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796
FXUS62 KKEY 230152 RRA
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS...CORRECTED
NATIONAL WEATHER SERVICE KEY WEST FL
950 PM EDT MON SEP 22 2014

CORRECTED DATE

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST
AVAILABLE IR IMAGERY OVERLAID AS OF 900 PM OVERLAID WITH MODEL
STREAMLINE ANALYSIS CONTINUES TO DEPICT A UNSEASONABLY DEEP AND
SHARP FULL LATITUDINAL TROUGH AXIS EXTENDING SOUTHWARD INTO THE
EASTERN GULF OF MEXICO FROM EASTERN CANADA. A MORE INTERESTING
FEATURE WITHIN THIS TROUGH IS A COLD CORE MID-LEVEL LOW 570-575 DM
CLOSED LOW PRESSURE SYSTEM NOW SWEEPING ACROSS THE SOUTHERN SMOKY
MOUNTAINS TOWARDS THE ATLANTIC...AND THIS FEATURE IS IN TANDEM WITH
THE DEEP TROUGH AXIS. WELL TO THE EAST OF THIS FEATURE...ONE CENTER
OF A DEEP AND WARM CORE ANTICYCLONE IS POSITIONED ACROSS THE WESTERN
ATLANTIC NEAR 30 NORTH 65 WEST...AND ANOTHER SYNOPTIC SCALE WARM
CORE ANTICYCLONE IS WELL TO THE WEST...CENTERED OVER NORTHERN OLD
MEXICO. AS A RESULT OF THIS CONFIGURATION...CLUSTERS OF
THUNDERSTORMS ASSOCIATED WITH EXCEPTIONAL PVA (POSITIVE VORTICITY
ADVECTION) IS OCCURRING ACROSS THE SOUTHEASTERN GULF OF MEXICO ON
THE LOWER RIGHT FLANK OF THE TROUGH EXTENDING TOWARDS THE KEYS.

AT THE SURFACE AND IN THE LOWER TO MIDDLE LEVELS...AS OF 900
PM...THE LATEST AVAILABLE IR IMAGERY OVERLAID WITH MARINE AND LAND
SURFACE OBSERVATIONS AND ANALYSIS ARE ILLUSTRATING A FRONTAL
BOUNDARY SITUATED ALONG THE SOUTHEASTERN UNITED STATES COAST WEST
SOUTHWESTWARD TO ALONG THE FLORIDA GULF COAST...WITH WEAK 1013 MB
LOW PRESSURE JUST OFF THE GEORGIA COAST. TO THE SOUTH OF THAT
FEATURE...BROAD 1013 MB LOW PRESSURE ACROSS THE SOUTHEASTERN GULF OF
MEXICO NEAR THE LOOP CURRENT ABOUT 75 TO 150 MILES WEST OF KEY WEST.
THE SOUTHWESTERN PERIPHERY OF SURFACE RIDGING IS JUST ABOUT REACHING
THE FLORIDA PENINSULA FROM THE WEST CENTRAL ATLANTIC. THE LEADING
EDGE OF A TROPICAL WAVE IS MOVING WESTWARD TOWARDS THE EASTERN
FLORIDA STRAITS FROM THE CAY SAL BANK.

.CURRENTLY...LATEST IR IMAGERY COMBINED WITH RADAR AS OF 900 PM
DETAIL CLUSTERS AND BANDS OF HEAVY SHOWERS AND THUNDERSTORMS
EXTENDING FROM NEAR DRY TORTUGAS LIGHT WESTWARD INTO THE OPEN
GULF OF MEXICO WESTWARD TO OPEN WATERS OF THE SOUTHEASTERN GULF OF
MEXICO BEYOND 100 NM WEST OF KEY WEST. SMALL ISOLATED SHOWERS AND
THUNDERSTORMS ARE DEVELOPING IN THE CAY SAL BANK AREA AND MOVING
TOWARDS THE FLORIDA STRAITS. TEMPERATURES ACROSS THE ISLANDS REMAIN
IN THE LOWER 80S WITH DEWPOINTS IN THE MIDDLE 70S. C-MAN STATIONS
ALONG THE FLORIDA REEF ARE REGISTERING NORTHEAST TO SOUTHEAST WINDS
AT 5 TO 10 KNOTS.

