[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210008
TWDAT

TROPICAL WEATHER DISCUSSION...
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED AUG 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...
FAY IS NOW OVER WATER AND SLIGHTLY STRONGER. THE MAIN THREAT
CONTINUES TO BE THE TORRENTIAL RAINS ALONG ITS PATH. AT
21/0000...TROPICAL STORM FAY IS CENTERED NEAR 29.0N 80.3W JUST
OFF THE EAST COAST OF CENTRAL FLORIDA AND ABOUT 40 MILES...75
KM...EAST-SOUTHEAST OF DAYTONA BEACH FLORIDA. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 993 MB. MAXIMUM SUSTAINED WIND SPEED IS 55
KT WITH HIGHER GUSTS. PLEASE SEE THE LATEST NHC THE
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
AND PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31
KNHC FOR MORE DETAILS. FAY HAS BEEN NEARLY STATIONARY DURING THE
PAST FEW HOURS. THE MID-LEVEL RIDGE DEVELOPING NORTH OF FAY IS
BLOCKING ITS NORTHWARD PROGRESSION AND THE STORM SHOULD SOON
BEGIN TO MOVE VERY SLOWLY TOWARD THE NORTHWEST AND THE
WEST-NORTHWEST. ON THIS TRACK...FAY IS FORECAST TO MOVE VERY
SLOWLY ACROSS NORTHERN FLORIDA ON THURSDAY. THERE ARE NUMEROUS
RAINBANDS SPIRALING AROUND FAY'S CENTER DRENCHING PORTIONS OF
FLORIDA. SOME OF THESE BANDS CONTINUES TO AFFECT SOUTH FLORIDA
WITH HEAVY SHOWERS AT TIME. THE HEAVIEST RAINBANDS ARE CURRENTLY
OVER THE ATLANTIC COASTAL WATERS OF CENTRAL FLORIDA AS NOTED ON
DOPPLER RADAR. FAY IS EXPECTED TO PRODUCE ADDITIONAL RAINFALL
ACCUMULATIONS OF 5 TO 10 INCHES OVER EAST-CENTRAL AND
NORTHEASTERN FLORIDA...WITH 3 TO 6 INCHES OVER SOUTHEASTERN
GEORGIA. ISOLATED STORM TOTAL AMOUNTS OF 30 INCHES ARE POSSIBLE
IN FLORIDA. ACCUMULATIONS OF 3 TO 5 INCHES ARE POSSIBLE IN THE
NORTHWESTERN BAHAMAS.

...TROPICAL WAVES...
A TROPICAL WAVE IS IN THE CENTRAL ATLC ALONG 52W S OF 18N MOVING
W 10-15 KT. NO ASSOCIATED DEEP CONVECTION IS OBSERVED. THE WAVE
HAS LEFT BEHIND A 1008 MB SFC LOW. THIS SYSTEM HAS CHANGED
LITTLE DURING THE DAY...AND ANY DEVELOPMENT IS EXPECTED TO BE
SLOW TO OCCUR DURING THE NEXT COUPLE OF DAYS. THE GFS MODEL NOW
MOVES THE LOW FASTER THAN THE PREVIOUS DAYS. MOISTURE FROM THIS
TROPICAL WAVE IS FORECAST TO REACH THE NORTHERN LEEWARD ISLANDS
THU NIGHT INTO FRI...AND AFFECT THE VIRGIN ISLANDS AND PUERTO
RICO FRIDAY NIGHT THROUGH SATURDAY.

A WEAK TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 72W AND
EXTENDS FROM HAITI TO THE VENEZUELA/COLOMBIA BORDER. THE WAVE IS
ENHANCING SOME SHOWER/TSTM ACTIVITY OVER DOMINICAN REPUBLIC
WHILE CLUSTERS OF MODERATE TO STRONG CONVECTION ARE OVER THE
LAKE MARACAIBO AREA.

...THE ITCZ...
THE ITCZ IS CENTERED ALONG 16N16W 15N25W 11N33W 12N50W 9N60W. A
LARGE CLUSTER OF MODERATE TO STRONG CONVECTION IS MOVING OFF THE
WEST AFRICAN COAST JUST N OF THE ITCZ AXIS. ANOTHER LARGE
CLUSTER WITH SIMILAR CONVECTION COVERS THE AREA FROM 6N-11N
BETWEEN 32W-36W. IN BETWEEN...THERE IS A 1009 MB LOW NEAR 14N26W
GENERATING A SMALL AREA OF SHOWERS AND TSTMS WITHIN 70 NM SW
QUADRANT.

