Alert archive / Florida / Tornado Watches in 2009
Tornado Watch 795
The Storm Prediction Center issued this tornado watch at Dec 5, 2009, 8:57 AM EST for 11 counties in Florida. It was in force for 4 hr.
The area
The outline as issued.
The facts
- Issued
- Dec 5, 2009, 8:57 AM EST (13:57 UTC)
- Expired
- Dec 5, 2009, 1:00 PM EST
- In force
- 4 hr
- Issued by
- the Storm Prediction Center
- Largest hail expected
- 0.5 in
- Strongest gust expected
- 60 kt
Counties Broward County, FL, Collier County, FL, Glades County, FL, Hendry County, FL, Indian River 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), 74 km from the middle of the area, began a volume at 13:58 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
- 10%
- Ten or more severe wind reports
- 30%
- 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
- 60%
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 12:00Z, 2.0 hours before the alert went out and 79 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
- 1444 J/kg
- Mixed-layer CIN
- -7 J/kg
- Mixed-layer LCL
- 712 m above ground
- 0-6 km bulk shear
- 46 kt
- 0-1 km storm-relative helicity
- 210 m²/s²
- 0-3 km storm-relative helicity
- 232 m²/s²
- Significant tornado parameter
- 1.9
- Supercell composite
- 14.1
The text
As transmitted, in the capitals the NWS used until 2016.
111
WWUS20 KWNS 051356
SEL5
SPC WW 051356
FLZ000-CWZ000-052000-
URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 795...RESENT
NWS STORM PREDICTION CENTER NORMAN OK
900 AM EST SAT DEC 5 2009
THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF
SOUTH AND SOUTHEAST FLORIDA
COASTAL WATERS
EFFECTIVE THIS SATURDAY MORNING AND AFTERNOON FROM 900 AM UNTIL
300 PM EST.
TORNADOES...HAIL TO 0.5 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 90 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 30 MILES NORTH NORTHWEST OF
KEY WEST FLORIDA TO 20 MILES EAST OF WEST PALM BEACH FLORIDA.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU5).
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 794. WATCH NUMBER 794 WILL NOT BE IN EFFECT AFTER
900 AM EST.
DISCUSSION...ANOTHER BAND OF THUNDERSTORMS IN ADVANCE OF A SURFACE
COLD FRONT AND MID LEVEL TROUGH WILL MOVE INLAND ACROSS S FL THROUGH
THE MORNING AND INTO EARLY AFTERNOON. WEAK-MODERATE INSTABILITY AND
EFFECTIVE BULK SHEAR OF 40-50 KT WILL FAVOR BOTH SUPERCELL AND
EMBEDDED BOW STRUCTURES WITH THE POTENTIAL TO PRODUCE DAMAGING GUSTS
AND A BRIEF TORNADO OR TWO.
AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 26035.
...THOMPSONSPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Dec 4, 10:24 PM EST | Mesoscale Discussion | SPC | Broward, Collier, Miami-Dade, Monroe, Palm Beach | 96 min |
| Dec 5, 12:48 AM EST | Tornado Watch | SPC | Broward, Collier, Hendry, Martin, Miami-Dade, Monroe and 2 more | 8 hr |
| Dec 5, 4:08 AM EST | Mesoscale Discussion | SPC | Broward, Collier, Hendry, Martin, Miami-Dade, Monroe and 2 more | 97 min |
| Dec 5, 7:00 AM EST | Mesoscale Discussion | SPC | Broward, Collier, Glades, Hendry, Martin, Miami-Dade and 3 more | 30 min |
| Dec 5, 8:40 AM EST | Mesoscale Discussion | SPC | Broward, Collier, Glades, Hendry, Lee, Martin and 5 more | 35 min |
| Dec 5, 11:14 AM EST | Mesoscale Discussion | SPC | Broward, Collier, Hendry, Martin, Miami-Dade, Monroe and 1 more | 61 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.