[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 010554
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU OCT 01 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0545 UTC.

...SPECIAL FEATURES...

JOAQUIN BECOMES A CATEGORY 3 HURRICANE AS IT MOVES TOWARD THE
CENTRAL BAHAMAS. THE CENTER OF JOAQUIN IS LOCATED NEAR 23.8N
73.1W AT 01/0300 UTC OR ABOUT 148 NM E OF THE CENTRAL BAHAMAS
MOVING TOWARD THE SOUTHWEST AT 5 KT. THE CENTER OF JOAQUIN IS
EXPECTED TO MOVE NEAR OR OVER PORTIONS OF THE CENTRAL BAHAMAS
OVERNIGHT AND THU. MAXIMUM SUSTAINED WIND SPEED IS 100 KT WITH
GUSTS TO 120 KT. NUMEROUS STRONG CONVECTION IS FROM 22N TO 25N
BETWEEN 71W AND 74W. NUMEROUS MODERATE CONVECTION IS ELSEWHERE
FROM 20N TO 26N BETWEEN 69W AND 76W. THE OUTER RAINBANDS OF
JOAQUIN ARE ALSO AFFECTING EASTERN CUBA...THE WINDWARD PASSAGE
AND HISPANIOLA WHERE SCATTERED MODERATE CONVECTION AND TSTMS ARE
NOTED IN SATELLITE IMAGERY. JOAQUIN IS EXPECTED TO PRODUCE 10-15
INCHES OF RAIN OVER MUCH OF THE CENTRAL BAHAMAS AND 5-10 INCHES
OVER THE SOUTHEASTERN BAHAMAS THROUGH FRI NIGHT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS.

A 1008 MB LOW PRES IS ANALYZED NEAR 25N56W ALONG WITH AN OLD
FRONTAL TROUGH THAT EXTENDS FROM 26N63W TO THE LOW CENTER TO
24N51W. SCATTERED TO ISOLATED MODERATE CONVECTION AND TSTMS ARE
FROM 20N TO 29N BETWEEN 48W AND 64W. CLOUDINESS AND TSTMS
ASSOCIATED WITH THIS SYSTEM HAVE BECOME A LITTLE BETTER
ORGANIZED. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE CONDUCIVE
FOR A TROPICAL DEPRESSION TO FORM BY THE WEEKEND WHILE THE LOW
MOVES SLOWLY NW TO N. 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 OVER THE E ATLC MOVING ACROSS THE CAPE VERDE
ISLANDS WITH AXIS NEAR 23W...MOVING W AT 5 KT. CIRA LAYER
PRECIPITABLE WATER IMAGERY SHOW THE WAVE IS EMBEDDED IN A
MODERATE MOIST ENVIRONMENT FROM THE SURFACE TO 850 MB THAT ALONG
WITH MIDDLE TO UPPER LEVEL DIFFLUENCE IN THE WAVE REGION SUPPORT
SCATTERED MODERATE CONVECTION FROM 10N TO 18N BETWEEN 18W AND
28W.

A TROPICAL WAVE IS IN THE CENTRAL ATLC WITH AXIS NEAR
40W...MOVING W AT 5-10 KT. CIRA LAYER PRECIPITABLE WATER IMAGERY
SHOW THE WAVE IS EMBEDDED IN A MODERATE MOIST ENVIRONMENT FROM
THE SURFACE TO 850 MB. HOWEVER...SOME DRY AIR INTRUSION IS ALSO
DEPICTED IN THE N-NW WAVE ENVIRONMENT...WHERE METEOSAT ENHANCED
IMAGERY SHOW DRY AIR AND DUST. STRONG DEEP LAYER WIND SHEAR
INFLUENCES LACK OF CONVECTION.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE COAST OF AFRICA NEAR 14N17W
TO 13N23W...THEN RESUMES W OF A TROPICAL WAVE NEAR 12N25W TO
13N39W...RESUMING W OF A SECOND TROPICAL WAVE NEAR 12N41W TO
09N49W. THE ITCZ CONTINUES FROM 09N49W TO 10N61W. FOR CONVECTION
INFORMATION SEE THE TROPICAL WAVES SECTION.

...DISCUSSION...

GULF OF MEXICO...

A SHARP MIDDLE- TO UPPER-LEVEL TROUGH EXTENDS FROM ILLINOIS TO
LOUISIANA SW TO A BASE OVER THE SW GULF OF MEXICO. 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. THE
TROUGH ALOFT SUPPORTS A FRONTAL SYSTEM ANALYZED AS A COLD FRONT
FROM THE FLORIDA PANHANDLE NEAR 30N87W TO SOUTHERN LOUISIANA
NEAR 29N91W TO 29N94W. IT ALSO SUPPORTS A 1009 MB LOW PRES
LOCATED NEAR 24N91W WITH A TROUGH EXTENDING NE TO 28N84W. EXCEPT
FOR THE SE GULF AND THE YUCATAN CHANNEL...THE CIRA LPW IMAGERY
SHOW LOW LEVEL DRY AIR ACROSS THE BASIN THAT ALONG WITH STRONG
DEEP LAYER ENVIRONMENTAL WIND SHEAR HINDER CONVECTION. LOOKING
AHEAD...THE COLD FRONT IS FORECAST TO REACH THE SE GULF AND
START TO DISSIPATE LATE THU. 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 CENTRAL
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 OVERNIGHT 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. THE OUTER RAINBANDS OF JOAQUIN REACH EASTERN CUBA...THE
WINDWARD PASSAGE AND GREAT PORTIONS OF HISPANIOLA WHERE
SCATTERED MODERATE CONVECTION AND TSTMS ARE OBSERVED. IN THE SW
BASIN...THE MONSOON TROUGH GENERATES SOME SHOWER AND TSTMS
ACTIVITY OVER PARTS OF PANAMA AND COSTA RICA AND ADJACENT
WATERS. 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 E 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 REACH THE NORTHERN AND
WESTERN PORTIONS OF THE ISLAND WHERE SCATTERED HEAVY SHOWERS AND
TSTMS ARE OBSERVED. SIMILAR ACTIVITY IS EXPECTED TO CONTINUE
THROUGH THE NEXT 24 HOURS AS HURRICANE JOAQUIN MOVES SW TOWARD
THE BAHAMAS OVERNIGHT 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 1008 MB LOW PRES IS NEAR 25N56W ALONG WITH
AN OLD FRONTAL TROUGH THAT EXTENDS FROM 26N63W TO THE LOW CENTER
TO 24N51W. 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. PLEASE REFER TO THE SPECIAL
FEATURES SECTION FOR MORE DETAILS. A WEAKENING STATIONARY FRONT
ENTERS THE FORECAST AREA NEAR 31N23W THEN CONTINUES SW TO NEAR
28N31W TO 26N38W TO 28N43W. SCATTERED MODERATE CONVECTION IS N
OF 25N BETWEEN 21W AND 40W. A WEAK SURFACE RIDGE DOMINATES THE
MADEIRA/CANARY ISLANDS.

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

$$
NR
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