[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 181150
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SUN NOV 18 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...ITCZ/MONSOON TROUGH...

MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL ATLC
NEAR 11N15W TO 8N19W WHERE THE ITCZ AXIS CONTINUES ALONG 4N36W
5N48W TO SOUTH AMERICA NEAR 6N56W. A SURFACE TROUGH IS N OF THE
ITCZ ALONG THE E SIDE OF AN UPPER TROUGH FROM 21N29W ALONG
18N37W TO 13N42W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
WITHIN 260 NM EITHER SIDE OF THE TROUGH AXIS. SCATTERED
MODERATE/STRONG CONVECTION IS OFF THE COAST OF LIBERIA AND
SIERRA LEONE WITHIN 60 NM OF LINE FROM 4N11W TO 8N14W. SCATTERED
MODERATE CONVECTION IS FROM 2N-5N BETWEEN 28W-30W.

...DISCUSSION...

GULF OF MEXICO...
A SHORTWAVE UPPER TROUGH EXTENDS FROM W PENNSYLVANIA TO GEORGIA
THEN INTO THE GULF OF MEXICO CONTINUING S TO OVER THE YUCATAN
PENINSULA AND THE NW CARIBBEAN. A BROAD UPPER RIDGE ANCHORED
OVER THE E PACIFIC REGION COVERS THE FAR W GULF WITH THE RIDGE
AXIS EXTENDING OVER TEXAS TO THE CENTRAL PLAIN STATES COVERING
THE GULF W OF 93W. A SURFACE RIDGE DOMINATES THE GULF EXTENDING
A RIDGE AXIS EXTENDING FROM A 1031 MB HIGH OVER S ILLINOIS TO
OVER TEXAS AND NE MEXICO. A WEAKENING SURFACE TROUGH IS THAT WAS
ALONG THE COAST OF MEXICO HAS DISSIPATED AT 18/0900 UTC.
HOWEVER...DENSE CLOUD COVER WITH POSSIBLE ISOLATED SHOWERS
REMAIN WITHIN 90/120 NM ALONG THE COAST S OF 25N W OF 93W. A
SECOND STRONGER SURFACE TROUGH REMAINS IN THE SE GULF EXTENDING
FROM THE STRAITS OF FLORIDA NEAR 24N82W ALONG THE NW COAST OF
CUBA INTO THE FAR NW CARIBBEAN NEAR 21N86W WITH SCATTERED
SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 60 NM OF LINE
FROM 24N81W ALONG 23N85W TO 22N87W. THE REMAINDER OF THE GULF IS
UNDER FAIR WEATHER AGAIN THIS MORNING. SURFACE RIDGE WILL WEAKEN
MON AND TUE. A TIGHT PRESSURE GRADIENT BETWEEN THE RIDGE AND
BROAD TROUGHING OVER THE W ATLC WILL MAINTAIN FRESH NE WINDS
OVER THE NE GULF THROUGH MUCH OF TODAY. THE PRESSURE GRADIENT
WILL INCREASE IN THE E GULF AGAIN WED INTO THU AS HIGH PRESSURE
OVER THE SE CONUS BUILDS S OVER THE AREA.

