[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 180556
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST SUN DEC 18 2011

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...ITCZ/MONSOON TROUGH...

THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N13W TO
07N30W TO 07N47W. SCATTERED MODERATE CONVECTION IS FROM 05N-09N
BETWEEN 30W-44W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL CONFLUENCE IS NOTED ACROSS THE GULF THIS EVENING AS
AN UPPER LEVEL LONGWAVE TROUGH REMAINS TO THE NORTH ACROSS THE
SE CONUS AND AN UPPER LEVEL RIDGE REMAINS ANCHORED OVER THE
WESTERN CARIBBEAN SEA. WITH THE UPPER LEVEL TROUGHING CONTINUING
TO SLIDE E-SE INTO NORTHERN PORTIONS OF THE SW NORTH ATLC...A
DISSIPATING COLD FRONT IS ANALYZED AT 18/0300 UTC FROM THE
SOUTHERN FLORIDA PENINSULA NEAR 26N81W TO 26N90W AND BECOMES
STATIONARY ALONG 26N95W TO 22N96W TO 21N97W THEN INLAND OVER
EAST-CENTRAL INTERIOR MEXICO. LOW-LEVEL MOISTURE REMAINS LIMITED
ALONG THE COLD FRONT...HOWEVER...ISOLATED SHOWERS ARE POSSIBLE
THROUGH THE OVERNIGHT HOURS WITHIN 90 NM EITHER SIDE OF THE
STATIONARY FRONT. THE FRONT IS EXPECTED TO CONTINUE DISSIPATING
AS SURFACE HIGH PRESSURE CURRENTLY ANCHORED AS A 1031 MB HIGH
CENTERED OVER NORTH TEXAS BUILDS EASTWARD ACROSS THE SE CONUS
THROUGH LATE SUNDAY AND PROVIDES MOSTLY EAST TO NORTHEAST WINDS
ACROSS MUCH OF THE GULF. BY MONDAY...SOUTHERLY RETURN FLOW IS
EXPECTED TO RE-ESTABLISH OVER PORTIONS OF THE WESTERN GULF AS AN
AREA OF LOW PRESSURE DEVELOPS OVER NORTH TEXAS AND OKLAHOMA. THE
NEXT COLD FRONT IS THEN FORECAST TO ENTER THE NW GULF WATERS
EARLY TUESDAY.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONIC CIRCULATION INFLUENCES MUCH OF THE
WESTERN CARIBBEAN CENTERED NEAR 16N76W WITH AXIS EXTENDING NW TO
NEAR 22N85W. ON THE WESTERN PERIPHERY OF THE RIDGE...SOUTHERLY
DIFFLUENT FLOW ALOFT CONTINUES TO ENHANCE SCATTERED SHOWERS AND
ISOLATED TSTMS S OF 17N BETWEEN 78W-85W...INCLUDING PORTIONS OF
PANAMA...COSTA RICA...AND EASTERN NICARAGUA. MOST OF THIS
CONVECTIVE ACTIVITY IS FOCUSED IN THE VICINITY AND NORTH OF THE
MONSOON TROUGH AXIS EXTENDING FROM THE E PACIFIC ALONG 10N TO
NORTHERN COLOMBIA. OTHERWISE THE REMAINDER OF THE WESTERN
CARIBBEAN W OF 70W IS UNDER STRONG NE TRADES DUE TO AN INCREASED
PRESSURE GRADIENT FROM A HIGH PRESSURE CENTER OVER THE SW NORTH
ATLC. FARTHER EAST...A VERY DRY AND STABLE ATMOSPHERE IS NOTED
UNDER NW FLOW ALOFT ON THE EASTERN PERIPHERY OF THE PREVIOUSLY
MENTIONED UPPER LEVEL RIDGE. NE TRADES PREVAIL E OF 70W AS
WELL...HOWEVER REMAIN GENERALLY FROM 10 TO 15 KT. TWO AREAS OF
ISOLATED SHOWERS ARE ALSO NOTED ON SATELLITE IMAGERY...ONE N OF
16N E OF 70W...AND THE OTHER S OF 14N E OF 70W. HIGH PRESSURE IS
FORECAST TO REMAIN ANCHORED NE OF THE BAHAMAS THROUGH LATE
SUNDAY MAINTAINING THE AREA OF INCREASED E-NE TRADES.

ATLANTIC OCEAN...
AN UPPER LEVEL LONGWAVE TROUGH IS PROGRESSING OVER THE EASTERN
CONUS AND SUPPORTS A COLD FRONT ANALYZED INTO THE DISCUSSION
AREA NEAR 32N73W THAT EXTENDS SW TO THE SOUTHERN FLORIDA
PENINSULA NEAR 27N80W. POSSIBLE ISOLATED SHOWERS ARE OCCURRING
WITHIN 90 NM EITHER SIDE OF THE FRONT. TO THE SE OF THE COLD
FRONT...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE WESTERN
CARIBBEAN SEA ALONG 20N74W TO BEYOND 32N62W AND SUPPORTS A
WEAKENING 1021 MB SURFACE HIGH CENTERED NEAR 27N69W. MOSTLY NE
WINDS ARE NOTED WITHIN THE SOUTHEASTERN PERIPHERY OF THE HIGH AS
A RECENT ASCAT PASS AROUND 18/0052 UTC DEPICTED WINDS IN THE
RANGE OF 10 TO 15 KT. OVER THE CENTRAL ATLC...AN UPPER LEVEL LOW
IS CENTERED NEAR 27N50W AND EXTENDS TROUGHING SOUTHWARD TO 08N
BETWEEN 43W-64W. THE UPPER LEVEL LOW SUPPORTS A COLLOCATED
SURFACE LOW WITH A SET OF FRONTAL BOUNDARIES ASSOCIATED WITH THE
SYSTEM. A STATIONARY FRONT EXTENDS FROM NE OF THE LOW CENTER
ALONG 29N47W TO 24N45W TO 17N48W THEN AS SURFACE TROUGH TO
12N50W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 240 NM
EAST OF THE BOUNDARY N OF 17N. CLOSER TO THE LOW CENTER...A
SECONDARY COLD FRONT IS ANALYZED FROM 26N50W TO 24N48W TO
20N53W. SCATTERED SHOWERS ARE OCCURRING FROM 25N-29N BETWEEN
47W-50W. BOTH OF THESE CONVECTIVELY ACTIVE AREAS ARE ENHANCED
EAST OF THE UPPER LEVEL TROUGH AXIS DUE TO STRONG UPPER LEVEL
DIFFLUENCE. THE REMAINDER OF THE EASTERN ATLC IS UNDER THE
INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1034 MB HIGH CENTERED
SE OF THE AZORES NEAR 36N24W. THE RIDGE AXIS EXTENDS SW FROM THE
HIGH TO 15N32W.

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

$$
HUFFMAN




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