[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251205
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT AUG 25 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1145 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM ISAAC AT 25/1200 UTC WAS LOCATED
NEAR 19.7N 73.8W. THIS POSITION IS ABOUT 150 KM ESE OF
GUANTANAMO CUBA. ISAAC IS MOVING NW AT 12 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 998 MB. THE MAXIMUM SUSTAINED WIND
SPEED IS 50 KT WITH GUSTS TO 60 KT. PLEASE READ THE
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
AND THE PUBLIC ADVISORY...MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS.

A 1006 MB LOW AND ASSOCIATED TROPICAL WAVE AXIS IS LOCATED SW OF
THE CAPE VERDE ISLANDS NEAR 13N28W MOVING WNW AT ABOUT 12 KT.
THIS FEATURE IS EMBEDDED IN THE BROAD SCALE MONSOON GYRE ON
SATELLITE IMAGERY...WITHIN A LARGE SURGE OF DEEP LAYER MOISTURE
PRESENT ACROSS MUCH OF THE EASTERN TROPICAL ATLC. A THICK LAYER
OF SAHARAN DUST SURROUNDS THE WAVE AND ASSOCIATED LOW...
INHIBITING THIS SYSTEM TO GENERATE CONVECTION NEAR THE CENTER.
THEREFORE...THE SYSTEM REMAINS FAIRLY DISORGANIZED WITH THE
MAJORITY OF THE CONVECTION TO THE WEST AND WELL TO THE SW OF THE
LOW CENTER. SCATTERED MODERATE CONVECTION IS FROM 11N-17N
BETWEEN 27W-32W...AND FORM 7N-10N BETWEEN 32W-42W. ENVIRONMENTAL
CONDITIONS ARE MARGINALLY CONDUCIVE FOR DEVELOPMENT. THIS SYSTEM
HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

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

THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA...ENTERING THE ERN
TROPICAL ATLC OVER THE COAST OF MAURITANIA AT 20N16W CONTINUING
WSW TO THE SPECIAL FEATURE 1006 MB LOW AND ASSOCIATED TROPICAL
WAVE AT 13N28W AND ALONG 8N35W TO 9N44W...WHERE THE ITCZ
CONTINUES ALONG 12N53W TO NEAR THE COAST OF VENEZUELA AT 11N63W.
WHILE NO CONVECTION IS NOTED AROUND THE ITCZ...THE CONVECTION
NEAR THE MONSOON TROUGH IS DISCUSSED IN THE SPECIAL FEATURES
SECTION ABOVE.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL NORTHERLY FLOW COVERS MOST OF THE BASIN...BEHIND THE
BASE OF AN UPPER TROUGH THAT MOVES ACROSS THE FAR ERN REGION OF
THE GULF. THIS FEATURE IS PROVIDING SOME WEAK TO MODERATE
DIFFLUENCE ALOFT OVER THE N-CENTRAL BASIN...GENERATING AN AREA
OF WIDELY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS N OF 26N
BETWEEN 87W-95W. DRY AIR AND STRONG SUBSIDENCE IS SINKING ACROSS
THE ERN BASIN PROVIDING FAIR CONDITIONS E OF 87W. HOWEVER...LOW
LEVEL MOISTURE AND STRONG CONVECTION IS BEING BROUGHT FROM THE
EAST ACROSS THE STRAITS OF FLORIDA DUE TO THE LARGE CYCLONIC
WIND FIELD OF TROPICAL STORM ISAAC. SOME OF THIS ACTIVITY HAS
ENTERED THE AREA THIS MORNING NOTED ON DOPPLER RADAR AS A FEW
SQUALL LINES S OF 25N E OF 83W. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO REMAIN OVER THE NW GULF. SIMILAR CONVECTION 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.

CARIBBEAN SEA...
TROPICAL STORM ISAAC CONTINUES TO BE THE MAIN WEATHER CONCERN IN
THE CARIBBEAN SEA...GENERATING CONSIDERABLE CONVECTION OVER THE
CENTRAL AND ERN BASIN. ALL INTERESTS IN THE NORTHERN CARIBBEAN
SHOULD MONITOR THE PROGRESS ON ISAAC. FLOODING AND MUDSLIDES ARE
DEFINITE HAZARDS ACROSS THE ISLANDS IMPACTED. THE W AND SW
CARIBBEAN BASINS ARE STILL UNDER FAIR CONDITIONS DUE TO TO DRY
AIR ALOFT COVERING MUCH OF THE AREA WEST OF 80W. 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 AND THUNDERSTORMS HAVE ALSO RECENTLY POPPED
UP OVER MUCH OF PANAMA AND NRN COLOMBIA...LIKELY INFLUENCED BY
THE ERN PACIFIC MONSOON TROUGH. ISAAC WILL CONTINUE TO DOMINATE
THE WEATHER PATTERN ACROSS THE CARIBBEAN AS IT CONTINUES TO MOVE
NW ACROSS THE WINDWARD PASSAGE AND THEN ERN CUBA BEFORE HEADING
INTO THE FLORIDA STRAITS.

ATLANTIC OCEAN...
THE COMBINATION OF LOW-LEVEL MOISTURE BEING DRAWN ACROSS THE NW
BAHAMAS DUE TO TROPICAL STORM ISAAC AND DIFFLUENCE ALOFT AROUND
AN UPPER TROUGH OVER THE EASTERN GULF IS HELPING PRODUCE
SCATTERED HEAVY SHOWERS AND THUNDERSTORMS ACROSS THE BAHAMAS AND
STRAITS OF FLORIDA S OF 28N W OF 71W. THE OUTER CONVECTION BANDS
ASSOCIATED TO ISAAC ARE ALSO AFFECTING THE NRN COASTAL WATERS OF
HISPANIOLA...ERN CUBA...AND TURKS AND CAICOS. TO THE ENE OF
THESE AREAS OF CONVECTION...A WEAK SURFACE TROUGH IS ANALYZED
ALONG 31N62W TO 26N63W WITH MINIMAL ACTIVITY IN THE WRN VICINITY
OF ITS AXIS. AN ELONGATED UPPER LEVEL LOW IS CENTERED NEAR
25N57W. THIS FEATURE HAS TAKEN OVER THE REMNANTS OF FORMER
TROPICAL STORM JOYCE...NOW ANALYZED AS A SURFACE TROUGH FROM
25N52W TO 18N50W. SCATTERED SHOWERS AND THUNDERSTORMS ARE FROM
22N-29N BETWEEN 51W-56W. THE REMAINDER OF THE ATLC BASIN
DISCUSSION AREA IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED
BY A 1023 MB HIGH NEAR 34N45W AND A 1022 MB HIGH NEAR 33N35W.
THE FAIR WEATHER IS ENHANCED ALOFT BY SAHARAN DUST NOTED ON
METEOSAT-9 IMAGERY. EMBEDDED IN THIS DRY ENVIRONMENT...AN UPPER
LOW WOBBLES NEAR 31N22W. EXPECT WEATHER CONDITIONS TO
DETERIORATE OVER THE NRN COASTAL WATERS OF HISPANIOLA...TURKS
AND CAICOS...AND THE BAHAMAS DURING THE NEXT FEW DAYS AS
TROPICAL STORM ISAAC MOVES OVER HAITI AND CUBA BEFORE HEADING
INTO THE FLORIDA STRAITS.

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

$$

GARCIA



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