Alert archive / Florida / Severe Thunderstorm Watches in 2011

Severe Thunderstorm Watch 71

March 28, 201113 counties in Florida

The Storm Prediction Center issued this severe thunderstorm watch at Mar 28, 2011, 6:48 AM EDT for 13 counties in Florida. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued
Mar 28, 2011, 6:48 AM EDT (10:48 UTC)
Expired
Mar 28, 2011, 11:31 AM EDT
In force
5 hr
Issued by
the Storm Prediction Center
Largest hail expected
1 in
Strongest gust expected
60 kt

Counties Broward County, FL, Charlotte County, FL, Collier County, FL, DeSoto County, FL, Glades County, FL, Hendry County, FL, Highlands County, FL, Indian River County, FL, Lee County, FL, Martin County, FL, Okeechobee County, FL, Palm Beach County, FL, Saint Lucie County, FL

The radar

The Tampa radar (KTBW), 141 km from the middle of the area, began a volume at 10:51 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.

What SPC expected

The probabilities SPC published with the watch, for the watch area over its life.

Two or more tornadoes
20%
One or more EF2 to EF5 tornadoes
5%
Ten or more severe wind reports
30%
One or more gusts of 65 knots or more
20%
Ten or more severe hail reports
20%
One or more hailstones of 2 inches or more
5%
Six or more combined severe hail and wind reports
70%

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Tampa Bay, FL (KTBW), launched 00:00Z, 10.8 hours before the alert went out and 141 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-pSkew-T log-p diagram, Tampa Bay, FL at 00:00Z on 2011-03-28Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 289 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Tampa Bay, FL at 00:00Z on 2011-03-28The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 46 square meters per square second.19395878Sfc1 km3 km6 km9 kmRMLM
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
289 J/kg
Mixed-layer CIN
-80 J/kg
Mixed-layer LCL
1324 m above ground
0-6 km bulk shear
36 kt
0-1 km storm-relative helicity
46 m²/s²
0-3 km storm-relative helicity
112 m²/s²
Significant tornado parameter
0.0
Supercell composite
1.0

Open this sounding in Storm Lab

The text

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

195 
WWUS20 KWNS 281050
SEL1  
SPC WW 281050
FLZ000-CWZ000-281600-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 71
NWS STORM PREDICTION CENTER NORMAN OK
650 AM EDT MON MAR 28 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 

       CENTRAL AND SOUTH FLORIDA
       COASTAL WATERS

EFFECTIVE THIS MONDAY MORNING FROM 650 AM UNTIL NOON EDT.

HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 45
STATUTE MILES EITHER SIDE OF A LINE FROM 25 MILES SOUTHWEST OF
FORT MEYERS FLORIDA TO 35 MILES SOUTHEAST OF VERO BEACH FLORIDA. 
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU1).

REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.

DISCUSSION...LONG-LIVED MCS WITH EMBEDDED BOWING STRUCTURES EXPECTED
TO CONTINUE GENERALLY ESE AT 25-30 KTS ACROSS CNTRL AND S FL.  WHILE
DEEP WIND FIELD IS MODERATE IN STRENGTH...HIGH PW VALUES AND
LIKELIHOOD FOR MERGING STORMS/LEWP STRUCTURES SUGGEST POTENTIAL FOR
A FEW POCKETS/SHORT SWATHS OF DMGG WIND AND POSSIBLY MARGINALLY SVR
HAIL.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.
A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION
VECTOR 29030.


...CORFIDI

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Mar 28, 1:59 AM EDTMesoscale DiscussionSPCAlachua, Baker, Bradford, Columbia, Dixie, Gadsden and 11 more91 min
Mar 28, 2:43 AM EDTSevere Thunderstorm WatchSPCAlachua, Baker, Bradford, Columbia, Dixie, Franklin and 12 more3 hr
Mar 28, 6:31 AM EDTMesoscale DiscussionSPCCharlotte, Collier, Glades, Hendry, Lee, Martin and 3 more59 min
Mar 28, 5:49 PM EDTMesoscale DiscussionSPCBroward, Charlotte, Collier, Hendry, Lee, Miami-Dade and 1 more56 min
Mar 28, 6:12 PM EDTMesoscale DiscussionSPCBaker, Calhoun, Columbia, Gadsden, Gulf, Hamilton and 9 more63 min

Nearby

Severe Thunderstorm Watches in Florida, 2011Every severe thunderstorm watch in 2011

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.