[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 191758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED DEC 19 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 1715 UTC

...THE ITCZ...

FROM NORTHERN COASTAL LIBERIA TO 5N20W 4N30W 2N40W...THROUGH
THE EQUATOR AT 50W...TO JUST SOUTH OF THE EQUATOR ALONG 53W.
SCATTERED STRONG SHOWERS/THUNDERSTORMS FROM 6N TO 7N BETWEEN
24W AND 27W...AND FROM 3N TO 4N BETWEEN 41W AND 45W. ISOLATED
MODERATE SHOWERS TO LOCALLY STRONG THUNDERSTORMS ARE ELSEWHERE
WITHIN 60 NM TO 120 NM ON EITHER SIDE OF 6N16W 5N27W 3N31W 3N50W.
SCATTERED MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS ARE
FROM 5N TO 6N BETWEEN 51W AND 53W...AND FROM 9N TO 10N BETWEEN
55W AND 57W.

...DISCUSSION...

THE GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM ARIZONA INTO THE
NORTHERN HALF OF BAJA CALIFORNIA RIDGE. UPPER LEVEL ANTICYCLONIC
FLOW IS RIGHT BEHIND THE TROUGH...MOVING FROM NEVADA AND
CALIFORNIA TO 30N120W. UPPER LEVEL SOUTHWESTERLY WIND FLOW MOVES
FROM THE EASTERN PACIFIC OCEAN ACROSS THE SOUTHERN HALF OF BAJA
CALIFORNIA...ACROSS MEXICO FROM 20N TO 30N. AN UPPER LEVEL RIDGE
IS ALONG 96W FROM THE CENTRAL COASTAL PLAINS OF EASTERN MEXICO
NORTHWARD BEYOND EAST TEXAS. A MIDDLE TO UPPER LEVEL TROUGH
PASSES THROUGH SOUTH CAROLINA TO THE SOUTHERN TIP OF FLORIDA.
BROAD SURFACE LOW PRESSURE EXTENDS FROM A SHALLOW TEXAS FRONTAL
BOUNDARY THAT IS UNDER THE UPPER LEVEL RIDGE...INTO THE
SOUTHWESTERN CORNER OF THE AREA. A SURFACE RIDGE REMAINS FROM
A 1026 MB SOUTHWESTERN GEORGIA HIGH PRESSURE CENTER TO THE SOUTH
CENTRAL GULF OF MEXICO.

THE CARIBBEAN SEA...
A MIDDLE LEVEL TROUGH CONTINUES FROM THE NORTHEASTERN CORNER OF
THE AREA TO THE SOUTH CENTRAL COASTAL WATERS OF VENEZUELA AND
THE NETHERLANDS ANTILLES...TO THE SOUTHWESTERN CORNER OF THE
AREA NEAR THE COLOMBIA/PANAMA BORDER. MIDDLE TO UPPER LEVEL DRY
AIR/SUBSIDENCE COVERS THE ENTIRE AREA...EXCEPT FOR THE EXTREME
SOUTHEASTERN CORNER. MOISTURE IS STREAMING NORTHWARD WITH AN
UPPER LEVEL RIDGE FROM THE WESTERN END OF THE ITCZ TO ITS PEAK
NEAR 19N57W. A SURFACE TROUGH CONTINUES FROM EASTERN CUBA NEAR
21N77W TO 20N80W 18N84W AND CURVING SOUTHWESTWARD TO THE
HONDURAS/NICARAGUA BORDER NEAR 14N86W. SHOWERS ARE DISSIPATING
WITHIN A 30 NM RADIUS OF 18N84W.

THE ATLANTIC OCEAN...
THE SOUTH CAROLINA-TO-FLORIDA MIDDLE TO UPPER LEVEL TROUGH MOVES
EASTWARD. CYCLONIC FLOW ON THE EASTERN SIDE OF THE TROUGH AFFECTS
THE ATLANTIC OCEAN NORTH OF THE BAHAMAS. A SEPARATE MIDDLE LEVEL
CYCLONIC CIRCULATION CENTER IS NEAR 24N72W JUST EAST OF THE
BAHAMAS. BROAD AND NOT-WELL-DEFINED CYCLONIC FLOW IS ASSOCIATED
WITH A DISORGANIZED MIDDLE TO UPPER LEVEL TROUGH THAT ROUGHLY
PASSES THROUGH 32N53W TO 26N66W. A COLD FRONT PASSING THROUGH
32N50W TO 24N70W WAS BEING SUPPORTED BY THE NOT-WELL-DEFINED
MIDDLE TO UPPER LEVEL TROUGH. AN UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTER IS NEAR 28N37W. ANTICYCLONIC FLOW IS WITHIN
450 NM OF THE CENTER IN THE NORTHERN SEMICIRCLE...AND WITHIN
600 NM OF THE CENTER IN THE SOUTHERN SEMICIRCLE. A DEEP LAYER
TROUGH PASSES THROUGH 32N15W...PASSING OVER THE CANARY
ISLANDS...TO 22N22W TO 21N29W. A COLD FRONT PASSES THROUGH
32N12W TO 22N20W TO 19N25W. A DISSIPATING COLD FRONT CONTINUES
FROM 19N25W TO 18N34W TO 19N42W. A DISSIPATING STATIONARY FRONT
CONTINUES FROM 19N42W TO 24N48W TO 27N50W. ANY SHOWERS WITH THIS
FRONT ARE NORTH OF 26N BETWEEN 6W AND 15W. UPPER LEVEL
SOUTHWESTERLY WIND FLOW IS SOUTH OF 12N55W 16N35W BEYOND 18N16W.

$$
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