[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181735
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SAT 18 DEC 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM
THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON
SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...ITCZ...

ITCZ IS CENTERED ALONG 7N10W 4N18W 4N27W 1N40W. SCATTERED
MODERATE CONVECTION FROM 6N-11N BETWEEN 18W-27W. WIDELY
SCATTERED MODERATE 150 NM S OF THE AXIS BETWEEN 16W-21W. WIDELY
SCATTERED MODERATE WITHIN 30 NM OF THE AXIS BETWEEN 36W-41W.

...DISCUSSION...

GULF OF MEXICO AND FAR W ATLANTIC...
THE WIDESPREAD MID/UPPER LEVEL CLOUDINESS THAT WAS OVER THE GULF
YESTERDAY HAS SHIFTED TO THE E OF FLORIDA AND HAS MADE THE SFC
ANALYSIS MUCH EASIER NOW THAT THE LOW LEVEL CLOUDS ARE VISIBLE.
HIGH PRES IS SLIDING DOWN THE ERN SLOPES OF THE SIERRA MADRE
INTO THE W GULF WHICH AS USUAL IS PRODUCING LOW CLOUDS AND
VALLEY FOG OVER CNTRL AND SRN MEXICO. A WEAKENING 1017 MB LOW IS
CENTERED ABOUT 120 NM N OF THE YUCATAN COAST AND THE COLD FRONT
EXTENDING S OF THIS FEATURE HAS JUST PASSED CANCUN INTO THE
YUCATAN CHANNEL...THEN CURVES BACK ACROSS S BELIZE AND GUATEMALA
ALONG THE LEADING EDGE OF THE HIGH PRES. ELSEWHERE...A SECOND
COLD FRONT ORIGINATING FROM LOW PRES OFF THE CAROLINA COAST
EXTENDS SWD TO THE N BAHAMAS AND THEN W ACROSS THE FLORIDA
STRAITS CONNECTING TO THE AFOREMENTIONED GULF LOW. A STRONG
110-120 KT JET AT 250 MB EXTENDS ACROSS THE N GULF WITH
DIFFLUENT SPLIT FLOW LOCATED NEAR ITS EXIT REGION E OF
FLORIDA...AND THIS HAS MADE THE ENVIRONMENT FAVORABLE FOR
SCATTERED SHOWERS/TSTMS ALONG THE FRONT N OF 27N BETWEEN
74W-79W. WIDELY SCATTERED SHOWERS ARE ALSO LOCATED FARTHER S
ALONG THE FRONT ACROSS THE FLORIDA STRAITS AND SE GULF WITH
DOPPLER RADAR SHOWING THE HEAVIEST PRECIP ABOUT 30 NM S OF THE
FLORIDA KEYS. SHOWERS/TSTMS WILL CONTINUE TO DEVELOP OVER THE SE
GULF AND THE W ATLC THROUGH SUN NIGHT AHEAD OF THE NEXT SURGE OF
COLDER AND DRIER AIR.

CARIBBEAN...
STRONG UPPER LEVEL RIDGING IS CENTERED OVER W PANAMA RESULTING
IN DRY WESTERLY FLOW ACROSS THE ENTIRE BASIN. NEVERTHELESS...A
FEW LOW-LEVEL DISTURBANCES HAVE BEEN TRIGGERING A FEW SHOWERS
MAINLY ACROSS THE W PART. A REMNANT FRONTAL BOUNDARY IS BEING
PUSHED WWD WITHIN THE EASTERLY TRADES WITH ISOLATED SHOWERS
DEVELOPING ALONG A LINE FROM SW HAITI TO JAMAICA THEN SW TO
COSTA RICA...WHERE A LONE TSTM CLUSTER HAS BEEN HOLDING
TENACIOUSLY ALL MORNING. THE FLOW HAS ALREADY TURNED NLY OVER
THE NW CARIBBEAN AHEAD OF AN APPROACHING COLD FRONT...PRODUCING
LOW CLOUDS AND SHOWERS ACROSS MOST OF HONDURAS. FARTHER
E...ANOTHER LOW-LEVEL DISTURBANCE IS LOCATED E OF THE WINDWARD
ISLANDS WITH WIDELY SCATTERED SHOWERS/TSTMS FROM 10N-13N BETWEEN
55W-59W AND THESE SHOULD SPREAD FROM TRINIDAD AND TOBAGO NWD TO
ST. LUCIA LATER TODAY AND TONIGHT.

REMAINDER OF ATLANTIC...
A MID/UPPER LEVEL MID-OCEANIC TROF HAS NOT BUDGED OVER THE CNTRL
ATLC WATERS EXTENDING FROM 10N TO N OF THE AREA BETWEEN 30W-55W.
A STATIONARY FRONT LIES BENEATH THIS FEATURE ALONG 32N50W 22N70W
BUT IS REALLY STARTING TO FIZZLE FAST AS IT LOSES ITS UPPER
SUPPORT AND ALIGNS PARALLEL TO THE LOW-LEVEL FLOW. ONLY A FEW
SHOWERS ARE NOTED ABOUT 420 NM NNE OF PUERTO RICO OVER OPEN
WATERS. THE UPPER TROF IS HOSTING SEVERAL SMALLER-SCALE FEATURES
WITH A SHORTWAVE TROF MOVING E ALONG 32N51W 25N50W AND PRODUCING
WIDESPREAD HIGH CLOUDS N OF 25N BETWEEN 45W-50W...A SHORTWAVE
RIDGE ALONG 22N46W 32N42W...AND A CLOSED MID/UPPER LOW NEAR
26N35W. IN ADDITION...THE FLOW INTO THE BASE OF THE TROF IS
MERGING WITH FLOW COMING UP OUT OF NE BRAZIL TO PRODUCE A
WESTERLY 70 KT JET ALONG 10N AT 250 MB. THIS WESTERLY FLOW
DIVERGES OVER THE E ATLC WITH ONE BRANCH OF THE JET
RE-DEVELOPING FROM 20N30W EWD INTO WESTERN SAHARA AND ANOTHER
PART FLOWING DOWN TOWARDS THE EQUATOR. THIS HAS CAUSED THE ITCZ
E OF 30W TO BECOME QUITE ACTIVE WITH A GOOD-SIZE CLUSTER OF
TSTMS CENTERED BETWEEN IT AND THE CAPE VERDES.

$$
BERG






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