[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 281125
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST WED JAN 28 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N9W 3N18W 1N30W CROSSING THE
EQUATOR NEAR 45W TO 1S51W. SCATTERED MODERATE CONVECTION IS
WITHIN 60 NM EITHER SIDE OF THE AXIS BETWEEN 18W-36W AND FROM
2N-6N BETWEEN 40W-48W.

...DISCUSSION...

GULF OF MEXICO...
A STRONG COLD FRONT MOVED OFF THE TEXAS COAST AROUND MIDNIGHT
AND HAS SINCE MADE SE PROGRESS CURRENTLY EXTENDING FROM SE
LOUISIANA TO MEXICO NEAR 24N98W. N WINDS HAVE INCREASED TO 20-30
KT BEHIND THE FRONT...USHERING IN MUCH COOLER AIR. DOPPLER RADAR
REVEALS SCATTERED SHOWERS AND ISOLATED TSTMS ALONG AND BEHIND
THE BOUNDARY. AHEAD OF THE FRONT...SLY LOW-LEVEL FLOW AND DRY
AIR IN THE MID AND UPPER LEVELS ARE PROVIDING FAIR AND MILD
WEATHER. VISIBILITIES MAY BE REDUCED OVER THE N CENTRAL AND NE
WATERS IN FOG. THE FRONT WILL SLOW IN ITS FORWARD MOTION OVER
THE NEXT DAY OR SO BEFORE BECOMING REINFORCED BY A DEEPER UPPER
TROUGH... WHICH WILL SET UP GALE CONDITIONS IN THE ENHANCED
FUNNELING ZONE OVER THE FAR SW BAY OF CAMPECHE ON FRI. THE
BOUNDARY IS EXPECTED TO CLEAR THE ENTIRE REGION BY LATE FRI.

CARIBBEAN SEA...
SFC OBS AND QSCAT DATA REVEAL STRONG ELY TRADES ACROSS THE
CARIBBEAN WITH SPEEDS MAINLY IN THE 20-25 KT RANGE...EXCEPT TO
NEAR GALE FORCE ALONG THE COAST OF COLOMBIA ENHANCED BY
CLIMATOLOGICAL LOW PRES OVER SOUTH AMERICA AND HIGH TERRAIN.
THIS STRONG FLOW IS GENERATING ENOUGH INSTABILITY TO PRODUCE
PATCHES OF LOW-LEVEL CLOUDS WITH EMBEDDED SHOWERS. CLOUDINESS
APPEARS MOST ORGANIZED OVER THE E CARIBBEAN CLOSER TO A COUPLE
OF WEAK PERTURBATIONS IN THE TROPICAL ATLC. HOWEVER...ALL OF
THIS MOISTURE IS SHALLOW IN NATURE CAPPED BY ABUNDANT DRY STABLE
AIR ALOFT IN A GENERAL CONFLUENT AREA BETWEEN AN UPPER LOW OVER
HAITI AND AN UPPER HIGH OVER THE TROPICAL EPAC. TRADE WINDS ARE
ANTICIPATED TO SLACKEN OVER THE W CARIBBEAN LATER TODAY IN
RESPONSE TO A FRONTAL BOUNDARY...EXPECTED TO ENTER THE NW CARIB
ON FRI.

ATLANTIC OCEAN...
NOT MUCH TO DISCUSS ACROSS THE ATLC BASIN WITH ONLY A WEAK
TROUGH ANALYZED IN THE SUBTROPICS ALONG 61W FROM 25N-29N. THIS
WEAK BOUNDARY MAINLY REPRESENTS A MODEST WIND SHIFT THAT IS
GENERATING SCATTERED SHOWERS WITHIN 120 NM OF THE AXIS. THERE
ARE A COUPLE OF WEAK FRONTS JUST N OF THE ZONE...BUT THESE ARE
NOT PRODUCING ANY SENSIBLE WEATHER IN THE DISCUSSION ZONE. TRADE
WINDS REMAIN 20-25 KT ACROSS A LARGE PORTION OF THE AREA...
GENERALLY S OF 24N E OF THE BAHAMAS SUPPORTED BY AN E-W HIGH
PRES RIDGE ALONG 32N/33N. THE UPPER PATTERN IS RATHER
FLAT...WHICH IS NOT SURPRISING GIVEN THE ABSENCE OF SFC
FEATURES. MOST OF THE AREA LIES UNDER A SUBSIDENT ENVIRONMENT
PROMOTING FAIR WEATHER. HOWEVER...AN UPPER DIFFLUENT PATTERN
OVER THE DEEP TROPICS IS AIDING IN THE DEVELOPMENT OF CONVECTION
WITHIN THE ITCZ W OF 40W.

$$
CANGIALOSI






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