[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 191735
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN 19 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 5N30W 7N36W 4N46W. WIDELY SCATTERED
MODERATE CONVECTION IN CLUSTERS 250/300 NM S OF THE AXIS BETWEEN
10W-20W. SCATTERED MODERATE WITHIN 90 NM OF THE AXIS BETWEEN
25W-45W AND FROM 1N-5N BETWEEN 32W-38W.

...DISCUSSION...

GULF OF MEXICO...
THE UPPER LEVEL PATTERN OVER CONUS HAS NOT CHANGED FOR SEVERAL
DAYS NOW AND CONTINUES TO SHOWCASE A DEEP-LAYERED TROF EXTENDING
FROM THE GREAT LAKES SWD TO THE MISSISSIPPI VALLEY THEN LAGGING
BACK ACROSS TEXAS. THE TROF IS SLOWLY SAGGING S AND CARVING OUT
ITS NICHE OVER THE GULF WITH A STRONG NLY COMPONENT TO THE FLOW
BRINGING IN SUCCESSIVE ROUNDS OF COLDER AIR. PACIFIC MOISTURE IS
RIDING ACROSS MEXICO INTO THE BASE OF THE TROF ALONG A VIGOROUS
130 KT JET WHICH EXTENDS ACROSS THE N GULF AND N FLORIDA INTO
THE W ATLC AT THE 250 MB LEVEL. THIS HAS BROUGHT IN SOME UPPER
LEVEL CLOUDS...ESPECIALLY OVER THE W GULF...BUT MORE IMPORTANTLY
IS A POST-FRONTAL TROF EXTENDING FROM ANDROS ISLAND TO THE W TIP
OF CUBA INTO THE BAY OF CAMPECHE WHICH HAS BEEN OFFERING A FEW
SHOWERS ACROSS THE S GULF. LOOKING UPSTREAM...VERY COLD AIR IS
LOOMING OMINOUSLY OVER THE SOUTHERN PLAINS AND THE ASSOCIATED
COLD FRONT IS PROGGED TO MOVE INTO THE GULF LATER THIS AFTERNOON
AND SPREAD DOWN THROUGH FLORIDA OVERNIGHT. SUB-FREEZING
TEMPERATURES ARE EXPECTED TO REACH THE GULF COAST TONIGHT AS THE
COLDEST AIR OF THE SEASON PLUNGES S.

CARIBBEAN...
A STRONG MID/UPPER LEVEL RIDGE IS CENTERED OVER N COLOMBIA AND
BROAD SW/W FLOW IS BRINGING DRY AIR FROM THE PACIFIC ACROSS
CNTRL AMERICA TO THE ENTIRE CARIBBEAN BASIN. A WEAK COLD FRONT
HAS MOVED INTO THE AREA FROM SE CUBA TO JUST SE OF THE CAYMAN
ISLANDS THEN TO N NICARAGUA BUT RECENT SATELLITE IMAGERY AND
OBSERVATIONS SUGGEST THE BOUNDARY MAY HAVE BECOME
STATIONARY...AT LEAST FOR NOW. A SFC TROF IS LOCATED ABOUT 140
NM SE OF THE FRONT FROM THE E TIP OF CUBA ACROSS JAMAICA TO THE
NICARAGUA/COSTA RICA COAST AND THIS FEATURE IS PRODUCING
ISOLATED SHOWERS/TSTMS WITHIN 30 NM OF THE AXIS. ELSEWHERE...A
TROF HAS JUST MOVED W OF THE WINDWARD ISLANDS BUT IS ONLY
PRODUCING SPORADIC SHOWERS OVER THE SE CARIBBEAN.

WEST ATLANTIC...
MID/UPPER LEVEL PACIFIC MOISTURE IS STREAMING EWD ACROSS THE
GULF OF MEXICO WITHIN A NARROW BAND AND THEN EXPANDS IN AREA
WITHIN A LARGE DIFFLUENT AREA OVER THE W ATLC WATERS. A WEAK
COLD FRONT HAS BEEN MOVING EWD OVER THE AREA BUT HAS BECOME
STATIONARY ALONG A LINE FROM 32N72W TO THE SRN BAHAMAS TO SE
CUBA AS IT OUTRAN THE STRONGEST UPPER LEVEL SUPPORT (WHICH IS
STILL OVER THE EASTERN U.S.). A CONVERGENCE LINE HAS SET UP
ABOUT 200/250 NM E OF THE FRONT ALONG THE EDGE OF THE
SUBTROPICAL RIDGE WITH WIDELY SCATTERED MODERATE CONVECTION
FORMING N OF 23N BETWEEN 59W-71W. IN ADDITION...A POST-FRONTAL
TROF IS CRAWLING THROUGH THE NRN BAHAMAS WITH MOSTLY STRATIFORM
RAIN FROM 24N-29N BETWEEN 73W-79W. A STRONG COLD FRONT WILL PUSH
THROUGH FLORIDA TONIGHT AND RE-KICK THE W ATLC COLD FRONT TO THE
E BEGINNING MON MORNING/AFTERNOON...EVENTUALLY CLEARING MOST OF
THE AREA OF THE WET WEATHER.

REMAINDER OF ATLANTIC...
A BROAD MID/UPPER LEVEL TROF REMAINS PLANTED ACROSS THE E/CNTRL
ATLC BETWEEN 25W-55W BUT HAS FLATTENED OUT A BIT SINCE YESTERDAY
WITH MORE PRONOUNCED ZONAL FLOW DEVELOPING ACROSS THE TROPICS. A
70 KT JET IS WITHIN THIS FLOW AT 250 MB ALONG ABOUT 12N AND IS
COINCIDENT WITH A SFC TROF ALONG 36W WHICH IS MOVING W WITHIN
THE TRADES. CONVECTION HAS BEEN FLARING ALONG THE ITCZ IN THE
VICINITY OF THE TROF BUT SCATTERED MODERATE CONVECTION HAS ALSO
BEEN E OF THE TROF FROM 10N-17N BETWEEN 30W-35W. FARTHER N...TWO
UPPER LOWS ARE EMBEDDED WITHIN THE TROF NEAR 26N37W AND
27N47W...BOTH HAVING SFC REFLECTIONS ALONG 25N35W 30N38W AND
20N49W 28N52W RESPECTIVELY. ISOLATED SHOWERS HAVE BEEN FORMING
IN THE VICINITY OF BOTH TROFS. A STRONG UPPER RIDGE HAS BEEN
BUILDING NEAR THE W COAST OF AFRICA WITH UPPER LEVEL MOISTURE
FLARING NWD TOWARDS THE CANARY ISLANDS WITHIN THE AMPLIFYING
FLOW.

$$
BERG


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