[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 161801
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 16 2011

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

HURRICANE MARIA IS CENTERED NEAR 46.4N 53.8W AT 16/1800 UTC OR
ABOUT 35 NM W-SW OF CAPE RACE NEWFOUNDLAND MOVING NE AT 45 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 983 MB. MAXIMUM SUSTAINED
WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. ISOLATED MODERATE
CONVECTION IS FROM 44N-47N BETWEEN 54W-56W. AS MARIA BECOMES
ABSORBED BY A COLD FRONT ACROSS THE WESTERN NORTH ATLC WATERS
OVER THE NEXT 24 HOURS...SURFACE TROUGHING EXTENDS FROM SE OF
THE CENTER OF MARIA NEAR 41N55W TO 30N69W. ISOLATED MODERATE
CONVECTION IS WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH.
SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT4/WTNT34 KNHC AND THE FULL FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W
ALONG 11N26W TO 09N31W TO 07N45W. THE INTERTROPICAL CONVERGENCE
ZONE AXIS EXTENDS FROM 07N45W TO 08N59W. A PAIR OF 1012 MB
SURFACE LOWS ARE LOCATED ALONG THE MONSOON TROUGH NEAR 11N17W
AND 09N31W WHICH CONTINUES TO FOCUS LOW-LEVEL DEEP TROPICAL
MOISTURE FROM 04N-15N E OF 40W. THIS LARGE AND STRETCHED OUT
AREA ALONG THE MONSOON TROUGH IS PRODUCING WIDELY SCATTERED
MODERATE CONVECTION FROM 04N-11N BETWEEN 11W-40W...AND FROM
11N-14N BETWEEN 18W-24W. FARTHER WEST...WIDELY SCATTERED
MODERATE CONVECTION IS FROM 08N-12N BETWEEN 52W-64W...LOCATED N
OF THE ITCZ AXIS. THIS AREA OF CONVECTION IS LIKELY ENHANCED DUE
TO SOUTHWESTERLY MIDDLE TO UPPER LEVEL FLOW ASSOCIATED WITH AN
UPPER LEVEL LOW CENTERED NEAR 18N62W.

...DISCUSSION...

GULF OF MEXICO...
NORTHWEST TO NORTH FLOW ALOFT IS DOMINATE OVER THE GULF BASIN
THIS AFTERNOON ON THE EASTERN PERIPHERY OF A LARGE ANTICYCLONIC
CIRCULATION CENTERED OVER CENTRAL MEXICO NEAR 22N102W. WATER
VAPOR IMAGERY INDICATES THAT MUCH OF THE GULF IS UNDER THE
INFLUENCE OF MODERATE TO STRONG MIDDLE TO UPPER LEVEL SUBSIDENCE
AND DRY AIR. THIS UPPER LEVEL RIDGING IS SUPPORTIVE OF A SURFACE
RIDGE EXTENDING FROM THE SW NORTH ATLC WATERS ACROSS THE
SOUTHERN FLORIDA PENINSULA TO A 1018 MB HIGH CENTERED NEAR
27N85W THEN EXTENDS SW TO THE MEXICO COAST NEAR 20N97W. THE
RIDGE IS FORECAST TO DISSIPATE OVER THE NEXT 24 HOURS AS A COLD
FRONT IS CURRENTLY ANALYZED FROM THE BIG BEND REGION OF FLORIDA
NEAR 30N83W SW TO 27N90W WHERE IT BECOMES STATIONARY TO THE
TEXAS COAST NEAR GALVESTON ISLAND. THIS COLD FRONT HAS
INTRODUCED A MILDER AIRMASS TO THE NORTH-CENTRAL AND PORTIONS OF
THE NE GULF WATERS WHICH IS EXPECTED TO WEAKEN AND BECOME MORE
DIFFUSE THROUGH SATURDAY. SOUTH OF THE FRONT...MUCH OF THE
REMAINDER OF THE GULF IS UNDER MOSTLY CLEAR SKIES AND FAIR
WEATHER CONDITIONS HOWEVER A FEW ISOLATED SHOWERS AND TSTMS ARE
OCCURRING ACROSS THE WESTERN GULF W OF A LINE FROM 28N96W TO
19N91W DUE TO LOW-LEVEL MOISTURE RETURN FLOW ON 10 TO 15 KT SE
WINDS.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH EXTENDS ACROSS THE SW NORTH ATLC WITH AXIS
ALONG 80W TO A BASE IN THE WESTERN CARIBBEAN NEAR 20N80W. WATER
VAPOR IMAGERY INDICATES THAT MOSTLY DRY AIR AND STRONG
SUBSIDENCE IS EVIDENT OVER MUCH OF THE NW CARIBBEAN THIS
AFTERNOON. HOWEVER...WEAK SURFACE TROUGHING REMAINS IN PLACE W
OF 72W AND LOW-LEVEL MOISTURE CONTINUES TO FOCUS ALONG A SURFACE
TROUGH ANALYZED FROM 12N-17N ALONG 80W. SCATTERED SHOWERS AND
TSTMS ARE OCCURRING OVER THE SW CARIBBEAN FROM 10N-14N BETWEEN
79W-82W...WITH MORE ISOLATED SHOWERS AND TSTMS COVERING A LARGER
AREA FROM 09N-21N BETWEEN 75W-85W...INCLUDING PORTIONS OF
EASTERN CUBA. THIS AREA OF LOW-LEVEL MOISTURE IS FORECAST TO
SLIDE WESTWARD OVER THE NEXT FEW DAYS AND PROVIDE CONVECTIVE
ACTIVITY TO MUCH OF CENTRAL AMERICA THROUGH THE WEEKEND. FARTHER
TO THE EAST...AN UPPER LEVEL LOW IS CENTERED OVER THE LEEWARD
ISLANDS NEAR 18N62W AND HAS CONTINUED TO SLOWLY DRIFT WESTWARD.
SOUTHWESTERLY MIDDLE TO UPPER LEVEL FLOW IS ADVECTING MOISTURE
NORTHWARD FROM THE INTERTROPICAL CONVERGENCE ZONE BETWEEN
54W-64W AND IS GENERATING WIDELY SCATTERED SHOWERS AND ISOLATED
TSTMS OVER PORTIONS OF THE WINDWARD ISLANDS AND SE CARIBBEAN S
OF 14N E OF 66W. CLOSER NEAR THE CENTER OF THE UPPER LOW...
ISOLATED SHOWERS AND TSTMS ARE N OF 18N BETWEEN 61W-64W.

