[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211722
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED NOV 21 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
1700 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 09N13W TO
06N18W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
06N18W TO 04N25W TO 05N32W TO 04N38W TO 05N44W TO 04N51W. WIDELY
SCATTERED MODERATE CONVECTION IS FROM 03N-09N BETWEEN 06W-20W.
ISOLATED MODERATE CONVECTION IS FROM 03N-13N BETWEEN 32W-40W.
MUCH OF THIS CONVECTION IS ENHANCED BY AN UPPER LEVEL TROUGH
WITH AXIS ALONG 20N37W TO 07N50W PROVIDING MAXIMUM DIFFLUENCE
EAST OF THE UPPER LEVEL TROUGH AXIS BETWEEN 25W-44W. A SURFACE
TROUGH IS EMBEDDED WITHIN THE ITCZ FROM 04N-09N ALONG 44W
PROVIDING FOCUS FOR ISOLATED MODERATE CONVECTION FROM 06N-09N
BETWEEN 42W-46W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES FAIRLY ZONAL WESTERLY FLOW OVER
MUCH OF THE GULF THIS AFTERNOON...HOWEVER A MIDDLE TO UPPER
LEVEL SHORTWAVE TROUGH IS PROGRESSING OVER THE SE CONUS AND
PROVIDING FOR A REINFORCING SWATH OF DRIER AIR ALOFT N OF 27N E
OF 92W. ELSEWHERE OVER THE GULF...SURFACE RIDGING REMAINS
ANCHORED OVER THE NW AND NORTH-CENTRAL GULF WATERS PROVIDING
NORTH-NORTHEASTERLY WINDS IN THE RANGE OF 10 TO 20 KT WITH THE
SURFACE RIDGE AXIS EXTENDING SOUTHWARD ALONG 98W AND THE EASTERN
MEXICO COAST. DUE TO LOW-LEVEL CONVERGENCE...A SURFACE TROUGH IS
ANALYZED FROM 18N94W TO 22N96W AND IS PROVIDING FOCUS FOR
MOISTURE CONVERGENCE AND ISOLATED SHOWERS S OF 24N BETWEEN
92W-98W. THE RIDGING IS FORECAST TO REMAIN ANCHORED OVER THE SE
CONUS WITH NE TO E WINDS PERSISTING THROUGH EARLY THURSDAY.

CARIBBEAN SEA...
SOUTHWESTERLY TO WESTERLY UPPER LEVEL FLOW DOMINATES OVER THE
CARIBBEAN AND IS PROVIDING FOR MAXIMUM UPPER LEVEL DIFFLUENCE
EAST OF A WEAK UPPER LEVEL TROUGH AXIS FROM 20N88W TO 10N92W.
LOW-LEVEL CONVERGENCE IS ALSO MAXIMIZED OVER THE SW CARIBBEAN
EAST OF THE UPPER LEVEL TROUGH AND IS GENERATING SCATTERED
SHOWERS AND TSTMS FROM 07N-15N BETWEEN 75W-84W. FURTHER AIDING
DEVELOPMENT OF CONVECTION IS THE CLOSE PROXIMITY OF THE MONSOON
TROUGH AXIS ALONG 08N EXTENDING FROM SOUTHERN COSTA RICA TO
NORTHERN COLOMBIA. FARTHER EAST...BROAD SURFACE TROUGHING
EXTENDS FROM THE ABC ISLANDS NEAR 12N69W TO 19N65W NE OF PUERTO
RICO. LOW-LEVEL CONVERGENCE IS GENERATING ISOLATED SHOWERS N OF
16N WITHIN 240 NM EITHER SIDE OF THE BOUNDARY. OTHERWISE...THE
OVERALL SYNOPTIC PATTERN IS LIKELY TO CHANGE LITTLE OVER THE
NEXT FEW DAYS AS A LOW PRESSURE AREA REMAINS OVER THE SW NORTH
ATLC WITH TROUGHING DIPPING SOUTHWARD ACROSS THE EASTERN
CARIBBEAN AND RIDGING WITH ACCOMPANYING NORTHERLY WINDS HOLDING
IN PLACE OVER THE NW CARIBBEAN.

ATLANTIC OCEAN...
WATER VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL TROUGH IS
PROGRESSING EASTWARD OFF THE EASTERN SEABOARD OF THE U.S. AND
SUPPORTS A RATHER BROAD AREA OF SURFACE LOW PRESSURE OVER A
LARGE PORTION OF THE WESTERN ATLC. THIS AREA OF TROUGHING IS
NOTED BETWEEN 45W-78W WITH AN AREA OF COMPLEX LOWS MOSTLY
LOCATED NORTH OF THE DISCUSSION AREA. EXTENDING FROM A 1001 MB
OCCLUDED LOW CENTERED NEAR 37N50W...A COLD FRONT IS ANALYZED
INTO THE AREA NEAR 32N52W AND EXTENDS S-SW ALONG 25N60W TO
20N65W. WIDELY SCATTERED SHOWERS AND TSTMS ARE OCCURRING N OF
28N BETWEEN 43W AND THE COLD FRONT...AND ISOLATED SHOWERS ARE
OCCURRING WITHIN 180 NM EAST OF THE FRONT S OF 25N. ELSEWHERE
OVER THE SW NORTH ATLC...WHILE LOWER PRESSURES PREVAIL...OVERALL
NORTHWEST TO WESTERLY WINDS IN THE RANGE OF 10 TO 20 KT ARE
NOTED IN SHIP AND BUOY OBSERVATIONS...ALONG WITH EARLIER
SCATTEROMETER DATA. FARTHER EAST...THE REMAINDER OF THE CENTRAL
AND EASTERN ATLC IS UNDER THE INFLUENCE OF SURFACE RIDGING
ANCHORED BY A 1027 MB HIGH CENTERED NEAR 35N23W. HOWEVER...WATER
VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL SHORTWAVE TROUGH
EXTENDS FROM 32N13W TO 24N15W AND SUPPORTS A COLD FRONT ANALYZED
FROM 32N13W TO 28N18W. ISOLATED SHOWERS ARE OCCURRING WITHIN 120
NM EITHER SIDE OF THE FRONTAL BOUNDARY. FINALLY...AN UPPER LEVEL
TROUGH AXIS EXTENDS FROM 20N37W TO 07N50W AND CONTINUES TO
PROVIDING MAXIMUM UPPER LEVEL DIFFLUENCE E OF 40W. ISOLATED
SHOWERS AND TSTMS ARE OCCURRING FROM 13N-20N BETWEEN 27W-39W.

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

$$
HUFFMAN



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