[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 302353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED SEP 30 2015

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

JOAQUIN BECAME A HURRICANE THIS MORNING AND CONTINUES TO
STRENGTHEN JUST E OF THE BAHAMAS. IT IS CENTERED NEAR 24.3N
73.1W AT 30/2100Z OR ABOUT 190 MI...305 KM ENE OF THE CENTRAL
BAHAMAS MOVING TOWARD THE SOUTHWEST OR 225 DEGREES AT 7 KT. ON
THE FORECAST TRACK...THE CENTER OF JOAQUIN IS EXPECTED TO MOVE
NEAR OR OVER PORTIONS OF THE CENTRAL BAHAMAS TONIGHT AND THU.
MAXIMUM SUSTAINED WIND SPEED IS 75 KT WITH GUSTS TO 90 KT.
NUMEROUS STRONG CONVECTION IS WITHIN 90 NM OF CENTER...EXCEPT SW
QUADRANT. NUMEROUS MODERATE ISOLATED STRONG CONVECTION IS NOTED
ELSEWHERE FROM 21N-26N BETWEEN 70W-75W. PART OF THE CONVECTION
ASSOCIATED WITH THE OVERALL CIRCULATION OF JOAQUIN IS AFFECTING
THE SE BAHAMAS AND THE TURKS AND CAICOS ISLANDS AS WELL AS
EASTERN CUBA. JOAQUIN IS EXPECTED TO PRODUCE 5-10 INCHES OF RAIN
OVER MUCH OF THE CENTRAL BAHAMAS, WITH ISOLATED MAXIMUM AMOUNTS
OF 20 INCHES POSSIBLE OVER SAN SALVADOR AND RUM CAY THROUGH FRI
NIGHT. RAINFALL AMOUNTS OF 3-5 INCHES ARE POSSIBLE OVER
SOUTHEASTERN BAHAMAS THROUGH FRI NIGHT...WITH 2-4 INCHES
EXPECTED OVER THE NW BAHAMAS. SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

A 1009 MB LOW PRES IS ANALYZED NEAR 25.5N 57.5W ALONG AN OLD
FRONTAL TROUGH THAT EXTENDS FROM 25N51W TO THE LOW CENTER TO
27N64W. A LARGE AREA OF CLOUDINESS WITH EMBEDDED TSTMS IS NOTED
MAINLY E OF THE LOW CENTER COVERING THE AREA FROM 24N-27N
BETWEEN 54W-57W. THIS SYSTEM HAS BECOME A LITTLE BETTER
ORGANIZED SINCE YESTERDAY..AND ADDITIONAL GRADUAL DEVELOPMENT IS
POSSIBLE DURING THE NEXT SEVERAL DAYS WHILE IT MOVES SLOWLY
NORTHWESTWARD TO NORTHWARD. THE LATEST NHC TROPICAL WEATHER
OUTLOOK GIVES THIS LOW PRES AREA A MEDIUM CHANCE OF DEVELOPING
INTO A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

...TROPICAL WAVES...

A TROPICAL WAVE IS NEAR THE CAPE VERDE ISLANDS WITH AN AXIS
EXTENDING FROM 19N22W TO 12N24W...MOVING SLOWLY W AT 5-10 KT.
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED AHEAD OF
THE WAVE AXIS FROM 12N-15N BETWEEN 23W-27W. THE WAVE IS WELL
DEPICTED IN THE LATEST GFS 700 MB STREAMLINES AND 850 MB
VORTICITY ANALYSIS...AND IS ALSO REFLECTED IN A SURGE OF
MOISTURE ON THE TPW SATELLITE IMAGERY.

A SECOND TROPICAL WAVE IS IN THE CENTRAL ATLANTIC EXTENDING FROM
18N37W TO 10N40W...MOVING W AT 5 KT. AN INVERTED-V PATTERN IS
NOTED IN THE CLOUD FIELD. A SMALL CLUSTER OF MODERATE CONVECTION
IS WHERE THE WAVE MEETS THE MONSOON TROUGH. TPW IMAGERY SHOWS
THE WAVE EMBEDDED IN A MODERATE MOIST ENVIRONMENT.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE COAST OF AFRICA NEAR 14N17W
TO 11N26W TO 12N38W TO 10N49W. THE ITCZ CONTINUES FROM 10N49W TO
11N55W TO 9N61W. SCATTERED MODERATE ISOLATED STRONG CONVECTION
IS FROM 7N-11N BETWEEN 19.5W-22W. SCATTERED MODERATE IS FROM 10N-
11N BETWEEN 42W-46W.

...DISCUSSION...

GULF OF MEXICO...

