[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 092259
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SUN DEC 09 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2145 UTC

...SPECIAL FEATURE...
AN AREA OF SHOWERS AND THUNDERSTORMS HAS BECOME BETTER ORGANIZED
TODAY ABOUT 550 MILES ENE OF PUERTO RICO AND THE LEEWARD
ISLANDS...IN ASSOCIATION WITH A SHARP SURFACE TROUGH EXTENDING
FROM 24N55W 17N58W TO 9N57W AND A LARGE UPPER-LEVEL LOW NEAR
20N58W. THE SYSTEM IS ALREADY PRODUCING GALE FORCE WINDS...
MAINLY TO THE N AND NE OF THE MAIN AREA OF THUNDERSTORMS. THE
SURFACE TROUGH IS MOVING W NEAR 15 KT...AND THIS MOTION IS
EXPECTED TO CONTINUE OVER THE NEXT DAY OR TWO. WATER
TEMPERATURES REMAIN WARM ENOUGH IN THIS AREA TO SUPPORT TROPICAL
CYCLONE FORMATION...AND UPPER-LEVEL WINDS ARE NOT ESPECIALLY
PROHIBITIVE FOR DEVELOPMENT. THIS SYSTEM HAS THE POTENTIAL TO
BECOME A TROPICAL OR SUBTROPICAL STORM DURING THE NEXT 24 HOURS.
INTERESTS IN THE N LEEWARD ISLANDS...THE VIRGIN ISLANDS...PUERTO
RICO...HISPANIOLA...AND THE E BAHAMAS SHOULD MONITOR THE
PROGRESS OF THIS SYSTEM.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N12W 5N26W 5N41W 2N51W. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE 150 NM OF LINE
FROM 3N32W TO 7N42W AND IS ASSOCIATED WITH AN UPPER HIGH.

DISCUSSION...
GULF OF MEXICO...
BROAD UPPER RIDGE EXTENDS FROM THE CARIBBEAN THROUGH THE YUCATAN
CHANNEL TO OVER LOUISIANA COVERING THE ENTIRE GULF. A SURFACE
RIDGE AXIS EXTENDS FROM THE W ATLC ACROSS THE SE US TO S TEXAS
COVERING THE ENTIRE GULF. DRY STABLE AIR COVERS THE GULF EXCEPT
WITH SOME ISOLATED LOW LEVEL RETURN FLOW SHOWERS IN THE CENTRAL
GULF WITHIN 45 NM OF LINE FROM 24N87W TO 27N90W. OTHERWISE SKIES
ARE CLEAR THIS EVENING.

CARIBBEAN SEA...
BROAD UPPER RIDGE COVERS THE W CARIBBEAN W OF 80W ANCHORED BY AN
UPPER HIGH INLAND OVER HONDURAS NEAR 15N86W N THROUGH THE
YUCATAN CHANNEL INTO THE GULF OF MEXICO. BROAD UPPER TROUGH
COVERS THE REMAINDER OF THE CARIBBEAN EXTENDING FROM THE UPPER
LOW MENTIONED IN THE SPECIAL FEATURES ABOVE. STRONG NE TO E
SURFACE WINDS COVER THE CARIBBEAN DUE TO THE TIGHT PRESSURE
GRADIENT INDUCED BY THE STRONG SURFACE RIDGE ACROSS THE ATLC.
SCATTERED SHOWERS/WIDELY ISOLATED THUNDERSTORMS OVER THE NE
CARIBBEAN N OF 17N E OF 70W INCLUDING PORTIONS OF HISPANIOLA TO
OVER THE LEEWARD ISLANDS AND ARE ALSO ASSOCIATED WITH THE SYSTEM
IN THE SPECIAL FEATURES. THE REMAINDER OF THE CARIBBEAN REMAINS
MOSTLY CLEAR THIS EVENING WITH SOME ISOLATED SHOWERS INLAND AND
WITHIN 60 NM ALONG THE COAST OF PANAMA AND COSTA RICA DUE TO THE
CLOSE PROXIMITY OF THE ITCZ AXIS IN THE E PACIFIC REGION.

ATLANTIC OCEAN...
THE MOST SIGNIFICANT FEATURE THIS EVENING IS IN THE SPECIAL
FEATURES ABOVE. OTHERWISE...BROAD UPPER RIDGE EXTENDING FROM THE
CARIBBEAN OVER THE GULF OF MEXICO COVERS THE FAR W ATLC W OF
75W. UPPER TROUGH EXTENDS INTO THE CENTRAL ATLC N OF 27N FROM
39W-55W WITH THE ASSOCIATED FRONTAL BOUNDARY STILL N OF THE
REGION. A CUT-OFF UPPER LOW IS IN THE E ATLC NEAR 29N33W
COVERING THE AREA N OF 25N FROM 23W-39W. AN UPPER HIGH IS IN THE
TROPICAL ATLC NEAR 4N42W COVERING THE AREA S OF 19N FROM 19W-54W
PROVIDING UPPER DIFFLUENCE GENERATING THE ACTIVITY IN THE ITCZ
SECTION ABOVE. BROAD SURFACE RIDGE COVERS THE ENTIRE ATLC AND
THE GULF OF MEXICO WITH A WEAKNESS ALONG THE SURFACE TROUGH IN
THE SPECIAL FEATURES.

$$
WALLACE


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