[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 011032
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1030 UTC.

...SPECIAL FEATURES...

MAJOR HURRICANE JOAQUIN WILL BATTER THE CENTRAL BAHAMAS WITH
HURRICANE FORCE WINDS...STORM SURGE...AND HEAVY RAIN THROUGH
TONIGHT. THE CENTER OF JOAQUIN AT 0900 UTC IS LOCATED NEAR 23.4N
73.7W OR ABOUT 19 NM N OF SAMANA CAYS BAHAMAS AND MOVES WSW AT 4
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 105 KT WITH GUSTS TO 130 KT. NUMEROUS
STRONG CONVECTION IS FROM 21N TO 25N BETWEEN 71W AND 75W.
NUMEROUS MODERATE CONVECTION IS ELSEWHERE FROM 18N TO 26N
BETWEEN 69W AND 77W. 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 27N65W TO THE LOW CENTER TO
24N48W. SCATTERED TO ISOLATED MODERATE CONVECTION AND TSTMS ARE
FROM 20N TO 29N BETWEEN 50W 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 24W...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 06N TO 18N BETWEEN 19W AND
28W.

A TROPICAL WAVE IS IN THE CENTRAL ATLC WITH AXIS NEAR 42W
CONNECTED TO A 1009 MB LOW OBSERVED IN ASCAT DATA NEAR 11N42W
...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 13N16W
TO 12N23W...THEN RESUMES W OF A TROPICAL WAVE NEAR 11N25W TO
13N37W TO 10N52W. THE ITCZ WAS NOT DISCERNIBLE. 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 30N84W TO 28N90W TO 28N96W. IT
ALSO SUPPORTS A 1009 MB LOW PRES LOCATED NEAR 23N91W WITH A
TROUGH EXTENDING FROM 26N88W TO THE LOW TO 22N94W. 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 TODAY...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 20-30 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 EXTEND ACROSS THE
ISLAND WHERE SCATTERED SHOWERS AND TSTMS ARE OBSERVED. SIMILAR
ACTIVITY IS EXPECTED TO CONTINUE THROUGH THE NEXT 24 HOURS AS
HURRICANE JOAQUIN MOVES SW TOWARD THE BAHAMAS TODAY.

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 27N65W TO THE LOW CENTER
TO 24N48W. 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 30N22W THEN CONTINUES SW TO NEAR
28N30W TO 27N40W TO 29N46W. SCATTERED MODERATE CONVECTION IS N
OF 26N BETWEEN 16W AND 50W. A WEAK SURFACE RIDGE DOMINATES THE
MADEIRA/CANARY ISLANDS.

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

$$
NR
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