[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301041
TWDAT

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

...SPECIAL FEATURES...

TROPICAL STORM JOAQUIN IS CENTERED NEAR 25.4N 72.5W AT 30/0900
UTC OR ABOUT 210 NM ENE OF THE CENTRAL BAHAMAS MOVING WSW AT 5
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM
SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. NUMEROUS
MODERATE/ISOLATED STRONG CONVECTION AND ISOLATED TSTMS ARE FROM
22N TO 28N BETWEEN 69W AND 75W AND FROM 19N TO 23N BETWEEN 68W
AND 73W. JOAQUIN IS EXPECTED TO BECOME A HURRICANE TODAY. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

A TROPICAL WAVE IS OVER THE E ATLC NEAR THE CAPE VERDE ISLANDS
WITH TILTED AXIS EXTENDING FROM 16N21W SW TO A 1009 MB LOW
PRESSURE CENTER EMBEDDED IN THE MONSOON TROUGH NEAR
11N23W...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 TO ISOLATED
MODERATE CONVECTION FROM 06N TO 16N E OF 31W.

A TROPICAL WAVE IS IN THE CENTRAL ATLC WITH TILTED AXIS
EXTENDING FROM 16N36W SW TO A 1009 MB LOW PRESSURE CENTER
EMBEDDED IN THE MONSOON TROUGH NEAR 11N39W...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. SCATTERED MODERATE CONVECTION IS FROM 07N TO 10N
BETWEEN 36W AND 44W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE COAST OF SENEGAL NEAR 14N16W
SW TO A 1009 MB LOW NEAR 11N23W TO 11N33W TO A 1009 MB LOW NEAR
11N39W TO 09N47W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 09N47W TO 09N60W. FOR CONVECTION INFORMATION SEE
THE TROPICAL WAVES SECTION.

...DISCUSSION...

GULF OF MEXICO...

SOUTHWESTERLY FLOW CONTINUE TO DOMINATE THE GULF WATERS BETWEEN
A MIDDLE TO UPPER LEVEL TROUGH EXTENDING FROM OVER THE MID-
MISSISSIPPI RIVER VALLEY SW TO A BASE OVER NE MEXICO AND AN
ELONGATED MIDDLE TO UPPER LEVEL RIDGE ANCHORED OVER THE YUCATAN
CHANNEL. AT THE SURFACE...LOW PRESSURE PREVAILS...EXCEPT IN THE
SW BASIN WHERE A WEAK 1012 MB HIGH PRESSURE CENTER IS BEING
ANALYZED. A 1009 MB LOW IS IN THE NW GULF NEAR 26N93W WITH
ASSOCIATED TROUGH EXTENDING NE TO 28N90W. DRY AIR AND STRONG
DEEP LAYER WIND SHEAR INHIBIT CONVECTION NEAR THE LOW.
FINALLY...A SURFACE TROUGH CONTINUES OVER THE YUCATAN PENINSULA
WITH AXIS EXTENDING NE ACROSS THE SE GULF TO 23N85W. MODERATE
MOIST LOW LEVEL ENVIRONMENT ENHANCES SCATTERED TO ISOLATED
SHOWERS AND TSTMS S OF 25N BETWEEN 85W AND 90W. LOOKING
AHEAD...A COLD FRONT IS FORECAST TO FORM AND MOVE ACROSS THE
GULF LATE THURSDAY INTO FRIDAY INTRODUCING MODERATE TO FRESH
NORTH-NORTHEASTERLY WINDS THROUGH SATURDAY.

CARIBBEAN SEA...

NORTHEASTERLY FLOW PREVAILS OVER MUCH OF THE CENTRAL AND WESTERN
CARIBBEAN AND PROVIDES OVERALL STABLE CONDITIONS AND FAIR
WEATHER. HOWEVER...ONE EXCEPTION LIES ACROSS THE FAR NW
CARIBBEAN WHERE UPPER LEVEL DIFFLUENCE ALONG WITH A LOW LEVEL
MOIST ENVIRONMENT SUPPORT ISOLATED SHOWERS W OF 85W. ANOTHER
AREA OF ONGOING CONVECTION IS OCCURRING IN THE SW BASIN IN
ASSOCIATION WITH CLOSE PROXIMITY OF THE MONSOON TROUGH ANALYZED
JUST S OF 10N FROM COSTA RICA TO NORTHERN COLOMBIA OFFSHORE
WATERS. CLOUDINESS AND SCATTERED/ISOLATED SHOWERS CONTINUES OVER
HISPANIOLA BEING SUPPORTED BY THE OUTER RAIN BANDS OF TROPICAL
STORM JOAQUIN IN THE SW N ATLC. OTHERWISE...MOSTLY CLEAR SKIES
PREVAIL ELSEWHERE SUPPORTED BY DRY AIR SUBSIDENCE FROM ALOFT AS
SHOWN BY WATER VAPOR IMAGERY. MAINLY MODERATE TO FRESH TRADES
PERSIST WITH THE STRONGEST WINDS NOTED ACROSS SOUTH-CENTRAL
PORTIONS.

...HISPANIOLA...

THE OUTER CLOUD/RAIN BANDS OF TROPICAL STORM JOAQUIN IN THE SW N
ATLC CONTINUE TO SUPPORT CLOUDINESS ACROSS THE ISLAND WITH
POSSIBLE ISOLATED SHOWERS OVER THE W AND CENTRAL HISPANIOLA THIS
MORNING. SCATTERED SHOWERS AND ISOLATED TSTMS ARE ALONG THE
NORTHERN COAST OF THE ISLAND AND OVER THE EASTERN DOMINICAN
REPUBLIC. INTERMITTENT SHOWERS ARE EXPECTED TO CONTINUE THROUGH
LATE THURSDAY AS JOAQUIN INTENSIFY INTO A HURRICANE AND MOVES
WSW TOWARDS THE BAHAMAS BEFORE TAKING A NORTHWARD TURN FRIDAY.

ATLANTIC OCEAN...

THE MAIN FEATURE OVER THE ATLC IS TROPICAL STORM JOAQUIN THAT IS
EXPECTED TO BECOME A HURRICANE TODAY. SEE SPECIAL FEATURES.
AHEAD OF JOAQUIN...REMNANTS OF A FORMER TROUGH ENHANCES
SCATTERED MODERATE CONVECTION FROM 27N TO 30N BETWEEN 77W AND
79W. TO THE EAST OF JOAQUIN...A LARGE AREA OF DISTURBED WEATHER
IS IN THE CENTRAL ATLC ASSOCIATED WITH A FRONTAL TROUGH AND THE
REMNANTS OF IDA. THE CENTER OF THIS DISTURBANCE IS A 1009 MB LOW
NEAR 24N57W FROM WHICH A TROUGH EXTENDS TO 22N51W. SCATTERED
MODERATE CONVECTION AND TSTMS ARE FROM 23N TO 30N BETWEEN 50W
AND 63W. A BROAD UPPER TROUGH OVER THE CENTRAL N ATLC SUPPORTS A
COLD FRONT ALONG 30N24W TO 28N29W WHERE IT TRANSITIONS INTO A
STATIONARY FRONT TO 23N40W TO 24N48W. SCATTERED MODERATE
CONVECTION IS WITHIN 120 NM N OF THE FRONTAL BOUNDARY.

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

$$
NR
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