[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 172339
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST FRI 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...ITCZ...

ITCZ IS CENTERED ALONG 7N10W 5N20W 4N50W 2N60W 6N70W 4N80W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 9N-14N
BETWEEN 29W-35W.  ISOLATED MODERATE CONVECTION IS IS FROM 4N-8N
BETWEEN 15W-29W.

...DISCUSSION...

GULF OF MEXICO...
VISIBLE IMAGERY SHOWS A WEAK 1018 MB LOW IN THE BAY OF CAMPECHE
NEAR 19N93W MOVING S.  AN OVERCAST LAYER OF LOW CLOUDS EXTENDS
UP TO 150/200 NM INLAND OF THE MEXICAN COAST AND S OF THE RIO
GRANDE AS MOIST AND CHILLY FLOW BANKS UP AGAINST THE MOUNTAINS.
ELSEWHERE...A SECOND WEAK 1019 MB LOW IS CENTERED BENEATH THE
THICK CLOUD SHIELD NEAR 25N90W WITH A COLD FRONT TRAILING SW TO
THE CAMPECHE LOW.  A STATIONARY FRONT STRETCHES E TO THE FLORIDA
STRAITS FROM THE 1019 MB LOW.  DIFFLUENT WESTERLY FLOW IN THE
UPPER LEVELS OVER THE SYSTEM IS PRODUCING SCATTERED SHOWERS AND
A FEW EMBEDDED TSTMS FROM 22N-27N BETWEEN 87W-94W AND THIS WHOLE
AREA IS EXPECTED TO MOVE E OVER THE NEXT 2 DAYS POSSIBLY
SPREADING OVER S FLORIDA DURING THE WEEKEND. A STRONGER COLD
FRONT WILL MOVE OFF THE TEXAS COAST SAT NIGHT AND WILL BRING
STRONG NLY WINDS OVER THE ENTIRE AREA BY SUN NIGHT.

CARIBBEAN...
UPPER LEVEL RIDGE AXIS IS CENTERED OVER NRN VENEZUELA AND NRN
COLOMBIA REACHING OUT IN THE PACIFIC OCEAN AND IS BRINGING
UNIFORM WESTERLY UPPER LEVEL FLOW AND MOSTLY DRY AIR ACROSS THE
AREA. ON THE SURFACE...THE PRESSURE GRADIENT REMAINS TIGHT WITH
STRONG HIGH PRESSURE OVER THE W ATLC SO SURFACE WINDS ARE STILL
A LITTLE BLUSTERY ESPECIALLY WHERE THE NE FLOW MOVES THROUGH THE
PASSAGES. THE NE FLOW IS PRODUCING SOME CLOUDINESS OVER E CNTRL
AMERICA FROM HONDURAS TO W PANAMA WITH EVEN ISOLATED MODERATE
CONVECTION UP TO 90 NM OFF THE COAST OF COSTA RICA.

WEST ATLANTIC...
A SURFACE TROUGH WITH A SHARP WIND SHIFT IS LOCATED JUST OFF THE
FLORIDA EAST COAST EXTENDING FROM ABOUT KEY LARGO NWD ALONG 80W
TO OFF THE SOUTH CAROLINA COAST. DOPPLER RADAR INDICATES A
BROKEN BAND OF SHOWERS SITTING STATIONARY ABOUT 50 NM OFFSHORE
ALTHOUGH A FEW SHOWERS HAVE BEEN MOVING INLAND OVER PARTS OF S
FLORIDA MUCH OF THE DAY. THE TROUGH IS EXPECTED TO JOIN WITH THE
FRONTAL SYSTEM OVER THE GULF OF MEXICO BY SAT AND THEN MOVE OUT
TO SEA. BROAD UPPER LEVEL RIDGING EXTENDS E OF THE FLORIDA COAST
ALONG 70W AND TRANSITIONS TO A TROUGH ALONG 55W. THE TROUGH IS
SUPPORTING A STATIONARY FRONT FROM 32N50W TO THE DOMINICAN
REPUBLIC. WIDELY SCATTERED SHOWERS EXTEND UP TO 75 NM E OF THE
FRONT PRIMARILY N OF 25N.

CENTRAL/EAST ATLANTIC...
A NARROW UPPER TROUGH EXTENDS DOWN THE CENTER OF THE ATLC BASIN
ALONG 30N30W 20N38W 10N40W WITH A LARGE AREA OF DIFFLUENT FLOW
PRODUCING A CONVECTIVELY-ACTIVE PATTERN OVER THE TROPICS. ASIDE
FROM ITCZ CONVECTION CIRRUS OUTFLOW EXPANDS TOWARDS W AFRICA IN
BROAD ANTICYCLONIC FLOW N OF 10N AND E OF 40W. A SHEARED UPPER
TROUGH EXTENDS FROM N MOROCCO SW ACROSS THE CANARY ISLANDS TO
27N30W WITH MODERATE/STRONG SUBSIDENCE PRODUCING A STABLE LAYER
OVER THE NE ATLC.

$$
FORMOSA



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