[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 242351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI AUG 24 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...

THE CENTER OF TROPICAL STORM ISAAC AT 24/0000 UTC IS NEAR 17.3N
72.0W. THIS POSITION IS ABOUT 80 NM SSE OF PORT AU PRINCE
HAITI...OR ABOUT 235 NM SE OF GUANTANAMO CUBA. ISAAC IS MOVING
NW AT 9 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 992 MB.
THE MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 KT.
PLEASE READ THE FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY...MIATCPAT4/WTNT34
KNHC FOR MORE DETAILS. A LARGE RAINBAND ON THE EAST SIDE OF
ISAAC IS PRODUCING A LARGE AREA OF STRONG CONVECTION FROM
14N-18N BETWEEN 67W-69W. NUMEROUS MODERATE CONVECTION IS
ELSEWHERE FROM 12N-20N BETWEEN 66W-75W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS ALSO IMPACTING THE
BAHAMAS AND SOUTH FLORIDA. ALTHOUGH THIS AREA OF CONVECTION IS
REMOVED FROM THE MAIN RAINBANDS AROUND ISAAC...THE WIDE CYCLONIC
CIRCULATION OF ISAAC DOES EXTEND ACROSS THESE AREAS AND IS
CONTRIBUTING TO THE ACTIVITY. AN UPPER LEVEL TROUGH OVER THE
EASTERN GULF OF MEXICO IS ALSO PROVIDING DIFFLUENCE ALOFT OVER
SE FLORIDA AND THE BAHAMAS...WHICH IS FURTHER CONTRIBUTING TO
THE DEVELOPMENT OF STRONG CONVECTION.

A TROPICAL WAVE EXTENDS FROM 20N20W ACROSS THE CAPE VERDE
ISLANDS TO A 1007 MB SURFACE LOW NEAR 14N25W MOVING WNW NEAR 12
KT. THE WAVE/LOW LIES WITHIN A LARGE SURGE OF DEEP LAYER
MOISTURE PRESENT ACROSS MUCH OF THE EASTERN TROPICAL ATLC. THE
SYSTEM IS FAIRLY DISORGANIZED WITH THE MAJORITY OF THE
CONVECTION WELL TO THE WEST OF THE LOW CENTER. CURRENTLY
SCATTERED MODERATE/STRONG CONVECTION IS FROM 7N-11N BETWEEN
27W-35W...WITH SCATTERED MODERATE/ISOLATED STRONG CONVECTION
FROM 13N-16N BETWEEN 26W-30W. ENVIRONMENTAL CONDITIONS ARE
SOMEWHAT CONDUCIVE FOR FURTHER DEVELOPMENT OF THE SYSTEM OVER
THE NEXT COUPLE OF DAYS.

...TROPICAL WAVES...

A TROPICAL WAVE IS IN THE VICINITY OF THE CAPE VERDE ISLANDS.
SEE SPECIAL FEATURES SECTION ABOVE.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
MAURITANIA AT 18N16W CONTINUING TO A 1007 MB SURFACE LOW
CONNECTED TO A TROPICAL WAVE AT 13N25W AND ALONG 11N31W 13N41W.
THE ITCZ BEGINS AT 10N50W TO 8N59W. NO DEEP CONVECTION IS NEAR
THE MONSOON TROUGH/ITCZ AXIS EXCEPT FOR CONVECTION ALREADY
DISCUSSED WITH THE TROPICAL WAVE IN THE SPECIAL FEATURES SECTION.

...DISCUSSION...

THE GULF OF MEXICO...
WEAK SURFACE RIDGING REMAINS OVER THE GULF OF MEXICO EXTENDING
FROM THE NE CONUS. HOWEVER...AN UPPER LEVEL TROUGH COVERS THE
BASIN EXTENDING FROM SOUTH CAROLINA TO WESTERN CUBA. DRY AIR IS
SINKING ACROSS THE NE CORNER OF THE BASIN PROVIDING FAIR
CONDITIONS...BUT SOUTH FLORIDA LIES IN THE DIFFLUENT SIDE OF THE
UPPER TROUGH...WHICH IS HELPING ENHANCE
SHOWERS/THUNDERSTORMS...SOME WHICH ARE SEVERE. LOW-LEVEL
MOISTURE IS BEING BROUGHT FROM THE EAST ACROSS THIS AREA DUE TO
THE LARGE CYCLONIC CIRCULATION OF TROPICAL STORM ISAAC SOUTH OF
HISPANIOLA. STRONG SHOWERS/THUNDERSTORMS ARE ALSO OVER THE
YUCATAN PENINSULA. A SHORTWAVE UPPER TROUGH IS OVER THE FAR
WESTERN GULF...WHICH IS HELPING SUPPORT SHOWERS/THUNDERSTORMS IN
THE NW GULF N OF 25N BETWEEN 90W-96W. SHOWERS/THUNDERSTORMS ARE
EXPECTED TO REMAIN OVER THE NW GULF. SHOWERS/THUNDERSTORMS WILL
ALSO CONTINUE ACROSS THE SE GULF AS TROPICAL STORM ISAAC MOVES
CLOSER. WINDS WILL ALSO BEGIN TO INCREASE OVER THE SE GULF
THROUGHOUT THE WEEKEND. ALL INTERESTS IN THE EASTERN GULF SHOULD
MONITOR THE PROGRESS OF ISAAC.

