[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 112342 AAA
TWDAT

TROPICAL WEATHER DISCUSSION...AMENDMENT
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST TUE DEC 11 2007

...TRANSITION OLGA TO TROPICAL STORM AND UPDATE POSITION...

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...
DATA FROM A HURRICANE HUNTER PLANE INDICATE THAT THE STRONGER
WINDS ARE NOW CLOSER TO THE CENTER SUGGESTING THAT OLGA HAS
TRANSITIONED TO A TROPICAL STORM. TROPICAL STORM OLGA IS
CENTERED NEAR 18.8N 69.5W AT 12/0000 UTC WHICH IS INLAND OVER
THE DOMINICAN REPUBLIC ABOUT 26 NM NNE OF SANTO DOMINGO AND JUST
S OF BAHIA DE SAMANA IN THE DOMINICAN REPUBLIC MOVING W AT 11
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM
SUSTAINED WIND SPEED HAS INCREASED TO 50 KT WITH GUSTS TO 60 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.
THIS SYSTEM LACKS THE DEEP CONVECTION USUALLY ASSOCIATED WITH A
TROPICAL SYSTEM. HOWEVER A BROAD AREA OF HEAVY RAINS WITH
EMBEDDED THUNDERSTORMS COVERS THE AREA FROM 18N-22N BETWEEN
65W-71W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM
17N-23N BETWEEN 62W-73W. THE PRIMARY THREAT FROM OLGA REMAINS
HEAVY RAINFALL MAINLY OVER HISPANIOLA TONIGHT AND IS REDUCING
FREQUENCY OVER PUERTO RICO AS WELL AS MOVING OVER THE TURKS AND
CAICOS. THESE RAINS COULD PRODUCE FLASH FLOODS AND MUD SLIDES.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 6N8W 5N20W 7N40W 6N58W. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 180 NM
OF THE ITCZ AXIS BETWEEN 22W-38W AND S OF 4N W OF 41W TO INLAND
OVER SOUTH AMERICA.

DISCUSSION...
GULF OF MEXICO...
BROAD UPPER RIDGE COVERS THE ENTIRE GULF ANCHORED BY AN UPPER
HIGH OVER NE FLORIDA. A SURFACE RIDGE AXIS EXTENDS FROM THE W
ATLC ACROSS THE SE US TO E TEXAS ALSO COVERING THE ENTIRE GULF.
DRY STABLE AIR COVERS THE GULF EXCEPT WITH SOME ISOLATED LOW
LEVEL RETURN FLOW SHOWERS DOTTING THE CENTRAL GULF. OTHERWISE
SKIES ARE CLEAR THIS EVENING.

CARIBBEAN SEA...
THE MOST SIGNIFICANT FEATURE THIS EVENING IS TROPICAL STORM
OLGA IN THE SPECIAL FEATURES ABOVE. OTHERWISE...BROAD UPPER
RIDGE COVERS THE CARIBBEAN S OF 16N ANCHORED IN THE W TROPICAL
ATLC. BROAD UPPER RIDGE OVER THE GULF OF MEXICO IS INDUCING AN
UPPER TROUGH OVER THE N CARIBBEAN EXTENDING FROM W  OF OLGA
ALONG THE LENGTH OF CUBA TO THE YUCATAN CHANNEL. MODERATE/STRONG
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 STORM OLGA. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE WITHIN 90 EITHER SIDE OF THE LESSER ANTILLES
DUE TO THE UPPER AND LOWER LEVEL CONVERGENCE OVER THE AREA. THE
REMAINDER OF THE CARIBBEAN REMAINS MOSTLY CLEAR THIS EVENING
WITH SOME ISOLATED SHOWERS INLAND AND WITHIN 60 NM ALONG THE
COAST OF PANAMA...COSTA RICA...AND NICARAGUA DUE TO THE CLOSE
PROXIMITY OF THE ITCZ AXIS IN THE E PACIFIC REGION.

ATLANTIC OCEAN...
THE MOST SIGNIFICANT FEATURE THIS EVENING IS TROPICAL STORM
OLGA IN THE SPECIAL FEATURES ABOVE. OTHERWISE...BROAD UPPER
RIDGE COVERING THE GULF OF MEXICO EXTENDS OVER THE FAR W ATLC W
OF 75W. THE UPPER HIGH ASSOCIATED WITH OLGA IS PRODUCING
GENEROUS OUTFLOW MAINLY TO THE N OF THE STORM. BROAD UPPER
TROUGH COVERS THE CENTRAL AND E ATLC N OF 20N FROM 17W-55W WITH
AN UPPER LOW CENTERED NEAR 27N25W. A SURFACE TROUGH EXTENDS
ALONG THE NW COAST OF AFRICA FROM WESTERN SAHARA TO THE STRAITS
OF GIBRALTAR. AN UPPER HIGH IS IN THE TROPICAL ATLC NEAR 3N42W
COVERING THE AREA S OF 20N FROM OVER THE CARIBBEAN TO AFRICA
PROVIDING UPPER DIFFLUENCE ENHANCING THE ACTIVITY IN THE ITCZ
SECTION ABOVE. BROAD SURFACE RIDGE COVERS THE ENTIRE ATLC AND
THE GULF OF MEXICO EXCEPT IN THE IMMEDIATE VICINITY OF
TROPICAL STORM OLGA AND WITH A WEAKNESS NEAR THE SURFACE
TROUGH ALONG THE COAST OF AFRICA.

$$
WALLACE



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