[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 191738
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU NOV 19 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1700 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N13W 6N20W 9N30W 6N44W 11N57W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS ALONG THE AXIS
BETWEEN 25W-29W. AN EMBEDDED SURFACE TROUGH IS ANALYZED FROM
11N32W TO 4N30W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS SHEARED E OF THE TROUGH AXIS FROM 9N-11N BETWEEN 25W-31W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-14N
BETWEEN 50W-55W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A DYING STATIONARY FRONT EXTENDS ACROSS
CENTRAL FLORIDA N OF LAKE OKEECHOBEE ENTERING THE GULF OF MEXICO
S OF FORT MYERS NEAR 26N82W CONTINUING ALONG 24N86W 22N91W. THE
FRONT IS SUPPORTED BY A DEEP-LAYER TROUGH OVER THE ERN CONUS
EXTENDING TO THE NRN GULF OF MEXICO. THE FRONT PROTRUDES INTO A
SURFACE RIDGE COVERING THE MAJORITY OF THE BASIN CENTERED N OF
THE AREA NEAR A 1024 MB HIGH OVER THE MISSISSIPPI/ALABAMA
BORDER. ANTI-CYCLONIC SURFACE WINDS OF 10-15 KTS ARE AROUND THE
SURFACE RIDGE. IN THE UPPER LEVELS... MAINLY ZONAL WLY FLOW
ALOFT IS DRAWING SLIGHTLY MOIST AIR ACROSS THE BASIN. EXPECT THE
FRONT TO BECOME DIFFUSE LATER TODAY AS HIGH PRESSURE BUILDS FROM
THE N AHEAD OF LOW PRESSURE EXPECTED TO MOVE OFF THE TEXAS COAST
FRI.

CARIBBEAN SEA...
MUCH OF THE CARIBBEAN IS EXPERIENCING GENERALLY FAIR WEATHER
UNDER THE INFLUENCE OF DRY AIR AND STRONG SUBSIDENCE ASSOCIATED
WITH A BROAD UPPER LEVEL RIDGE EXTENDING FROM HONDURAS ACROSS
ERN CUBA AND INTO THE WRN ATLC. ISOLATED SHOWERS ARE NOTED
ACROSS THE NW CARIBBEAN AFFECTING JAMAICA...CAYMAN ISLANDS...AND
HONDURAS. SCATTERED SHOWERS/THUNDERSTORMS ARE IN THE SW
CARIBBEAN AFFECTING PORTIONS OF COSTA RICA/PANAMA S OF 10N
BETWEEN 76W-80W DUE TO SURFACE CONVERGENCE NEAR THE E PACIFIC
ITCZ ALONG WITH DIFFLUENT FLOW ALOFT. THE TAIL END OF A SURFACE
TROUGH EXTENDING FROM THE CENTRAL ATLC CROSSES INTO THE NE
CARIBBEAN TO 17N65W. ISOLATED SHOWERS ARE POSSIBLE NEAR THE
TROUGH AXIS. SHOWERS/POSSIBLE THUNDERSTORMS ARE ALSO BEGINNING
TO AFFECT THE LESSER ANTILLES WITH THE APPROACH OF A SURFACE
TROUGH JUST E OF THE ISLANDS. MODERATE TO FRESH TRADE WINDS ARE
ACROSS MUCH OF THE BASIN WITH HIGHER WINDS NEAR THE COAST OF
COLOMBIA AND S AMERICA. EXPECT SHOWERS TO CONTINUE OVER THE
LESSER ANTILLES.

ATLANTIC OCEAN...
BROAD LOW PRESSURE CONTINUES OVER THE W/CENTRAL ATLC. AS OF 1500
UTC...A STATIONARY FRONT EXTENDS FROM A 1017 MB LOW OFF THE S
CAROLINA COAST NEAR 33N78W TO THE CENTRAL FLORIDA COAST NEAR
28N80W CONTINUING AS A DYING STATIONARY FRONT ACROSS THE SE GULF
OF MEXICO. ISOLATED SHOWERS/THUNDERSTORMS ARE POSSIBLE ALONG THE
FRONT AXIS.THE FRONT IS SUPPORTED BY A DEEP LAYER TROUGH OVER
THE ERN CONUS. UPPER DIFFLUENT FLOW ALOFT BETWEEN THIS UPPER
TROUGH AND A BROAD UPPER LEVEL RIDGE EXTENDING FROM THE WRN
CARIBBEAN ACROSS THE WRN ATLC TO NEAR 39N69W...NW OF
BERMUDA...IS ENHANCING SCATTERED SHOWERS/THUNDERSTORMS FROM
29N-33N BETWEEN 71W-75W. A SURFACE TROUGH EXTENDS ALONG 26N61W
21N62W INTO THE FAR NE CARIBBEAN NEAR 17N65W. THE TROUGH IS
SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING FROM 31N58W TO E OF
THE LESSER ANTILLES NEAR 10N51W. THIS UPPER LEVEL TROUGH ALSO
SUPPORTS A SECOND SURFACE TROUGH E OF THE LESSER ANTILLES WITH
AXIS FROM 16N59W TO 9N59W. ISOLATED SHOWERS/POSSIBLE
THUNDERSTORMS ARE WITHIN 100 NM W OF THE TROUGH AXIS. SCATTERED
SHOWERS/THUNDERSTORMS ARE WITHIN 250 NM E OF THE TROUGH AXIS. TO
THE N...A 1016 MB LOW IS CENTERED NEAR 30N50W. A COLD FRONT E OF
THE LOW CENTER ENTERS THE DISCUSSION AREA NEAR 32N34W BECOMING
STATIONARY AT 30N41W CONTINUING THROUGH THE LOW CENTER ALONG
30N50W 30N62W. SCATTERED SHOWERS/THUNDERSTORMS ARE WITHIN 100 NM
OF THE FRONT...AND N OF 23N BETWEEN 47W-58W. ACROSS THE ERN
ATLC... A WEAK SURFACE RIDGE IS ANCHORED BY A 1023 MB HIGH NEAR
35N11W PROVIDING GENERALLY FAIR WEATHER ACROSS THE AREA. A PAIR
OF SURFACE TROUGHS PROTRUDE INTO THE RIDGE. THE FIRST IS FROM
23N42W TO 18N46W. THE SECOND IS FROM 22N34W TO 16N36W. ISOLATED
SHOWERS ARE POSSIBLE ALONG BOTH TROUGH AXES. THESE SMALL SURFACE
TROUGHS ARE SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING ACROSS
NW AFRICA TO W OF THE CAPE VERDE ISLANDS TO NEAR 12N40W. THIS
UPPER LEVEL TROUGH AND ASSOCIATED UPPER JET TO THE E SIDE OF THE
TROUGH IS SHEARING MOISTURE AND SHOWER ACTIVITY FROM THE ITCZ TO
THE NE-E.

$$
WALTON





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