ATLANTIC OCEAN...
HURRICANE MARIA IS WELL NORTH OF THE DISCUSSION AREA...AND IS
QUICKLY BECOMING ABSORBED INTO A COLD FRONTAL BOUNDARY EXTENDING
FROM EAST OF NOVA SCOTIA NEAR 46N60W SOUTHWESTWARD INTO THE AREA
NEAR 32N80W THEN TO NE FLORIDA NEAR 30N82W. THIS FRONT IS
SUPPORTED ALOFT BY AN UPPER LEVEL TROUGH AXIS OFF THE EASTERN
SEABOARD OF THE U.S. FROM WEST OF MARIA NEAR NOVA SCOTIA TO
32N75W AND INTO THE WESTERN CARIBBEAN SEA. THE COLD FRONT
REMAINS RELATIVELY INACTIVE CONVECTIVELY... HOWEVER A FEW
ISOLATED SHOWERS AND TSTMS ARE OCCURRING FROM 31N-33N BETWEEN
76W-79W. FARTHER EAST...A SURFACE TROUGH...ANALYZED IN THE WAKE
OF MARIA...EXTENDS INTO THE DISCUSSION AREA NEAR 32N64W TO
30N70W TO THE SE BAHAMAS NEAR 23N75W TO EASTERN CUBA. LOW-LEVEL
CONVERGENCE IS MAXIMIZED ALONG THIS BOUNDARY GENERATING WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 120 NM EITHER SIDE
OF A LINE FROM 32N65W TO 21N78W. FARTHER SE...A CUT OFF UPPER
LEVEL LOW IS CENTERED NEAR 18N62W. A FEW ISOLATED SHOWERS AND
TSTMS ARE OCCURRING FROM 06N-24N BETWEEN 54W-64W. THE REMAINDER
OF THE CENTRAL ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE N
OF 20N BETWEEN 40W-62W ANCHORED BY A 1024 MB HIGH CENTERED NEAR
34N49W. FINALLY...OVER THE EASTERN ATLC...AN UPPER LEVEL LOW
CENTERED SOUTH OF THE AZORES NEAR 35N31W SUPPORTS A 1019 MB LOW
NEAR 35N30W AND ASSOCIATED COLD FRONT DRAPED SW FROM THE LOW TO
31N39W. AN EARLIER MORNING ASCAT PASS AROUND 16/1158 UTC SHOWED
THE FRONT REMAINS RATHER WEAK WITH NE WINDS NORTH OF THE
BOUNDARY TO 20 KT. EMBEDDED WITHIN THE SURFACE TROUGHING TO THE
SE OF THE FRONT...A 1018 MB LOW IS CENTERED NEAR 28N30W WITH A
NARROW LINE OF ISOLATED SHOWERS EXTENDING SW FROM THE LOW TO
21N38W.

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

$$
HUFFMAN




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