Alert archive / Florida / Mesoscale Discussions in 2012

Mesoscale Discussion 579

April 21, 201216 counties in Florida

The Storm Prediction Center issued this mesoscale discussion at Apr 21, 2012, 10:10 PM EDT for 16 counties in Florida. It was in force for 65 min.

The area

The outline as issued.

The facts

Issued: Apr 21, 2012, 10:10 PM EDT (02:10 UTC)
Expired: Apr 21, 2012, 11:15 PM EDT
In force: 65 min
Issued by: the Storm Prediction Center

Counties Charlotte County, FL, Collier County, FL, DeSoto County, FL, Glades County, FL, Hardee County, FL, Hendry County, FL, Hernando County, FL, Highlands County, FL, Hillsborough County, FL, Lee County, FL, Manatee County, FL, Monroe County, FL, Pasco County, FL, Pinellas County, FL, Polk County, FL, Sarasota County, FL

The radar

The Tampa radar (KTBW), 125 km from the middle of the area, began a volume at 02:11 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

Tornado Watch 186Apr 21, 11:10 PM EDT

The nearest sounding before it

Tampa Bay, FL (KTBW), launched 00:00Z, 2.2 hours before the alert went out and 125 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: 12 J/kg
Mixed-layer CIN: -208 J/kg
Mixed-layer LCL: 622 m above ground
0-6 km bulk shear: 32 kt
0-1 km storm-relative helicity: 228 m²/s²
0-3 km storm-relative helicity: 217 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.3

Open this sounding in Storm Lab

The text

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

879 
ACUS11 KWNS 220211
SWOMCD
SPC MCD 220210
FLZ000-220315-

MESOSCALE DISCUSSION 0579
NWS STORM PREDICTION CENTER NORMAN OK
0910 PM CDT SAT APR 21 2012

AREAS AFFECTED...WRN PORTIONS OF THE CNTRL AND SRN FL PENINSULA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 220210Z - 220315Z

A STRONG TO LOWER END SEVERE STRAIGHT-LINE WIND GUST RISK MAY MOVE
ONSHORE NEAR THE TAMPA/ST. PETE METRO IN A FEW HOURS.  A POTENTIALLY
GREATER SEVERE THREAT MAY EVOLVE FARTHER S WHERE A MORE UNSTABLE
AIRMASS MAY DEVELOP LATER THIS EVENING AND POSE AN ISOLD DMGG WIND
AND PERHAPS ISOLD TORNADO THREAT CONTINGENT LARGELY UPON SUPERCELL
DEVELOPMENT.  CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED.

LATEST SURFACE/RADAR MESOANALYSIS PLACES AN INTENSIFYING QLCS 40 MI
W OF PINELLAS COUNTY MOVING TOWARDS THE COAST AS TEMPS HOLD STEADY
NEAR 70 DEG F NEAR THE COASTLINE.  WATER VAPOR IMAGERY SHOWS A
POWERFUL UPPER TROUGH/ATTENDANT VORT MAX MOVING ENEWD ACROSS THE ERN
GULF -- AND FORCING FOR ASCENT ATTENDANT TO THIS FEATURE WILL LIKELY
CONTINUE TO AID MAINTAINING UPDRAFT VIGOR FOR THE QLCS THE NEXT FEW
HOURS.  WITH THAT STATED...CONSIDERABLE CONVECTIVE OVERTURNING OVER
THE REGION DURING THE PAST 24 HRS HAS LIMITED THE DEGREE OF
INSTABILITY VIA MARGINAL LAPSE RATES DESPITE MID 60S DEWPOINTS /REF.
00Z TBW RAOB/.  FARTHER S...THERE IS HIGHER CONFIDENCE THAT SLIGHTLY
GREATER MLCAPE /400-800 J/KG/ WILL DEVELOP AS THE AIRMASS CONTINUES
TO RECOVER.  ADDITIONALLY...STRENGTHENING WIND PROFILES OWING TO THE
APPROACH OF THE UPPER TROUGH AND AN INCREASING SWLY LLJ /35 KTS/ BY
06Z MAY LEAD TO GREATER POTENTIAL FOR ISOLD UPDRAFT ROTATION AND
POSSIBLE WIND DAMAGE AND TORNADO RISKS.

..SMITH.. 04/22/2012

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

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

LAT...LON   25648193 27128285 28218303 28708234 28628167 27808114
            25788077 24768118 24648164 25648193

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 21, 11:08 PM EDT	Tornado Watch	SPC	Brevard, Broward, Charlotte, Citrus, Collier, DeSoto and 21 more	7 hr
Apr 22, 2:21 AM EDT	Mesoscale Discussion	SPC	Brevard, Broward, Charlotte, Citrus, Collier, DeSoto and 22 more	54 min

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.