[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 281151
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED SEP 28 2011

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
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM PHILIPPE IS CENTERED NEAR 16.5N 38.0W AT 28/0900
UTC OR ABOUT 810 NM W OF THE CAPE VERDE ISLANDS MOVING W-NW AT 10
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. PLEASE SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/
WTNT22 KNHC FOR MORE DETAILS. PHILIPPE REMAINS SHEARED WITH THE
DEEP CONVECTION TO THE N OF THE LOW LEVEL CENTER. SCATTERED
MODERATE/STRONG CONVECTION IS FROM 16N-20N BETWEEN 35W-39W.

TROPICAL DEPRESSION OPHELIA IS CENTERED NEAR 18.6N 60.0W AT
28/0900 UTC OR ABOUT 180 NM E OF THE NORTHERN LEEWARD ISLANDS
MOVING NW AT 3 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008
MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT.
PLEASE SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. OPHELIA APPEARS TO BE
GRADUALLY ORGANIZING. SCATTERED MODERATE/STRONG CONVECTION IS
FROM 14N-20N BETWEEN 57W-60W WITH SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS OVER THE LESSER ANTILLES FROM SAINT LUCIA TO
ANGUILLA. TROPICAL DEPRESSION OPHELIA IS FORECAST TO INTENSITY
TO HURRICANE STRENGTH AS IT MOVES THROUGH THE CENTRAL ATLC
THROUGH FRI THEN N OF THE DISCUSSION AREA EARLY SAT.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED ALONG 28W BETWEEN 5N-11N MOVING W NEAR
20 KT. WAVE IS DIFFICULT TO DISCERN IN SATELLITE IMAGERY BUT IS
EVIDENT IN LOW LEVEL STREAMLINE ANALYSIS AND IN THE UPPER LEVEL
SATELLITE WINDS. NO ASSOCIATED SHOWERS/CONVECTION.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA ENTERING THE E TROPICAL
ATLC NEAR 17N16W TO 16N20W. SCATTERED MODERATE CONVECTION IS OFF
SW AFRICA WITHIN 60/75 NM OF A LINE FROM 6N12W TO 9N17W WITH
SMALL CLUSTERS FROM 6N-10N BETWEEN 36W-45W.

...DISCUSSION...

GULF OF MEXICO...
THE LARGE UPPER LOW IS CENTERED OVER THE GREAT LAKES EXTENDING A
BROAD UPPER TROUGH INTO THE NE GULF AND W ATLC N OF 27N E OF 86W
SUPPORTING A FRONTAL BOUNDARY THAT REMAINS INLAND OVER THE SE
CONUS AND PRODUCING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
WITHIN 60 NM ALONG THE N GULF COAST FROM THE FLORIDA/ALABAMA
BORDER TO THE MISSISSIPPI DELTA. A SURFACE TROUGH AT 28/0900 UTC
IS OVER SE FLORIDA EXTENDING FROM LAKE OKEECHOBEE ACROSS THE
UPPER FLORIDA KEYS TO 25N81W. A BROAD UPPER RIDGE COVERS THE
REMAINDER OF THE GULF ANCHORED OVER S MEXICO PROVIDING A
DIFFLUENT ENVIRONMENT TO GENERATE CLUSTERS OF SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS OVER THE SW GULF S OF 25N W OF 90W. WEAK
HIGH PRESSURE COVERS THE GULF E OF 94W WITH A 1015 MB HIGH
LOCATED NEAR 27N88W AT 28/0900 UTC. CLEAR SKIES DOMINATE THE
REMAINDER OF THE GULF THIS MORNING. WEAK HIGH PRESSURE WILL
PERSIST THROUGH TONIGHT THEN SHIFT TO THE NW GULF THU AND FRI. A
COLD FRONT WILL MOVE INTO THE NW GULF FRI REACHING FROM NEAR
TAMPA FLORIDA TO NE MEXICO SAT AND FROM S FLORIDA TO THE BAY OF
CAMPECHE SUN. STRONG HIGH PRESSURE WILL THEN BUILD SE BEHIND THE
FRONT ACROSS THE N/CENTRAL GULF.