...DISCUSSION...

GULF OF MEXICO...
RAINBANDS ASSOCIATED WITH THE OVERALL CIRCULATION OF FAY
CONTINUES TO BRING MORE RAIN TO THE STATE OF FLORIDA AND THE E
GULF. ONE OF THESE BAND IS APPROACHING THE TAMPA BAY AREA.
OTHERS ARE FORMING OVER SOUTH FLORIDA. AN UPPER-LEVEL LOW
REMAINS OVER NE TEXAS WITH TROUGHING EXTENDING INTO THE FAR NW
GULF. MOIST ONSHORE WINDS COMBINED WITH THIS UPPER TROUGH ARE
HELPING TO INDUCE SCATTERED SHOWERS AND TSTMS OVER THE NW CORNER
OF THE GULF AND ALONG THE TEXAS COAST. A LINE OF SHOWERS AND
TSTMS IS OVER THE YUCATAN PENINSULA AND A SFC TROUGH WAS
ANALYZED IN THAT AREA AT 2100 UTC. A 1015 MB HIGH REMAINS OVER
THE N-CENTRAL GULF NEAR 28N90W EXTENDING A RIDGE OVER THE W GULF
WHERE SLY WINDS OF 10 TO 15 KT PREVAIL.

CARIBBEAN SEA...
AN UPPER-LEVEL HIGH CENTERED OVER WESTERN CUBA COVERS THE NW
CARIBBEAN WITH THE RIDGE AXIS EXTENDING TO NRN BELIZE. THIS
FEATURE IS SUPPORTING THE DEVELOPMENT OF SOME SHOWER ACTIVITY
OVER PARTS OF CUBA...THE COASTAL WATERS OF THE CAYMAN ISLANDS
AND JAMAICA. A SECOND UPPER-LEVEL RIDGE ANCHORED ON A HIGH NEAR
27N60W DOMINATES THE E CARIBBEAN. AN UPPER-LEVEL TROUGH THAT
ENTERS THE BASIN THROUGH THE MONA PASSAGE SEPARATES THESE TWO
UPPER HIGHS. THE ITCZ AXIS CONTINUES TO ENHANCE CONVECTION OVER
PARTS OF COSTA RICA AND PANAMA. A SURGE IN THE TRADE WINDS
PAIRED WITH UPPER DIFFLUENCE IS PRODUCING SOME SHOWER ACTIVITY
OVER THE LESSER ANTILLES AND THE E CARIBBEAN. A TROPICAL WAVE IS
OVER THE CENTRAL CARIBBEAN. SEE ABOVE. THE REMAINDER OF THE AREA
IS DOMINATED BY MODERATE TO STRONG SUBSIDENCE AND DRY STABLE AIR.

ATLANTIC OCEAN...
SPIRAL RAINBANDS ASSOCIATED WITH T.S. FAY ARE OVER THE W ATLC
MAINLY W OF 78W. THERE ARE ALSO SOME SHOWER ACTIVITY N OF 25N W
OF 70W DUE TO UPPER DIFFLUENCE BETWEEN THE BASE OF AN UPPER
TROUGH AND THE UPPER HIGH ASSOCIATED WITH FAY. AN UPPER-LEVEL
LOW IS NEAR 23N67W WITH A TROUGH EXTENDING SW INTO THE CARIBBEAN
SEA THROUGH THE MONA PASSAGE. FURTHER EAST...A LARGE UPPER-LEVEL
LOW CENTERED NEAR 21N50W IS SPINNING OVER THE CENTRAL ATLC. A
TROUGH CONNECTS THIS LOW WITH A WEAKER UPPER LOW JUST NW OF THE
MADEIRA ISLANDS NEAR 34N18W. BOTH OF THESE LOWS ARE BENIGN
FEATURES. MODERATE SUBSIDENCE AND SOMEWHAT DRY STABLE AIR COVERS
THE ATLC E OF 60W GIVING THE REMAINDER OF THE AREA MOSTLY FAIR
WEATHER CONDITIONS. AT THE SURFACE...THE AZORES HIGH CONTINUES
TO DOMINATE MOST OF THE ATLC N OF 20N E OF 60W. THIS ANTICYCLONE
IS FORECAST BY THE COMPUTER MODELS TO SLIGHTLY STRENGTHEN DURING
THE NEXT 24 HOURS OR SO PRODUCING A SWATH OF MODERATE TO STRONG
TRADE WINDS ACROSS THE TROPICAL ATLC...PARTICULARLY FROM
16N-22N.

$$
GR



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