[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 212345
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED OCT 21 2009

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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 31W/32W S OF 18N MOVING W NEAR 10 KT.
WAVE EXHIBITS A VERY SHARP AND NARROW AXIS WITH CYCLONIC
CURVATURE OF THE LOW LEVEL CLOUD FIELD NOTED ON SATELLITE
IMAGERY. SCATTERED SHOWERS ARE FROM 12N-17N BETWEEN 25W-30W
ENHANCED BY AN UPPER RIDGE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N15W 8N24W 8N37W 10N47W 9N62W.
CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 2N-8N BETWEEN
22W-42W.

...DISCUSSION...

GULF OF MEXICO...
THE GULF IS DOMINATED BY A SURFACE RIDGE ANCHORED IN THE W ATLC
OFF THE NORTH CAROLINA COAST. THE RETURN FLOW AROUND THIS
SURFACE RIDGE AND THE INCREASE PRESSURE GRADIENT HAS INCREASED
WINDS ACROSS THE GULF. PATCHES OF BROKEN LOW CLOUDS ARE ACROSS
MOST OF THE GULF BECOMING MOSTLY OVERCAST WITH SCATTERED SHOWERS
ALONG THE N GULF COAST N OF 27N W OF 87W. SIMILAR ACTIVITY IS
OVER THE STRAITS OF FLORIDA FROM THE FLORIDA KEYS TO THE N COAST
OF CUBA E OF 84W. A HIGHLY AMPLIFIED UPPER RIDGE EXTENDS FROM S
MEXICO ACROSS THE BAY OF CAMPECHE TO OVER THE LOWER MISSISSIPPI
VALLEY WITH AN EQUALLY AMPLIFIED UPPER TROUGH COVERING THE E
GULF EXTENDING S INTO THE CARIBBEAN AND E TO OVER THE W ATLC AND
STRONG SUBSIDENCE OVER THE E GULF E OF 86W. THE SURFACE RIDGE IS
EXPECTED TO RETREAT E AS A COLD FRONT MOVES OFF THE TEXAS COAST
LATE THU.

CARIBBEAN SEA...
A 1008 MB LOW IS IN THE SW CARIBBEAN OFF THE COAST OF NICARAGUA
NEAR 11N83W THAT HAS A LOW POTENTIAL OF TROPICAL DEVELOPMENT.
THE UPPER TROUGH THAT COVERS THE E GULF OF MEXICO DIPS S OVER
THE NW CARIBBEAN N OF 17N W OF 74W TO OVER THE YUCATAN. AN UPPER
RIDGE ANCHORED OVER NW VENEZUELA COVERS THE S CARIBBEAN S OF 16N
FROM 67W-83W. THIS SCENARIO IS PROVIDING DIFFLUENCE ALOFT TO
GENERATE A BROAD AREA OF MULTILAYERED OVERCAST CLOUDS WITH
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS E OF A LINE FROM CUBA
NEAR 22N81W TO HONDURAS NEAR 16N87W AND W OF LINE FROM
HISPANIOLA NEAR 18N71W TO PANAMA NEAR 9N78W. AND UPPER TROUGH
FROM THE CENTRAL ATLC EXTENDS SW OVER THE E CARIBBEAN PROVIDING
DRY STABLE AIRMASS E OF 70W THUS GIVING THE E CARIBBEAN CLEAR
SKIES THIS EVENING. THE LOW IN THE SW CARIBBEAN IS EXPECTED TO
REMAIN STATIONARY OVER THE NEXT 24 HOURS.

ATLANTIC OCEAN...
A BROAD UPPER TROUGH COVERS THE W INTO THE CENTRAL ATLC N OF 30N
WITH A NARROW AMPLIFIED AXIS EXTENDING S OVER THE W ATLC THROUGH
30N74W ACROSS CUBA INTO THE CARIBBEAN NEAR 23N80W AND W OVER THE
E GULF OF MEXICO PROVIDING STRONG SUBSIDENCE AND MOSTLY DRY
STABLE AIR W OF 76W. THE BROAD UPPER TROUGH IS SUPPORTING THE
REMNANTS OF A STATIONARY FRONT ENTERING THE W/CENTRAL ATLC NEAR
32N52W EXTENDING SW TO 25N64W WHILE THE REMAINDER OF THE W ATLC
TO INLAND OVER THE E US AND THE GULF OF MEXICO IS DOMINATED BY A
SURFACE RIDGE ANCHORED BY A 1024 MB HIGH OFF THE COAST OF NORTH
CAROLINA. AN UPPER RIDGE EXTENDS FROM NEAR 21N66W TO 29N54W
PROVIDING DIFFLUENCE ALOFT TO GENERATE AN AREA OF SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS S OF 27N TO OVER HISPANIOLA AND
CUBA BETWEEN 67W-76W. A SURFACE TROUGH EXTENDS FROM 27N50W TO
23N55W. A SECOND UPPER TROUGH IS OVER THE E/CENTRAL ATLC
EXTENDING FROM 29N45W THROUGH AN UPPER LOW NEAR 22N48W THEN SW
TO OVER THE E CARIBBEAN GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS WITHIN 60/75 NM OF LINE FROM 22N48W 24N43W TO
32N38W WHILE A WEAK SURFACE RIDGE DOMINATES THE REMAINDER OF THE
E ATLC ANCHORED BY A 1017 MB HIGH NEAR 30N29W. IN THE TROPICS...
A 1009 MB LOW IS N OF THE ITCZ NEAR 14N42W WITH SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS E OF THE LOW FROM 12N-16N BETWEEN
38W-42W.

$$
WALLACE



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