Severe Thunderstorm Warning 119, NWS Miami, FL

000
WWUS52 KMFL 201744
SVSMFL

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE MIAMI FL
143 PM EDT THU SEP 20 2007

FLC099-201753-
/O.CAN.KMFL.SV.W.0119.000000T0000Z-070920T1800Z/
PALM BEACH FL-
143 PM EDT THU SEP 20 2007

...THE SEVERE THUNDERSTORM WARNING FOR SOUTHEASTERN PALM BEACH COUNTY
IS CANCELLED...

NATIONAL WEATHER SERVICE RADAR INDICATED THAT THE THUNDERSTORM HAS 
WEAKENED AND IS NO LONGER SEVERE. THUS THE THUNDERSTORM WARNING HAS 
BEEN CANCELLED. HOWEVER...ADDITIONAL STORMS ARE LIKELY TO DEVELOP 
THROUGH THE REMAINDER OF THIS AFTERNOON.

LAT...LON 2634 8026 2648 8018 2647 8009 2647 8007
      2646 8006 2638 8008 2635 8009 2634 8010
TIME...MOT...LOC 1743Z 212DEG 14KT 2642 8011

$$

KOB

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MIAMI FL
1109 AM EDT THU SEP 20 2007

.UPDATE...TRICKY WEATHER SITUATION UNFOLDING ACROSS THE CWA TODAY.
SATELLITE AND RADAR DATA...ALONG WITH SURFACE AND BUOY OBS...SHOW
AN APPROXIMATELY 1007MB BROAD SFC LOW CENTERED 60-80 MILES OFF THE
SOUTH FL WEST COAST...JUST ON THE SE SIDE OF THE MID/UPPER LEVEL
CIRCULATIONS. THE GRADIENT HAS BEEN INCREASING THIS MORNING ACROSS
THE CWA...WITH S/SSE WINDS GUSTING TO 20 MPH OUTSIDE OF
PRECIPITATION ACROSS THE INTERIOR AND WEST COAST...WITH GUSTS AT
FMY AND APF TO 30 MPH IN HEAVIER SHOWERS. RADAR IMAGERY SHOWS A
SOLID LINE OF HEAVY SHOWERS/TSTMS FORMING FROM WESTERN GLADES
COUNTY TO NEAR CAPE ROMANO. THIS LINE IS MARCHING EAST AT A STEADY
CLIP INTO AN UNSTABLE ATMOSPHERE...AND THERE IS NOT MUCH REASON
FOR IT TO FALL APART AS IT TRAVERSES THE PENINSULA. AGITATED CU
FIELD IS DEVELOPING AHEAD OF THE LINE SO EXPECT AT LEAST SCATTERED
PRE-LINE TSTMS TO DEVELOP OVER THE CWA THIS AFTERNOON.

FEEL THAT THERE IS A THREAT FOR ISOLATED WEAK TORNADOES ACROSS THE
CWA THIS AFTERNOON. S/SSE SFC WINDS ARE BECOMING STRONGER...WITH
THE 12Z MIAMI SOUNDING SHOWING UNIDIRECTIONAL SOUTHERLY FLOW
ABOVE THE SFC...HOWEVER THE FLOW IS FAIRLY STRONG AT 20-30 KNOTS.
WHILE THERE IS NOT MUCH TURNING/LOW LEVEL HELICITY...GIVEN THESE
MODEST WIND FIELDS FOR SOUTH FL OVER THE BOUNDARY LAYER AND MID
LEVELS...THINK THAT LOCALIZED STORM-RELATIVE HELICITY COULD BE
ENOUGH FOR A FEW BRIEF SPIN-UPS TODAY...ESPECIALLY ACROSS THE
WESTERN HALF THROUGH THIS EVENING WHERE SFC FLOW IS STRONGEST AND MOST
BACKED. THIS THREAT MAY SPREAD TO THE EAST COAST FOR THE MID
AFTERNOON-EARLY EVENING HOURS. HERE...INITIALLY S/SSW SFC WINDS
ARE PRETTY LIGHT AND SHOULD ALLOW FOR SEA BREEZE DEVELOPMENT BY
LATE AFTERNOON...OR THE PRESSURE GRADIENT WILL ALLOW WINDS TO BACK
VIA SYNOPTIC PROCESSES. THIS WOULD CREATE SLIGHTLY MORE HELICITY
ACROSS THE EAST COAST THIS AFTERNOON...AND ENHANCE THE TORNADO
THREAT...ESPECIALLY INVOF ANY BOUNDARIES OR SEA BREEZE INTERACTION
AS STORMS CROSS THE BOUNDARIES. A FEW CELLS OVER THE GULF AND
ATLANTIC WATERS HAVE ALREADY SHOWN MINI SUPERCELLULAR
CHARACTERISTICS WITH BRIEF ROTATION THIS MORNING.

