[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 012348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT DEC 01 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...
A 1008 MB SURFACE LOW CONTINUES TO SPIN IN THE CENTRAL ATLC NEAR
27N41W. THE CENTER REMAINS EXPOSED AS DRY AIR ALOFT SINKS AROUND
THE WEST SIDE OF A NARROW UPPER LEVEL TROUGH ALONG 33N48W TO
24N38W. STRONG DIFFLUENCE ALOFT AROUND THE EAST SIDE OF THE
UPPER TROUGH IS HELPING PRODUCE SCATTERED MODERATE/STRONG
CONVECTION BOTH EAST AND NORTH OF THE LOW CENTER FROM 23N-31N
BETWEEN 35W-40W...AND NORTH OF 28N BETWEEN 40W-44W. A SURFACE
TROUGH ALONG EXTENDS THROUGH THE LOW CENTER ALONG 31N41W 27N41W
15N46W. THIS SYSTEM IS BEING MONITORED CLOSELY FOR FURTHER
DEVELOPMENT WITH A MEDIUM CHANCE OF BECOMING A TROPICAL OR
SUBTROPICAL CYCLONE OVER THE NEXT 48 HOURS AS THE LOW MOVES
NORTHWARD AND THEN MERGES WITH A FRONTAL BOUNDARY.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE NORTHERN
COAST OF SIERRA LEONE AT 9N13W TO 7N17W. THE ITCZ BEGINS AT
7N17W AND CONTINUES ALONG 9N31W 7N41W 9N49W 7N59W. TWO SURFACE
TROUGHS ARE EMBEDDED WITHIN THE ITCZ. THE FIRST IS ALONG 11N30W
TO 7N35W. THE SECOND IS ALONG 12N47W TO 7N50W. A 1010 MB SURFACE
LOW IS ALSO ALONG THE TROUGH AXIS AT 9N49W. SCATTERED
MODERATE/STRONG CONVECTION IS FROM 5N-7N BETWEEN 15W-18W.
ISOLATED MODERATE CONVECTION IS FROM 7N-10N BETWEEN 20W-28W.

...DISCUSSION...

GULF OF MEXICO...
THE GULF OF MEXICO IS UNDER PLEASANT CONDITIONS DUE TO A DRY
AIRMASS COVERING THE BASIN. MAINLY WEST TO NORTHWEST FLOW COVERS
THE AREA AROUND A BROAD UPPER TROUGH THAT EXTENDS ACROSS CENTRAL
FLORIDA INTO THE SOUTH CENTRAL GULF. AT THE SURFACE...WEAK
SURFACE RIDGING EXTENDS ACROSS THE AREA FROM THE SE CONUS
TOWARDS THE SW GULF WHERE A 1022 MB HIGH IS ANALYZED OVER INLAND
MEXICO. EAST TO SOUTHEAST FLOW IS AROUND THE RIDGE WITH SPEEDS
OF 20 KT IN THE SE GULF BECOMING LIGHTER TO 10 KT ACROSS THE NW
GULF. ONLY A SMALL LINE OF SHOWERS IS MOVING WESTWARD THROUGH
THE BASIN ALONG 28N92W 23N90W. EXPECT LITTLE CHANGE OVER THE
NEXT 24 HOURS.

CARIBBEAN SEA...
MAINLY SOUTHWEST TO WEST FLOW COVERS THE CARIBBEAN AROUND A
BROAD UPPER LEVEL RIDGE COVERING THE AREA AND CONTINUING INTO
PORTIONS OF THE SW NORTH ATLC. WHILE MOSTLY DRY AIR ALOFT IS
HELPING MAINTAIN FAIR CONDITIONS BASIN-WIDE...A FEW PATCHES OF
SHOWERS ARE OVER THE NORTHERN CARIBBEAN ISLANDS INCLUDING
EASTERN CUBA...HISPANIOLA...AND PUERTO RICO. A FEW ISOLATED
SHOWERS ARE ALSO ACROSS COSTA RICA AND PANAMA. RATHER LIGHT
TRADEWIND FLOW OF 10-15 KT IS PRESENT ACROSS THE AREA. LITTLE
CHANGE IS EXPECTED OVER THE NEXT 24 HOURS.

ATLANTIC OCEAN...
A WEAK UPPER LEVEL TROUGH EXTENDS OVER THE FAR WESTERN SW NORTH
ATLC. MOSTLY FAIR CONDITIONS ARE SEEN AT THE SURFACE...ALTHOUGH
SOME UPPER LEVEL CLOUD COVER IS TO THE EAST NEAR THE AREA OF
MOIST SOUTHWESTERLY FLOW BETWEEN THE UPPER TROUGH AND AN UPPER
LEVEL RIDGE COVERING THE REMAINDER OF THE WEST ATLC ALONG 60W. A
SHEAR AXIS...REMNANTS OF A FRONTAL BOUNDARY EXTENDS FROM NEAR
28N51W ALONG 25N60W 24N69W 21N76W. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE MAINLY NORTH OF THE AXIS FROM 23N-29N BETWEEN
61W-70W WITH A FEW ISOLATED SHOWERS/THUNDERSTORMS WITHIN 75 NM
OF THE AXIS ELSEWHERE. A SURFACE TROUGH IS SOUTH OF THE SHEAR
AXIS ALONG 23N68W TO 19N67W. ISOLATED SHOWERS ARE WITHIN 200 NM
EAST OF THE AXIS. FARTHER EAST...A SURFACE LOW AND SURFACE
TROUGH ALONG WITH AN UPPER LEVEL TROUGH ARE CAUSING AN AREA OF
DISTURBED WEATHER. SEE SPECIAL FEATURES FOR MORE DETAILS. A
NARROW UPPER LEVEL RIDGE IS IMMEDIATELY TO THE EAST ALONG 22N30W
37N37W CONTINUING TOWARDS THE NORTHEAST. THE UPPER RIDGE
SUPPORTS A SURFACE RIDGE AROUND A 1032 MB AZORES HIGH WHICH IS
HELPING PROVIDE FAIR CONDITIONS ACROSS THE EASTERN ATLC.

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

$$
WALTON




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