[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 261806
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST MON DEC 26 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...ITCZ/MONSOON TROUGH...

THE ITCZ AXIS EXTENDS FROM 7N13W TO 4N22W TO 3N30W TO ABOUT
3N41W WHERE IT BECOMES ILL-DEFINED. THE MONSOON TROUGH IS
ANALYZED E OF THE AREA WELL INLAND AFRICA. SCATTERED WEAK
CONVECTION IS ALONG AND WITHIN 60 NM EITHER SIDE OF THE AXIS
BETWEEN 24W-28W.

...DISCUSSION...

GULF OF MEXICO...
SATELLITE IMAGERY FROM THROUGHOUT THE MORNING AND EARLY AFTERNOON
SHOWS A SWATH OF UPPER LEVEL MOISTURE STREAMING NEWD ACROSS THE
FAR NW GULF...AND EWD OVER THE NRN PORTION OF THE GULF E OF 90W
AND TO ACROSS FLORIDA AND TO THE NW ATLC OCEAN. THE PRESENT SET
UP OF AN UPPER LEVEL LOW OVER N CENTRAL TEXAS NOW PROGRESSING EWD
AND AN AMPLIFYING RIDGE CREST AHEAD OF IT GRADUALLY SHIFTING EWD
OVER THE SE U.S. IS ALLOWING FOR STRONG UPPER SW TO W FLOW IN
A JET STREAM BRANCH S OF THESE FEATURES TO TAP PACIFIC MOISTURE
...AND ADVECT IT ACROSS THE THE AFOREMENTIONED GULF SECTIONS.
THE SURFACE ANALYSIS HAS A STATIONARY FRONT EXTENDING FROM S
CENTRAL LOUISIANA TO 25N92W AND TO INLAND MEXICO NEAR VERACRUZ.
A VERY WEAK FRONTAL BOUNDARY EXTENDS FROM CENTRAL FLORIDA NW TO
29N85W...THEN WNW AS A DEVELOPING WARM FRONT INTO A WEAK LOW
OVER SE LOUISIANA. THE SATELLITE IMAGERY ALSO SHOWS EXTENSIVE
OVERCAST CONDITIONS IN LOW TO MID LEVEL CLOUDS TO THE W OF THE
STATIONARY FRONT WITH AREAS OF RAIN AND SCATTERED SHOWERS.
SCATTERED SHOWERS AND ISOLATED TSTMS ARE SEEN ALONG AND JUST TO
THE E OF THE STATIONARY FRONT...AND OVER THE NORTHERN WATERS N
OF 28N E OF 92W WHERE REDUCED VISIBILITIES ARE BEING REPORTED
IN RAIN IN A FEW SPOTS. A SMALL PATCH OF BROKEN LOW CLOUDS WITH
ISOLATED SHOWERS MOVING NW TO N IS OVER THE SE GULF FROM 23N-25N
BETWEEN 83W-86W.

A SHORTWAVE TROUGH EXTENDING SW FROM THE UPPER LOW TO N CENTRAL
MEXICO WILL MOVE TO THE N CENTRAL GULF TUE LIFTING THE WARM
FRONT TO N OF THE AREA. THE TROUGH IS EXPECTED TO MAINTAIN
SURFACE LOW PRES OVER THE LOWER MISSISSIPPI RIVER VALLEY. THIS
LOW WILL THEN QUICKLY PULL TO THE NE OVER THE NEXT 18-24 HRS.
THE MUCH COLDER AIR MASS IN THE WAKE OF THE OF THE TROUGH WILL
ENERGIZE THE STATIONARY FRONT INTO A COLD FRONT THROUGHOUT
TODAY AND INTO TONIGHT. IT IS FORECAST TO REACH FROM THE FLORIDA
PANHANDLE TO EASTERN BAY OF CAMPECHE EARLY TUE...AND TO E OF THE
GULF TUE NIGHT. HIGH PRES WILL BUILD ACROSS THE AREA IN THE WAKE
OF THE FRONT USHERING A DRIER AND COOLER AIR MASS THROUGHOUT.

