[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251727
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN NOV 25 2012

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1630 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF
SIERRA LEONE AT 7N12W TO 6N17W. THE ITCZ BEGINS AT 6N17W AND
CONTINUES ALONG 5N30W 6N44W 5N54W. ISOLATED MODERATE/STRONG
CONVECTION IS FROM 5N-7N BETWEEN 11W-16W. ISOLATED MODERATE
CONVECTION IS FROM 4N-9N BETWEEN 25W-47W.

...DISCUSSION...

GULF OF MEXICO...
ZONAL WESTERLY FLOW ALOFT CONTINUES TO COVER THE GULF OF MEXICO
TODAY ACCOMPANIED BY A DRY AIRMASS. A BROAD UPPER TROUGH OVER
THE NW ATLC SUPPORTS A COLD FRONT THAT EXTENDS THROUGH THE SW
NORTH ATLC AND CONTINUES THROUGH THE FLORIDA STRAITS INTO THE
SOUTHERN GULF ALONG 25N80W 24N84W 24N91W...AS OF 1500 UTC. A
SURFACE TROUGH IS IN THE WESTERN CARIBBEAN ALONG 26N95W TO
19N94W...THE REMNANTS OF THE TAIL END OF THE FRONT WHICH HAS NOW
DISSIPATED. DUE TO THE DRY AIRMASS...ONLY A FEW ISOLATED SHOWERS
ARE WITHIN 45 NM SOUTH OF THE FRONTAL BOUNDARY AND WITHIN 75 NM
EITHER SIDE OF THE SURFACE TROUGH. SURFACE RIDGING AROUND A 1023
MB HIGH CENTERED OVER ALABAMA AND GEORGIA CONTINUES INTO THE
NORTHERN GULF BEHIND THE FRONT. THE FRONT WILL CONTINUE EASTWARD
INTO THE ATLC ALLOWING SURFACE RIDGING TO DOMINATE UNTIL ANOTHER
FRONT MOVES INTO THE GULF ON TUESDAY.

CARIBBEAN SEA...
MAINLY ZONAL WESTERLY FLOW ALOFT ALSO COVERS THE CARIBBEAN
AROUND A BROAD UPPER LEVEL RIDGE WITH A RATHER HORIZONTAL AXIS
ALONG 12N. ONLY A SMALL AREA OF MORE SOUTHWESTERLY WINDS COVER
THE AREA FROM THE SW CARIBBEAN TO HISPANIOLA WHERE MORE MODERATE
MOISTURE IS PRESENT. THIS ALSO IS ATOP AN AREA OF SURFACE
CONVERGENCE NEAR A SURFACE TROUGH ALONG 17N73W TO 10N80W. THE
CONVERGENCE IS OCCURRING BETWEEN STRONG NORTHERLY WINDS UP TO 20
KT ACROSS THE WESTERN CARIBBEAN AND 15-20 KT EASTERLY TRADEWIND
FLOW ACROSS THE EASTERN CARIBBEAN. ISOLATED SHOWERS ARE WITHIN
120 NM OF THE AXIS WITH SCATTERED SHOWERS/THUNDERSTORMS ACROSS
THE EXTREME SW CARIBBEAN NORTH OF COSTA RICA AND PANAMA. THIS
STRONGER ACTIVITY IS ALSO LIKELY INFLUENCED BY THE MONSOON
TROUGH THAT IS JUST SOUTH OF BOTH THE COUNTRIES. AN AREA OF
SHOWERS/THUNDERSTORMS IS ALSO IN THE SE CARIBBEAN FROM 11N-14N
BETWEEN 63W-71W. THIS ACTIVITY IS ASSOCIATED WITH A SMALL AREA
OF ENHANCED MOISTURE THAT TRACKED WESTWARD FROM THE TROPICAL
ATLC. THIS AREA OF MOISTURE IS EXPECTED TO CONTINUE MOVING
WESTWARD AND WILL THEN MERGE WITH THE SURFACE TROUGH IN THE
CENTRAL CARIBBEAN LIKELY INCREASING SHOWER/THUNDERSTORM
ACTIVITY.

ATLANTIC OCEAN...
A BROAD UPPER LEVEL TROUGH COVERS THE NW ATLC SUPPORTING A COLD
FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N61W AND CONTINUES
TOWARDS THE NW BAHAMAS ALONG 27N73W 25N80W. DUE TO MOSTLY DRY
AIR ALOFT...ONLY A FEW POSSIBLE ISOLATED SHOWERS ARE ALONG THE
AXIS. THE SYSTEM ALSO SUPPORTS A SECOND COLD FRONT FARTHER EAST
ENTERING THE AREA NEAR 32N45W AND CONTINUES ALONG 27N48W 24N55W
WHERE IT CONTINUES AS A SURFACE TROUGH TO 19N64W. SIMILAR TO THE
WESTWARD FRONT....ONLY POSSIBLE ISOLATED SHOWERS ARE ALONG THE
FRONT/TROUGH AXIS. AN UPPER LEVEL RIDGE COVERS THE CENTRAL ATLC
WITH AXIS EXTENDING FROM THE SOUTHERN CARIBBEAN AND CONTINUING
NE UNTIL IT BECOMES VERTICAL ALONG 34W. THE UPPER RIDGE SUPPORTS
A SURFACE RIDGE ACROSS THE MAJORITY OF THE EASTERN TROPICAL ATLC
ANCHORED BY A 1030 MB AZORES HIGH. HOWEVER...A DEEP LAYERED LOW
WITH SURFACE CENTER NEAR THE MADEIRA ISLANDS SUPPORTS A COLD
FRONT THAT CROSS THE CANARY ISLANDS AND EXTENDS TO 22N28W. THE
TIGHT GRADIENT NEAR THE SURFACE LOW IS PRODUCING GALE FORCE
WINDS NEAR 30N BEHIND THE FRONT WITH STORM FORCE WINDS FARTHER
NORTH.

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

$$
WALTON





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