[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 272356
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON AUG 27 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 28/0000 UTC IS NEAR 26.7N
86.5W. THIS POSITION IS ABOUT 200 NM SE OF THE MOUTH OF THE
MISSISSIPPI RIVER...AND ABOUT 255 NM SSE OF MOBILE ALABAMA.
ISAAC IS MOVING NW AT 9 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 981 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 60 KT
WITH GUSTS TO 75 KT. PLEASE READ THE FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC
ADVISORY...MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. NUMEROUS
MODERATE/SCATTERED STRONG CONVECTION IS NEAR THE CENTER AND TO
THE WEST FROM 25N-28N BETWEEN 85W-90W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS ELSEWHERE FROM 24N-30N
BETWEEN 83W-91W. EVEN THOUGH ISAAC IS MOVING AWAY FROM THE
FLORIDA PENINSULA...A LARGE AREA OF SHOWERS/THUNDERSTORMS IS
STILL IMPACTING THE STATE. RADAR IMAGERY INDICATES A SWATH OF
HEAVY SHOWERS/ISOLATED THUNDERSTORMS IS ALONG THE EASTERN
FLORIDA COAST EXTENDING OFFSHORE TO 79W AND CONTINUING FARTHER
OFF THE NE COAST OF FLORIDA TO 77W.

A 1011 MB SURFACE LOW IS CENTERED NEAR 21N42W IN THE CENTRAL
TROPICAL ATLC. THE LOW HAS BEEN MOVING NW AT ABOUT 15 KT. THE
SYSTEM IS CURRENTLY SHEARED WITH CONVECTION EXTENDING NE OF THE
LOW CENTER WHERE A CLUSTER OF STRONG CONVECTION IS FROM 23N-26N
BETWEEN 38W-42W. FURTHER DEVELOPMENT OF THIS SYSTEM IS POSSIBLE
OVER THE NEXT COUPLE OF DAYS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 22N21W TO A 1011 MB SURFACE LOW AT
11N22W MOVING W NEAR 12 KT. THE WAVE/LOW COINCIDES WITH A LARGE
SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER
IMAGERY. BROAD LOW-LEVEL CYCLONIC FLOW IS ALSO ABOUT THE WAVE
AND LOW...BUT IS NOT WELL ORGANIZED. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 9N-12N BETWEEN 23W-32W. A CLUSTER OF
SCATTERED STRONG CONVECTION IS ALSO MOVING OFF THE COAST OF
AFRICA BEHIND THE WAVE FROM 11N-15N BETWEEN 13W-18W.

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

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
MAURITANIA AT 15N17W CONTINUING TO A SURFACE LOW EMBEDDED WITHIN
THE MONSOON TROUGH AND ATTACHED TO A TROPICAL WAVE AT 11N22W.
THE MONSOON TROUGH BEGINS AGAIN SOUTH OF A SURFACE LOW IN THE
CENTRAL ATLC ALONG 16N42W 13N46W 10N54W. THE ITCZ CONTINUES FROM
10N54W TO 8N61W. SCATTERED MODERATE CONVECTION IS FROM 10N-15N
BETWEEN 52W-57W.

...DISCUSSION...

THE GULF OF MEXICO...
TROPICAL STORM ISAAC CONTINUES TO IMPACT THE GULF OF MEXICO AS
IT MOVES INTO THE NORTH CENTRAL GULF. THE STRONGEST CONVECTION
IS NEAR THE CENTER AND TO THE WEST WITH SOME LIGHTER SHOWERS
ALREADY MOVING INTO THE FLORIDA PANHANDLE AND SOUTHERN ALABAMA.
AN OUTER RAINBAND...WHICH HAS NOW MOSTLY CUT OFF FROM THE
STORM...CONTINUES TO IMPACT EASTERN FLORIDA. ISOLATED TORNADOES
HAVE ALSO POPPED UP THROUGHOUT THE FLORIDA PENINSULA THROUGHOUT
THE DAY AND THE RISK IS STILL PRESENT. THE CYCLONIC CIRCULATION
OF ISAAC COVERS THE ENTIRE BASIN...BUT WINDS ACROSS THE WESTERN
GULF ARE STILL LIGHT AT THIS TIME WITH MOSTLY CLEAR SKIES. THE
FAIR WEATHER CAN BE ATTRIBUTED TO DRY AIR ALOFT WRAPPING AROUND
AN UPPER LEVEL LOW CENTERED IN THE WESTERN GULF NEAR 23N92W.
STORMY CONDITIONS WILL REMAIN ACROSS A LARGE PORTION OF THE GULF
FOR THE NEXT SEVERAL DAYS. INTERESTS IN THE ENTIRE GULF COAST
SHOULD MONITOR THE PROGRESS OF ISAAC.