CARIBBEAN SEA...
HIGH PRES BOTH AT THE MID AND UPPER LEVELS CONTINUES TO PUT A
CAP OVER THE AREA AS IT MAINTAINS RATHER STABLE ATMOSPHERIC
CONDITIONS SUPPRESSING ANY DEEP CONVECTION FROM DEVELOPING
ACROSS THE BASIN AS OBSERVED BY THE PRESENCE OF STRONG
SUBSIDENCE IN WATER VAPOR IMAGERY. HIGH PRES CENTERED OVER THE
WESTERN ATLC OCEAN IS INTERACTING WITH LOW PRES OVER NW COLOMBIA
RESULTING IN FRESH TO STRONG TRADES OVER THE CENTRAL AND SOUTHERN
PORTIONS OF THE CARIBBEAN W OF ABOUT 69W. LOW LEVEL SPEED
CONVERGENCE IN THE TRADE WIND FLOW IS PRODUCING MOSTLY LOW-TOP
ISOLATED WEAK SHOWERS FROM 13N-15N W OF 71W...AND FROM 13N-15N E
OF 65W. A SMALL AREA OF SCATTERED SHOWERS AND RAPIDLY WEAKENING
ISOLATED TSTMS IS OFFSHORE THE NE COAST OF HONDURAS AND
NICARAGUA FROM 14N-18N BETWEEN 80W-84W. OVERCAST TO BROKEN LOW
CLOUDS WITH EMBEDDED ISOLATED SHOWERS AND POSSIBLE RAIN HAVE
MOVE INLAND HONDURAS AND NICARAGUA FROM 13N-16N AND 84W-86W.
ISOLATED SHOWERS MOVING WWD IN TRADE WIND FLOW ARE ALSO NOTED
OVER THE FAR NE CARIBBEAN IN THE VICINITY OF PUERTO RICO AND
VIRGIN ISLANDS. SIMILAR TYPE SHOWERS ARE BEGINNING TO MOVE
ACROSS THE WINDWARD ISLANDS AS WELL.

ATLANTIC OCEAN...
A COLD FRONT HAS PUSHED INTO THE NW PORTION OF THE BASIN FROM
32N71W SW TO E CENTRAL FLORIDA WHERE IT BECOMES DIFFUSE WWD FROM
THERE ACROSS CENTRAL FLORIDA. SCATTERED SHOWERS ARE ALONG...AND
WITHIN 60-90 NM SE OF THE FRONT. THE FRONT WILL CONTINUE TO
TRACK EASTWARD WITH POSSIBLE INCREASING SHOWER AND TSTM
ACTIVITY. IN THE MEAN TIME...AN UPPER LEVEL RIDGE IS EVIDENT
ACROSS MUCH OF THE AREA W OF 47W WITH VERY DRY AIR ALOFT AND
STRONG SUBSIDENCE NOTICED ON WATER VAPOR IMAGERY. THIS FEATURE
SUPPORTS A 1022 MB HIGH CENTERED NEAR 27N74W WITH A RIDGE E
TO 27N61W. A DISSIPATING STATIONARY FRONT BISECTS THE RIDGE
FROM 27N61W NW TO 28N62W. A COLD FRONT EXTENDS TO THE E OF
STATIONARY FRONT TO 28N54W AND NEWD TO BEYOND THE REGION AT
32N45W. ISOLATED SHOWERS ARE POSSIBLE ALONG AND WITHIN 60 NM
EITHER SIDE OF THE FRONT. TO THE E OF THIS FRONT...AN EARLIER
ASCAT PASS REVEALED AN AREA OF LOW LEVEL CONFLUENCE OF LIGHT
WINDS ANALYZED AS A WEAK SURFACE TROUGH FROM 32N43W SW TO
25N48W. A SIMILAR SURFACE TROUGH IS ALSO ANALYZED FROM 18N46W TO
10N51W. FARTHER E...AN UPPER LEVEL LOW IS CENTERED NEAR
20N38W. THIS UPPER LEVEL CIRCULATION IS GENERATING A BROAD AREA
OF DIFFLUENCE FLOW ALOFT THAT COVERS THE ERN ATLC S OF 25N E OF
38W. SCATTERED SHOWERS AND POSSIBLE ISOLATED TSTMS ARE WITHIN
THIS REGION...WITH NE WINDS UP TO 25 KT.

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

$$

AGUIRRE






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