12/3/09 FCST: FL & GA

[Jason Harris]

SPC has Day 5-6 threat of squall line with severe potential for Wed/Thurs. but looking at GFS the CAPE seems minimal (500)--any thoughts on how this might develop? Hope it's Thurs. daytime and not Wed night. (also, while looking for any input I finally noticed Ed Berry's blog is retired since July). The local forecast discussion for Melbourne includes mention of the strength of the forecast upper level winds:
--

A COLD FRONT WED NGT/THU MORNING.
ADVERTISED BAROCLINIC PATTERN FAVORS GOMEX SQLN FORMATION WITH
STRONG 120KT+ JET OVER NERN GOMEX AND DECENT AMPLITUDE TROUGH AT H50
LEADING TO STRONG MID/UPR FORCING. 50-60KT H85 JET ALSO CROSSES THE
NRN HALF OF FL WED MORNING/AFTN. SO THERE IS SOME POTENTIAL FOR
STRONG TO SVR STORMS OVER ECFL DURING THIS WINDOW

My ignorant guess would be since the SB CAPE starts off around 1500 offshore then degrades to 500 overland this would be a rapidly weakening squall line, so the West coast has the best shot, though with some higher CAPE in S. FL, perhaps a chance of some action down there. Not confident that E. FL. will see much. Will be interesting nevertheless to see how models develop by Tues.

 

[dmckemy]

I think eastern/central North and South Carolina could also stand a chance to see some severe weather Wednesday evening...The 00z NAM 500mb heights shows a very impressive negatively tilted trough across the Southeast with a 90+ jet across Alabama/Georgia. Vertical wind shear and helicity values are extremely high across the southeast as well, as soundings indicated a strong veering profile that could easily support severe storms....From about 00z Thursday onward through 12z Thursday, CAPE increases across Eastern North and South Carolina. EHI values for most of Wednesday evening are over 1, and even approach values over 2 in Eastern North Carolina at 09z.

The Raleigh AFD from earlier this morning indicated that this could become a potential tornado outbreak if enough instability can be realized (and North Carolina seems prone to night-time tornadoes)....something to definitly keep an eye on.

 

[Morgan Palmer]

Looks like we'll be seeing best overall dynamics north of us folks here in south Florida, not to mention the expected squall line will probably be after dark. Strong wind gusts main threat south of Interstate 4 owing to strong jet though that will be decreasing as time goes on.

 

[Jason Harris]

We should get this thread merged with Mike Johnston's since we're talking about the same event which is clearly Dec. 2 late Wed. With those 500+ helicity values in Georgia/SC overlapping with minimal cape, I'll do my cash-free bet on one of the isolated LEWP or out-ahead-of-the-line supercell tornadoes along that border area sometime around 10:30-11:30 PM. Anyone near Savannah? Check out what's noted in the local forecast discussion there:

--
LONG TRACK TORNADOES OF EF2 STRENGTH OR GREATER
ALONG MUCH OF COASTAL SOUTH CAROLINA AND GEORGIA.
---
also there's a MD for AL and FL panhandle that observes that:
--
WIND PROFILES ARE
ALREADY STRONGLY SUPPORTIVE OF SUPERCELLS WITH TORNADIC POTENTIAL

 

[Bob Hartig]

WIND PROFILES ARE
ALREADY STRONGLY SUPPORTIVE OF SUPERCELLS WITH TORNADIC POTENTIAL

I surely wouldn't dispute that statement. Here's the 0-6km NAM hodo for 6Z at Talahasee. That look curved to you? It's pretty representative of northern Florida.

But the winds veer considerably over time, and by afternoon when you start seeing a little SBCAPE starting to show, the low-level helicities aren't nearly as dramatic. Still something to work with, though. Could be entertaining down there tomorrow.

NOTE: Crap. Image quality sucks. But you can still see it well enough to get the gist of it.

 

[JF Massicotte]

Pretty classic 'winter' setup for the SE I would say. NAM shows a smaller embedded 700mb shortwave timed pretty well in the evening for coasal GA and SC. These regiond might be in trouble after dark if this should turn out to be right.

 

[Brandon Sullivan]

I have created a Now Thread..