.FORECAST...OVERNIGHT...THE MID-LEVEL 500 MB LOW WILL CONTINUE TO
MOVE EASTWARD OVERNIGHT TOWARDS THE COAST FROM THE SOUTHERN
MOUNTAINS. AS THE SHARP TROUGH AXIS MOVES JUST TO THE NORTH OF THE
KEYS...THE ENHANCED VORTICITY CENTERS AND ASSOCIATED DEEP CONVECTION
WILL REORIENT ITSELF EASTWARD (FROM THE WEST) TOWARDS THE KEYS. THIS
IN COMBINATION WITH THE APPROACHING WEAK TROPICAL WAVE FROM THE EAST
WILL LIKELY RESULT IN A PROLIFERATION OF SHOWERS AND THUNDERSTORMS
DURING THE LATE NIGHT HOURS. GIVEN THE SLOWER SPEED OF SOME OF THESE
SHOWERS AND THUNDERSTORMS...VERY HEAVY RAINFALL IS LIKELY WITH CELLS
THAT IMPACT THE KEYS. IN ADDITION...THESE SHOWERS AND STORMS WILL
CONTAIN FREQUENT LIGHTNING AND WIND GUSTS OVER 35 KNOTS. BELIEVE
THAT THIS ACTIVITY WILL GRADUALLY INCREASE AFTER MIDNIGHT...BUT THE
BETTER COVERAGE OF THESE SHOWERS AND THUNDERSTORMS WOULD OCCUR
CLOSER TO DAWN. UPDATED TO THE FORECAST WILL BE ISSUED TO RAISE POPS
ACROSS THE ISLANDS AND SURROUNDING WATERS.

&&

.AVIATION...THINKING HAS CHANGED VERY LITTLE FROM PREVIOUS FORECASTS
DURING THIS UPDATE CYCLE. SHOWERS AND THUNDERSTORMS SHOULD INCREASE
IN COVERAGE OVERNIGHT...WITH AT LEAST MVFR CATEGORY CONDITIONS A
HIGH LIKELIHOOD AFTER 09Z TONIGHT. AN INCREASED RISK OF
SHOWERS...THUNDERSTORMS...AND POSSIBLY PROLONGED PERIODS OF STEADY
RAIN EXIST MAINLY AFTER SUNRISE THROUGH 18Z...BUT CURRENT CONFIDENCE
IN THIS FORECAST DOES NOT WARRANT AN EXPLICIT MENTION IN THE TAF
FORECASTS.

&&

.MARINE...OVERNIGHT AND TUESDAY...TROPICAL WAVE AXIS WILL MOVE
ACROSS THE KEYS OVERNIGHT...SO NORTHEAST TO EAST WINDS NEAR 10 KNOTS
WILL INCREASE TO BETWEEN 10 AND 15 KNOTS FROM THE SOUTHEAST BY
MORNING. THE BEST COVERAGE OF SHOWERS AND STORMS WILL OCCUR FROM
BEFORE DAWN THROUGH MID MORNING. GIVEN COVERAGE OF CONVECTION
EXPECTED TO INCREASE...SPECIAL MARINE WARNINGS WILL BE LIKELY
CONTINUE TO BE ISSUED OVERNIGHT...AS SOME CELLS THAT WILL CONTINUE
TO BE CAPABLE OF PRODUCING WIND GUSTS IN EXCESS OF 40 KNOTS.
MARINERS SHOULD KEEP NOAA WEATHER RADIO TUNED IN AT ALL TIMES AND
LISTEN FOR ADDITIONAL STATEMENTS AND WARNINGS THROUGHOUT THE REST OF
THE NIGHT.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...NONE.
&&

$$

PUBLIC/MARINE/GRIDS.............DAF
AVIATION/NOWCASTS/CLIMATE.......MSB
DATA COLLECTION/UPPER AIR.......EV

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