[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 100541
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT OCT 10 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0315 UTC FOR GOES-12 IMAGERY...AND THROUGH 0515 UTC
FOR METEOSAT-8 IMAGERY.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 34W/36W TO THE SOUTH OF
15N MOVING WESTWARD 15 TO 20 KT. THIS WAVE IS MOVING THROUGH THE
AREA OF A PRE-EXISTING UPPER LEVEL TROUGH. THE TROUGH EXTENDS
FROM A CYCLONIC CIRCULATION CENTER NEAR 30N26W TO A SECOND
CYCLONIC CENTER NEAR 24N32W TO 17N33W TO 8N37W BECOMING
INDISTINCT. THE PRECIPITATION PATTERN IS BECOMING DRAWN OUT AND
ELONGATED AND STRETCHED ALONG A NORTHEAST-TO-SOUTHWEST LINE.
SHOWERS AND POSSIBLE THUNDERSTORMS FROM 13N TO 17N BETWEEN 29W
AND 33W...AND FROM 6N TO 10N BETWEEN 30W AND 40W IN THE ITCZ.

A TROPICAL WAVE IS ALONG 67W/68W TO THE SOUTH OF 18N MOVING
WESTWARD 10 TO 15 KT. STRONG SHOWERS AND THUNDERSTORMS
APPEARED ON SATELLITE IMAGERY ON TOP OF TRINIDAD DURING THE
MORNING HOURS OF FRIDAY 09 OCTOBER. THAT AREA OF DEEP CONVECTIVE
PRECIPITATION MAINTAINED ITSELF...AS IT MOVED ACROSS NORTHERN
VENEZUELA...FOR SEVERAL HOURS UNTIL ABOUT THREE HOURS AGO WHEN
THE PRECIPITATION STARTED TO WEAKEN AND DISSIPATE. UPPER LEVEL
DRY AIR IN SUBSIDENCE GRADUALLY HAS BEEN MOVING SOUTHWARD INTO
THE AREA TO THE EAST OF 70W...AND NOW IS TO THE NORTH OF 14N.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 86W/87W TO THE SOUTH OF
16N MOVING WESTWARD 10 TO 15 KT. THIS WAVE COVERS THE AREAS
FROM NORTH CENTRAL HONDURAS THROUGH WESTERN NICARAGUA...INTO
THE EASTERN PACIFIC OCEAN. STRONG SHOWERS AND THUNDERSTORMS
IN THE NORTHWESTERN CARIBBEAN SEA HAS BEEN DISSIPATING SINCE
09/2245 UTC. ONE CELL OF SHOWERS AND THUNDERSTORMS IS ABOUT
60 NM TO THE EAST OF NICARAGUA FROM 12N TO 13N. OTHER STRONG
SHOWERS AND THUNDERSTORMS ARE TO THE SOUTH OF 12N...FROM
SOUTHERN NICARAGUA TO THE COSTA RICA BORDER WITH PANAMA.

...THE ITCZ...

FROM 10N14W TO 11N35W INTO FRENCH GUIANA NEAR 5N53W. ISOLATED
MODERATE SHOWERS ARE WITHIN 60 NM TO THE NORTHEAST OF 5N10W
9N32W. STRONG SHOWERS AND THUNDERSTORMS FROM 7N TO 8N BETWEEN
42W AND 45W. WIDELY SCATTERED MODERATE SHOWERS TO ISOLATED
STRONG THUNDERSTORMS COVER THE REST OF THE AREA FROM 6N TO 10N
BETWEEN 38W AND 55W.

...DISCUSSION...

THE GULF OF MEXICO...
A CENTRAL U.S.A. DEEP LAYER TROUGH IS DRIVING THE CURRENT
NORTHWESTERN GULF OF MEXICO COLD FRONT. THIS FRONT PASSES
THROUGH SOUTHEASTERN MISSISSIPPI INTO SOUTHEASTERN LOUISIANA
TO THE MEXICO COAST NEAR 22N98W. STRONG SHOWERS AND
THUNDERSTORMS ARE WITHIN A 30 NM RADIUS OF 21N99W. THE LINE
OF PRECIPITATION THAT WAS ACCOMPANYING THIS FRONT SIX HOURS
EARLIER HAS LOST ITS CONVECTIVE FIREPOWER...AND LITTLE TO NO
PRECIPITATION ACCOMPANIES THE FRONT RIGHT NOW. BROAD UPPER
LEVEL ANTICYCLONIC WIND FLOW AND DRY AIR IN SUBSIDENCE COVER
THE REST OF THE AREA.

THE CARIBBEAN SEA...
THE 15N75W UPPER LEVEL CYCLONIC CIRCULATION CENTER FROM
16 TO 24 HOURS AGO IS INDISTINCT AT THIS MOMENT. IT MAY BE
CAUGHT UP IN THE LARGER-SCALE CYCLONIC ENVELOPE THAT IS
SMOTHERING THE AREA TO THE WEST OF 70W. UPPER LEVEL ANTICYCLONIC
FLOW IS ON TOP OF THE CYCLONIC ENVELOPE. ALL OF THE DEEP LAYER
CONVECTIVE PRECIPITATION 09/1015 UTC HAS BEEN STRETCHED AND
SHEARED BY THE UPPER LEVEL ANTICYCLONIC FLOW. A SECOND UPPER
LEVEL CYCLONIC CENTER IS NEAR 14N92W...JUST OFF THE COAST OF
SOUTHWESTERN GUATEMALA.

THE ATLANTIC OCEAN...
THE REMNANT OF HENRI IS A SURFACE TROUGH ALONG 24N61W 21N65W
TO 19N66W. IT LOOKS LIKE A SURFACE LOW PRESSURE CENTER MAY
REMAIN STILL NEAR 21N66W ALONG THE TROUGH. WE WILL CONTINUE TO
MONITOR THE SITUATION ON SHORTWAVE INFRARED IMAGERY FOR THE
10/0600 UTC SURFACE MAP ANALYSIS. SHOWERS ARE POSSIBLE WITHIN
60 NM ON EITHER SIDE OF THE TROUGH. ANTICYCLONIC FLOW COVERS THE
ENTIRE AREA TO THE NORTH OF 20N TO THE WEST OF 46W. THE FLOW TO
THE EAST OF 46W FEEDS INTO THE DEEP LAYER TROUGH THAT PASSES
THROUGH 32N43W TO 26N42W TO 22N45W...WITH A SHEAR AXIS FROM
22N45W TO 20N57W. THIS TROUGH SUPPORTS A COLD FRONT THAT PASSES
THROUGH 32N41W TO 27N44W TO 24N52W. ISOLATED MODERATE SHOWERS
ARE WITHIN 30 NM TO 60 NM ON EITHER SIDE OF 23N54W 25N46W 28N40W
BEYOND 32N39W.

$$
MT





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