CENTRAL AND SOUTH FLORIDA ---- SEVERE WX POSSIBLE SUN:

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CENTRAL AND SOUTH FLORIDA ---- SEVERE WX POSSIBLE SUN:

#1 Postby FLguy » Fri Jan 30, 2004 7:01 pm

The potential does exist for a moderate to significant severe weather event across central and southern Florida on Sunday. Lets look at why.

The overall synoptic set-up shows us a strong STJ s/w across the NW Gulf of Mexico at 36hrs:

36hr ETA valid 00z SUN 2/1:

Image

By 54hrs (18z SUN), the STJ s/w begins to weaken in response to the building ridge across the eastern half of the united states, perpetuated in part by the additional energy digging into the central plains and departing 50/50 low.

Image

The surface low pressure area remains rather weak and moves northeastward from the central gulf beginning 0z Sunday and crosses the panhandle by the early evening hours on Sunday.

36hr ETA (SLP/6hr precip) valid 0z Sunday.

Image

54hr ETA (SLP/6hr precip) valid 18z Sunday.

[/img]http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/eta/12/images/eta_p06_054s.gif[/img]

Notice that 850mb temps surge to well over +10C by 18z Sunday evening across all of central and southern Florida.

Image

ML CAPE values of between 500-1000 J/kg (surface-based convective available potential energy measured in Joules per kilogram) on average combined with good storm-relative helicity values of over 250 m^2/s^2 across central and southern Florida should support a few strong/rotating convective updrafts in the warm sector.

http://weather.unisys.com/eta/misc/eta_cape_4panel.html

http://weather.unisys.com/eta/misc/eta_hel_4panel.gif
Although with that said, the ETA implies that the best SRH does not geographically coincide with the strongest surface based and mixed layer CAPE. So with this in mind, I’m more inclined to think that pulse variety thunderstorms are more likely, with a few tornado thunderstorms possible as well but a widespread/major outbreak is NOT likely IMO.

UVM should be sufficient to compensate for the slightly weaker CAPE values further north along the warm frontal boundary to lift parcels to where they need to be in order to initiate convection. Convective temps will also be met. This could be the area which sees the best tornadic potential given the VERY strong SRH values approaching 1050 m^2/s^2 across the region and the strong lift ahead of the s/w.

EHI values (or energy-helicity index values) are generally near 1.00 across most of the central part of the state, which is considered to be the minimum value needed to get rotation.

Areas which see considerable amounts of sun (surface warming) will be most susceptible given the strong influx of moisture and warm advection to see the best action as CAPE values will elevate quickly. Those which do not will be reliant on strong UVV in order to initiate convection.
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#2 Postby mf_dolphin » Fri Jan 30, 2004 7:35 pm

Well it looks like it could get a little exciting here in the Tampa Bay area. Thanks for the info :-)
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#3 Postby FLguy » Fri Jan 30, 2004 7:46 pm

the greatest threat for severe would be south and east of a line from spring hill to palm coast.
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ColdFront77

#4 Postby ColdFront77 » Fri Jan 30, 2004 8:04 pm

National Weather Service forecasts aren't mentioning such weather as of yet. They should be in the next forecast.

The forecast for Polk county, FL was issued only an hour ago (at 7:00 pm Eastern).
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#5 Postby FLguy » Fri Jan 30, 2004 8:08 pm

ColdFront77 wrote:National Weather Service forecasts aren't mentioning such weather as of yet. They should be in the next forecast.

The forecast for Polk county, FL was issued only an hour ago (at 7:00 pm Eastern).


JAX and Melbourne probably wont until the SPC upgrades the region to a slight risk. even in spite of whats already clear to most others.
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#6 Postby ColdFront77 » Fri Jan 30, 2004 8:15 pm

Hopefully if the data continues to indicate such a potential. Other times they at least allude to the chances in a "Hazardous Weather Outlook" 24 to 48 hours ahead of a potential event.
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Josephine96

#7 Postby Josephine96 » Fri Jan 30, 2004 8:16 pm

A moderate to signifigant risk of severe weather? :eek:

{looks at 1998 tornado scar and says to self "Hope that's the only severe weather scar I ever have to deal with}
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chadtm80

#8 Postby chadtm80 » Fri Jan 30, 2004 8:25 pm

Mwatkins followint this event as well in the thread below.. This is MUCH needed rain for us.. Bring it on ;-)
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#9 Postby MWatkins » Fri Jan 30, 2004 8:57 pm

ColdFront77 wrote:National Weather Service forecasts aren't mentioning such weather as of yet. They should be in the next forecast.