OTHER MAIN CHANGE WAS TO BUMP HIGHS UP ACROSS THE EAST COAST METRO
WHERE SLIGHT OFFSHORE COMPONENT TO THE SFC FLOW AND PLENTY OF SUNSHINE
WERE ALREADY PUSHING TEMPS INTO THE MID 80S.

&&

.AVIATION...AREA OF LOW PRESS OVER GULF WATERS JUST OFFSHORE OF
THE SW FL COAST BECOMING MORE ACTIVE THIS MORNING WITH
SHWRS/TSTMS MOVING ONSHORE INVOF KAPF. MOST TSRA WELL W OF KAPF
BUT NONETHELESS IS INCREASING AND WILL CONTINUE THE VCTS FOR KAPF
AFT 14Z. OVER THE ERN TERMINALS...MOSTLY VFR CONDITIONS WILL
CONTINUE THROUGH THIS MORNING EXCEPT FOR A SHRA OR TWO INVOF KTMB
AND KMIA. NEVERTHELESS...TSTMS SHOULD BE EXPECTED INVOF ALL
TERMINALS THIS AFTERNOON AND SO WILL KEEP VCTS FROM 19Z TO 00Z
TONIGHT BUT IF THE CONVECTION DOES BEGIN EARLIER WILL AMEND AS
NECESSARY.

&&

.MARINE...MAIN CHANGE TO THE MARINE WAS TO INCREASE WINDS TO
AROUND 15 KNOTS OVER LAKE OKEE. PER MORNING LAKE TOWER OBS.
OTHERWISE...BUOY OBS AND 10Z QUICKSCAT PASS SHOW MARINE FORECAST
IS ON TRACK FOR TODAY. SMALL CRAFT SHOULD EXERCISE CAUTION
OUTER GULF WATERS...AND WINDS AND SEAS WILL BE HIGHER IN ANY
THUNDERSTORMS TODAY. THERE IS ALSO THE RISK OF WATERSPOUTS WITH
ANY SHOWER/TSTM AND MARINERS SHOULD BE ON ALERT.

UPDATE/MARINE: STRASSBERG
AVIATION: KOB

&&

.PREV DISCUSSION... /ISSUED 339 AM EDT THU SEP 20 2007/

DISCUSSION...
CURRENTLY A SURFACE LOW ROTATING NW ACROSS N CENTRAL FLA WITHIN A
BROAD AREA OF LOW PRES ACROSS S CENTRAL/S FLA. A MID TO UPPER LEVEL
LOW PRES SYSTEM IN THE SE GULF OF MEX WITH SURFACE LAPS WINDS INDIC
-ATING A SECONDARY LOW PRES DEVELOPING. AS THE DAY PROGRESSES...THE
GULF SURFACE LOW WILL CONSOLIDATE UNDER THE UPPER LOW AND BECOME THE
PRIMARY FEATURE IN THE SHORT TERM...TODAY THROUGH SAT.

DEEP MOISTURE WRAPPING TIGHTLY ABOUT UPPER LOW IN GULF CURRENTLY
WITH SHOWERS AND SOME THUNDER...WHILE OVER THE PENINSULA AND
ADJACENT ATLC...ONLY ISOLATED SHOWERS AT BEST AS VERY DRY AIR ALOFT
FROM LOWER FLA STRAITS/W CUBA BEING CIRCULATED OVER THIS AREA.

SOME VARIATION IN GUIDANCE DEPENDANT UPON GULF DEVELOPMENT. S FLA
WILL BE BENEATH A DEEP SOUTHERLY WIND FLOW THAT WILL GRADUALLY
MOISTEN UP TODAY FROM W TO E AS MOISTURE PULEED NORTHWARD TO WRAP
ABOUT THE UPPER LOW. TODAY...DEEPER MOISTURE AND BEST CHANCES OF
RAIN ON THE W COAST WITH POPS WILL BE LIKELY THERE AND DECREASING
INCREMENTALLY EASTWARD. BY FRI AND SAT...THE ATMOSPHERE WILL BE
AMPLY MOIST ACROSS ALL OF S FLA.

EXTENDED...SUNDAY THROUGH WEDNESDAY...UPPER-LEVEL RIDGE AND
SLIGHTLY DRIER AIR BECOMES ESTABLISHED OVER THE AREA WITH A RETURN
TO SCATTERED DIURNAL CONVECTION. THE DEEPER EASTERLY FLOW WILL HAVE
THE HIGHER POPS INTERIOR AND W.

