[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200512
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST THU NOV 20 2008

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 54W S OF 15N MOVING W NEAR 15 KT. A
MAXIMUM IN DEEP LAYER MOISTURE COINCIDES WITH THIS WAVE BASED ON
TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SATELLITE IMAGERY
INDICATES AN INVERTED-V PATTERN TO THE CLOUD COVERAGE IN THE
VICINITY OF THIS WAVE. SCATTERED MODERATE CONVECTION IS E OF THE
WAVE AXIS FROM 9N-12N BETWEEN 51W-53W.

THE TROPICAL WAVE THAT WAS PREVIOUSLY ALONG 76W S OF 17N FOR THE
19/1800 UTC SURFACE ANALYSIS HAS BEEN REMOVED FOR THE
20/0000 UTC SURFACE ANALYSIS. NE LOW LEVEL FLOW ACROSS THE W AND
CENTRAL CARIBBEAN SEA HAS OVERTAKEN THIS FORMER WAVE TO THE E OF
A SURFACE STATIONARY FRONT THAT EXTENDS FROM NE OF JAMAICA NEAR
18N76W TO 14N81W TO N OF COSTA RICA NEAR 9N82W.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 11N14W 8N22W 6N36W 7N44W 7N53W.
SCATTERED MODERATE CONVECTION IS WITHIN 180 NM S OF THE ITCZ
AXIS BETWEEN 21W-33W. SCATTERED MODERATE CONVECTION IS FROM
7N-10N BETWEEN 36W-41W. SIMILAR CONVECTION IS FROM 10N-16N
BETWEEN 43W-48W.

...DISCUSSION...

GULF OF MEXICO...
STRONG WESTERLY FLOW ALOFT AND DEEP LAYER DRY AIR ARE PRESENT
OVER MUCH OF THE GULF REGION. HOWEVER...UPPER LEVEL MOISTURE IS
STREAMING FROM THE E PACIFIC REGION TO THE W GULF. ALSO...A
MODIFIED CONTINENTAL POLAR AIRMASS PERSISTS ACROSS THE GULF
REGION. AS A RESULT...TEMPERATURES ACROSS THE GULF REGION ARE
BELOW SEASONAL AVERAGES. FREEZE WARNINGS ARE IN EFFECT FOR
TONIGHT THROUGH THURSDAY MORNING FOR PORTIONS OF FLORIDA. THIS
RELATIVELY COOLER AND DRIER AIRMASS IS BEING SUPPORTED BY A 1025
MB SURFACE HIGH S OF MOBILE ALABAMA NEAR 30N88W...WITH AN
ASSOCIATED SURFACE RIDGE AFFECTING MUCH OF THE GULF REGION. AS
THE COOLER AIR IS BEING ADVECTED OVER THE RELATIVELY WARMER GULF
WATERS...WEAK LOW LEVEL INSTABILITY IS SUPPORTING SCATTERED
STRATOCUMULUS CLOUDS ACROSS THE GULF MAINLY S OF 25N.
HOWEVER...SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS HIGHER IN
THE ATMOSPHERE ARE INHIBITING DEEP CONVECTION ACROSS THE GULF
REGION. OVER THE NEXT DAY...ANOTHER SURFACE COLD FRONT...
CURRENTLY EXTENDING FROM THE GREAT LAKES TO THE PLAINS OF THE
CONUS TO THE NORTHERN ROCKY MOUNTAINS...WILL MOVE SOUTHWARD AND
APPROACH THE N GULF COAST. THIS COLD FRONT WILL REINFORCE THE
MODIFIED CONTINENTAL POLAR AIRMASS ALREADY IN PLACE ACROSS THE
GULF REGION. ADDITIONALLY...STRONG N TO NE SURFACE WINDS ARE
BLOWING THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE
FORCE WINDS IN THE E PACIFIC REGION.

CARIBBEAN SEA...
ACROSS THE W CARIBBEAN...A SURFACE COLD FRONT EXTENDS FROM W
HAITI NEAR 20N72W TO NE OF JAMAICA NEAR 18N76W...WITH A SURFACE
STATIONARY FRONT EXTENDING FROM 18N76W TO 14N81W TO N OF COSTA
RICA NEAR 9N82W. LOW LEVEL CONVERGENCE NEAR THESE FRONTS IS
INTERACTING WITH DEEP MOISTURE OVER THE SW CARIBBEAN TO GENERATE
SCATTERED SHOWERS AND THUNDERSTORMS OVER THE SW CARIBBEAN S OF
14N W OF 76W...INCLUDING ADJACENT PORTIONS OF COLOMBIA...
PANAMA...AND COSTA RICA. THIS ACTIVITY IS BEING ENHANCED BY
UPPER LEVEL DIFFLUENCE IN THE VICINITY OF AN UPPER RIDGE PRESENT
OVER THE W CARIBBEAN...WITH THE AXIS OF THIS UPPER RIDGE
EXTENDING FROM N COLOMBIA NEAR 11N74W TO 14N79W TO 17N83W.
ALSO...A DISSIPATING SURFACE COLD FRONT OVER THE NW CARIBBEAN
EXTENDS FROM 18N80W TO 20N85W TO THE YUCATAN PENINSULA NEAR
21N88W...WITH DEEP LAYER DRY AIR INHIBITING DEEP CONVECTION IN
THE VICINITY OF THIS FRONT. OVER THE E CARIBBEAN...AN UPPER
LEVEL RIDGE AXIS EXTENDS FROM NE VENEZUELA NEAR 10N66W TO 16N64W
TO 14N63W...WITH UPPER LEVEL DIVERGENCE SUPPORTING SCATTERED
SHOWERS OVER THE E CARIBBEAN S OF 15N E OF 69W.

ATLANTIC OCEAN...
A VIGOROUS UPPER TROUGH IS OVER THE W ATLC...WHICH IS SUPPORTING
A SURFACE COLD FRONT THAT EXTENDS FROM W HAITI NEAR 20N72W TO
26N63W TO 32N57W AND EXTENDS TO THE N OF THE DISCUSSION AREA.
ISOLATED SHOWERS ARE WITHIN 60 NM W AND 120 NM E OF THIS COLD
FRONT. TO THE W OF THIS COLD FRONT...A MODIFIED CONTINENTAL
POLAR AIRMASS IS IN PLACE...WITH TEMPERATURES BELOW SEASONAL
AVERAGES ACROSS FLORIDA AND SCATTERED STRATOCUMULUS CLOUDS
BETWEEN THIS FRONT AND THE COAST OF THE SE CONUS. IN THE WAKE OF
THE COLD FRONT...GALE FORCE WINDS ARE OCCURRING WITHIN 45 TO 60
NM OF A LINE FROM 16N95W TO 13N97W...WHERE N TO NE SURFACE WINDS
OF 30 TO 45 KT ARE OCCURRING. FARTHER TO THE E...A 1011 MB
SURFACE LOW IS CENTERED NEAR 28N45W. DEEP LAYER DRY AIR IS
INHIBITING DEEP CONVECTION NEAR THIS SURFACE LOW. ALSO...A
SURFACE RIDGE IS N OF 19N BETWEEN 18W-33W...RESULTING IN FAIR
WEATHER CONDITIONS ACROSS THE E ATLC.

$$
COHEN




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