[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251754
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM ISAAC AT 25/1800 UTC WAS LOCATED
NEAR 20.8N 75.3W. THIS POSITION IS ABOUT 65 KM N OF GUANTANAMO
CUBA. ISAAC IS MOVING NW AT 15 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1000 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 1009 MB LOW AND ASSOCIATED TROPICAL WAVE AXIS IS LOCATED SW OF
THE CAPE VERDE ISLANDS NEAR 13N30W MOVING W AT ABOUT 15 KT.
THIS FEATURE IS EMBEDDED IN THE BROAD SCALE MONSOON GYRE ON
SATELLITE IMAGERY...WITHIN A SURGE OF DEEP LAYER MOISTURE
PRESENT ACROSS MUCH OF THE EASTERN TROPICAL ATLC AS INDICATED BY
THE GOES-R PG AIRMASS PRODUCT. HOWEVER...THE GOES-R PG SAL
PRODUCT INDICATED A THICK LAYER OF SAHARAN DUST AT SOME DISTANCE
FROM THE WAVE AND ASSOCIATED LOW WITH SOME OF THE SAL WRAPPING
INTO THE CIRCULATION IN THE W SEMICIRCLE. THE SYSTEM IS BECOMING
BETTER ORGANIZED WITH CONVECTION DEVELOPING NEAR THE LOW LEVEL
CENTER. SCATTERED MODERATE TO STRONG CONVECTION WAS INDICATED
FROM 14N TO 18N BETWEEN 31W AND 33W. SCATTERED MODERATE WAS
NOTED ELSEWHERE FROM 13N TO 18N BETWEEN 28W AND 35W.
ENVIRONMENTAL CONDITIONS REMAIN 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 19N17W CONTINUING
WSW TO THE SPECIAL FEATURE 1009 MB LOW AND ASSOCIATED TROPICAL
WAVE NEAR 13N30W...CONTINUING THROUGH 11N40W TO 11N45W...WHERE
THE ITCZ CONTINUES ALONG 11N53W TO NEAR TRINIDAD. SCATTERED
MODERATE ISOLATED STRONG CONVECTION WAS NOTED WITHIN 180 NM S OF
THE MONSOON TROUGH BETWEEN 37W AND 42W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL NORTHERLY FLOW COVERS THE WESTERN TWO-THIRDS OF THE
GULF AND WAS OCCURRING BEHIND A SHARP UPPER LEVEL TROUGH/SHEAR
AXIS WHICH EXTENDED FROM THE FLORIDA BIG BEND TO THE NE YUCATAN
PENINSULA. THE SHEAR AXIS APPEARED TO BE DRIFTING TO THE WEST
WITH TIME. THE FLOW IS VERY DIFFLUENT E OF THE SHEAR AXIS WHICH
WAS AIDING IN PROVIDING SOME LIFT OVER THE S FLORIDA AND THE
FLORIDA STRAITS AND SUPPORTING AN AREA OF SCATTERED TO LOCALLY
NUMEROUS SHOWERS AND THUNDERSTORMS OVER THE REGION WITH LOCALLY
HEAVY RAINFALL ALREADY BEING REPORTED. INCREASING LOW LEVEL
EASTERLY WINDS AROUND THE PERIPHERY OF TROPICAL STORM ISAAC
WAS ADVECTING ABUNDANT LOW LEVEL MOISTURE FROM THE EAST THROUGH
ACROSS THE STRAITS OF FLORIDA AND EXACERBATING THE ALREADY HEAVY
RAINFALL IN THE AREA. ADDITIONAL SCATTERED THUNDERSTORMS WERE
OCCURRING OVER THE FAR NW GULF ALONG THE UPPER TEXAS AND
LOUISIANA COASTS IN AN AREA OF INCREASING LOW LEVEL RETURN FLOW.
WINDS WILL BEGIN TO INCREASE OVER THE SE GULF TONIGHT THROUGH
SUNDAY. ALL INTERESTS IN THE EASTERN GULF SHOULD MONITOR THE
PROGRESS OF ISAAC.

CARIBBEAN SEA...
TROPICAL STORM ISAAC IS THE MAIN WEATHER CONCERN IN THE
CARIBBEAN SEA...GENERATING CONSIDERABLE CONVECTION OVER THE
NORTH-CENTRAL AND NE PORTIONS OF THE BASIN. TOTAL RAINFALL
ACCUMULATIONS OF 8 TO 12 INCHES...WITH MAXIMUM AMOUNTS OF 20
INCHES...ARE POSSIBLE OVER HISPANIOLA. THESE RAINS COULD CAUSE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. AN ADDITIONAL AREA
OF SCATTERED THUNDERSTORMS WAS OCCURRING IN THE VICINITY OF THE
CAYMAN ISLANDS EXTENDING NORTHWESTWARD TO THE ISLE OF YOUTH
IN CUBA AND WERE ASSOCIATED WITH A SURFACE TROUGH WHICH EXTENDED
FROM THE VICINITY OF ISAAC WESTWARD ACROSS THE NW CARIBBEAN.
THE FAR W AND SW PORTION OF THE CARIBBEAN 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 ARE OCCURRING OVER MUCH OF PANAMA...LIKELY
INFLUENCED BY THE ERN PACIFIC MONSOON TROUGH. ISAAC'S INFLUENCE
ON THE WEATHER PATTERN ACROSS THE CARIBBEAN WILL GRADUALLY WANE
LATER TODAY AND TONIGHT AS IT CONTINUES TO MOVE ACROSS THE
EASTERN TIP OF CUBA TOWARD THE STRAITS OF FLORIDA.

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 TO NUMEROUS HEAVY SHOWERS AND THUNDERSTORMS ACROSS THE
BAHAMAS AND STRAITS OF FLORIDA S OF 27N W OF 71W. THE CONVECTIVE
RAINBANDS ASSOCIATED WITH ISAAC ARE SPREADING ACROSS HISPANIOLA
EASTERN CUBA...AND THE SE BAHAMAS INCLUDING THE TURKS AND CAICOS
ISLANDS.  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.

ELSEWHERE OVER THE ATLANTIC...A WEAK SURFACE TROUGH IS ANALYZED
ALONG 32N62W TO 26N64W WITH MINIMAL CONVECTIVE ACTIVITY
ASSOCIATED WITH THIS FEATURE. AN UPPER LEVEL TROUGH/SHEAR AXIS
EXTENDS FROM 31N62W SSE TO AN ELONGATED UPPER LEVEL LOW CENTERED
NEAR 22N58W. A SURFACE TROUGH EXTENDS FROM 26N54W TO A SPOT 1014
MB SURFACE LOW NEAR 20N52W...WHICH IS ALL THAT REMAINS OF FORMER
T.S. JOYCE. SCATTERED SHOWERS AND THUNDERSTORMS WERE NOTED WELL
TO THE N OF THE REMNANT LOW FROM 23N-27N BETWEEN 51W-57W. THE
REMAINDER OF THE ATLC BASIN DISCUSSION AREA IS DOMINATED BY A
BROAD SURFACE RIDGE ANCHORED BY A 1023 MB HIGH NEAR 33N44W AND A
1022 MB HIGH NEAR 33N32W. 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.

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

$$

COBB





This weather bulletin was brought to you by:
www.nashvilleweather.net