[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 300603
TWDAT

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

...SPECIAL FEATURES...

TROPICAL STORM JOAQUIN IS CENTERED NEAR 25.8N 71.7W AT 30/0300
UTC OR ABOUT 313 NM E OF THE NORTHWESTERN BAHAMAS MOVING WSW AT
4 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
24N TO 28N BETWEEN 68W AND 73W AND FROM 21N TO 24N BETWEEN 68W
AND 75W. JOAQUIN IS EXPECTED TO BECOME A HURRICANE LATER TONIGHT
OR WEDNESDAY. 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 16N19W 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 30W.

A TROPICAL WAVE IS IN THE CENTRAL ATLC WITH TILTED AXIS
EXTENDING FROM 16N36W SW TO A 1010 MB LOW PRESSURE CENTER
EMBEDDED IN THE MONSOON TROUGH NEAR 10N39W...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 08N TO 11N
BETWEEN 37W AND 44W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM A 1009 MB LOW IN THE E ATLC NEAR
11N23W TO 11N34W TO A 1010 MB LOW NEAR 10N39W TO 09N46W. THE
INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 09N46W TO
06N54W. 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 STRAITS
OF FLORIDA. AT THE SURFACE...LOW PRESSURE PREVAILS...EXCEPT IN
THE SW BASIN WHERE A WEAK 1011 MB HIGH PRESSURE CENTER IS BEING
ANALYZED. A 1010 MB LOW IS IN THE NW GULF NEAR 26N93W WITH
ASSOCIATED TROUGH EXTENDING NE TO 29N90W. DRY AIR AND STRONG
DEEP LAYER WIND SHEAR INHIBIT CONVECTION NEAR THE LOW. A SECOND
LOW OF 1008 MB IS OVER THE BORDER BETWEEN S-SW GEORGIA AND
NORTHERN FLORIDA WITH ASSOCIATED TROUGH EXTENDING FROM SOUTHERN
MISSISSIPPI TO THE LOW TO SE TO NE FLORIDA OFFSHORE WATERS.
FINALLY...A SURFACE TROUGH CONTINUES OVER THE YUCATAN PENINSULA
WITH AXIS EXTENDING NE ACROSS THE SE GULF TO 26N84W. BOTH AREAS
OF LOW PRESSURE ARE EMBEDDED IN A MODERATE MOIST LOW LEVEL
ENVIRONMENT THAT ENHANCES SCATTERED TO ISOLATED SHOWERS E OF
89W. LOOKING AHEAD...A COLD FRONT IS FORECAST TO FORM AND MOVE
ACROSS THE WESTERN 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 THAT IS PROVIDING 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
ALONG 10N FROM COSTA RICA TO NORTHERN COLOMBIA. CLOUDINESS AND
POSSIBLE 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 AND POSSIBLE ISOLATED
SHOWERS ACROSS THE ISLAND. 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 LATER TONIGHT OR WEDNESDAY. SEE
SPECIAL FEATURES. AHEAD OF JOAQUIN...A LOW PRESSURE CENTER
BETWEEN SOUTHERN GEORGIA AND NORTHERN FLORIDA IS ASSOCIATED WITH
A TROUGH THAT EXTENDS SE TO NE FLORIDA OFFSHORE WATERS WHERE IT
ENHANCES SCATTERED MODERATE CONVECTION AND TSTMS FROM 27N TO 31N
W OF 78W. 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 FROM 25N61W
TO THE LOW TO 23N55W. SCATTERED MODERATE CONVECTION AND TSTMS
ARE FROM 22N TO 26N BETWEEN 51W AND 60W. A BROAD UPPER TROUGH
OVER THE CENTRAL N ATLC SUPPORTS A COLD FRONT ALONG 30N25W TO
28N29W WHERE IT TRANSITIONS INTO A STATIONARY FRONT TO A 1014 MB
LOW NEAR 25N37W TO 25N50W TO 29N58W. SCATTERED MODERATE
CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE FRONTAL BOUNDARY.

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

$$
NR
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