[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 092357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
85 PM EDT SAT AUG 09 2008

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...
AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 37W/38W SOUTH OF 16N
MOVING WEST 15 KT. ISOLATED MODERATE SHOWERS THAT ARE ALONG THE
NORTHERN FRINGES OF THE ITCZ ARE FROM 10N TO 14N BETWEEN 34W
AND 40W.

AN ATLANTIC OCEAN TROPICAL WAVE WAS ALONG 57W/58W SOUTH OF 24N
MOVING WEST 15 KT. THE WAVE IS NOT ALL THAT WELL-DEFINED IN THE
VISIBLE SATELLITE IMAGERY NORTH OF 16N THAT ENDS AT 09/1745 UTC.
NO DEEP CONVECTIVE PRECIPITATION ACCOMPANIES THIS WAVE.

THE LAST VISIBLE SATELLITE IMAGES FROM 09/1800 UTC APPEAR TO
SHOW THE WAVE THAT THE TAFB GROUP HAS ANALYZED ALONG 70W REALLY
TO BE ALONG A NORTHEAST-TO-SOUTHWEST CURVE FROM THE NETHERLANDS
ANTILLES BEYOND PUERTO RICO. THE POSITION ON THE TAFB 09/1800 UTC
SURFACE MAP MAY BE ABOUT 120 NM TO THE FAR TO THE WEST ACCORDING
TO THE VISIBLE SATELLITE IMAGERY. WE WILL HAVE TO CHECK ON THIS
ONE. POSSIBLE SHOWERS IN CLOUDS LINES FROM SURFACE WIND
CONFLUENCE AROUND THE WAVE.

A TROPICAL WAVE IS ALONG 95W/96W SOUTH OF 18N MOVING WEST
10 TO 15 KT. WIDELY SCATTERED MODERATE SHOWERS TO ISOLATED
STRONG THUNDERSTORMS IN MEXICO BETWEEN 92W AND 96W. BROAD
SURFACE TO LOW LEVEL WIND FLOW AROUND THE WAVE IS MIXED WITH
UPPER LEVEL ANTICYCLONIC WIND FLOW ON TOP OF THE SAME AREA.

...THE ITCZ...
10N14W 9N18W 11N27W 10N41W 13N55W 10N61W. SCATTERED STRONG
SHOWERS AND THUNDERSTORMS FROM 8N TO 12N BETWEEN 27W AND 32W.
ISOLATED MODERATE SHOWERS TO POSSIBLE THUNDERSTORMS FROM
6N TO 14N EAST OF 48W.

...DISCUSSION...

THE GULF OF MEXICO...
A DEEP LAYER TROUGH EXTENDS FROM THE ATLANTIC OCEAN OFF THE
U.S.A. EAST COAST TO NORTHEASTERN FLORIDA AND INTO THE CENTRAL
GULF OF MEXICO. THIS TROUGH SUPPORTS A COLD FRONT THAT PASSES
FROM THE ATLANTIC OCEAN THROUGH 31N78W TO FLORIDA NEAR 29N82W
TO THE NORTH CENTRAL GULF OF MEXICO NEAR 29N87W. DRY AIR IN
SUBSIDENCE IS NORTH OF THE TROUGH EAST OF 93W. UPPER LEVEL
ANTICYCLONIC WIND FLOW MOVES ACROSS NORTHERN ALABAMA...THROUGH
LOUISIANA INTO THE GULF WATERS NORTH OF 28N...AND TO THE LOWER
TEXAS GULF COAST. ISOLATED MODERATE SHOWERS ARE FROM 24N TO 28N
EAST OF 94W IN THE GULF OF MEXICO. A COMPARATIVELY WEAK MIDDLE
LEVEL CYCLONIC CIRCULATION CENTER GRAZES THE NORTHERN COAST OF
THE YUCATAN PENINSULA WHILE UPPER LEVEL ANTICYCLONIC WIND FLOW
MOVES RIGHT ON TOP OF THE SAME AREA OF THE YUCATAN PENINSULA.
SCATTERED STRONG SHOWERS AND THUNDERSTORMS ARE OCCURRING IN
MANY AREAS OF THE PENINSULA.

THE CARIBBEAN SEA...
BROAD UPPER LEVEL CYCLONIC FLOW COVERS THE AREA FROM 17N TO 27N
IN THE ATLANTIC OCEAN BETWEEN 70W AND 80W. ISOLATED MODERATE
SHOWERS ARE IN CUBA. BROAD SURFACE LOW PRESSURE IS UNDERNEATH
UPPER LEVEL ANTICYCLONIC WIND FLOW IN THE SOUTHWESTERN CARIBBEAN
SEA. SHOWERS AND THUNDERSTORMS WERE IN THE SOUTHWESTERN CORNER
OF THE AREA WITHIN 120 NM TO THE NORTH OF THE ITCZ. THAT
PRECIPITATION HAS BEEN WEAKENING DURING THE LAST SIX HOURS.
STRONG SHOWERS AND THUNDERSTORMS ARE ALONG THE ITCZ FROM 68W
IN NORTHERN VENEZUELA TO 75W/76W IN NORTHERN COASTAL COLOMBIA.
THE NORTHEASTERN CORNER OF THE AREA NORTH OF 17N EAST OF 73W
IS UNDER THE INFLUENCE OF CYCLONIC FLOW AT THE BASE OF AN
ATLANTIC OCEAN-TO-CARIBBEAN SEA TROUGH. ISOLATED MODERATE
SHOWERS TO LOCALLY STRONG THUNDERSTORMS FROM THE VIRGIN ISLANDS
AND PUERTO RICO TO 20N BETWEEN 65W AND SOUTHWESTERN
HAITI...INCLUDING ALONG THE CENTRAL BORDER OF HAITI AND THE
DOMINICAN REPUBLIC.

THE ATLANTIC OCEAN...
BROAD UPPER LEVEL CYCLONIC FLOW COVERS THE AREA FROM CUBA TO 27N
BETWEEN 70W AND 80W. SCATTERED MODERATE TO STRONG SHOWERS AND
THUNDERSTORMS ARE FROM 25N IN THE BAHAMAS TO 28N BETWEEN 70W AND
78W. A CENTRAL ATLANTIC TROUGH EXTENDS FROM 32N62W TO A CYCLONIC
CIRCULATION CENTER NEAR 28N62W TO 23N63W AND 20N66W TO NORTHERN
PUERTO RICO. ISOLATED MODERATE SHOWERS TO LOCALLY STRONG
THUNDERSTORMS FROM THE VIRGIN ISLANDS AND PUERTO RICO TO 20N
BETWEEN 65W AND SOUTHWESTERN HAITI...INCLUDING ALONG THE CENTRAL
BORDER OF HAITI AND THE DOMINICAN REPUBLIC. ISOLATED MODERATE
SHOWERS ARE WITHIN 30 NM TO 60 NM ON EITHER SIDE OF 21N65W
24N63W 28N62W. A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM
A 27N46W CYCLONIC CIRCULATION CENTER TO 21N47W TO 10N51W.
THIS TROUGH IS SURROUNDED BY DRY AIR IN SUBSIDENCE.

$$
MT



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