[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 291732
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU JAN 29 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N9W 1N20W 1S30W 2N45W 2N51W.
SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF THE AXIS
BETWEEN 15W-27W. ISOLATED MODERATE CONVECTION IS WITHIN 90 NM N
OF THE AXIS BETWEEN 37W-45W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYER TROUGH OVER THE ERN CONUS IS SUPPORTING A COLD
FRONT EXTENDING FROM JACKSONVILLE FLORIDA SW THROUGH 26N90W TO
23N94W THEN S THROUGH THE BAY OF CAMPECHE TO SRN MEXICO NEAR
18N94W. IN THE WAKE OF THE FRONT...A COOLER AIRMASS IS IN PLACE
ADVECTED BY N-NE 15-20 KT WINDS ACROSS THE NRN AND WRN GULF. LOW
LEVEL CONVERGENCE IS SUPPORTING SCATTERED SHOWERS AND ISOLATED
TSTMS WITHIN 60 NM ON EITHER SIDE OF THE FRONT N OF 25N. SOME OF
THIS ACTIVITY IS BEING ENHANCED BY UPPER DIVERGENCE ASSOCIATED
WITH A JET STREAM MAXIMUM OVER THE SE CONUS. AHEAD OF THE
FRONT...DRY AIR AND ATMOSPHERIC STABILITY IS INHIBITING ANY DEEP
CONVECTION. THE AFOREMENTIONED FRONT HAS SLOWED ITS SE
PROGRESSION...BUT IS FORECAST TO SURGE SEWD EARLY FRI AS AN
UPPER TROUGH OVER THE WRN CONUS SHIFTS E AND SURFACE HIGH
PRESSURE BUILDS OVER THE SE CONUS...LEADING TO GALE CONDITIONS
OVER THE SW GULF.

CARIBBEAN SEA...
A TIGHT PRESSURE GRADIENT...BETWEEN STRONG HIGH PRESSURE OVER
THE CENTRAL ATLC AND LOWER PRESSURE OVER SOUTH AMERICA...IS
GENERATING MODERATE TO FRESH TRADES ACROSS THE CARIBBEAN BASIN.
THESE WINDS ARE FORECAST TO DECREASE ON FRI AS THE HIGH MOVES
EWD AND A COLD FRONT POSITIONS ITSELF ACROSS THE NW CARIBBEAN.
NE 20-25 KT WINDS AND RELATIVELY COOLER AND DRIER AIR ARE
EXPECTED TO BUILD BEHIND THE FRONT BEGINNING FRI NIGHT. IN THE
MEANTIME...GENERALLY FAIR CONDITIONS PERSIST WITH DEEP LAYER
SUBSIDENCE AND DRY AIR IN PLACE. HOWEVER...TYPICAL ISOLATED LOW
LEVEL SHOWERS ARE BEING CARRIED BY THE TRADE WINDS ACROSS THE E
CARIBBEAN...WHERE SOME UPPER LEVEL MOISTURE IS BEING ADVECTED BY
SW FLOW ALOFT.

ATLANTIC OCEAN...
TRANQUIL WEATHER IS THE THEME ACROSS MUCH OF THE DISCUSSION ZONE
AS A 1032 MB SURFACE HIGH PRESSURE CENTERED NORTH OF THE AREA
NEAR 35N46W EXTENDS RIDGING ACROSS THE BAHAMAS TO THE WEST AND
ALSO ACROSS THE CAPE VERDE ISLANDS TO THE SE. THE ASSOCIATED
PRESSURE GRADIENT ON ITS SRN PERIPHERY IS PRODUCING A LARGE AREA
OF NE/E 20-25 KT TRADES S OF 23N E OF 62W. HOWEVER...THE RIDGE
HAS BEEN WEAKENED OVER THE FAR NW AND NE PARTS OF THE AREA DUE
TO A PAIR OF COLD FRONTS. THE FRONT OVER THE W ATLC CLIPS THE
AREA FROM 32N77W TO JACKSONVILLE FLORIDA. WITH SCATTERED SHOWERS
AND POSSIBLE ISOLATED TSTMS WITHIN 90 NM OF THE FRONT. STRONG
SLY WINDS ARE BLOWING WITHIN A FEW HUNDRED NM E OF THE BOUNDARY
WITH SCATTERED SHOWERS AND POSSIBLE ISOLATED TSTMS WITHIN 90 NM
OF THE FRONT. THE OTHER FRONT EXTENDS FROM 30N31W TO BEYOND
32N26W. THE ASSOCIATED UPPER SUPPORT IS FORECAST TO SHARPEN
WHICH WILL ALLOW THE FRONT TO LINGER ACROSS THE NERN ATLC OVER
THE NEXT 12 TO 24 HOURS. OTHERWISE...ABUNDANT DRY STABLE AIR IS
LIMITING THE DEVELOPMENT OF DEEP CONVECTION...WITH ONLY THE
TYPICAL PATCHES OF LOW CLOUDS WITH EMBEDDED ISOLATED SHOWERS
TRACKING WWD WITHIN THE TRADE WIND FLOW.

$$
HUFFMAN




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