The forecast for Polk county, FL was issued only an hour ago (at 7:00 pm Eastern).


There's still some uncertanity surrounding the timing of the low forecast to develop and move over Florida...as well as whether or not there will be enough instability to get things going. There is tons of convective activity over Florida...and if the widespread rain contiues as advertised...things may not destabilize enough.

But...the timing of these surface/mid-level features is a little different than advertised earlier and as the AFD from MLB noted earlier today...there may be enough forcing to make up for less than ideal thermodynamic instability...(also the warm sector has more or less taken over all of SFL this evening). I would tend to bet that the best chance for severe may be between 18Z tomorrow and 12Z Sunday morning.

Also...I think the MFL prog that the heaviest rain will remain south of Aligator Alley is off...looks like the bulk may come in along and north of there over the next 24 hours.

But we'll see. I would imagine they (NWS for Central Florida) will make something of the severe threat in the next full forecast package in a few hours (after midnight).

MW
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#10 Postby MWatkins » Fri Jan 30, 2004 9:03 pm

Also...I though the local NWS offices were going to take over severe watch issuance late last year. Does anyone know what happened to that plan?

MW
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ColdFront77

#11 Postby ColdFront77 » Fri Jan 30, 2004 9:23 pm

MW, I read the NSSFC's Convective Outlook mentioning the uncertainty surrounding the timing and whether or not there will be enough instability to get things going. I wouldn't think they would issue such outlooks without at least a minimal chance of development of at least some strong thunderstorms.

It was mentioned in the Storm2K Chatroom several months ago that the NWS offices were going to issue Severe Thunderstorm and Tornado Watches. I would think we would see some information about this on their (NSSFC's) website. Where did people here about this change?
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#12 Postby MWatkins » Fri Jan 30, 2004 9:55 pm

Hey Tom...

I would bet that we will see a slight risk for the southern half of Florida for tomorrow's first convective outlook (from your area southward). Also...interesting note from the 9:30PM AFD update from Miami:

EVENING SOUNDING AT MIAMI PRODUCED AN UNSETTLING 361 HELICITY CALCULATION. GOOD THING IS THAT POTENTIAL FOR THUNDER APPEARS TO BE RAPIDLY WANING AS LOW-LEVEL STABILIZATION CONTINUES.

That's a pretty good number. I didn't see a forecast sounding above 250...

MW
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ColdFront77

#13 Postby ColdFront77 » Sat Jan 31, 2004 9:22 am

...GULF COAST STATES/FLORIDA PENINSULA...
WEAK WAVE IS PROGGED TO EVOLVE OVER THE SOUTHEASTERN GULF OF MEXICO
TODAY...ALONG SURFACE FRONT CURRENTLY SOUTH OF THE FLORIDA KEYS.
MODELS SUGGEST THIS WAVE WILL MIGRATE NORTHEASTWARD TOWARD THE
CENTRAL FLORIDA PENINSULA TONIGHT...WITH WARM FRONT DEVELOPING
NORTHWARD THROUGH THE SOUTHERN/CENTRAL FLORIDA PENINSULA. SCATTERED
THUNDERSTORMS APPEAR POSSIBLE ACROSS THE PENINSULA AS LOW-LEVELS
CONTINUE TO SLOWLY MOISTEN AND ISENTROPIC ASCENT STRENGTHENS.
HOWEVER...WITH SURFACE DEW POINTS STILL ONLY IN THE LOWER 50S TO
LOWER 60S ACROSS THE EASTERN GULF OF MEXICO...AND WEAK MID-LEVEL
LAPSE RATES NOT LIKELY TO STEEPEN SIGNIFICANTLY...CAPE AND
ASSOCIATED CONVECTIVE DEVELOPMENT ARE EXPECTED TO REMAIN WEAK.
POSSIBLE EXCEPTION MAY BE NEAR THE KEYS AND SOUTHEASTERN COASTAL
AREAS...WHERE DESTABILIZATION WILL BE BASED IN THE BOUNDARY
LAYER...AND HODOGRAPHS WILL BE SUFFICIENT FOR ISOLATED SUPERCELLS.