CARIBBEAN SEA...
THE PRIMARY CONCERN THIS MORNING IS TROPICAL DEPRESSION OPHELIA
NE OF THE LEEWARD ISLANDS...SEE SPECIAL FEATURE SECTION ABOVE.
THE UPPER RIDGE OVER THE GULF OF MEXICO EXTENDS OVER THE W
CARIBBEAN N OF 12N W OF 70W PROVIDING A DIFFLUENT ENVIRONMENT TO
GENERATE ISOLATED CLUSTERS OF SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS N OF A LINE FROM 15N68W TO 20N83W AND WITHIN 60 NM
ALONG THE COAST OF NICARAGUA N OF 13N. THE MONSOON TROUGH
EXTENDS FROM COLOMBIA AND PANAMA GENERATING ISOLATED SHOWERS/
THUNDERSTORMS S OF 12N TO OVER PANAMA BETWEEN 79W-82W. THIS IS
LEAVING THE REMAINDER OF THE CARIBBEAN UNDER MOSTLY CLEAR SKIES
THIS MORNING. A WEAK PRESSURE PATTERN WILL EXIST OVER MUCH OF
THE AREA THROUGH SUN.

ATLANTIC OCEAN...
THE PRIMARY CONCERN THIS MORNING IS TROPICAL DEPRESSION OPHELIA
NE OF THE LEEWARD ISLANDS...SEE SPECIAL FEATURE SECTION ABOVE.
THE UPPER TROUGH OVER THE GULF OF MEXICO AND THE SE CONUS
EXTENDS OVER THE W ATLC WITH A SHORTWAVE UPPER TROUGH EXTENDING
FROM THE N BAHAMA ISLANDS TO 31N76W AND A NARROW UPPER RIDGE TO
THE E EXTENDING FROM THE N COAST OF CUBA NEAR 21N76W TO BEYOND
32N71W PROVIDING A DIFFLUENT ENVIRONMENT ALOFT TO GENERATE
SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN
90/120 NM OF LINE FROM THE COAST OF CUBA NEAR 22N77W ACROSS THE
BAHAMAS ALONG 26N75W TO BEYOND 32N74W. AN ELONGATED UPPER TROUGH
EXTENDS FROM 30N68W THROUGH AN UPPER LOW NEAR 26N67W TO THE
VIRGIN ISLANDS. SCATTERED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS ARE WITHIN 90 NM OF LINE FROM 24N65W TO 28N69W.
THE UPPER RIDGE ASSOCIATED WITH OPHELIA COVERS THE AREA FROM
10N-27N BETWEEN 53W-64W. A WEAK SURFACE RIDGE DOMINATES THE W
AND CENTRAL ATLC N OF 25N BETWEEN 55W-80W ANCHORED BY 1019 MB
HIGH JUST W OF BERMUDA. AN UPPER TROUGH EXTENDS S OVER THE E
ATLC TO 21N BETWEEN 18W-35W WITH TRAILING A SURFACE TROUGH THAT
EXTENDS FROM 32N39W TO 27N45W AND CLUSTERS OF SCATTERED SHOWERS
AND POSSIBLE ISOLATED THUNDERSTORMS ARE WITHIN 120 NM E OF THE
TROUGH AXIS. A WEAK SURFACE RIDGE COVERS THE REMAINDER OF THE E
ATLC ANCHORED BY A 1020 MB HIGH S OF THE MADEIRA ISLANDS NEAR
21N18W. HIGH PRESSURE OVER THE W/CENTRAL ATLC WILL REMAIN
STATIONARY BUT GRADUALLY WEAKEN THROUGH THU THEN SHIFT NE OF THE
AREA FRI AND SAT. A WEAK FRONT WILL MOVE INTO THE FAR W ATLC THU
TO FRI AND WILL REACH THE CENTRAL BAHAMAS SAT. A STRONGER FRONT
WILL MOVE INTO THE FAR W ATLC SAT AND RAPIDLY MOVE E MERGING
WITH THE WEAK FRONT ON SUN.

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

$$
PAW




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