1/25/11 FCST: FL

[Jason Harris]

You've probably seen the slight risk for FL for Tuesday afternoon and especially evening.
The SB CAPE looks to stay under 750, which is discouraging, but an impressive blob of 0-1KM helicity of 350-400 shows up in the WRF last time I checked this morning by about 1 AM EST near the East Central Florida coast.

The local forecast discussion is taking this seriously, alluding to bow echoes, supercells ahead of the squall line, and embedded storms producing a few significant tornadic results:

STRENGTH OF DEEP LAYER SHEAR / LOW
LVL HELICITY / FAVORABLE LOW TRACK AND TIME OF DAY (NIGHT) WITH
LOWER LCLS ALL FAVOR THE POSSIBILITY OF A FEW STRONG AND VIOLENT
TORNADOES

Any further thoughts on this set-up?

 

[Jason Harris]

Latest helicity forecast has moved that blob up to the panhandle, leaving East Central Fl with 250+. Mid-level lapse rates look to be best in the panhandle as well, getting in sync with the high helicity still very late, around 1 AM EST: http://www.emc.ncep.noaa.gov/mmb/namsvrfcst/

Still dubious with the CAPE but with a forecast high of 77 in Melbourne and no doubt 80 or so in surrounding areas, will be interesting to see how things develop, hoping not too much overcast and that there's something to show before it's dark. Going to be fairly windy, so hard to time things with storm movement.

 

[cdcollura]

Good day all,

The major issue with this setup is the timing. Unfortunately (yeah, I know) ... The best dynamics appear to be crossing Florida after Midnight, and it will be confined to the northern half of the state.

The only hope for anything convective will be the seabreeze boundaries, but I assume most of th activity will be in the form of a squall line overnight along the surging cold front. Look for anything embedded and / or ahead of this line for rotating storms.

The CAPE will be rather low away from any forcing mechanisms, such as the front, so I do not see any heating / destabilization being anything to get excited about just yet.

I am keeping an eye on this one, but not yet targeting Central Florida for any chases just yet.

I remember these setups in the older days, before I went to the Plains each year (early 90's) and getting fired / written up (and busting too) because of them

 

[Mike Moore]

Yet another overnight squall line... I agree that timing is an issue. I might make a move for anything that develops tomorrow late afternoon, but I'll skip the overnight line.

The CAPE forecast is a let down so I guess I'll check out the cloud deck in the morning before deciding.

 

[Jason Harris]

Notice that Talahassee mets have pointed out that the marine layer from the cold gulf waters will probably undercut the severe threat in the panhandle. I asked the local Melbourne met about whether that would mitigate things down here, and he thought perhaps not:
--

We looked today at the possibility of cool coastal waters limiting instabilty, and while it could be a factor, we think the low level trajectory feeding into the convective complex will be southerly, up the spine of peninsula Tue aftn/evng, thus limiting impact of cool shelf waters.

Large scale factors still appear quite favorable for svr, psbl signif svr, but it all may come down to how local environment sets up in final few hours. This will likely determine dvlpmnt and impact of psbl supercells

 

[cdcollura]

Good day all,

As per SPC, they maintained a 5% tornado probability from the upper Keys northward to just south of the I-10 corridor. Cooler Gulf waters preclude the SVR threat in the panhandle (cooler marine air).

Two areas of possible severe weather are dictated, one with the cold front (overnight on Jan 25 / 26) which will be a squall line, but another (more interesting area) in the southern part of the state due to a pre-frontal convergence area and "secondary" warm front moving up from the Caribbean airmass (dewpoints upper 60's).

If this secondary area materializes, the higher CAPE (near 1000) and backed surface flow will introduce a higher tornado probability in the convection that forms there.