[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231155
TWDAT

TROPICAL WEATHER DISCUSSION...
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT AUG 23 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURES...
RADAR AND SURFACE DATA INDICATE THAT THE CENTER OF FAY HAS AGAIN
MADE LANDFALL...THIS TIME JUST SOUTHWEST OF CARRABELLE FLORIDA
AROUND 0600 UTC. THIS MARKS FAY'S FOURTH LANDFALL IN FLORIDA
OVER THE PAST 6 SIX DAYS...AN UNUSUAL FEAT FOR ANY TROPICAL
CYCLONE. AT 23/1200 UTC FAY IS CENTERED INLAND OVER THE CENTRAL
FLORIDA PANHANDLE ABOUT 20 MILES/35 KM SOUTHEAST OF PANAMA CITY
FLORIDA...NEAR 29.9N 85.3W MOVING WEST AT 6 KT...AND THIS
GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 TO
48 HOURS. ON THE FORECAST TRACK...FAY WILL BE NEAR OR OVER
THE GULF COAST OF THE WESTERN FLORIDA PANHANDLE TODAY AND
TONIGHT...AND NEAR OR OVER THE GULF COAST OF MISSISSIPPI AND
ALABAMA ON SUNDAY. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB.
MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT.
LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 24 TO
48 HOURS...AND FAY IS EXPECTED TO REMAIN A TROPICAL STORM INTO
SUNDAY. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND PUBLIC ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC FOR MORE DETAILS.
OVER THE NEXT TWO DAYS...FAY IS EXPECTED TO PRODUCE TOTAL
RAINFALL ACCUMULATIONS OF 5 TO 10 INCHES ACROSS THE WESTERN
PORTION OF THE NORTHERN FLORIDA PENINSULA...THE FLORIDA
PANHANDLE...SOUTHWESTERN GEORGIA...AND THE SOUTHERN HALF OF
BOTH MISSISSIPPI AND ALABAMA...WITH ISOLATED MAXIMUM AMOUNTS
OF 15 INCHES POSSIBLE.  ADDITIONAL RAINFALL ACCUMULATIONS
OF 1 TO 3 INCHES ARE POSSIBLE OVER THE REMAINDER OF THE
FLORIDA PENINSULA AND SOUTHEASTERN GEORGIA. ISOLATED TORNADOES
ARE POSSIBLE TODAY AND TONIGHT IN PORTIONS OF NORTHERN
FLORIDA...SOUTHERN GEORGIA...AND SOUTHERN ALABAMA. PRESENTLY
DOPPLER RADAR SHOWS RAINBANDS ASSOCIATED WITH THE CIRCULATION
OF FAY OVER N FLORIDA...THE FLORIDA PANHANDLE...S GEORGIA AND
PARTS OF ALABAMA. A BAND OF SHOWERS WITH ISOLATED TSTMS IS ALONG
THE GEORGIA/SOUTH CAROLINA BORDER. NEW CELLS ARE FORMING ALONG
THE WEST COAST OF FLORIDA ALL THE WAY SOUTH TO THE FLORIDA KEYS
UNDER A WEST AND SW FLOW.

...TROPICAL WAVES...
A TROPICAL WAVE HAS RECENTLY EMERGED OFF THE COAST OF W AFRICA
AND IS NOW ALONG 22W S OF 19N MOVING W AT 10-15 KT. THE 23/0000
UTC DAKAR VERTICAL SOUNDING SHOWED THE PASSAGE OF THE WAVE VERY
CLEAR. AN EARLIER QSCAT PASS AND FIRST VIS IMAGERY FOR THE DAY
REVEAL A BROAD AREA OF CYCLONIC TURNING JUST SOUTH OF THE CAPE
VERDE ISLANDS. SCATTERED SHOWERS AND ISOLATED TSTMS ARE AHEAD
OF THE WAVE LINE AND WITHIN 200 NM OF THE SOUTHERN CAPE VERDE
ISLANDS.

A TROPICAL WAVE IS ALONG 44W/45W S OF 20N. SCATTERED MODERATE
CONVECTION IS NOTED NEAR THE NORTHERN END OF THE WAVE AXIS FROM
18N-21N BETWEEN 43W-48W. SIGNIFICANT DEVELOPMENT OF THIS SYSTEM
IS UNLIKELY DURING THE NEXT COUPLE OF DAYS AS THE WAVE MOVES
WESTWARD AT ABOUT 15 KT.

THE 1009 MB AREA OF LOW PRESSURE IS RELOCATED NEAR 11N55 BASED
ON LATEST SATELLITE PHOTOS. CONVECTION IS ON THE INCREASE AROUND
THE LOW CENTER. GRADUAL DEVELOPMENT OF THIS SYSTEM IS POSSIBLE
DURING THE NEXT COUPLE OF DAYS AS IT MOVES GENERALLY WESTWARD
AT 10 TO 15 MPH. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINS
AND GUSTY WINDS ARE EXPECTED TO SPREAD OVER PORTIONS OF THE
WINDWARD AND LEEWARD ISLANDS TODAY.

A TROPICAL WAVE IS OVER THE E CARIBBEAN ALONG 62W S OF 16N
MOVING SLOWLY WWD. SCATTERED SHOWERS AND TSTMS ARE WITHIN 100 NM
EITHER SIDE OF THE WAVE AXIS.

