Alert archive / Florida / Mesoscale Discussions in 2012

Mesoscale Discussion 161

February 27, 201220 counties in Florida

The Storm Prediction Center issued this mesoscale discussion at Feb 27, 2012, 1:34 PM EST for 20 counties in Florida. It was in force for 116 min.

The area

The outline as issued.

The facts

Issued: Feb 27, 2012, 1:34 PM EST (18:34 UTC)
Expired: Feb 27, 2012, 3:30 PM EST
In force: 116 min
Issued by: the Storm Prediction Center

Counties Brevard County, FL, Charlotte County, FL, DeSoto County, FL, Glades County, FL, Hardee County, FL, Hendry County, FL, Highlands County, FL, Hillsborough County, FL, Indian River County, FL, Lee County, FL, Manatee County, FL, Martin County, FL, Okeechobee County, FL, Orange County, FL, Osceola County, FL, Palm Beach County, FL, Pasco County, FL, Polk County, FL, Saint Lucie County, FL, Sarasota County, FL

The radar

The Melbourne radar (KMLB), 96 km from the middle of the area, began a volume at 18:35 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.

The nearest sounding before it

Tampa Bay, FL (KTBW), launched 12:00Z, 6.6 hours before the alert went out and 101 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 637 J/kg
Mixed-layer CIN: -39 J/kg
Mixed-layer LCL: 580 m above ground
0-6 km bulk shear: 39 kt
0-1 km storm-relative helicity: 102 m²/s²
0-3 km storm-relative helicity: 158 m²/s²
Significant tornado parameter: 0.3
Supercell composite: 1.8

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

192 
ACUS11 KWNS 271835
SWOMCD
SPC MCD 271834
FLZ000-272030-

MESOSCALE DISCUSSION 0161
NWS STORM PREDICTION CENTER NORMAN OK
1234 PM CST MON FEB 27 2012

AREAS AFFECTED...CNTRL/SRN FL PENINSULA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 271834Z - 272030Z

A THREAT FOR ISOLATED SVR THUNDERSTORMS WILL DEVELOP ACROSS THE
CNTRL/SRN FL PENINSULA BETWEEN 19-20Z AND CONTINUE THROUGH LATE
AFTERNOON. THE SPORADIC NATURE OF ANY SVR CONVECTION WILL LIKELY
PRECLUDE THE NEED FOR A WW.

EARLY AFTERNOON SFC MESOANALYSIS INDICATES A DIFFUSE/W-E ORIENTED
QUASI-STATIONARY FRONT EXTENDING FROM THE E FL COAST NEAR CAPE
CANAVERAL TO THE W FL COAST 35 MILES N OF SAINT PETERSBURG.
CLOUDINESS AND SHOWERS IN ASSOCIATION WITH A LOW-LATITUDE IMPULSE
CROSSING THE FL PENINSULA HAVE MAINTAINED STABLE CONDITIONS NORTH OF
THE BOUNDARY...WITH DIFFERENTIAL HEATING AND BAROCLINICITY ACROSS
THE BOUNDARY AIDED BY ABUNDANT DIABATIC HEATING TO ITS SOUTH.
MODIFIED SOUNDINGS FROM 12Z RAOBS AT TAMPA AND CAPE CANAVERAL TO
ACCOUNT FOR SFC TEMPS ALREADY IN THE LOWER/MIDDLE 80S AND DEWPOINTS
IN THE MIDDLE 60S SOUTH OF THE BOUNDARY SUGGEST THAT MLCAPE VALUES
HAVE ALREADY INCREASED TO 1500-2500 J/KG WITH NEGLIGIBLE INHIBITION.
RECENT VISIBLE SATELLITE AND RADAR IMAGES SUGGEST THAT CUMULUS
CONVECTION CONTINUES TO DEEPEN WITHIN 80-MILES SOUTH OF THE
FRONT...WHILE BEING ENHANCED ALONG A NW-SE-ORIENTED CONVERGENCE AXIS
INTERSECTING THE FRONT OVER ERN PASCO COUNTY AND EXTENDING SEWD OFF
THE COAST OF PALM BEACH COUNTY. THUNDERSTORMS WILL LIKELY EVOLVE
WITHIN THIS AREA IN THE 19-20Z TIME FRAME...WITH ADDITIONAL
CONVECTION DEVELOPING ALONG THE STRENGTHENING WEST/EAST COAST SEA
BREEZE CONVERGENCE ZONES.

MODEST WLY MID-LEVEL FLOW IS IN PLACE...AS MELBOURNE VWP DATA
CURRENTLY INDICATE AROUND 30 KT OF FLOW AROUND 5 KM AGL. WHILE SOME
WEAKENING OF THE MID-LEVEL FLOW IS ANTICIPATED WITH TIME...EFFECTIVE
BULK SHEAR MAGNITUDES ARE EXPECTED TO REMAIN 20-30 KT SUPPORTING A
MULTICELL MODE OWING TO THE DEGREE OF INSTABILITY IN PLACE. ISOLATED
INSTANCES OF DMGG WIND GUSTS WILL BE POSSIBLE WITH THE STRONGEST
STORMS...ESPECIALLY IN CASES WHERE MERGING COLD POOLS YIELD
LOCALIZED AREAS OF UPSCALE GROWTH AND INVOF OF INTERSECTING
BOUNDARIES. COOL 500-MB TEMPERATURES /-13C TO -11C/ WILL SUPPORT
SUFFICIENTLY STEEP MID-LEVEL LAPSE RATES FOR AN ISOLATED MARGINALLY
SVR HAIL THREAT.

AS THE LOW-LEVEL FLOW GRADUALLY BACKS TO NELY OVER CNTRL PARTS OF
THE FL PENINSULA FOLLOWING THE PASSAGE OF THE AFOREMENTIONED
MID-LEVEL IMPULSE...COLD POOLS WILL HAVE A TENDENCY TO ATTAIN A
COMPONENT OF MOTION TOWARD SOUTH FLORIDA THROUGH LATE AFTERNOON.
HOWEVER...THE CAPPING LAYER JUST ABOVE 700 MB EVIDENT IN THE 12Z
MIAMI RAOB SUGGESTS THAT CONVECTIVE PROPAGATION TOWARD S FL MAY BE
LIMITED...ESPECIALLY BY EARLY EVENING ONCE NOCTURNAL STABILITY
STRENGTHENS AND CONVECTIVE UPDRAFTS WEAKEN.

..COHEN.. 02/27/2012

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

ATTN...WFO...MFL...MLB...TBW...

LAT...LON   28548250 28648167 28728078 27898031 27188015 26628005
            26288044 26128108 26328186 27458260 28258274 28548250

Nearby

Mesoscale Discussions in Florida, 2012 Every mesoscale discussion in 2012

Sources

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.