[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 172351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI AUG 17 2012

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM HELENE IS CENTERED NEAR 20.7N 96.1W AT 18/0000
UTC OR ABOUT 80 NM ESE OF TUXPAN MEXICO AND ABOUT 140 NM SE OF
TAMPICO MEXICO MOVING N AT 02 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH
GUSTS TO 50 KT. WIDELY SCATTERED MODERATE CONVECTION IS FROM
19N-23N BETWEEN 93W-99W. SEE LATEST NHC INTERMEDIATE PUBLIC
ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC AND THE
FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22
KNHC FOR MORE DETAILS.

TROPICAL STORM GORDON IS CENTERED NEAR 34.3N 44.0W AT 17/2100
UTC OR ABOUT 850 NM W OF THE AZORES MOVING E AT 17 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 993 MB. MAXIMUM SUSTAINED WIND SPEED
IS 55 KT WITH GUSTS TO 65 KT. WIDELY SCATTERED MODERATE
CONVECTION IS FROM 33N-36N BETWEEN 41W-45W. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 11N24W TO 17N21W MOVING W AT 15-20
KT. THE WAVE IS EMBEDDED WITHIN AN EASTERN ATLC MONSOON GYRE
FOCUSED AROUND A 1009 MB LOW CENTERED NEAR 11N24W. TOTAL
PRECIPITABLE WATER IMAGERY INDICATES DEEP LAYER MOISTURE IN THE
VICINITY OF THE WAVE FROM 08N-15N BETWEEN 18W-24W WITH ISOLATED
MODERATE CONVECTION OCCURRING WITHIN 180 NM EITHER SIDE OF THE
WAVE AXIS.

TROPICAL WAVE EXTENDS FROM 10N39W TO 18N38W MOVING W AT 15-20
KT. THE WAVE REMAINS EMBEDDED WITHIN A BROAD AREA OF ENHANCED
DEEP LAYER MOISTURE AS NOTED ON THE TOTAL PRECIPITABLE WATER
IMAGERY FROM 06N-16N BETWEEN 30W-41W. GLOBAL MODEL DATA SHOWS
THAT THE WAVE COINCIDES WITH A 700 MB TROUGH AXIS ALONG 37W. DUE
TO A LARGE DRY AIRMASS ASSOCIATED WITH A SAHARAN AIR LAYER...NO
DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE.

TROPICAL WAVE EXTENDS FROM 12N63W TO 20N65W MOVING W AT 20-25
KT. MOVING WEST OF THE AREA OF SAHARAN DUST...ISOLATED SHOWERS
ARE MORE PLENTIFUL THIS EVENING ACROSS PUERTO RICO...THE LESSER
ANTILLES...AND THE EASTERN CARIBBEAN SEA OCCURRING FROM 13N-22N
BETWEEN 61W-69W. BROAD LOW-LEVEL CYCLONIC FLOW IS NOTED ACROSS
THE CARIBBEAN BETWEEN 60W-70W AND IS EXPECTED TO RESULT IN
INCREASED CLOUDINESS AND PRECIPITATION ACROSS HISPANIOLA THROUGH
THE WEEKEND.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 21N17W TO
17N20W THEN FROM 11N24W TO A 1010 LOW PRESSURE ARE NEAR 09N35W
TO 09N46W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
09N46W TO 08N53W TO 10N61W. SCATTERED MODERATE CONVECTION IS
FROM 05N-12N BETWEEN 26W-41W.

...DISCUSSION...