THE CARIBBEAN SEA...
SOME STRONG WINDS UP TO 25 KT ARE STILL ACROSS THE NW CARIBBEAN
NEAR AN AREA OF SHOWERS/THUNDERSTORMS N OF 20N BETWEEN 79W-82W.
SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS EASTERN CUBA AND
PORTIONS OF HISPANIOLA. DEEP LAYER MOISTURE REMAINS ACROSS MUCH
OF THE BASIN EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY...BUT
DRY AIR ALOFT IS HELPING PROVIDE FAIR CONDITIONS ACROSS THE
MAJORITY OF THE WESTERN CARIBBEAN. AN ELONGATED UPPER LEVEL
LOW/TROUGH EXTENDS FROM HISPANIOLA TO NORTHERN COLOMBIA...WHICH
IS PROVIDING MOIST DIFFLUENCE ALOFT OVER THE EASTERN CARIBBEAN.
THIS IS HELPING SUPPORT SOME CLUSTERS OF STRONG CONVECTION
ACROSS NORTHERN VENEZUELA WITH SOME ISOLATED SHOWERS ACROSS THE
REMAINDER OF THE EASTERN CARIBBEAN. STRONG TRADEWIND FLOW OF
MOSTLY 20 KT IS ACROSS MUCH OF THE CENTRAL AND EASTERN PORTIONS
OF THE BASIN WITH SOME STRONGER WINDS N OF VENEZUELA AND
COLOMBIA. EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS.

THE ATLANTIC OCEAN...
WIDESPREAD SHOWERS/THUNDERSTORMS EXTEND ALONG THE ENTIRE FLORIDA
EAST COAST AND CONTINUE FARTHER EAST N OF THE BAHAMAS OUT TO
77W. THIS ACTIVITY BEGAN AS AN OUTER BAND OF ISAAC...BUT HAS NOW
SEPARATED FROM THE MAIN CONVECTIVE PATTERN OF THE STORM...AS
INDICATED IN RADAR IMAGERY. THE REMAINDER OF THE WEST ATLC IS
MOSTLY DRY EXCEPT FOR SOME SHOWERS N OF THE EASTERN CARIBBEAN
FROM 19N-22N BETWEEN 65W-68W. THIS ACTIVITY IS ENHANCED BY
DIFFLUENCE ALOFT AROUND THE EAST SIDE OF AN UPPER LEVEL TROUGH
EXTENDING ACROSS HISPANIOLA TO NORTHERN COLOMBIA. FARTHER E...A
BROAD UPPER LEVEL RIDGE COVERS THE TROPICAL ATLC CENTERED NEAR
23N33W...EAST OF A SURFACE LOW THAT IS PRODUCING SOME
SHOWERS/THUNDERSTORMS. THE UPPER RIDGE SUPPORTS A PAIR OF
SURFACE HIGH CENTERS. ONE IS NEAR 32N49W PROVIDING SURFACE
RIDGING ACROSS THE CENTRAL ATLC. THE SECOND IS CENTERED NEAR THE
AZORES ISLANDS PROVIDING SURFACE RIDGING ACROSS THE FAR EASTERN
ATLC. GOES-R ENHANCED SATELLITE IMAGERY CONTINUES TO SHOW THAT
AN AREA OF DUST EXTENDS AROUND THE TROPICAL WAVE IN THE EAST
ATLC TO THE SURFACE LOW IN THE CENTRAL ATLC. AN AREA OF DUST IS
ALSO WEST OF THE LOW IN THE CENTRAL ATLC AND IS APPROACHING THE
NE CARIBBEAN.

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

$$
WALTON





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