CARIBBEAN SEA...
A WEAK PRESSURE PATTERN REMAINS ACROSS THE CARIBBEAN THIS
MORNING. THE UPPER TROUGH OVER THE GULF OF MEXICO EXTENDS OVER
THE NW CARIBBEAN AND CENTRAL AMERICA N OF 14N W OF 78W WHILE AN
UPPER RIDGE DOMINATES THE REMAINDER OF THE CARIBBEAN. THE UPPER
RIDGE AXIS EXTENDS FROM AN UPPER HIGH OVER VENEZUELA TO OVER THE
LESSER ANTILLES CONTINUING INTO THE CENTRAL ATLC. THE MONSOON
TROUGH EXTENDS FROM COLOMBIA NEAR 10N74W INTO THE SW CARIBBEAN
THROUGH A 1010 MB LOW NEAR 11N76W CROSSING PANAMA/COSTA RICA
NEAR 9N82W INTO THE E PACIFIC REGION. CLUSTERS OF SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 14N BETWEEN 71W-78W AND
S OF 13N BETWEEN 80W-83W. THE UPPER RIDGE IS PROVIDING
DIFFLUENCE ALOFT TO GENERATE SCATTERED SHOWERS AND POSSIBLE
ISOLATED THUNDERSTORMS ACROSS THE CENTRAL CARIBBEAN WITHIN 150
NM OF LINE FROM 14N75W ACROSS HISPANIOLA TO NEAR 20N71W AND
WITHIN 75/90 NM OF LINE FROM 13N81W TO OVER THE CAYMAN ISLANDS.
THIS IS LEAVING THE REMAINDER OF THE NW AND ALL OF THE E
CARIBBEAN WITH FAIR WEATHER AGAIN THIS MORNING. THE WEAK
PRESSURE PATTERN OVER THE CENTRAL AND E CARIBBEAN WILL MAINTAIN
MODERATE TRADE WINDS. A TIGHTER PRESSURE GRADIENT IS ALLOWING
FOR FRESH NORTHERLY WINDS TO BE CONFINED TO THE NW CARIBBEAN .
LITTLE CHANGE IS EXPECTED WITH THE WINDS IN THE CARIBBEAN
THROUGH THU. ANOTHER SURGE OF HIGH PRESSURE WILL SURGE S INTO
THE NW CARIBBEAN WED AND THU INCREASING NORTHERLY WINDS IN THE
NW CARIBBEAN.

ATLANTIC OCEAN...
THE UPPER TROUGH IN THE GULF OF MEXICO COVERS THE FAR W ATLC W
OF 70W SUPPORTING A WEAK STATIONARY FRONT THAT EXTENDS FROM A
1016 MB LOW NEAR 32N77W S ALONG 28N78W TO 26N80W. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE N OF 30N W OF THE FRONT AND N
OF 26N W OF 80W. THE BROAD UPPER RIDGE OVER THE CARIBBEAN
EXTENDS OVER THE W/CENTRAL ATLC ACROSS THE LEEWARD ISLANDS NEAR
18N63W TO BEYOND 32N52W. A SURFACE TROUGH IS BENEATH THE UPPER
RIDGE EXTENDING FROM 31N58W ALONG 27N63W TO 22N68W. THE SURFACE
TROUGH COUPLED WITH THE UPPER RIDGE THAT IS PROVIDING DIFFLUENCE
ALOFT ARE GENERATING CLUSTERS OF SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS WITHIN 120 NM OF LINE FROM HISPANIOLA NEAR 20N71W
TO 23N68W AND WITHIN 180/200 NM E OF THE SURFACE TROUGH AND N OF
28N W OF THE SURFACE TROUGH TO 74W. THE CUTOFF UPPER LOW IN THE
CENTRAL ATLC IS CENTERED NEAR 20N42W WITH THE UPPER TROUGH
EXTENDING S INTO THE TROPICS TO NEAR 10N50W AND IS ALSO
ENHANCING THE ACTIVITY ASSOCIATED WITH THE SURFACE TROUGH IN THE
ITCZ/MONSOON TROUGH SECTION ABOVE. A LARGE SURFACE RIDGE
DOMINATES THE ATLC BETWEEN 10W-60W AND IS ANCHORED BY A 1025 MB
HIGH NEAR 33N38W. W ATLC STATIONARY FRONT WILL REMAIN THROUGH
TUE WITH A GRADUALLY WEAKENING SURFACE RIDGE BEHIND IT OVER THE
SE CONUS. A BROAD AREA OF LOW PRESSURE IS FORECAST TO DEVELOP
TODAY OVER W/CENTRAL ATLC N OF 25N AND LIFT N OF THE AREA LATE
MON INTO TUE. A COLD FRONT WILL MOVE INTO NW WATERS WED AND
REACH FROM 32N64W THROUGH THE CENTRAL BAHAMAS THU. HIGH PRESSURE
WILL BUILD IN BEHIND THIS FRONT.

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

$$
PAW






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