[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202345
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT DEC 20 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.

...THE ITCZ...
ITCZ IS CENTERED ALONG 5N7W 4N20W 6N33W 6N37W 9N48W 7N52W 5N58W.
A PAIR OF SURFACE TROUGHS ARE EMBEDDED WITHIN THE ITCZ. ONE IS
ALONG 34W/35W S OF 12N AND THE OTHER IS ALONG 51W S OF 15N.
SCATTERED MODERATE CONVECTION IS NOTED WITHIN 250 NM ON EITHER
SIDE OF BOTH TROUGHS. IN ADDITION...SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 2N-7N BETWEEN 18W-28W.

...DISCUSSION...

GULF OF MEXICO...
A 1020 MB SURFACE HIGH IS CENTERED OVER THE ERN GULF NEAR 26N83W
AND EXTENDS A RIDGE SW TO OVER E/CENTRAL MEXICO NEAR TUXPAN.
ALOFT...BROAD ANTICYCLONIC FLOW ASSOCIATED WITH AN UPPER LEVEL
RIDGE EXTENDS FROM THE WRN CARIBBEAN TO ACROSS CUBA AND THE
FLORIDA PENINSULA DOMINATING THE ENTIRE GULF INCLUDING THE
YUCATAN PENINSULA AND SRN MEXICO. STRONG UPPER LEVEL SUBSIDENCE
ASSOCIATED WITH THIS HIGH IS RESULTING IN ATMOSPHERIC STABILITY
AND FAIR WEATHER CONDITIONS ACROSS MUCH OF THE GULF REGION.
FARTHER TO THE N...A DEEP LONGWAVE TROUGH IS ACROSS THE CENTRAL
CONUS AND SUPPORTS A FRONTAL SYSTEM FORECAST TO ENTER THE NW
GULF EARLY SUN MORNING FOLLOWED BY STRONG N-NE WINDS.

CARIBBEAN SEA...
THE CARIBBEAN IS UNDER THE INFLUENCE OF A BROAD RIDGE ALOFT
WHICH IS PRODUCING STRONG SUBSIDENCE ACROSS THE BASIN. THIS
UPPER-LEVEL RIDGE ALSO ENVELOPS CENTRAL AMERICA AND THE NW
PORTION OF SOUTH AMERICA. AS A RESULT...FRAGMENTS OF LOW LEVEL
CLOUDS WITH EMBEDDED LIGHT SHOWERS ARE NOTED ACROSS THE REGION
USHERED IN ON NE WINDS. THE LARGEST CLUSTER OF LOW LEVEL
CLOUDINESS IS OBSERVED S OF 19N AND W OF 83W. A SURFACE TROUGH
EXTENDS FROM THE W ATLC ACROSS PUERTO RICO TO 17N70W. ISOLATED
SHOWERS ARE ACROSS PUERTO RICO AND FROM 16N-18N BETWEEN 67W-73W.

ATLANTIC OCEAN...
A 1020 MB SURFACE HIGH IS LOCATED OVER THE W ATLC NEAR 28N73W
AND EXTENDS INFLUENCE W OF 60W TO OVER THE FLORIDA PENINSULA AND
INTO THE GULF OF MEXICO. BROKEN TO OVERCAST STRATOCUMULUS CLOUDS
ARE NOTED OVER THE NW BAHAMAS N OF 24N AND W OF 71W. ON THE ERN
FRINGE OF THIS HIGH PRESSURE RIDGE...A SURFACE TROUGH EXTENDS
FROM 26N60W TO PUERTO RICO. ACROSS THE CENTRAL ATLC A SURFACE
TROUGH IS ANALYZED ALONG 47W FROM 22N-30N. THIS TROUGH IS
SUPPORTED BY AN UPPER-LEVEL TROUGH THAT EXTENDS ALONG 32N41W TO
22N47W AND SW TO THE N LEEWARD ISLANDS. UPPER DIFFLUENCE E OF
THIS TROUGH IS GENERATING SCATTERED MODERATE CONVECTION FROM
23N-30N BETWEEN 35W-44W. ANOTHER AREA OF CLOUDINESS WITH
EMBEDDED SHOWERS IS FROM 15N-22N BETWEEN 34W-45W. THIS ACTIVITY
IS BEING ENHANCED BY A DIFFLUENT PATTERN ALOFT. THE REMAINDER OF
THE ATLC FORECAST REGION IS DOMINATED BY A SURFACE RIDGE ALONG
32N25W TO 19N37W. IN THE UPPER LEVELS...AN UPPER LOW IS LOCATED
NEAR THE MADEIRA ISLANDS WITH GENERALLY ZONAL WESTERLY UPPER
FLOW ACROSS THE E ATLC E OF 35W.

$$
HUFFMAN





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