, I feel it's a losing battle to even try, but I will say this: a week ago, the GFS had a death ridge over the area of interest, and at this time, for the same time period, now it does not. Anyhow, let the season begin It's about time.

Now: storms

Well, it appears I was a touch too far south with my forecast. But here's a screen capture of the RADAR as the storms happen right now. Wow.

November severe weather setup

Down south storms can happen almost any month out of the year.

Including November.

Tomorrow looks to be a really good setup for severe weather in north-central Texas. So let's go through the checklist in our ingredients-based forecast.

Moisture:
Surface dews look to be over 60 in the region and even over 65. Easily plentiful for this time of year. And to boot, it's not a wishcast of the model--the dews over 60 are already in place. 850 moisture looks good, too.





Instability:
MLCAPE is progged to be in excess of 1500 J/kg. Lots. No CIN.





Lift:
The model indicates good convergence along the fronts, but in the warm sector not much is shown. This could be a limiting factor. However, we can infer strong synoptic-scale lift from the cooling and strong winds at 500 mb.



Shear:
Tons, both at low levels and at high. Winds at 850 mb should be in the 30 to 40 knot range, and at 500 mb, around 50 to 60 knots. Veering looks to be pretty good, so the deep shear values will easily support supercells and low-level shear will support low-level rotation.







So what do I think will happen?

Notice the time in all the maps above: 18Z. Included in that is the cap strength, which is nil by 18Z. That's noon, CST. However, with subtle warming going on at 700 mb, storms may be slightly capped. On the other hand, strong winds and cooling at 500 mb indicate likely strong lift. Therefore, I expect there to be storms ongoing late in the morning and, as long as the warm sector remains at least partly sunny, they should intensify through the afternoon. Looking at the forecast soundings below, the low-level jet is forecast to intensify through the afternoon, lengthening hodographs and increasing low-level shear. So the ongoing storms will become more and more likely to rotate at low levels. Provided one storm can stay discrete, tornadoes look to be likely, along with big hail and strong winds.

My target area is between Seymour, TX and Wichita Falls, TX. Prime time will be about 3 PM. Sunset is about 5:30 PM this time of year, so the viewing time will be much shorter than at other times of year. Storm motion won't even be too crazy--20 to 25 knots.

If I were out in that part of the world, I would definitely try to catch a November tornado.

EHI:



Storm motion:


18Z prog sounding:



21Z prog sounding and hodograph:

Back to regular life and setups

So wouldn't you know it, there's a setup on the way that looks really good. I'm talking spectacular. Let's talk about it.

Moisture is at its peak right now. Surface dews are progged to be in the low 20s. Up to 850, even, it looks to be moist--dews over 15°C.





That will lead to slightly-capped MLCAPEs in excess of 1000 and even 1500 J/kg. Not too shabby, if you ask me.





With 500 mb flow increasing with the approach of a vigorous trough, deep-layer shear will be good--great, if you add in the 850 mb winds crossing rather nicely (shown above).



Surface lifting will, I suppose, be a question but if a front or outflow boundary sharpens up, the game will be on.

If I were chasing, I would aim for Weyburn, SK, for an initial target and go from there.