[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 311750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST FRI 31 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 11N10W 3N30W 8N60W 5N80W.  SCATTERED
MODERATE/ISOLATED STRONG CONVECTION FROM THE EQUATOR TO 8N
BETWEEN 10W-13W.  WIDELY SCATTERED MODERATE CONVECTION FROM
6N-12N BETWEEN 52W-62W.

...DISCUSSION...

GULF OF MEXICO...
SHARP MIDDLE TO UPPER LEVEL RIDGE REMAINS IN CONTROL WITH AXIS
CUTTING ACROSS THE AREA FROM CENTRAL MEXICO NEAR MEXICO CITY
INTO THE W ATLC OVER N FLORIDA.  AS A RESULT...MID-LATITUDE
DISTURBANCES AND CONTINENTAL AIR IS CONFINED OVER THE CONUS
CREATING A RATHER STAGNANT PATTERN.  THE ONLY WEATHER SYSTEM OF
NOTE IS A WEAK S STREAM SHORTWAVE TROUGH MOVING QUICKLY EWD
ALONG THE N GULF COAST RESULTING IN BROKEN/OVERCAST HIGH
CLOUDINESS AND ISOLATED SHOWERS N OF 26N.  THIS SYSTEM WILL
CONTINUE TO PRODUCE CLOUDINESS AND A FEW SHOWERS AS IT MOVES
ACROSS N FLORIDA AND EXITS THE AREA TONIGHT.  S OF 26N...
CONFLUENT UPPER LEVEL FLOW ON THE EQUATORWARD SIDE OF THE UPPER
RIDGE AXIX IS PRODUCING DRY/STABLE CONDITIONS THROUGH ALL BUT
THE LOWEST LEVELS.  AT THE SURFACE...A STRONG HIGH PRES RIDGE
EXTENDS FROM THE W ATLC ACROSS N FLORIDA AND THE N GULF COAST.
THIS PATTERN IS PRODUCING MODERATE RETURN FLOW OVER THE W GULF
WITH STRONG ELY FLOW FUNNELING THROUGH THE FLORIDA STRAITS INTO
THE CENTRAL GULF.  THIS OVERALL PATTERN WILL REMAIN ESSENTIALLY
UNCHANGED THROUGH THE WEEKEND WITH EXCEPTION TO LOW LEVEL
MOISTURE AND SHOWER ACTIVITY WHICH WILL BE ON THE INCREASE OVER
THE W GULF LATE SAT INTO SUN AS AN ELY DISTURBANCE CURRENTLY
OVER THE NW CARIBBEAN MOVES INTO THE AREA.  THIS MOISTURE
EVENTUALLY GETS PULLED NWD OVER TEXAS AND LOUISIANA WITHIN THE
ESTABLISHED RETURN FLOW.

CARIBBEAN...
IN THE ABSENCE OF SIGNIFICANT MIDDLE AND UPPER LEVEL
FEATURES...THE WEATHER IS PRIMARILY DOMINATED BY LOW LEVEL
FEATURES. THE OLD FRONTAL BOUNDARY WHICH WAS DRAPED ACROSS THE
CARIBBEAN WATERS YESTERDAY HAS DISSIPATED BUT POCKETS OF
ASSOCIATED LOW LEVEL MOISTURE CONTINUE TO PRODUCE SCATTERED
SHOWERS/TSTMS OVER THE W HALF OF THE CARIBBEAN PRIMARILY W OF
80W. THE MOST SIGNIFICANT/NUMEROUS OF THIS ACTIVITY IS CURRENTLY
APPROACHING THE YUCATAN W OF 83W WHERE AN UPPER TROUGH IS
PRODUCING ENHANCED INSTABILITY.  A SECOND AREA IS NOTED OVER THE
SW CARIBBEAN APPROACHING NICARAGUA/COSTA RICA.  THESE AREAS WILL
CONTINUE TO SPREAD WEST OVER CENTRAL AMERICA WITHIN THE STRONG
EASTERLY FLOW WHICH WILL PERSIST OVER THE CARIBBEAN THROUGH THE
WEEKEND. OVER THE E CARIBBEAN...A WEAK SFC TROF/REMNANT FRONTAL
BOUNDARY EXTENDS FROM THE CENTRAL ATLC OVER THE LEEWARD ISLANDS
NEAR GUADELOUPE TO THE ABC ISLANDS.  SCATTERED SHOWERS LIE
WITHIN 60 NM EITHER SIDE OF THE BOUNDARY. THE TROUGH SHOULD
REMAIN ESSENTIALLY STATIONARY OR DRIFT SWD DURING THE NEXT 24
HOURS KEEPING THE E CARIBBEAN UNSETTLED AND WET. FINALLY...AN
AREA OF MOISTURE AND ASSOCIATED SHOWERS IS OBSERVED MOVING
QUICKLY SW OVER THE CENTRAL ATLC AND WILL OVERSPREAD THE VIRGIN
ISLANDS...PUERTO RICO...AND HISPANIOLA THIS EVENING AND
TONIGHT.