EAST CENTRAL FLORIDA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MELBOURNE FL
535 AM EST SAT JAN 31 2004

AMZ550-555-570-575-FLZ041-044>047-053-054-058-059-064-141-144-147-
312100-
COASTAL VOLUSIA-COCOA BEACH TO JUPITER INLET 20 NM TO 60 NM OFFSHORE-
COCOA BEACH TO JUPITER INLET OUT TO 20 NM-
FLAGLER BEACH TO COCOA BEACH 20 NM TO 60 NM OFFSHORE-
FLAGLER BEACH TO COCOA BEACH OUT TO 20 NM-INDIAN RIVER-
INLAND VOLUSIA-MARTIN-NORTHERN BREVARD-NORTHERN LAKE-OKEECHOBEE-
ORANGE-OSCEOLA-SEMINOLE-SOUTHERN BREVARD-SOUTHERN LAKE-ST. LUCIE-
535 AM EST SAT JAN 31 2004

.DAY ONE...TODAY AND TONIGHT:

...RAIN BECOMING WIDESPREAD BY TONIGHT WITH SCATTERED THUNDERSTORMS
DEVELOPING...A FEW STORMS COULD BE STRONG...

RAIN HAS DECREASED THIS MORNING AS A DISTURBANCE ALOFT HAS PASSED TO
THE EAST OF THE STATE. THERE MAY BE A BREAK IN THE RAINFALL FOR
SEVERAL HOURS TODAY...HOWEVER CONDITIONS WILL BECOME FAVORABLE FOR
RAIN LATER TODAY WITH RAINFALL EXPECTED TO BECOME WIDESPREAD TONIGHT.
DEEP MOISTURE WILL CONTINUE TO FEED OVER THE AREA AND AN UPPER LEVEL
DISTURBANCE WILL APPROACH TONIGHT. ADDITIONALLY...WIND SHEAR AND LOW
LEVEL CONVERGENCE WILL INCREASE AS A SURFACE LOW DEVELOPS OVER THE
GULF ALONG AN OLD FRONTAL BOUNDARY AND PUSHES THE BOUNDARY BACK NORTH
OVER THE PENINSULA.

THE MAIN THREATS TONIGHT WILL BE LOCALLY HEAVY RAINFALL AND THE
POTENTIAL FOR ROTATING STORMS...LEADING TO AN ISOLATED TORNADO OR
WATERSPOUT. PERSONS IN EAST CENTRAL FLORIDA SHOULD KEEP INFORMED OF
THE WEATHER THROUGH TONIGHT.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY:

RAIN AND A FEW THUNDERSTORMS WILL LINGER INTO SUNDAY MORNING THEN
TAPER OFF IN THE AFTERNOON.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BECOME NEEDED TONIGHT.

$$

GLITTO


HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
600 AM EST SAT JAN 31 2004

FLZ039-042-043-048>052-055>057-060>062-065-311500-
CHARLOTTE-CITRUS-DE SOTO-HARDEE-HERNANDO-HIGHLANDS-HILLSBOROUGH-LEE-
LEVY-MANATEE-PASCO-PINELLAS-POLK-SARASOTA-SUMTER-
600 AM EST SAT JAN 31 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WEST CENTRAL AND SOUTHWEST
FLORIDA.

.DAY ONE...TODAY:

SHOWERS AND THUNDERSTORMS WILL CONTINUE TODAY AS A WARM FRONT SOUTH
OF FLORIDA LIFTS NORTH AND LOW PRESSURE DEVELOPS OVER THE CENTRAL
GULF OF MEXICO. SOME THUNDERSTORMS THIS EVENING MAY BECOME STRONG
WITH WIND GUSTS TO 50 MPH AND SMALL HAIL POSSIBLE. HEAVY RAINS MAY
ALSO CAUSE MINOR FLOODING OF POOR DRAINAGE AND LOW LYING AREAS.

STAY TUNED TO NOAA WEATHER RADIO OR YOUR LOCAL MEDIA OUTLETS FOR
UPDATES.


The Hazardous Weather Outlook from the Jacksonville, FL National Weather Service says no hazardous weather is expected. The Melbourne and Ruskin, FL coverage area isn't that far from Marion county (which the Jacksonville office covers) may get some of this weather.
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