[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 282321
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU DEC 28 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...
CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...
NORTHEASTERN SECTIONS OF SOUTH AMERICA...AND THE 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 2315 UTC.

...THE ITCZ...
ITCZ IS CENTERED ALONG 9N12W 5N25W 3N40W TO THE EQUATOR AND 49W.
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF
THE AXIS BETWEEN 28W-40W. ISOLATED MODERATE IS WITHIN 240 NM N
OF THE AXIS W OF 42W.

...DISCUSSION...
THE GULF OF MEXICO...
THE BIGGEST WEATHER FACTOR THIS EVENING IS THE STRONG SOUTHERLY
WINDS IN THE WRN GULF. SFC OBSERVATIONS INDICATE SLY FLOW FROM
25-30 KT ACROSS THE WRN PORTION WHERE A FAIRLY TIGHT PRES GRAD
HAS SET UP BETWEEN A LARGE LOW PRES SYSTEM IN THE SW U.S. AND
HIGH PRES CENTERED OFF THE MID-ATLANTIC COAST. THE FRONTAL
BOUNDARIES... ASSOCIATED WITH THE SIGNIFICANT LOW IN THE
SW...REMAIN W OF THE AREA. THE SFC FLOW GRADUALLY RELAXES AND
VEERS MORE TO THE E IN THE E GULF...CLOSER TO THE SFC HIGH.
PLENTY OF DRY AIR IN THE MID AND UPPER LEVELS EXISTS ABOVE THE
AREA KEEPING THE SCATTERED LOW CLOUDS IN THE CENTRAL AND W GULF
CAPPED. LOOKING AHEAD...THE TRAILING COLD FRONT...CURRENTLY IN
MEXICO...WILL ENTER THE NW PORTION OF THE AREA LATE FRI/EARLY
SAT AND TRACK E ACROSS THE N GULF. THIS FRONT WILL ERODE THE
RIDGE AND BRING A SWATH OF MOISTURE WITH IT.

THE CARIBBEAN SEA...
THE TAIL END OF W ATLC FRONTAL BOUNDARY WAS ANALYZED ACROSS ERN
CUBA AND JAMAICA WITH A SFC TROUGH EXTENDING S OF JAMAICA TOWARD
PANAMA AT 18Z. EVIDENCE OF THIS SFC BOUNDARY IS DIMINISHING
AND WILL LIKELY BE REDUCED TO A SFC TROUGH OR EVEN REMOVED FROM
THE NEXT ANALYSIS AT 00 UTC. A VERY BROAD MID TO UPPER LEVEL
RIDGE STRETCHES ACROSS THE REGION WITH A ROUGH AXIS ALONG 75W.
VERY DRY AIR ALOFT LIES E OF 68W WHERE UPPER LEVEL CONFLUENCE IS
QUIET STRONG. MODESTLY STABLE CONDITIONS EXISTS W OF 68W WITH
ONLY A FEW PATCHES OF DEEP CLOUDINESS IN THE SW CARIB S OF 12N W
OF 79W...LIKELY ASSOCIATED WITH THE ITCZ. TRADE WINDS ARE ON THE
STRONG SIDE MAINLY IN THE 20 TO 25 KT RANGE ACROSS THE REGION.
THESE WINDS WILL LIKELY REMAIN THAT WAY OVER THE NEXT FEW DAYS
AS THE PRES GRAD IN THE AREA CHANGES LITTLE. MODELS ALSO SHOW
LITTLE CHANGE IN MOISTURE AND THE UPPER LEVEL PATTERN.

THE ATLANTIC OCEAN...
THE MAIN FEATURE IN THE CENTRAL AND WESTERN ATLC IS THE
GRADUALLY WEAKENING COLD FRONT WHICH RUNS ALONG 32N52W 26N65W
24N72W THEN STATIONARY ACROSS THE E BAHAMAS. MOIST SWLY UPPER
LEVEL FLOW AND LOW-LEVEL LIFT IS GENERATING A SWATH OF MOISTURE
MAINLY WITHIN 300 NM W OF THE FRONT N OF 23N. W OF THE MOISTURE
SWATH...SFC HIGH PRES AND PLENTY OF DRY AIR NOTED ON WATER VAPOR
IMAGERY IS THE RULE FROM BERMUDA TO FLORIDA. E OF THE FRONT...A
VERY LARGE DEEP LAYER RIDGE COVERS THE AREA BETWEEN 20W AND 55W.
WIDESPREAD DRY AIR IS ASSOCIATED WITH THIS RIDGE AND COVERS
NEARLY THE ENTIRE AREA OUTLINED. A WEAK UPPER LEVEL LOW HAS
PINCHED OFF NEAR 16N55W BUT IS CAUSING NO WEATHER DUE TO THE
VERY STABLE ENVIRONMENT IN PLACE. THE SFC HIGH IS ANALYZED AT
1026 MB NEAR 29N31W ENHANCING FAIR WEATHER ACROSS MUCH OF THE
ATLC. A SHARP TROUGH COVERS THE ERN-MOST ATLC WITH THE UPPER
LEVEL AXIS STRETCHING FROM A CYCLONIC CIRCULATION NEAR MOROCCO
TO 21N20W EXTENDING WELL SOUTH INTO THE DEEP TROPICS NEAR
15N32W. THE SRN END OF THIS TROUGH IS BREAKING OFF AND WILL
LIKELY TRACK NW AS A CUT OFF UPPER LOW OVER THE NEXT FEW DAYS AS
ADVERTISED BY GFS. A TROPICAL UPPER LEVEL JET BRANCH ORIGINATES
NEAR THE BASE OF THE TROUGH AND RACES NE ALONG 11N32W 19N21W TO
WRN AFRICA NEAR 24N12W. UW-CIMSS SATELLITE DERIVED WINDS SHOWS
CORE WINDS BETWEEN 100-120 KT OVER W AFRICA. BROKEN TO OVERCAST
SKIES AND SCATTERED SHOWERS ARE WITHIN 400 NM SE OF THE JET AXIS
WHICH INCLUDES MOST OF THE CAPE VERDE ISLANDS. THIS DIFFLUENT
PATTERN IS ALSO ENHANCING CONVECTION IN THE ITCZ BETWEEN 28W AND
40W.

$$
CANGIALOSI




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