GULF OF MEXICO...
TROPICAL STORM HELENE CONTINUES TO IMPACT THE SW GULF WATERS
THIS EVENING AND IS FORECAST TO TRACK INLAND ACROSS EAST-CENTRAL
MEXICO BY EARLY SATURDAY. SCATTERED SHOWERS AND TSTMS ARE
OCCURRING S OF 25N W OF 92W OVER THE GULF WATERS INCLUDING
INLAND PORTIONS OF EAST-CENTRAL MEXICO FROM 19N-24N FROM THE
COAST TO 100W. LOCALLY HEAVY RAINFALL IS EXPECTED TO REMAIN A
PRIME HAZARD OVER THE NEXT FEW DAYS AS HIGH POTENTIAL EXISTS FOR
FLASH FLOODING AND MUDSLIDES OVER HIGHER TERRAIN. ELSEWHERE OVER
THE GULF...BROAD UPPER LEVEL TROUGHING IS OVER THE EASTERN CONUS
THAT DIPS SOUTHWARD OVER PORTIONS OF THE NE GULF AND FLORIDA
PENINSULA. WITH WEAK PRESSURE TROUGHING ACROSS THE SE CONUS AND
PEAK DAYTIME HEATING AND INSTABILITY...SCATTERED SHOWERS AND
TSTMS ARE OCCURRING N OF 25N E OF A LINE FROM 25N88W TO
29N95W...INCLUDING INLAND PORTIONS OF LOUISIANA...MISSISSIPPI...
AND THE FLORIDA PANHANDLE. AT THE SURFACE HOWEVER...A WEAK RIDGE
AXIS EXTENDS FROM THE SW NORTH ATLC ALONG 26N BUT CONTINUES TO
BE SECONDARY TO THE STRONGER MIDDLE TO UPPER LEVEL DYNAMICS.

CARIBBEAN SEA...
NORTHEASTERLY FLOW ALOFT ASSOCIATED WITH AN UPPER LEVEL
ANTICYCLONIC CIRCULATION CENTERED IN THE GULF OF MEXICO NEAR
22N94W CONTINUES TO PROVIDE AN OVERALL STABLE ATMOSPHERE ACROSS
MUCH OF THE WESTERN CARIBBEAN W OF 74W. A FEW ISOLATED SHOWERS
AND TSTMS ARE OCCURRING OVER PORTIONS OF CUBA DUE TO PEAK
DAYTIME HEATING AND INSTABILITY...HOWEVER THESE ARE EXPECTED TO
DIMINISH WITH SUNSET. THE MONSOON TROUGH AXIS EXTENDS ALONG 09N
AND IS PROVIDING FOCUS FOR SCATTERED SHOWERS AND TSTMS ACROSS
THE SW CARIBBEAN S OF 12N BETWEEN 74W-85W. FARTHER EAST...UPPER
LEVEL TROUGHING COVERS THE REMAINDER OF THE CARIBBEAN BETWEEN
62W-74W WITH AXIS EXTENDING FROM AN UPPER LEVEL LOW IN THE ATLC
NEAR 26N64W TO 19N70W TO 12N80W. WHILE WATER VAPOR IMAGERY
INDICATES A RELATIVELY DRY ATMOSPHERE ALOFT...THE PRESENCE OF A
TROPICAL WAVE ALONG 64W IS GENERATING ISOLATED SHOWERS E OF 70W
THIS EVENING.

ATLANTIC OCEAN...
BROAD MIDDLE TO UPPER LEVEL TROUGHING IS OVER THE EASTERN CONUS
AND THE INFLUENCE OF THE TROUGHING AND ASSOCIATED DIFFLUENCE
ALOFT TO THE EAST OF THE TROUGH AXIS IS GENERATING SCATTERED
SHOWERS AND TSTMS ACROSS THE SW NORTH ATLC THIS EVENING N OF 23N
W OF 71W...INCLUDING PORTIONS OF THE FLORIDA PENINSULA. EMBEDDED
WITHIN THIS TROUGHING...AN UPPER LEVEL LOW IS CENTERED NEAR
27N64W THAT CONTINUES TO GENERATE ISOLATED SHOWERS OVER THE AREA
FROM 23N-32N BETWEEN 63W-71W. ELSEWHERE ACROSS THE REMAINDER OF
THE CENTRAL AND EASTERN ATLC...A BROAD SURFACE RIDGE SPANS THE
LENGTH OF THE BASIN ALONG 26N ANCHORED BY A 1020 MB HIGH
CENTERED NEAR 26N48W. THE RIDGE AXIS EXTENDS WESTWARD ALONG 26N
INTO THE GULF OF MEXICO...YET AS MENTIONED ABOVE...THE
OVERRIDING MIDDLE TO UPPER LEVEL DYNAMICS ACROSS THE SW NORTH
ATLC ARE CONTRIBUTING TO THE CONVECTION W OF 63W. OTHERWISE...
THE SAHARAN AIR LAYER AND ASSOCIATED DUST IS MAINTAINING STABLE
CONDITIONS FROM 20N-32N E OF 63W TO THE AFRICAN COAST.

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

$$
HUFFMAN




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