ATLANTIC...
THE PATTERN OVER W AND CENTRAL ATLC HAS BECOME QUITE PROGRESSIVE
COURTESY OF A TROUGH MOVING THROUGH THE E UNITED STATES.  A
NARROW RIDGE AHEAD OF THE TROUGH IS PUSHING SEWD OFF THE E
UNITED STATES COAST WITH AXIS CURRENTLY EXTENDING FROM FLORIDA
TO THE CANADIAN MARITIMES.  THIS IN TURN IS DRIVING AN UPPER
LOW... CURRENTLY JUST E OF BERMUDA NEAR 33N60W...SEWD INTO THE
CENTRAL ATLC WATERS. INSTABILITY ASSOCIATED WITH THE COLD CORE
LOW IS PRODUCING INCREASING SHOWERS SE OF BERMUDA WHILE
DIFFLUENT UPPER LEVEL FLOW TO THE EAST OF THE TROUGH IS
PRODUCING INCREASING THUNDERSTORM ACTIVITY WITHIN 120 NM EITHER
SIDE OF A DISSIPATING STATIONARY FRONT EXTENDING FROM 31N50W TO
THE LEEWARD ISLANDS NEAR GUADELOUPE.  ELSEWHERE OVER THE W
SUBTROPICAL ATLC...LEFTOVER COLD AIR STRATOCUMULUS CLOUDS AND
SHOWERS CONTINUE TO MOVE QUICKLY WESTWARD WITHIN THE ESTABLISHED
STRONG LOW LEVEL NE FLOW FLOW AND AFFECT THE BAHAMAS AND S
FLORIDA.  MEANWHILE OVER THE E ATLC...THE PATTERN IS
RETROGRESSIVE AS A LARGE UPPER LOW NEAR 25W MOVES WESTWARD ALONG
27N.  STRONG SUBSIDENCE OVER THE CONFLUENT SIDE OF THE UPPER LOW
IS PRODUCING DRY/STABLE CONDITION WITHIN THE MIDDLE AND UPPER
PORTION OF THE ATMOSPHERE BUT THERE IS JUST ENOUGH LOW LEVEL
MOISTURE TO PRODUCE BROKEN STRATOCUMULUS CLOUDS AND SHOWERS FROM
THE CANARY ISLANDS WESTWARD TO 42W.  EAST OF THE UPPER LOW...AN
UPPER JET IS ADVECTING TROPICAL MOISTURE INTO W AFRICA AS
EVIDENCED BY STREAKS OF CIRRUS CLOUDS. FURTHER S...THE ITCZ IS
ALSO RELATIVELY QUIET EXCEPT FOR CLUSTERS OF TSTMS BETWEEN
10W-20W.  VISIBLE SATELLITE IMAGERY INDICATES AN AREA SAHARAN
DUST HAS MADE ITS WAY OFF THE AFRICAN CONTINENT AND IS CURRENTLY
CONCENTRATED FROM THE ITCZ NWD TO 17N E OF 30W.

$$
RHOME




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