Daweathablog

Charles E. Roop giving his own forecasts, weather discussions, photos and adventures for the Starkville, MS area, Florida, and beyond.

Saturday, February 18, 2012

Severe Threat for Gulf Coast Today, North and Central Florida Sunday

Currently, a low pressure system is centered just off the coast of Texas with an associated warm from extends around the middle Gulf of Mexico coast and a cold front moving southwest through the Texas coast. Aloft, 12Z  data analysis showed a trough over western Texas. The latest RUC guidance shows that the trough has moved to the east over central Texas. Surface dewpoints of 60F and greater are currently along the gulf coast while the rain extends from off the Texas coast northeast to Alabama. 

Today's severe weather risk lies along the gulf coast from Louisiana - which warning have already been issued - to the Florida panhandle. Currently, radar is showing a line of potent storms near Slidell, La. and is moving northeasterly (see below).



Storm Relative Helicity numbers are greater behind the lines of storms based on SPC mesoanalysis, but the SRH values where the storms are in the 400-500 range. The lapse rates don't seem too impressive, but the 12Z soundings at KLIX showed a decent southeasterly flow at the surface. The RUC model sounding near Pensacola shows a good curved hodograph, which would show a decent potential for tornadoes. However, that sounding doesn't really scream instability.

For today, the atmospheric motion looks decent for a few tornadoes and strong winds. Instability looks to be a limiting factor in that area as lapse rates from the surface don't look too impressive and daytime heating will be abated due to cloudcover. Regardless, impressive storms are still showing up on radar with the possibility of rotation and damaging winds. 

For Sunday, the threat shifts to north and central Florida. The cold front should be approaching the Florida peninsula gulf coast in the late morning. Helicity values are expected to increase. The NAM sounding profiles near Gainesville and Orlando Sunday late morning/early afternoon show uniderectional hodographs (straight-line wind threat, typically) with steep environmental lapse rates (especially near Orlando by 1 PM ET). However, the NAM is a little more drier aloft at this time and location than the GFS, which could change the amount of instability. The NAM is also showing a decent low-level jet moving into the peninsula early in the afternoon Sunday. 

North and central Florida should be observant tomorrow as straight-line winds and bowing storms could be an issue along with a couple of isolated tornadoes. I might post another weather update tomorrow morning when conditions warrant. 

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