Mesoscale Discussion 1821

Issued

Aug 27, 2012, 11:54 AM EDT (15:54 UTC)

Expired

Aug 27, 2012, 2:00 PM EDT

In force

2 hr

Issued by

the Storm Prediction Center

Chance of a watch

40%

Counties Indian River County, FL, Lake County, FL, Marion County, FL, Orange County, FL, Osceola County, FL, Saint Lucie County, FL, Seminole County, FL, Sumter County, FL, Volusia County, FL

The Melbourne radar (KMLB), 100 km from the middle of the area, began a volume at 15:58 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

544 
ACUS11 KWNS 271554
SWOMCD
SPC MCD 271554 
FLZ000-271800-

MESOSCALE DISCUSSION 1821
NWS STORM PREDICTION CENTER NORMAN OK
1054 AM CDT MON AUG 27 2012

AREAS AFFECTED...PARTS OF EAST CENTRAL AND NRN FL

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 271554Z - 271800Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...THE POTENTIAL EXISTS FOR AN ISOLATED/BRIEF TORNADO THREAT
ACROSS PARTS OF EAST CENTRAL TO NWRN FL PENINSULA INTO THE
AFTERNOON.  IN ADDITION...HEAVY RAINFALL RATES EXCEEDING 2 INCH PER
HOUR WILL BE LIKELY WITHIN TWO DISTINCTIVE OUTER CONVECTIVE BANDS OF
ISAAC AS THEY MOVE/DEVELOP N/NWWD THROUGH EAST CENTRAL TO NRN FL.

DISCUSSION...REGIONAL RADAR AND SATELLITE IMAGERY TRENDS THIS
MORNING INDICATED THE DEVELOPMENT OF AT LEAST TWO WELL DEFINED OUTER
CONVECTIVE BANDS ATTENDANT TO TS ISAAC.  THESE BANDS...ALSO DETECTED
BY AN INCREASE AN INCREASE IN LIGHTNING DATA...EXTENDED NWD FROM
PALM BEACH AND MARTIN COUNTIES TO ORANGE AND SEMINOLE
COUNTIES...WHILE THE SECOND BAND WAS PRIMARILY OFFSHORE THE ERN FL
COAST /85 ENE VRB TO NEAR ST JOHNS COUNTY/.  THE THREAT FOR
ISOLATED/BRIEF TORNADOES IS ATTENDANT TO THE INLAND CONVECTIVE BAND
WHERE A COUPLE OF TRANSIENT LOW LEVEL ROTATIONAL COUPLETS HAVE BEEN
OBSERVED ON BOTH THE MLB WSR-88D ACROSS MARTIN/ST. LUCIE COUNTIES
AND IN OSCEOLA/ORANGE AND SEMINOLE COUNTIES PRIMARILY PER MCO
TERMINAL DOPPLER RADAR.  AN INCREASING TREND IN ROTATIONAL TRACKS
PER WDSSII HAVE ALSO BEEN DETECTED IN THIS LATTER REGION.  

STORM MOTIONS TOWARD THE NNW WITHIN A KINEMATIC ENVIRONMENT OF
VEERING AND INCREASING WINDS IN THE LOWEST 4 KM AGL ARE RESULTING IN
LOW LEVEL SHEAR OF 150-200 M2/S2.  THIS COMBINED WITH AN INCREASE IN
LOW LEVEL MOISTURE AND DESTABILIZATION SUGGESTS THE POTENTIAL FOR
ADDITIONAL TRANSIENT LOW LEVEL ROTATION WILL BE LIKELY...WITH THE
POSSIBILITY OF ISOLATED/BRIEF TORNADOES.

..PETERS/WEISS.. 08/27/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MLB...TBW...JAX...

LAT...LON   27098027 28048133 28748224 29028267 29628285 29638201
            29338125 29158107 28688092 27098027

Mesoscale Discussions in Florida, 2012Every mesoscale discussion in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.