Alert archive / Florida / Tornado Watches in 2011
Tornado Watch 868
The Storm Prediction Center issued this tornado watch at Oct 18, 2011, 9:54 PM EDT for 14 counties in Florida. It was in force for 6 hr.
The area
The outline as issued.
The facts
- Issued
- Oct 18, 2011, 9:54 PM EDT (01:54 UTC)
- Expired
- Oct 19, 2011, 4:16 AM EDT
- In force
- 6 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, Glades County, FL, Hendry County, FL, Highlands County, FL, Indian River County, FL, Lee County, FL, Martin County, FL, Miami-Dade County, FL, Monroe County, FL, Okeechobee County, FL, Palm Beach County, FL, Saint Lucie County, FL
The radar
The Miami radar (KAMX), 83 km from the middle of the area, began a volume at 01:54 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
- 40%
- One or more EF2 to EF5 tornadoes
- 20%
- Ten or more severe wind reports
- 40%
- One or more gusts of 65 knots or more
- 20%
- Ten or more severe hail reports
- 10%
- One or more hailstones of 2 inches or more
- 5%
- Six or more combined severe hail and wind reports
- 70%
Warnings issued inside it
2 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 18, 10:12 PM EDT | Tornado Warning | MFL | Broward, Palm Beach | 9 min |
| Oct 18, 11:37 PM EDT | Severe Thunderstorm Warning | TBW | Lee | 23 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
Miami, FL (KMFL), launched 00:00Z, 1.9 hours before the alert went out and 80 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
- 3389 J/kg
- Mixed-layer CIN
- -1 J/kg
- Mixed-layer LCL
- 454 m above ground
- 0-6 km bulk shear
- 47 kt
- 0-1 km storm-relative helicity
- 351 m²/s²
- 0-3 km storm-relative helicity
- 417 m²/s²
- Significant tornado parameter
- 7.8
- Supercell composite
- 32.0
The text
As transmitted, in the capitals the NWS used until 2016.
820
WWUS20 KWNS 190152
SEL8
SPC WW 190152
FLZ000-CWZ000-191000-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 868
NWS STORM PREDICTION CENTER NORMAN OK
955 PM EDT TUE OCT 18 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
SOUTH FLORIDA
COASTAL WATERS
EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 955 PM
UNTIL 600 AM EDT.
TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 65 STATUTE
MILES EAST AND WEST OF A LINE FROM 65 MILES NORTHEAST OF FORT
MEYERS FLORIDA TO 50 MILES EAST SOUTHEAST OF MARATHON FLORIDA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU8).
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...CONTINUE...WW 867...
DISCUSSION...SUBTROPICAL DISTURBANCE OVER THE ERN GULF WAS BEGINNING
TO ACCELERATE ENE AS IT BECOMES ABSORBED INTO LARGER SCALE UPR
SYSTEM OVER THE SERN CONUS. BANDS OF TSTMS WILL CONTINUE TO FORM
ALONG PRE-FRONTAL CONFLUENCE ACROSS SRN FL THROUGH THE NIGHT AS THE
DISTURBANCE MOVES ACROSS THE REGION. ALTHOUGH LLVL WIND PROFILES
WILL TEND TO VEER SOMEWHAT OVERNIGHT AS THE PRIMARY LLJ AXIS
DEVELOPS OVER THE SW ATLC...SUFFICIENT DIRECTIONAL/SPEED SHEAR WILL
EXIST FOR SUPERCELLS AND/OR LEWPS TO BE EMBEDDED WITHIN LINE
SEGMENTS FOR SVRL MORE HOURS. ISOLD TORNADOES AND DMGG WIND GUSTS
WILL BE THE PRIMARY THREATS.
AVIATION...TORNADOES AND 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 24035.
...RACYSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Oct 18, 8:39 PM EDT | Mesoscale Discussion | SPC | Broward, Charlotte, Collier, DeSoto, Glades, Hardee and 9 more | 66 min |
| Oct 19, 12:25 AM EDT | Mesoscale Discussion | SPC | Broward, Collier, Glades, Hendry, Martin, Miami-Dade and 2 more | 95 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.