04/23/08 Chase Forecast Update 1

Things have shifted around a bit on the latest runs with regard to the triple point location, but are still bullish on the early convection across the area. My gut instinct is still telling me that an evolution similar to what is depicted above will more likely happen, in regards to frontal position and dryline position.

I have this feeling, and I hope I am right, that the early convection is not going to be nearly as wide spread as advertised. In fact, I can’t stop thinking about how all the models on the bigger events this year brought the energy to get things fired off out way earlier than what actually happened when the event came. This resulted in firing around or after dark on a few occassions, rather than late afternoon. I can’t help but wonder if this will be the case this time, and in fact there won’t be any early convection due to the energy coming out later than forecast.

All that said, it’s time to start looking at what is happening NOW and how it evolves into tomorrow. That is an important step, and should be one of the first steps so you can see how it relates to how the model forecasts go, if they are verifying or not. Below is a quick hand analysis I did on the current surface conditions to get an idea of what is going on with this front and dewpoints etc. You can click on it to get a better look at what I am about to talk about.

I’ve been watching these observations for a few hours now. The front itself appears to have stalled across north central Texas and is only still moving to the sw from about Midland TX into SE NM. I expect that progression will stop very soon as it will be getting to the mountain foothills. I could still see moving southwest recently on the Midland, TX radar.

Secondly, I drew out the dewpoint lines from 50F degrees and higher, ever 5F degrees. There is some moisture up in OK that is moving in to the panhandle, south plains area of Texas, but the winds across that area have been slowly coming back around to the east all evening.

South of the front, we have a good general SE flow, albeit weak right now. Interesting to note what appears to be a very sharp dryline with a triple point in the Odessa, TX area, and the dryline extending southwest. This is noted by the mid/upper 50 dewpoints south of the Midland/Odessa area and the extremely dry dewpoints in far west Texas, either in the single digits or negative digits. This dryline appears to be moving west, at least just to the west of Odessa, because the station reporting in Wink and Pecos now have winds from the SE with dewpoints now in the 30s. I suspect the dryline just passed that location at the time this observation was recorded and in fact now as I write this I see they are at 38 and 48 respectively, so that verifies the dryline moving westward.

The next thing I wanted to take a look at was to see just what the low level jet was doing right now. I first looked at all the radar sites south of the front, and looked at the VWP product (vertical wind profile). This give me some idea of what the winds are doing above that station. In the area across where I drew the big arrow, the all appear to be out of the S or SE at around 35 kts at around 2-4000 feet. This is good, it means gulf moisture transport is underway already, although I would like to see those a little stronger, but as you can see, the moisture doesn’t have all that far to go, and the areas north of the front aren’t exactly dry. I also expect those speed to increase as the night progresses. I went ahead and took a look at the SPC Mesoscale Analysis tools just to see how that was playing with what I analyzed. Looks like that is in agreement so we are good there.

I took a look then at the water vapor satellite imagery loop, and noted a piece of energy coming ashore south of California headed this way. I eyeballed the timing of it, and if it stays consistent should arrive here by early afternoon.

So right now, I think some of the models are way off on the further south placement of the triple point. I expect to see the front start moving north again soon as the low level flow acts on it. Maybe not very fast though, given the speeds involved with the winds. This of course will drag the triple point north and probably even northwest given the dryline is on the retreat back to the west currently.

All and all, I still think we are on track for a triple point to be somewhere in the Lubbock vicinity by early afternoon, perhaps even a little west or northwest of Lubbock. A dryline bulge that has been depicted on the models all week south of Lubbock I believe is a reasonable expectation.

Now, IF we get a great deal of convection north of the front like the models are wanting to do, this would impede or even stop the northward progression of the front at that point. I’ve seen this many times. However, a few more isolated storms could lay down some very important outflow boundaries that could be a focus for afternoon convection tomorrow, or even for a storm to latch on to and go crazy with the tornadoes.

As for tornadoes, all other factors appear they will be adequate. IF we can get limited or no early convection, things should heat up nicely and result in a very unstable atmosphere where we could see explosive storms, very large hail, perhaps as large or larger than baseballs and of course with supercells that strong, always the risk of tornadoes.

So there is my take on things. SPC outlook should be out here in about 40 minutes or so and we’ll see what their thinking is. Should we get little or no convection in the early period, I would not be at all surprised to see a moderate risk by mid-morning, if they don’t decide to go ahead and do it on the first day 1 outlook. We’ll see.

At any rate, I WILL be chasing tomorrow, and we will have the LIVE ChaseCam going for you folks. My target is… a little east of the triple point, wherever that may end up. Any storms that form there and move in the vicinity of that front should have a good chance of producing tornadoes.

EDIT: After writing this I notice that Midland and Odessa observations report the winds now have veered back around to the southeast, the front is now retreating north in that area, just as expected!