A TROPICAL WAVE IS OVER CENTRAL AMERICA AND THE EPAC ALONG
87W/88W S OF 15N MOVING W 15-20 KT. MOST OF THE CONVECTION
ASSOCIATED WITH THE WAVE IS ON THE PACIFIC SIDE NEAR THE
INTERSECTION OF THE WAVE AXIS AND THE ITCZ.

...THE ITCZ...
THE ITCZ IS CENTERED ALONG 12N16W 12N30W 14N42W 13N50W 12N54W.
BESIDES THE CONVECTION MENTIONED ON THE TROPICAL WAVE SECTION...
A LARGE CLUSTER OF MODERATE TO STRONG CONVECTION IS INLAND OVER
WEST AFRICA APPROACHING THE COASTLINE. ISOLATED TO SCATTERED
MODERATE CONVECTION IS FROM 4N-7N BETWEEN 36W-42W.

...DISCUSSION...

GULF OF MEXICO...
T.S. FAY REMAINS THE MAIN FEATURE OF INTEREST OVER THE GULF
REGION AND THE STATE OF FLORIDA. IT IS MOVING SOUTH OF A
LOW/MID-LEVEL RIDGE OVER THE EASTERN UNITED STATES. SEE SPECIAL
FEATURES FOR DETAILS. A WEAK RIDGE ANCHORED ON A 1015 MB HIGH
NEAR 29N93W DOMINATES THE WESTERN HALF OF THE GULF WHILE MOST OF
THE EASTERN HALF REMAINS UNDER THE INFLUENCE OF THE OVERALL
CIRCULATION OF FAY GIVING THE AREA NW TO W WINDS. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS OVER THE DEEP SOUTH AND
NE MEXICO LIKELY DUE TO UPPER DIFFLUENCE BETWEEN AN UPPER-LEVEL
LOW SPINNING OVER THE STATE OF CHIHUAHUA MEXICO AND AN
UPPER-LEVEL HIGH OVER CENTRAL MEXICO. THIS HIGH DOMINATES THE
WESTERN GULF. AN INVERTED TROUGH IS OVER THE CENTRAL GULF
EXTENDING FROM AN UPPER LOW NEAR 24N88W TO THE E PORTION OF THE
BAY OF CAMPECHE WHERE THERE IS SOME SHOWER ACTIVITY. ANOTHER
UPPER-LEVEL HIGH CENTERED OVER WESTERN CUBA COVERS THE SE GULF.
A SMALL AREA OF SHOWER WITH EMBEDDED TSTMS HAS DEVELOPED NEAR
27N88W.

CARIBBEAN SEA...
THE SUBTROPICAL RIDGE EXTENDS OVER THE GREATER ANTILLES
PRODUCING MODERATE ELY TRADE WINDS. AN UPPER-LEVEL TROUGH
EXTENDS FROM AN UPPER LOW OVER THE W ATLC NEAR 21N65W THROUGH
THE MONA PASSAGE TO THE SW CARIBBEAN SEPARATING AN UPPER RIDGE
ANCHORED OVER WRN CUBA AND THE FLORIDA STRAITS AND A SECOND
UPPER RIDGE ANCHORED OVER THE FAR SE CARIBBEAN. THIS TROUGH IS
HELPING TO INDUCE SOME SHOWER ACTIVITY OVER THE E CARIBBEAN BUT
MAINLY SOUTH OF PUERTO RICO. A TROPICAL WAVE IS OVER THE E
CARIBBEAN. SEE ABOVE. MOISTURE FROM THIS FEATURE IS EXPECTED TO
REACH THE UK/US VIRGIN ISLANDS AND PUERTO RICO LATE TODAY. AN
AREA OF SHOWERS AND TSTMS HAS DEVELOPED OVER THE SW CARIBBEAN
THANKS TO DIFFLUENT PATTERN ALOFT AND THE CLOSE PROXIMITY OF
THE ITCZ. A SMALL AREA OF SHOWERS IS BETWEEN THE CAYMAN ISLANDS
AND JAMAICA. LOW TOPPED SHOWERS ARE SEEN OVER THE REMAINDER OF
THE BASIN.

ATLANTIC OCEAN...
THE AZORES HIGH DOMINATES THE FORECAST AREA PRODUCING MOSTLY
EASTERLY SURFACE FLOW OVER THE ATLANTIC PARTICULARLY FROM
20N-32N BETWEEN W AFRICA AND 60W. SHOWER ACTIVITY HAS DIMINISHED
OVER THE W ATLC AS FAY CONTINUES TO MOVE WWD OVER THE FLORIDA
PANHANDLE. IN THE UPPER LEVELS...AN UPPER-LEVEL HIGH SITUATED
OVER WRN CUBA EXTENDS A RIDGE NWD OVER THE BAHAMAS AND PART OF
THE W ATLC. AN UPPER-LEVEL TROUGH ENTERS THE AREA NEAR 32N68W
THEN CONTINUES MAINLY S TO ANOTHER UPPER LOW LOCATED N OF PUERTO
RICO NEAR 21N65W. UPPER DIFFLUENCE AHEAD OF THE TROUGH IS
GENERATING AN AREA OF SHOWERS WITH EMBEDDED TSTMS N OF 23N
BETWEEN 60W-70W. A SFC TROUGH IS ANALYZED OVER THAT AREA AND
RUNS FROM 31N63W TO 24N68W. AN UPPER LEVEL HIGH LOCATED NEAR
27N45W DOMINATES THE CENTRAL ATLC. A LARGE UPPER-LEVEL LOW IS
OVER THE E ATLANTIC NEAR 29N25W.

$$
GR





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