[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 122352
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED DEC 12 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
2315 UTC

...SPECIAL FEATURE...
TROPICAL STORM OLGA WAS DOWNGRADED TO TROPICAL DEPRESSION AT
12/2100 UTC. TROPICAL DEPRESSION OLGA IS CENTERED NEAR 18.9N
76.9W AT 12/2100 UTC WHICH IS 55 NM NORTH OF KINGSTON JAMAICA
AND ABOUT 245 NM EAST OF GRAND CAYMAN MOVING W AT 20 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED
WIND SPEED HAS DECREASED TO 30 KT WITH GUSTS TO 40 KT. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC AND THE NHC INTERMEDIATE PUBLIC ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS.
BROAD AREA OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS COVERS
PORTIONS OF THE N/CENTRAL CARIBBEAN AND THE SW ATLC FROM 17N-24N
BETWEEN 69W-78W INCLUDING JAMAICA...PORTIONS OF CUBA AND
HISPANIOLA...AS WELL AS THE TURKS AND CAICOS. THE UPPER LEVEL
SHEAR THAT HAS BEEN EXPECTED IS NOW WEAKENING OLGA AND IT IS
NOT EXPECTED TO REGENERATE.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 6N8W 4N13W 4N25W 3N34W 5N45W 3N52W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM THE EQUATOR TO 5W E OF 20W TO ACROSS THE PRIME MERIDIAN AND
FROM 1N-7N BETWEEN 23W-38W. CLUSTERS OF SCATTERED
MODERATE/STRONG CONVECTION ARE FROM 6N-11N BETWEEN 48W-50W
INCLUDING PORTIONS OF SOUTH AMERICA.

DISCUSSION...
GULF OF MEXICO...
A DEEP LAYERED TROUGH IS OVER THE CENTRAL PLAIN STATES ACROSS
MEXICO INTO THE E PACIFIC REGION EXTENDING A COLD FRONT ALONG
THE TEXAS COAST. THIS FRONT WILL MOVE INTO THE GULF OVERNIGHT
AND BEGIN TO WASHOUT AND MOVE NORTH AS A WARM FRONT ON FRI. A
SURFACE RIDGE AXIS EXTENDS FROM THE W ATLC OVER THE SE US AHEAD
OF THE FRONT WITH A 1024 MB HIGH OVER E ALABAMA. BROAD UPPER
RIDGE DOMINATES THE GULF AND EXTENDS INTO THE ATLC. DRY STABLE
AIR DOMINATES THE GULF EXCEPT WITH SOME ISOLATED LOW LEVEL
RETURN FLOW SHOWERS DOTTING THE CENTRAL GULF AND THE STRAITS OF
FLORIDA. OTHERWISE SKIES REMAIN CLEAR THIS EVENING.

CARIBBEAN SEA...
THE MOST SIGNIFICANT FEATURE THIS EVENING REMAINS TROPICAL
DEPRESSION OLGA IN THE SPECIAL FEATURES ABOVE. OTHERWISE...BROAD
UPPER RIDGE COVERS THE CARIBBEAN ANCHORED IN THE W TROPICAL
ATLC. MODERATE/STRONG N TO NE SURFACE WINDS COVER THE CARIBBEAN
DUE TO THE TIGHT PRESSURE GRADIENT IN PART DUE TO THE STRONG
SURFACE RIDGE ACROSS THE ATLC AND TROPICAL DEPRESSION OLGA.
SCATTERED SHOWERS ARE OVER THE SE CARIBBEAN S OF 13N E OF 70W
ACROSS THE WINDWARD ISLANDS AND WITHIN 120 NM ALONG THE COAST OF
PANAMA AND COSTA RICA. OTHERWISE SKIES REMAIN CLEAR THIS
EVENING.

ATLANTIC OCEAN...
THE MOST SIGNIFICANT FEATURE THIS EVENING IS TROPICAL DEPRESSION
OLGA IN THE SPECIAL FEATURES ABOVE. THE UPPER HIGH ASSOCIATED
WITH OLGA IS PRODUCING GENEROUS OUTFLOW MAINLY N OF THE GREATER
ANTILLES BETWEEN 65W-75W. BROAD UPPER RIDGE DOMINATES THE W ATLC
W OF 50W WHILE A BROAD UPPER TROUGH AXIS IS IN THE CENTRAL
EXTENDING THROUGH 32N32W TO 23N37W. AN CUTOFF UPPER LOW IS
CENTERED W OF THE CANARY ISLANDS NEAR 27N23W WITH A SURFACE
TROUGH EXTENDING JUST INLAND ALONG THE NW COAST OF AFRICA. AN
UPPER HIGH IS IN THE TROPICAL ATLC NEAR 2N46W COVERING THE
TROPICS S OF 16N FROM OVER THE CARIBBEAN TO AFRICA PROVIDING
UPPER DIFFLUENCE ENHANCING THE ACTIVITY ALONG THE COAST OF SOUTH
AMERICA IN THE ITCZ SECTION ABOVE. BROAD SURFACE RIDGE COVERS W
OF 20W AND THE GULF OF MEXICO EXCEPT IN THE IMMEDIATE VICINITY
OF TROPICAL DEPRESSION OLGA.

$$
WALLACE


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