Switching gears temporarily...

All along, I have been focusing on the threat from Feb. 17-24. I still believe the threat is there even though the models have been shying away from it. Except the Euro, now that it has entered its range.

Now, let's talk about the threat on Monday. Since two posts ago, I've been harping on the threat being minimal. Maybe doubting that call a bit. A few trends on the models have piqued my interest.

1) A small disturbance in the GOM that halts moisture transport on the eastern GOM. It is visible in water vapor imagery. This could become an issue, although I believe GFS may be suffering convective feedback and overdoing it a bit.

2) Strong dynamics, stronger mid level winds and stronger 850 LLJ. This is BIG and weakens the argument of deep layer shear being a problem. HOWEVER, winds in the upper levels are still lacking per the GFS, although not on the NAM. Now is the time where the NAM begins to shine, and this will again be straightened out over the next day.

3) Arctic High is now further north, with the bulk of it over Canada. This could shift southward though again - it is all up to the Polar Vortex over northeast Canada (which the easterners are discussing with regards to a possible snowstorm on Tuesday). But this is a big change from the oppressive arctic high in southern Canada, ready to dive into the Dakotas, that the models were showing a few days ago.

This will NOT be a dynamics driven event - if anything, given climo, the dynamics are lacking and the instability should not be a problem. The forecast soundings are showing minimal instability. I disagree. There's a 40 kt LLJ extending from the Yucatan, and no way are dewpoints merely in the upper 50's (per NAM). Considering 500T's are less than -15°C, that's a signal that instability will perhaps reach 1500 J/kg, perhaps even more if some sunshine comes out (and given the lack of strong forcing and cool mid level temps, along with hints of mid level drying on fcst soundings, that seems likely). Yes, the models show less than ideal temperatures at the surface, but they often underdo WAA. So, with that said, instability I think is there. However, this is only assuming that the arctic high remains up very far north, and the disturbance down in the GOM does not interfere with moisture transport from the Caribbean.

Just given the uncertainties, and the lack of speed shear, a SLGT remains the best call for now. However, with a bit more dynamics and a stronger surface low, I'd go moderate, but there's too many uncertainties for now.

With that said, here's my first call for Febrary 12-13. The threat on the 12th is mainly west of AL, 13th to the east.



Note: See Text - as the primary low occludes and the secondary coastal low (which leads to the snowstorm) forms, the severe threat should diminish. Still, enough instability should remain over Florida for a marginal threat.