4/2/04: FCST: Texas-Oklahoma

Dec 4, 2003
OK, when the Plains is ridged out, you can choose two ways to go insane: (1) succumb to the power of the ridge, or (2) start looking at ridiculously long-range progs. For fun I choose the latter. I got sick of looking at the Target Area and seeing nothing for the Plains.

The medium range progs have a long wave ridge locked in across the Rockies for nearly two weeks (yuck!). Finally around April 1-2 a major short wave trough carves a rex block under the ridge and brings a chunk of cold air into the southwest US. The surface system traverses the southern Plains around April 1-2, suggesting chase prospects on both days (W TX on the 1st, I-35 eastward on the 2nd). By the 3rd cold air invades and a squall line moves out into the lower Mississippi Valley.

Note to beginners: Forecasting this far out is like playing with an ouija board, but I'm doing it for the sake of it being fun. It will be educational to see how this scenario changes. If you're up to a little occult forecasting, the dubious crystal ball is at http://www.nco.ncep.noaa.gov/pmb/nwprod/an...2/model_m.shtml.

Yeah, I wouldn't get too focused on 4/2 or any other date in particular, just the changes in the general pattern. This time of year, if a good southwestern trough is progged to develop, the key is to actually watch what is going to the east. Historically, a lot of good patterns this early in the season are ruined by cold/dry air being "recycled" off the continent.

If the flow is marked by high amplitude/short wavelength waves, with a trough in the southwest, the result is often a big high pressure centered over the mid-Atlantic or southern Appalachians. When that happens, cold air often takes a path down the east coast, southward over Florida, then westward into the Gulf. So I'll be keeping an eye out in both directions from the plains as this pattern change develops.
It would be fun to save the 00 UTC, April 2nd, 500 mb z/vort forecast panel for every run of the GFS until that time to see how the model flip-flops. I think this would be educational ... we can see just how bad our long range prognostics are. :lol:

Actually I have computers here doing this already, so once we get up to a big tornado day I can put up all the panels and we can see how it did.

I was actually getting pretty excited about the GFS forecast for next Sunday and Mondy in the southern plains. This was 00Z Sunday. Now the 12Z run has weakened the shortwave considerably, and many other factors have changed substantially..and in only one run! Very annoying. That will teach me to look at the long range progs!

I'm still hoping for a chase day next weekend...

Jim Bishop
Looking at a single model that far out will never be of value - ensembles (single and multi-model) rule...
Well, looking at the models for 4/2, you may be surprised at how their forecasts from a week ago might verify (albeit SW texas). ETA is forecasting temps near 90 on Thursday near Midland and GFS has a good precip event breaking out on Friday.
It looks like any severe weather threat this weekend will be in deep south Texas, out of my chase territory. That said, I'm very happy with what I'm seeing...it looks like a prolonged period of widespread rain in the plains south of I-70 in the first week of April. This will really help boundary layer moisture via evapotranspiration later in the spring! 8)
For someone who is a "beginner" in storm chasing analysis, despite a lifetime interest in the weather, I would really like to thank you all for the informative discussion on these pages - especially the relevant links. Keep it up! "Thirsty for learning" in New Zealand, and will be chasing again for the 3rd time in the US this year. Cheers, Peter :)
Well, it looks like the biggest problem to overcome on Friday near Abilene is going to be the speed of the winds above the surface. Directional shear looks good, but winds at 250mb are only being forecasted at 20kts by GFS right now.

Hopefully it will change because everything else looks good -- 80 degrees for the high temp and dewpts in the mid to upper 60s as well as a surface low setting up in the southern texas panhandle to compliment the very strong system ejecting from the west.
Looks like SW Texas may have some "fun" later! Possible chance for some organization, however brief it may be, and isolated super cells! :D