Alert archive / Florida / Tornado Watches in 2011
Tornado Watch 81
The Storm Prediction Center issued this tornado watch at Mar 31, 2011, 12:46 PM EDT for 21 counties in Florida. It was in force for 7 hr.
The area
The outline as issued.
The facts
- Issued
- Mar 31, 2011, 12:46 PM EDT (16:46 UTC)
- Expired
- Mar 31, 2011, 8:00 PM EDT
- In force
- 7 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 1.5 in
- Strongest gust expected
- 70 kt
All 21 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, Pinellas County, FL, Polk County, FL, Saint Lucie County, FL, Sarasota County, FL, Seminole County, FL
The radar
The Tampa radar (KTBW), 99 km from the middle of the area, began a volume at 16:49 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
- 30%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 40%
- Ten or more severe hail reports
- 20%
- One or more hailstones of 2 inches or more
- 10%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
5 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 31, 1:05 PM EDT | Tornado Warning | MLB | Brevard, Osceola | 23 min |
| Mar 31, 1:29 PM EDT | Severe Thunderstorm Warning | TBW | Hillsborough, Manatee | 31 min |
| Mar 31, 4:39 PM EDT | Severe Thunderstorm Warning | TBW | Hardee, Hillsborough, Manatee, Sarasota | 36 min |
| Mar 31, 4:51 PM EDT | Severe Thunderstorm Warning | TBW | Manatee, Sarasota | 24 min |
| Mar 31, 6:03 PM EDT | Severe Thunderstorm Warning | TBW | Hillsborough, Pasco, Pinellas | 29 min |
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 12:00Z, 4.8 hours before the alert went out and 99 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.
- Mixed-layer CAPE
- 728 J/kg
- Mixed-layer CIN
- -58 J/kg
- Mixed-layer LCL
- 787 m above ground
- 0-6 km bulk shear
- 69 kt
- 0-1 km storm-relative helicity
- 543 m²/s²
- 0-3 km storm-relative helicity
- 606 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 8.9
The text
As transmitted, in the capitals the NWS used until 2016.
908
WWUS20 KWNS 311647
SEL1
SPC WW 311647
FLZ000-CWZ000-010000-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 81
NWS STORM PREDICTION CENTER NORMAN OK
1245 PM EDT THU MAR 31 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
CENTRAL AND SOUTHERN FLORIDA
COASTAL WATERS
EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 1245 PM UNTIL
800 PM EDT.
TORNADOES...HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE
MILES EAST AND WEST OF A LINE FROM 50 MILES EAST OF FORT MEYERS
FLORIDA TO 50 MILES NORTH NORTHWEST OF AVON PARK FLORIDA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU1).
REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.
OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 80. WATCH NUMBER 80 WILL NOT BE IN EFFECT AFTER 1245
PM EDT.
DISCUSSION...AN ONGOING QUASI-LINEAR COMPLEX OF STRONG/SEVERE
TSTMS...INCLUDING EMBEDDED SUPERCELLS AND BOW ECHOS...WILL CONTINUE
TO QUICKLY SPREAD EASTWARD...WHILE THE SEVERE THREAT OTHERWISE
GRADUALLY REFOCUSES SOUTHWARD ACROSS THE SOUTH-CENTRAL FL PENINSULA
ALONG AN EXISTING OUTFLOW BOUNDARY. FAVORABLE INSTABILITY/SHEAR AND
THE ONGOING STORM MODE WILL FAVOR BOTH SUPERCELLS/BOWS CAPABLE OF
DAMAGING WINDS AND A FEW TORNADOES.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 26045.
...GUYER/IMYSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Mar 31, 4:40 AM EDT | Mesoscale Discussion | SPC | Alachua, Bradford, Citrus, Columbia, Dixie, Franklin and 19 more | 2 hr |
| Mar 31, 6:00 AM EDT | Tornado Watch | SPC | Brevard, Charlotte, Citrus, DeSoto, Flagler, Glades and 25 more | 7 hr |
| Mar 31, 9:39 AM EDT | Mesoscale Discussion | SPC | Brevard, Charlotte, Citrus, DeSoto, Glades, Hardee and 21 more | 66 min |
| Mar 31, 12:12 PM EDT | Mesoscale Discussion | SPC | Brevard, Charlotte, Citrus, DeSoto, Glades, Hardee and 22 more | 63 min |
| Mar 31, 2:56 PM EDT | Mesoscale Discussion | SPC | Brevard, Charlotte, DeSoto, Glades, Hardee, Highlands and 10 more | 64 min |
| Mar 31, 6:22 PM EDT | Mesoscale Discussion | SPC | Brevard, Charlotte, DeSoto, Glades, Hardee, Highlands and 10 more | 83 min |
Nearby
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.