12/11/08 FCST: FL/GA/SC/NC

[Jason Harris]

Pretty much certain squall-line setup today with chance of embedded supercells, LEWPs, and Bows. Tornado watch already present in much of central to North FL. Fast moving setup that is supposed to race on through. Might not have much in the way of CAPE but there is a vertical shear scenario.
Somewhat similar situation to the last time with the Palm Bay tornado, but squall line is looking currently more developed to the South rather than further North--last time it was creeping South as day went on. I'm dubious whether many spots will see much beyond some period of heavy rain and chance of lightning. Tornado probs from SPC are 2-5%. Brevard County not identified in TWatch as of yet. Helicity levels at 0-1KM looking good throughout 150-350 within TW areas (highest in NW FL currently). MD mentions "SFC-1 KM SHEAR OF 30-40 KT" sufficient for embedded supercells. Helicity values were higher last time and we got some clear spots for heating, so upon reflection, probably not as likely to have isolated tornado reports. Dewpoints mainly high 60s, but at least one 72 reading showing up further South. Again, CAPE may be limited by limited period--with cloud cover draped around much of FL-- of heating before squall line arrives.
SB CAPE from 500-1000 in most of state and might not really exceed that as time goes on. Winds looking to Veer from S to SW with a high of about 79 predicted locally. Currently 73 F/69 Dew. Storm tops are low. So low, I can't really get interested even though size isn't everything, but c'mon everything under 20K?. Don't expect much lightning based on what's there currently and apparently the cooler offshore waters are dampening lightning chances.
Weather channel is emphasizing East of 95 later on (Daytona and Augustine in particular). We'll see.

Bottom line: rain will be nice vs. drought areas. Should be moderately windy.
Keep tabs on storms to see if anything significant develops but don't hold your breath.

 

[Mike Johnston]

If perhaps the mods could expand the thread title to include GA, SC, and NC, as watches have expanded.

The obvious limiting factor here in SC today will be instability. Although we have seen plenty of moisture advected into the area over the last two days, the environmental lapse rates are anemic. This morning, surface obs show 71t/67td and winds have started backing in response to the deepening surface low approaching from the southwest. We'll need at least a bit of heating early this afternoon to provide some chances for decent instability. Sun is peaking out from time to time, but cloud cover is still widespread. Otherwise, the parameters look very good - plenty of moisture, very low LCL's, supportive deep shear, and strong low level shear.

Like you, Jason, not holding my breath today but the setup does look interesting enough to follow. Storm motions will be very fast ~ 50mph. Over the next few hours, we'll see if we can get anything discrete just out ahead of the squall line which is now approaching the Savannah River.