[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI DEC 17 2010

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 05N07W 06N25W TO THE EQUATOR NEAR
50W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
01N-07N BETWEEN 34W AND 44W. A SHEAR LINE IS ANALYZED N OF THE
AXIS ALONG 05N37W 08N43W 08N49W. THE EASTERN PORTION OF THIS
SPEED CONVERGENCE AXIS IS ENHANCING CONVECTION ALONG THE ITCZ.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A COLD FRONT EXTENDS FROM A LOW PRESSURE SYSTEM
OVER SOUTH CAROLINA CROSSING THROUGH THE FLORIDA PANHANDLE NEAR
31N85W TO S OF MISSISSIPPI NEAR 29N89W WHERE IT BECOMES
STATIONARY ALONG 28N94W 24N98W CONTINUING NW INTO NORTHERN
MEXICO. SCATTERED SHOWERS ARE WITHING 45 NM EITHER SIDE OF THE
COLD FRONT. POSSIBLE SHOWERS ARE ALONG THE STATIONARY BOUNDARY.
THIS SYSTEM IS SUPPORTED BY AN UPPER LEVEL TROUGH MOVING TOWARDS
THE AREA FROM THE SOUTHERN ROCKIES AND SOUTHERN PLAINS. THE
REMAINDER OF THE AREA IS UNDER DRY AIR AND SUBSIDENCE AROUND A
BROAD UPPER RIDGE SUPPORTING MOSTLY FAIR WEATHER ACROSS THE
BASIN. A WEAK SURFACE TROUGH PARALLELS THE NE MEXICAN COASTLINE
ALONG 24N98W TO A WEAK 1010 MB LOW NEAR 20N96W WITH NO
ASSOCIATED SHOWERS. ISOLATED SHOWERS ARE ALSO NOTED IN THE
CENTRAL GULF FROM 24N-27N BETWEEN 86W AND 91W. EXPECT THE FRONT
TO REMAIN RELATIVELY STATIONARY OVER THE NEXT SEVERAL HOURS
UNTIL BEGINNING TO MOVE SE EARLY SATURDAY.

CARIBBEAN SEA...
VERY STRONG SUBSIDENCE AND DRY AIR ALOFT IS NOTED ACROSS THE NW
CARIBBEAN AROUND A BROAD UPPER RIDGE THAT CONTINUES TO SUPPORT A
SURFACE RIDGE EXTENDING FROM THE W ATLC AND CUBA TO THE GULF OF
HONDURAS N OF 17N AND W OF 80W ALLOWING MOSTLY FAIR WEATHER. A
SURFACE TROUGH IS ANALYZED FROM THE COAST OF COLOMBIA NEAR
09N77W ALONG 13N78W TO S OF JAMAICA NEAR 17N77W. SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS ARE ASSOCIATED WITH THE
TROUGH N OF 15N BETWEEN 73W AND 80W. A WEAK SHEAR LINE IS
ANALYZED FROM THE MARTINIQUE PASSAGE NEAR 15N61W ALONG 14N67W TO
15N74W ENHANCED BY STRONG TRADE WINDS ACROSS THE BASIN SUPPORTED
BY THE STRONG PRESSURE GRADIENT BETWEEN THE SURFACE RIDGE OVER
THE W ATLANTIC AND THE GENERAL LOW PRESSURE OVER SOUTH AMERICA.
THE WEAK SHEAR LINE DELINEATES THE SLIGHTLY WEAKER E-NE WINDS IN
THE SE CARIBBEAN FROM THE STRONGER E-NE WINDS IN THE NE
CARIBBEAN. THESE WINDS ARE ENHANCING CONVECTION N OF 14N BETWEEN
68W AND 73W. IT ALSO IS SUPPORTING THE CONVECTION ASSOCIATED
WITH THE SURFACE TROUGH. EXPECT LITTLE CHANGE OVER THE NEXT 24
HOURS.

ATLANTIC OCEAN...
MOSTLY DRY AIR AND STRONG SUBSIDENCE RESIDES WITHIN WESTERLY
ZONAL UPPER LEVEL FLOW ACROSS THE W ATLC W OF 50W THAT CONTINUES
TO SUPPORT A BROAD SURFACE RIDGE ANCHORED BY A 1021 MB HIGH
CENTERED NEAR 26N67W. MOSTLY FAIR CONDITIONS ARE FOUND WITHIN
THE INFLUENCE OF THIS FEATURE THIS MORNING. OVER THE CENTRAL
ATLC...AN UPPER LEVEL TROUGH NORTH OF THE DISCUSSION AREA IN THE
VICINITY OF 37N47W SUPPORTS A COLD FRONT ENTERING THE REGION
NEAR 32N42W THEN EXTENDING SW TO 24N47W AND CONTINUES AS A
SURFACE TROUGH TO 18N49W. ISOLATED SHOWERS REMAIN WITHIN 75 NM
EAST OF THE COLD FRONT S OF 31N. FARTHER EAST...AN UPPER LEVEL
LOW CENTERED NEAR 35N18W CONTINUES TO IMPACT MUCH OF THE EASTERN
ATLC E OF 35W SUPPORTING A 988 MB OCCLUDED LOW CENTERED WEST OF
THE MADEIRA ISLANDS NEAR 33N19W. A COLD FRONT EXTENDS INTO THE
AREA ALONG 32N13W ACROSS THE EASTERNMOST CANARY ISLANDS NEAR
28N14W THEN BECOMING DISSIPATING ALONG 26N16W TO 19N26W.
ISOLATED SHOWERS ARE MAINLY OCCURRING WITHIN 75 NM AHEAD OF THE
FRONT. WEAK SURFACE RIDGING AROUND A 1015 MB HIGH NEAR 24N41W IS
BETWEEN THE TWO FRONTAL SYSTEMS PROVIDING FAIR WEATHER BETWEEN
27W AND 42W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
MONTALVO/WALTON





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