A SHARP UPPER-LEVEL TROUGH IS OVER THE NW GULF EXTENDING FROM SE
LOUISIANA TO NEAR BROWNSVILLE TEXAS. SW FLOW AHEAD OF THE TROUGH
IS ADVECTING ABUNDANT MID TO UPPER-LEVEL MOISTURE FROM SOUTH-
CENTRAL MEXICO ALL THE WAY NE TO BEYOND FLORIDA. THIS TROUGH
SUPPORTS A WEAK 1009 MB LOW PRES LOCATED NEAR 26N92W WITH A
TROUGH EXTENDING NE TO THE FLORIDA PANHANDLE. VISIBLE SATELLITE
IMAGERY SHOWS A SWIRL OF LOW CLOUDS IN ASSOCIATION WITH THIS LOW
FORECAST TO WEAKEN TO A TROUGH TONIGHT. AT 2100 UTC...
SCATTEROMETER DATA INDICATE THE PRESENCE OF ANOTHER SURFACE
TROUGH OVER THE SE GULF AND STRETCHES FROM 25N84W TO 22N87W TO
THE NORTHERN YUCATAN PENINSULA NEAR 20N89W. THE TROUGH IS
GENERATING SOME SHOWER AND TSTM ACTIVITY OVER PARTS OF WESTERN
CUBA AND THE YUCATAN PENINSULA. LOOKING AHEAD...A COLD FRONT IS
FORECAST TO REACH THE NORTHERN GULF BY THU. THIS FRONT WILL MOVE
RAPIDLY SE AND EXTEND FROM TAMPA BAY TO THE BAY OF CAMPECHE
EARLY FRI AFTERNOON...AND MOVE SE OF GULF BY EARLY SAT AS
WEAKENING FRONT. FRESH TO STRONG NORTHERLY WINDS AND BUILDING
SEAS ARE EXPECTED IN THE WAKE OF THE FRONT.

CARIBBEAN SEA...

DUE TO THE PRESENCE OF HURRICANE JOAQUIN JUST E OF THE
BAHAMAS...MAINLY GENTLE TRADE WINDS ARE NOTED ACROSS THE BASIN
WITH THE EXCEPTION OF MODERATE TRADE WINDS OVER THE SOUTH-
CENTRAL CARIBBEAN. IN ADDITION...ANOMALOUS SW TO W WINDS ARE
SEEN PER SCATTEROMETER DATA OVER MUCH OF THE NW CARIBBEAN...
BETWEEN EASTERN CUBA AND JAMAICA AND INTO THE WINDWARD PASSAGE.
AS JOAQUIN APPROACHES THE CENTRAL BAHAMAS TONIGHT AND THU...THE
SW FLOW MAY INCREASE...PARTICULARLY ACROSS THE EASTERN HALF OF
CUBA AND REGIONAL WATERS...INCLUDING ALSO THE WINDWARD PASSAGE.
THE GFS COMPUTER MODEL SUGGESTS INCREASING WINDS TO 20-25 KT. AS
IT IS NORMAL FOR THIS TIME OF THE YEAR...THE MONSOON TROUGH IS
OVER THE FAR SOUTH-CENTRAL CARIBBEAN GENERATING SOME SHOWER AND
TSTM ACTIVITY OVER PARTS OF PANAMA AND COSTA RICA. ALOFT...
UPPER-LEVEL NLY FLOW PREVAILS OVER MOST OF THE CENTRAL AND
WESTERN CARIBBEAN. AN UPPER-LEVEL TROUGH EXTENDS FROM THE
LEEWARD ISLANDS TO THE ABC ISLANDS AND NW VENEZUELA. SW WINDS
AHEAD OF THE TROUGH AXIS ARE TRANSPORTING ABUNDANT MID-UPPER
LEVEL MOISTURE FROM SOUTH AMERICA ACROSS THE WINDWARD ISLANDS
INTO THE TROPICAL N ATLC WHERE SOME SHOWER ACTIVITY IS NOTED.

...HISPANIOLA...

THE OUTER RAINBANDS OF HURRICANE JOAQUIN SUPPORT CLOUDINESS
ACROSS THE ISLAND WITH POSSIBLE ISOLATED CONVECTION EXPECTED
ACROSS THE NORTHERN HALF OF THE ISLAND. SIMILAR ACTIVITY IS
EXPECTED TO CONTINUE THROUGH THE NEXT 24 HOURS AS HURRICANE
JOAQUIN MOVES SW TOWARD THE BAHAMAS TONIGHT AND THU.

ATLANTIC OCEAN...

THE MAIN FEATURE OVER THE ATLANTIC IS HURRICANE JOAQUIN...PLEASE
SEE SPECIAL FEATURES SECTION ABOVE FOR DETAILS. SWELLS GENERATED
BY JOAQUIN WILL AFFECT PORTIONS OF THE BAHAMAS DURING THE NEXT
FEW DAYS...AND WILL BEGIN TO AFFECT PORTIONS OF THE SOUTHEASTERN
COAST OF THE UNITED STATES BY THURSDAY. THESE SWELLS ARE LIKELY
TO CAUSE LIFE-THREATENING SURF AND RIP CURRENT CONDITIONS. TO
THE E OF JOAQUIN...A 1009 MB LOW PRES IS NEAR 25.5N 57.5W.
PLEASE REFER TO THE SPECIAL FEATURES SECTION FOR MORE DETAILS. A
WEAKENING STATIONARY FRONT ENTERS THE FORECAST AREA NEAR 31N21W
THEN CONTINUES SW TO NEAR 28N35W TO 24N45W TO 24N50W. SCATTERED
MODERATE CONVECTION IS WITHIN 120 NM S OF THE FRONT BETWEEN 27W-
36W. A WEAK PRES GRADIENT IS NOTED ACROSS MUCH OF THE FORECAST
REGION...EXCEPT OVER THE NORTH CENTRAL ATLC WHERE FRESH TO
STRONG EASTERLY WINDS ARE OBSERVED PER SCATTEROMETER DATA DUE TO
THE PRES GRADIENT BETWEEN THE ATLC RIDGE ANCHORED ON A HIGH PRES
LOCATED WELL N OF AREA AND THE AFOREMENTIONED LOW PRES. A WEAK
SURFACE RIDGE DOMINATES THE MADEIRA/CANARY ISLANDS.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
GR
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