THE CARIBBEAN SEA...
TROPICAL STORM ISAAC IS DOMINATING THE CENTRAL CARIBBEAN
PRODUCING WIDESPREAD SHOWERS/THUNDERSTORMS FROM VENEZUELA TO
HISPANIOLA AND CUBA. ALL INTERESTS IN THE NORTHERN CARIBBEAN
SHOULD MONITOR THE PROGRESS ON ISAAC. FLOODING AND MUDSLIDES ARE
POSSIBLE ACROSS THE ISLANDS IMPACTED. THE WESTERN CARIBBEAN IS
STILL UNDER FAIR CONDITIONS DUE TO TO DRY AIR ALOFT COVERING
MUCH OF THE AREA WEST OF 77W. THE LARGE CIRCULATION OF ISAAC IS
PROVIDING CYCLONIC SURFACE FLOW ACROSS THE ENTIRE BASIN WITH
LIGHT WINDS ONLY ACROSS THE SW CARIBBEAN. SOME STRONG
SHOWERS/THUNDERSTORMS HAVE ALSO RECENTLY POPPED UP OVER MUCH OF
PANAMA. THIS IS LIKELY INFLUENCED BY THE E PACIFIC MONSOON
TROUGH. TROPICAL STORM ISAAC WILL CONTINUE TO DOMINATE THE
WEATHER PATTERN ACROSS THE CARIBBEAN AS IT CONTINUES TO MOVE NW
ACROSS HAITI AND THEN CUBA BEFORE HEADING INTO THE FLORIDA
STRAITS.

THE ATLANTIC OCEAN...
THE COMBINATION OF LOW-LEVEL MOISTURE BEING DRAWN ACROSS THE
BAHAMAS DUE TO TROPICAL STORM ISAAC AND DIFFLUENCE ALOFT AROUND
AN UPPER TROUGH OVER THE EASTERN GULF IS HELPING PRODUCE
SCATTERED SHOWERS/THUNDERSTORMS ACROSS MUCH OF THE BAHAMAS AND
SOUTH FLORIDA S OF 28N W OF 70W. UPPER LEVEL RIDGING...OUTFLOW
FROM ISAAC COVERS THE MAJORITY OF THE WEST ATLC PROVIDING WEAK
SURFACE RIDGING N OF THE CIRCULATION OF ISAAC. AN UPPER LEVEL
LOW IS TO THE EAST NEAR 23N55W. IT IS HELPING PRODUCE SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS N OF 29N BETWEEN
60W-62W...ISOLATED SHOWERS/THUNDERSTORMS FROM 22N-30N BETWEEN
50W-58W...AND SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM
20N-23N BETWEEN 46W-49W. THIS LAST AREA OF ACTIVITY IS
ASSOCIATED WITH THE REMNANTS OF T.D. JOYCE CURRENTLY CENTERED
NEAR 18N47W. THE LOW CENTER HAS MOSTLY DISSIPATED AND WILL
LIKELY BE DROPPED FROM THE ANALYSIS AT 0000 UTC. THE REMAINDER
OF THE BASIN IS DOMINATED BY SURFACE RIDGING AROUND A 1022 MB
SURFACE HIGH AT 33N42W. THE HIGH IS SUPPORTED BY AN UPPER LEVEL
RIDGE CENTERED NEAR 33N36W. A NARROW UPPER TROUGH IS TO THE E
EXTENDING FROM THE MADEIRA ISLANDS TO W OF THE CAPE VERDE
ISLANDS...BUT IS NOT CAUSING ANY ACTIVE WEATHER IN THE
DISCUSSION AREA. THE LAST VISIBLE SATELLITE IMAGES OF THE DAY
INDICATE A LARGE AREA OF DUST EXTENDS AROUND THE TROPICAL WAVE
IN THE EAST TROPICAL ATLC AND AROUND THE REMNANTS OF T.D. JOYCE.
A FEW STATIONS IN THE EASTERN CARIBBEAN ARE ALSO REPORTING DUST.
THE DUST IS HELPING CONTRIBUTE TO FAIR CONDITIONS ACROSS MUCH OF
THE ATLC BASIN.

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

$$
WALTON





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