[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 212340
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED SEP 21 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED 13.6N 44.7W AT 21/2100 UTC OR
1115 NM E OF THE LEEWARD ISLANDS MOVING W AT 14 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND
SPEED IS 50 KT WITH GUSTS TO 60 KT. PLEASE SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/ WMO HEADERS MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS. SCATTERED/NUMEROUS STRONG CONVECTION IS FROM
13N-16N BETWEEN 42W-45W WITH SCATTERED MODERATE/ISOLATED STRONG
CONVECTION FROM 10N-18N BETWEEN 40W-44W AND SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS FROM 7N-10N BETWEEN 40W-50W.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 17N22W TO 7N30W MOVING W AT 10-15
KT. WAVE IS WELL DEFINED IN THE UPPER LEVEL SATELLITE WINDS AND
IS EMBEDDED WITHIN A SURGE OF DEEP LAYER MOISTURE AS DEPICTED BY
THE TOTAL PRECIPITABLE WATER IMAGERY. DRIER AIR IS BEGINNING TO
UNDERCUT THE WAVE NEAR 11N. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS STREAMING W OF THE WAVE WITHIN 45 NM OF LINE FROM
8N30W TO 9N35W. ISOLATED SHOWERS ARE WITHIN 200 NM EITHER SIDE
OF THE REMAINDER OF THE WAVE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS INLAND OVER AFRICA INTO THE E
TROPICAL ATLC NEAR 13N16W TO 12N19W AND DISRUPTED ACROSS THE
REMAINDER OF THE ATLC BY THE TROPICAL WAVE AND TROPICAL STORM
OPHELIA. SCATTERED MODERATE/STRONG CONVECTION IS INLAND AND
WITHIN 120 NM ALONG THE COAST OF LIBERIA AND SIERRA LEONE.

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER TROUGH COVERS THE CENTRAL PLAIN STATES TO OVER THE W
GULF N OF 21N W OF 88W. AN UPPER RIDGE ASSOCIATED WITH TROPICAL
STORM HILARY IN THE E PACIFIC REGION COVERS S MEXICO AND THE SW
GULF OF MEXICO S OF 21N W OF 90W. A SURFACE TROUGH IS OVER THE
CENTRAL GULF EXTENDING AT 21/2100 UTC FROM 29N87W TO 23N90W AND
COUPLED DIFFLUENT ENVIRONMENT OVER THE E GULF IS GENERATING
SCATTERED SHOWERS/THUNDERSTORMS N OF 25N E OF 91W TO INLAND OVER
SE CONUS INCLUDING THE FLORIDA PENINSULA. ISOLATED SHOWERS AND
POSSIBLE ISOLATED THUNDERSTORMS DOT THE REMAINDER OF THE GULF
WATERS. THE SURFACE TROUGH IN THE NW CARIBBEAN WILL MOVE ACROSS
THE YUCATAN PENINSULA TONIGHT THROUGH THU ENTERING THE BAY OF
CAMPECHE ON FRI. SURFACE TROUGH IN THE CENTRAL GULF WILL LINGER
THROUGH FRI WHEN A COLD FRONT WILL ENTER THE NW GULF THEN WEAKEN
AS IT MOVES THROUGH THE N CENTRAL AND NE GULF SAT. HIGH PRESSURE
WILL BUILD OVER THE N GULF MON.

CARIBBEAN SEA...
A WEAK SURFACE TROUGH IS OVER THE NW CARIBBEAN EXTENDING AT
21/2100 UTC FROM THE YUCATAN CHANNEL NEAR 22N86W TO 18N85W
GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
WITHIN 45 NM EITHER SIDE OF THE TROUGH AXIS. AN INVERTED UPPER
TROUGH IS OVER THE W CARIBBEAN EXTENDING THE NICARAGUA/COSTA
RICA BORDER TO THE W TIP OF JAMAICA. BROAD UPPER RIDGE ANCHORED
OVER VENEZUELA COVERS THE S CARIBBEAN S OF 16N E OF 76W TO OVER
THE WINDWARD ISLANDS. DIFFLUENT FLOW BETWEEN THE UPPER TROUGH
AND UPPER RIDGE IS GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS WITHIN 120/150 NM OF LINE FROM PANAMA NEAR 9N82W
TO 18N76W. A SMALL 1012 MB LOW IS CENTERED AT 21/1800 UTC NEAR
18N63W MOVING THROUGH THE VIRGIN ISLANDS AND GENERATING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90 NM OF THE
LESSER ANTILLES FROM 13N-19N. AFTERNOON HEATING HAS GENERATED
NUMEROUS THUNDERSTORMS INLAND OVER HISPANIOLA...CUBA...AND
JAMAICA MOVING INTO THE CARIBBEAN WATERS. WEAK SURFACE TROUGH
OVER THE NW CARIBBEAN WILL DRIFT W AND BE OVER THE YUCATAN
PENINSULA TONIGHT. THE 1012 MB LOW WILL MOVE THROUGH THE VIRGIN
ISLANDS TONIGHT AND INTO THE W ATLC BY THU. TROPICAL STORM
OPHELIA WILL APPROACH THE LEEWARD ISLANDS ON SAT MOVING NW OF
THE ISLANDS THROUGH SUN.

ATLANTIC OCEAN...
AN UPPER RIDGE IS ANCHORED IN THE W ATLC NEAR 29N70W WITH AN
UPPER LOW TO THE S APPROACHING THE BAHAMA ISLANDS NEAR 24N74W.
THIS IS GENERATING ISOLATED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS FROM THE BAHAMA ISLANDS TO 31N BETWEEN 70W-80W. AN
UPPER RIDGE AXIS EXTENDS FROM N OF PUERTO RICO NEAR 23N64W TO
BEYOND 30N59W PROVIDING DIFFLUENT ENVIRONMENT TO GENERATE
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 21N-25N BETWEEN
62W-70W. A LONG UPPER TROUGH EXTENDS FROM AN UPPER LOW IN THE E
ATLC NEAR 32N26W SW INTO THE CENTRAL ATLC ALONG 26N41W TO
25N52W. A BROAD BUT WEAK SURFACE RIDGE DOMINATES THE ATLC N OF
20N AND ANCHORED BY A 1026 MB HIGH NEAR 32N49W AND A SECOND 1026
MB HIGH WELL N OF THE DISCUSSION AREA. THE SURFACE RIDGE WILL
CONTINUE THROUGH MON. TROPICAL STORM OPHELIA WILL APPROACH THE
LEEWARD ISLANDS ON SAT MOVING NW OF THE ISLANDS THROUGH SUN AND
BE W OF THE TURKS AND CAICOS BY MON.

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

$$
PAW





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