AVIATION...AREA OF LOW PRESS OVER GULF WATERS SW OF KAPF BECOMING
MORE ACTIVE THIS MORNING WITH SHWRS/TSTMS RAPIDLY INCREASING OVER
WATER. DRAINAGE FLOW OVR WEST COAST MAY KEEP THIS ACTIVITY OFFSHORE
TIL SUNRISE BUT WILL EXPECT IT TO MOVE ONSHORE AFTER 12Z WHEN
DRAINAGE FLOW SUBSIDE. WILL INDICATE VCTS FOR KAPF FOR THE TIME
BEING DUE TO UNCERTAINTIES ON THE TIMING OF CONVECTION MOVING
INLAND...BUT WILL CONSIDER THE POSSIBILITY OF INDICATING PREVAILING
MVFR CONDITIONS FROM 12Z TO 18Z IN THE NEXT KAPF TAF. OVER THE ERN
TERMINALS...MOSTLY IFR CONDITIONS WILL CONTINUE THROUGH THIS MORNING
EXCEPT FOR A SHRA OR TWO INVOF KTMB AND KMIA. NEVERTHELESS...TSTMS
SHOULD BE EXPECTED INVOF ALL TERMINALS THIS AFTERNOON AND SO WILL
KEEP VCTS FROM 19Z TO 00Z TONIGHT.

MARINE...WITH THE LOW DEVELOPING IN THE GULF...AN INCREASING
SOUTHERLY WIND DEVELOPING WITH THE STRONGEST WINDS IN THE GULF
WATERS. EXERCISE CAUTION ON TAP TODAY  AND TONIGHT FOR THE OUTER
GULF WATERS BEYOND 20 NAUTICAL MILES AS S 15 TO 20 KNOT WINDS WILL
DEVELOP WITH SEAS TO 5 FEET. N SWELL OFF OF PALM BEACH COUNTY THIS
MORNING AROUND 2 FEET WILL GRADUALLY DISAPEAR TODAY IN THE
INCREASING SOUTHERLY WINDS.

FIRE WEATHER...NO FIRE WEATHER CONCERNS.

&&

.PRELIMINARY POINT TEMPS/POPS...
WEST PALM BEACH  90  77  90  78 / 50 30 60 40
FORT LAUDERDALE  90  77  88  78 / 50 30 60 40
MIAMI            90  76  89  79 / 60 30 60 40
NAPLES           85  75  89  75 / 70 60 60 50

&&

.MFL WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...NONE.
GM...NONE.
&&

LONG TERM...15/JR
SHORT TERM/AVIATION...47/RHG

HAZARDOUS WEATHER OUTLOOK FOR SOUTH FLORIDA
NATIONAL WEATHER SERVICE MIAMI FL
942 AM EDT THU SEP 20 2007

FLZ063-066>075-168-172>174-210130-
GLADES-HENDRY-INLAND PALM BEACH-METRO PALM BEACH-COASTAL COLLIER-
INLAND COLLIER-INLAND BROWARD-METRO BROWARD-INLAND MIAMI DADE-
METRO MIAMI DADE-MAINLAND MONROE-COASTAL PALM BEACH-
COASTAL BROWARD-COASTAL MIAMI DADE-FAR SOUTH MIAMI DADE-
930 AM EDT THU SEP 20 2007

...ISOLATED WEAK TORNADOES POSSIBLE THIS AFTERNOON...
...SCATTERED TO NUMEROUS THUNDERSTORMS EXPECTED TODAY...
...SLIGHT RISK OF WATERSPOUTS TODAY...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH FLORIDA.

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS: SCATTERED TO NUMEROUS THUNDERSTORMS ARE EXPECTED
ACROSS ALL OF MAINLAND SOUTH FLORIDA AND THE ADJACENT COASTAL
WATERS TODAY INTO EARLY THIS EVENING. FREQUENT LIGHTNING STRIKES,
LOCALLY HEAVY RAINS AND WIND GUSTS TO 50 MPH CAN BE EXPECTED IN
THE STRONGEST STORMS.

TORNADOES: COUNTERCLOCKWISE CIRCULATION AROUND A SURFACE LOW
PRESSURE SYSTEM IN THE SOUTHEAST GULF OF MEXICO MAY CAUSE A BRIEF
WEAK TORNADO TO OCCUR IN THE STRONGEST THUNDERSTORMS THIS AFTERNOON.

WATERSPOUTS: AN UPPER LEVEL LOW, AND ASSOCIATED SURFACE LOW
PRESSURE SYSTEM, OVER THE EASTERN GULF OF MEXICO, WILL RESULT IN FAVORABLE
ATMOSPHERIC CONDITIONS FOR WATERSPOUTS TO DEVELOP ACROSS ALL
COASTAL WATERS, EXCEPT LAKE OKEECHOBEE, TODAY.

WIND: THE STRONGEST THUNDERSTORMS MAY PRODUCE WIND GUSTS TO 50 MPH
THIS AFTERNOON.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

SCATTERED THUNDERSTORMS ARE EXPECTED TO OCCUR EACH DAY THROUGH THE
PERIOD. LIGHTNING STRIKES AND LOCALLY HEAVY RAINFALL WILL BE THE
MAIN IMPACTS FROM THE STORMS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUESTED THIS AFTERNOON.

FOR MORE INFORMATION...VISIT THE NATIONAL WEATHER SERVICE IN
MIAMI WEBSITE AT WWW.WEATHER.GOV/MIAMI.