The fall severe weather season has generally been quiet. We had the one tornado event just before that ushered my good friend Jason Kelley onto the FOX 6 StormWarn Team, but after that, things have really been quiet. I get the idea that may be changing. By Wednesday morning, an intense area of low pressure will be rapidly organizing at the surface near coastal areas of Louisiana, in response to a potent upper-level disturbance coming out of Texas. The surface low will lift to the northeast and rapidly deepen through the day as the upper-level disturbance takes on a negative tilt. Negatively tilted systems are often associated by very dynamic weather that changes very rapidly over short distances. From the looks of it now, 60-65+ dewpoints will come onshore south of a warm front that will lift northward with the surface low. Below is a plot from the 00Z NAM, that shows the CAPE and vertical wind shear at 6 pm Wednesday.

The NAM is projecting surface-based CAPE values to exceed 500 j/kg over west central Alabama by Wednesday evening, and this would progress eastward with time, as the storm system lifts off to the northeast and the cold front charges eastward. I think that 400-500 j/kg of CAPE is very doable up to near the warm front, in the warm sector of the storm system. The main question I have is the track of the surface low and how rapidly it lifts northeastward. This will determine whether any part of the FOX 6 viewing area breaks into the warm sector, or if the warm sector stays south and east of the coverage area. The NAM… and to a degree, the UKMET… lift the surface low across MS and west AL into TN Wednesday, and aren’t as fast as some of the other models in doing so. This allows the warm sector to lift as far north as central portions of Alabama during the day. Other models, such as the GFS, Canadian, Euro, and previous UKMET runs actually lift the storm system northeastward more rapidly and are also a little further east with the surface low track, generally lifting it uo I-65. This would keep the warm sector from ever reaching the FOX 6 coverage area, and would keep any threat of severe weather south and east of our area. It bares monitoring because the UKMET did shift westward on Sunday’s daytime run… and the GFS nudged slightly westward also. It’s a really murky situation right now. The dynamics and shear are there, and actually favor a higher-end event. However, that cannot happen if the instability and low-level moisture aren’t there also. I think that even in the worst-case scenario possible, there will NOT be enough instability and low-level moisture for a major severe weather event. Having said that, if a western and/or slower surface low track verifies, enough instability may creep into parts of central Alabama for a few warnings to occur…. possibly even a tornado warning or two. The track and speed of the surface low will be very crucial in determining what kind of threat, if any, the FOX 6 viewing area faces.

We urge you to be mindful of the weather situation as we approach midweek, and check back with FOX 6 and the weather blog here for updates as we get closer to this storm system. If you have a NOAA Weather Radio, check the batteries to make sure they’re fresh…. and if you don’t, think about buying one as you go out holiday shopping. You can get a great weather radio for around $35, and if your family is safe during a severe weather event because you were awakened for a weather warning during the overnight, it’s the best $35 you’ll ever spend.

Fred Gossage
Blog Contributor
http://www.twitter.com/fredgossage

Filed under: Birmingham, Regions, Thunderstorms, Tornadoes