[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 230600
TWDAT

TROPICAL WEATHER DISCUSSION...
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...
TROPICAL STORM FAY HAS DRENCHED FLORIDA FOR FIVE DAYS IN A ROW
CAUSING TORRENTIAL RAINS AND WIDESPREAD FLOODING. ISOLATED STORM
TOTAL RAINFALL AMOUNTS OF 20 TO 30 INCHES HAVE BEEN OBSERVED
WITH FAY ACROSS PORTIONS OF THE EAST-CENTRAL COAST OF FLORIDA.
AT 23/0600 UTC FAY IS CENTERED OVER WATER NEAR 29.8N 84.7W OF
JUST SOUTH OF CARRABELLE FLORIDA. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 997 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH
GUSTS TO 55 KT. 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. THE CENTER OF FAY CROSSED THE COAST OF THE BIG BEND
AREA OF FLORIDA NEAR KEATON BEACH AT ABOUT 2200 UTC...EMERGING
OVER APALACHEE BAY IN THE EXTREME NORTHEASTERN GULF OF MEXICO.
THE CENTER OF FAY WILL BE NEAR OR OVER WATER DURING THE NEXT 48
HOURS OR SO...WHILE ATMOSPHERIC CONDITIONS REMAIN CONDUCIVE TO
SUPPORT A TROPICAL STORM. FAY WILL BE MOVING RATHER SLOWLY
DURING THE NEXT SEVERAL DAYS...POSING A SIGNIFICANT HEAVY
RAINFALL AND FLOOD HAZARD TO A VERY LARGE AREA. FAY IS EXPECTED
TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 5 TO 10 INCHES ACROSS
THE NORTHERN FLORIDA PENINSULA...THE FLORIDA PANHANDLE...
SOUTHERN GEORGIA...SOUTHERN ALABAMA...AND SOUTHERN
MISSISSIPPI...WITH ISOLATED MAXIMUM AMOUNTS OF 15 INCHES
POSSIBLE.  ADDITIONAL RAIN ACCUMULATIONS OF 1 TO 2 INCHES ARE
POSSIBLE OVER CENTRAL AND SOUTHERN FLORIDA IN OUTER RAIN BANDS
ASSOCIATED WITH FAY. ADDITIONAL RAINFALL AMOUNTS OF 1 TO 2
INCHES ARE POSSIBLE OVER COASTAL SOUTHERN SOUTH CAROLINA.
PRESENTLY DOPPLER RADAR SHOWS RAINBANDS ASSOCIATED WITH THE
CIRCULATION OF FAY OVER N FLORIDA...THE FLORIDA PANHANDLE...S
GEORGIA AND SE ALABAMA. A BAND OF SHOWERS WITH EMBEDDED TSTMS IS
ALSO OVER SOUTHERN SOUTH CAROLINA.

...TROPICAL WAVES...
A TROPICAL WAVE HAS EMERGED OFF THE COAST OF W AFRICA AND IS
ALONG 21W S OF 19N MOVING W AT 10-15 KT. THE DAKAR VERTICAL
SOUNDING THAT SHOWED SE WINDS AT LOW LEVELS AND THE HOVMOLLER
DIAGRAM OVER W AFRICA HELPED LOCATE THE WAVE. IN ADDITION...A
CYCLONIC TURNING IS SEEN ALONG THE WAVE AXIS NEAR 13N. SCATTERED
MODERATE CONVECTION IS AHEAD OF THE WAVE LINE AND WITHIN 200 NM
OF THE SOUTHERN CAPE VERDE ISLANDS.

A TROPICAL WAVE IS ALONG 43W/44W S OF 20N. SCATTERED MODERATE
CONVECTION IS NOTED NEAR THE NORTHERN END OF THE WAVE AXIS FROM
18N-21N BETWEEN 43W-46W. SIGNIFICANT DEVELOPMENT OF THIS SYSTEM
IS UNLIKELY DURING THE NEXT COUPLE OF DAYS AS THE WAVE MOVES
WESTWARD AT ABOUT 15 KT.

A 1009 MB AREA OF LOW PRESSURE IS LOCATED NEAR 11N58W OR A
COUPLE HUNDRED MILES EAST OF THE WINDWARD ISLANDS. THIS LOW IS
PRODUCING A SMALL AREA OF SHOWERS AND THUNDERSTORMS. 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 W NEAR 15 KT. SCATTERED SHOWERS AND TSTMS ARE WITHIN
80-100 NM EITHER SIDE OF THE WAVE AXIS. CURRENTLY THE WINDWARD
ISLANDS ARE REPORTING MAINLY LIGHT SHOWERS...BUT THE CHANGE OF
RAIN WILL INCREASE TODAY AS THE LOW MENTIONED ABOVE MOVES ACROSS
THE AREA.

A TROPICAL WAVE IS OVER CENTRAL AMERICA AND THE EPAC ALONG 86W
S OF 15N MOVING W 15-20 KT. MOST OF THE STRONG CONVECTION
ASSOCIATED WITH THE WAVE IS ON THE PACIFIC SIDE. SCATTERED
MODERATE CONVECTION IS NEAR THE COSTA RICA/PANAMA BORDER.

...THE ITCZ...
THE ITCZ IS CENTERED ALONG 12N16W 10N25W 14N35W 11N57W. 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. SCATTERED MODERATE CONVECTION
IS NEAR 6N38W. SIMILAR CONVECTION IS OVER THE GUYANAS.

...DISCUSSION...

GULF OF MEXICO...
T.S. FAY REMAINS THE MAIN FEATURE OF INTEREST OVER THE GULF
REGION AND THE STATE OF FLORIDA. SEE SPECIAL FEATURES FOR
DETAILS. A WEAK RIDGE DOMINATES THE WESTERN HALF OF THE GULF
WHILE THE EASTERN HALF IS 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 25N87W TO THE E PORTION OF THE
BAY OF CAMPECHE. ANOTHER UPPER-LEVEL HIGH CENTERED OVER WESTERN
CUBA COVERS THE SE GULF.

CARIBBEAN SEA...
THE ATLANTIC RIDGE EXTENDS OVER THE GREATER ANTILLES PRODUCING
MODERATE ELY TRADE WINDS. AN INVERTED UPPER TROUGH EXTENDS FROM
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
SEEMS TO BE ENHANCING SOME SHOWER ACTIVITY OVER PUERTO RICO AND
COASTAL WATERS. 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.


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 EXTREME NE
GULF OF MEXICO. IN THE UPPER LEVELS...AN UPPER-LEVEL HIGH
SITUATED OVER E 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 22N
BETWEEN 60W-75W. AN EARLIER QSCAT PASS SHOWED SOME WIND SHIFT
OVER THAT AREA. BASED ON CONVECTIVE ACTIVITY AND THE QSCAT PASS
A SFC TROUGH WILL BE ADDED TO THE 0600 UTC MAP IN THAT REGION.
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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