[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 162359
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED DEC 16 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2200 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 7N12W 5N22W 6N40W 1N50W.
SCATTERED MODERATE CONVECTION IS WITHIN 30 NM EITHER SIDE OF THE
ITCZ AXIS BETWEEN 21W AND 24W AS WELL AS FROM 06N TO 12N BETWEEN
26W AND 33W.

...DISCUSSION...

GULF OF MEXICO...
A 1016 MB LOW PRES CENTER NEAR 25N96W WILL SLOWLY DEEPEN AND
LIFT NORTHEASTWARD OVER THE NEXT 24 HOURS...REMAINING IN THE
GULF OF MEXICO UNTIL THE UPPER LEVEL LOW CURRENTLY OVER TEXAS
FINALLY REACHES THE SURFACE SYSTEM. THE DEEP LAYERED SYSTEM WILL
THEN BE PROPELLED EASTWARD INTO NORTHERN FLORIDA/SOUTHERN
GEORGIA BY FRI AFTERNOON AS THE UPPER LOW DISSIPATES AND MOVES
INTO THE LEADING EDGE OF THE NORTHERN STREAM TROUGH AMPLIFYING
OVER THE PLAINS AND MISSISSIPPI VALLEY. THE SURFACE LOW WILL
DEEPEN RAPIDLY ON FRI AS THE DEEP LAYER SYSTEM MOVES INTO THIS
AMPLIFIED TROUGH. THE 1800 UTC SURFACE ANALYSIS SHOWS A TIGHT
PRES GRADIENT BETWEEN THE DEVELOPING LOW PRES AND A 1034 MB HIGH
PRES CENTER OVER NORTHERN MEXICO NEAR 27N102W AS WELL AS A 1036
MB HIGH PRES CENTER NEAR 38N88W. AS A RESULT...A GALE WARNING IS
IN EFFECT FOR THE NW GULF OF MEXICO. GALE FORCE WINDS ARE
EXPECTED SPREAD EASTWARD INTO THE CENTRAL GULF THROUGH THU AS
THE SYSTEM INCHES EASTWARD. GALE FORCE WINDS ARE FORECAST TO
DIMINISH BEFORE SUNRISE FRI AS THE HIGH PRES NORTH OF THE LOW
MIGRATES NORTHWARD INTO CANADA...DECREASING THE PRES GRADIENT.
RADAR SHOWS WIDESPREAD MODERATE TO HEAVY RAIN OVER SOUTH TEXAS
AND A DEVELOPING BAND OF SHOWERS AND THUNDERSTORMS ACROSS SOUTH
FLORIDA ALONG THE STATIONARY FRONT EXTENDING FROM THE LOW. THE
SYSTEM WILL CONTINUE TO BRING WIDESPREAD PRECIPITATION TO THE
GULF...THE GULF COAST...AND FL THROUGH THE FORECAST PERIOD.

CARIBBEAN SEA...
FRESH EASTERLY TRADES PREVAIL OVER THE CENTRAL CARIBBEAN AND
WILL CONTINUE THROUGH THU BEFORE THE DEEP LAYER HIGH PRES TO THE
NORTH BRAKES DOWN...DECREASING THE PRES GRADIENT BETWEEN IT AND
CLIMATOLOGICAL LOW PRES OVER NORTHERN COLOMBIA. 1019 MB HIGH
PRES CURRENTLY RESIDES NEAR 25N68W WITH A RIDGE EXTENDING SE OF
THE HIGH INTO THE LESSER ANTILLES. A FRONTAL BOUNDARY LIES OVER
THE WESTERN N ATLC INTO SOUTH FLORIDA AND TO LOW PRES IN THE
GULF OF MEXICO. THE COLD FRONTAL PORTION OF THIS BOUNDARY WILL
ADVANCE INTO THE CENTRAL ATLC WHILE THE REMAINDER STAYS
RELATIVELY STATIONARY OVER FL AND THE GULF ON THU. THE HIGH PRES
RIDGE WILL WEAKEN AND SHIFT SLIGHTLY SOUTHWARD AS A RESULT OF
THE ADVANCING PORTION OF THE FRONT. CONDITIONS WILL CHANGE
RAPIDLY ON FRI AS THE AFOREMENTIONED SURFACE LOW IN THE GULF
INTENSIFIES AND MOVES EASTWARD...SHIFTING THE SURFACE RIDGE WELL
E OF THE AREA. THE COLD FRONT ASSOCIATED WITH THIS GULF LOW WILL
MOVE INTO THE YUCATAN CHANNEL FRI NIGHT. SHOWERS AND
THUNDERSTORMS WILL BUILD OVER THE NW GULF FRI IN ADVANCE OF THE
FRONT. WINDS WILL DIMINISH TO 20 KT IN THE CENTRAL CARIBBEAN AS
A RESULT OF THE DECREASED PRES GRADIENT.

ATLANTIC OCEAN...
A STRONG SURFACE LOW NORTH OF THE FORECAST AREA NEAR 41N33W IS
GENERATING NW SWELL IN THE 8 TO 16 FOOT RANGE OVER MUCH OF THE
ATLC FORECAST WATERS E OF 55W. THIS SURFACE LOW IS ASSOCIATED
WITH A DEEP LAYER GYRE THAT ALSO ENCOMPASSES A SECOND SURFACE
LOW...1004 MB...OVER FORECAST WATERS NEAR 27N35W. THIS LOW IS
CURRENTLY PRODUCING 20 TO 25 KT WINDS AND IS EXPECTED TO
INTENSIFY AS IT LIFTS NORTHEASTWARD...EVENTUALLY OVERTAKING ITS
COUSIN TO THE NORTH. AS THE SYSTEM REORGANIZES FURTHER
NORTH...SEAS WILL SUBSIDE TO THE 7 TO 10 FOOT RANGE OVER THE
NEXT TWO DAYS. FARTHER W...THE COLD FRONT OVER THE WESTERN ATLC
WILL SLOWLY ADVANCE EASTWARD INTO THE CENTRAL ATLC OVER THE NEXT
48 HOURS. SEAS BEHIND THE FRONT WILL BUILD TO 8 TO 20 FT BY FRI.
MEANWHILE...THE SYSTEM IN THE GULF OF MEXICO THAT IS EXPECTED TO
INTENSIFY AND LIFT NORTHEASTWARD INTO NORTH FLORIDA/SOUTH
GEORGIA FRI AFTERNOON WILL BE THE FOCUS OF SHOWERS AND
THUNDERSTORMS BUILDING IN THE WESTERN ATLC FRI.

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

$$
SCHAUER


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