[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211734
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST TUE 21 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 AXIS IS CENTERED ALONG 8N10W 4N20W 5N32W 2N48W. ISOLATED
MODERATE CONVECTION S OF THE AXIS FROM EQ-4N BETWEEN 7W-27W.
WIDELY SCATTERED SHOWERS/TSTMS FROM 4N-8N BETWEEN 22W-29W.

...DISCUSSION...

GULF OF MEXICO AND WEST ATLANTIC...
THE TWO COLD FRONTS WHICH HAVE BEEN MOVING EWD ACROSS THE W ATLC
HAVE ESSENTIALLY MERGED INTO ONE BOUNDARY LOCATED ALONG 32N56W
27N60W 20N71W. THE ASSOCIATED UPPER LEVEL TROF IS LIFTING
QUICKLY N OF THE AREA BUT THERE IS STILL A NARROW ZONE OF
DIFFLUENCE THAT IS SUPPORTING SCATTERED SHOWERS/TSTMS UP TO 250
NM SE OF THE FRONT N OF 26N. STRONG HIGH PRES HAS BUILT IN
BEHIND THE FRONT AND COVERS THE W ATLC AND MOST OF THE GULF
WATERS...ANCHORED BY A 1028 MB HIGH LOCATED OFF THE CAROLINA
COAST NEAR 31N73W. THE HIGH IS QUITE PROGRESSIVE AND IS MOVING
QUICKLY TO THE E...BUT ENOUGH COLD AIR ADVECTION IS STILL
OCCURRING BEHIND THE FRONT TO PRODUCE BROKEN/OVERCAST STRATOCU N
OF 25N. FARTHER UPSTREAM...MOSTLY ZONAL FLOW EXTENDS ACROSS
MEXICO TOWARDS FLORIDA BUT A MID/UPPER LEVEL SHORTWAVE TROF
LOCATED OVER FLORIDA AT THE MOMENT IS PRODUCING AN AREA OF HIGH
LEVEL CLOUDINESS OVER THE N BAHAMAS MOVING INTO THE W ATLC. A
COLD FRONT IS BEGINNING TO MOVE S OVER TEXAS AND SFC PRESSURES
HAVE RESPONDED BY LOWERING OVER MOST OF N MEXICO...WITH A 1010
MB LOW FORMING JUST W OF BROWNSVILLE AND A TROF EXTENDING UP THE
RIO GRANDE. WIDELY SCATTERED CELLULAR-TYPE TSTMS HAVE FORMED OFF
THE TEXAS COAST AND ARE MOVING INLAND NEAR HOUSTON AND GALVESTON
BAY. SCATTERED SHOWERS/TSTMS WILL CONTINUE TO DEVELOP OVER THE N
GULF WATERS THROUGH THE WEEK AS THE COLD FRONT PUSHES EAST.

CARIBBEAN...
A STRONG UPPER LEVEL HIGH IS CENTERED NEAR LAKE MARACAIBO IN
VENEZUELA AND BROAD SW/W FLOW EXTENDS ACROSS THE ENTIRE
CARIBBEAN BASIN. A FLATTENED TROF IS CURRENTLY MOVING ACROSS THE
NW CARIBBEAN BUT SUBSIDENCE IS STRONG WITHIN ITS BASE ACROSS
NICARAGUA AND HONDURAS SO DEEP CONVECTION IS NON-EXISTENT. A
DISSIPATING FRONT EXTENDS FROM HAITI WWD ACROSS JAMAICA TO THE
COAST OF NICARAGUA AND SOME SHOWERS ARE MOVING INLAND ACROSS
NICARAGUA AND COSTA RICA...BUT THIS BOUNDARY WILL CONTINUE TO
BECOME MORE DIFFUSE AS THE EASTERLY TRADES TAKE OVER. A SFC TROF
CONTINUES TO BE ADVECTED TO THE W...JUST PASSING ARUBA EARLIER
THIS MORNING...AND SOME SHOWERS HAVE BEEN GRAZING THE ABC
ISLANDS AND N COAST OF COLOMBIA.

CENTRAL AND EASTERN ATLANTIC...
A DEEP MID/UPPER LEVEL TROF IS PLASTERED OVER THE CNTRL ATLC
WATERS AND THERE ARE INDICATIONS THAT THIS FEATURE IS MAKING ITS
WAY DOWN TO THE SFC. THE MAIN TROF AXIS EXTENDS ALONG A LINE
FROM 32N31W 27N41W 5N45W AND A WELL-DEFINED UPPER LOW IS
SPIRALING SWD NEAR 21N43W. THE TROF IS BECOMING INCREASINGLY
NEGATIVELY TILTED AND BROAD DIFFLUENCE EAST OF THE AXIS IS
PRODUCING SCATTERED MODERATE CONVECTION FROM 13N-23N BETWEEN
30W-42W. THE ASSOCIATED SFC TROF IS ALIGNED ALONG 8N39W 20N38W
BUT THE CONVECTION IS NOT REALLY FOCUSED NEAR THIS BOUNDARY AT
THE MOMENT. SEVERAL NUMERICAL MODELS...INCLUDING THE
GFS...NOGAPS...AND UKMET INITIATE A SFC LOW ALONG THE TROF OVER
THE NEXT 24 HOURS AND GIVEN THE FAVORABLE POSITIONING OF THE
TROF BENEATH THE UPPER LEVEL DIFFLUENCE THIS DOES NOT SEEM
OUTSIDE OF THE REALM OF POSSIBILITIES. THE MOST AGGRESSIVE OF
THE MODELS DEVELOP A SIGNIFICANT SUBTROPICAL-TYPE LOW THAT IS
FORECAST TO MOVE N AND REACH A CLIMAX BETWEEN FRI AND SUN.
ELSEWHERE...AN UPPER LEVEL ANTICYCLONE IS LOCATED JUST OFF THE
COAST OF LIBERIA WITH BROAD RIDGING EXTENDING NWD TO MOROCCO AND
THE CANARY ISLANDS. THE ASSOCIATED FLOW IS BRINGING AREAS OF
HIGH CLOUDINESS OVER THE E ATLC WATERS INTO W AFRICA.

$$
BERG


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