[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SAT 11 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 10N10W 5N25W 9N40W 9N60W 6N80W.
WIDELY SCATTERED MODERATE CONVECTION FROM 6N-8N BETWEEN 15W-30W.
SCATTERED MODERATE CONVECTION FROM 10N-14N BETWEEN 40W-50W.

...DISCUSSION...

GULF OF MEXICO...
A HIGH AMPLITUDE LONGWAVE TROUGH PATTERN HAS BECOME ESTABLISHED
OVER THE E HALF OF THE UNITED STATES PENETRATING WELL SWD INTO
THE GLFMEX.  ATTENDANT COLD FRONT AND ASSOCIATED
SHOWERS/THUNDERSTORMS IS NOW E OF THE AREA WITH MODERATE
SUBSIDENCE AND DRY/STABLE AIR COVERING THE ENTIRE GLFMEX AND
FLORIDA.  OVERCAST LOW CLOUDINESS AND WIDELY SCATTERED SHOWERS
REMAIN OVER S MEXICO MAINLY E OF 96W OWING TO NLY FLOW
ENCOUNTERING THE HIGHER TERRAIN.  HIGH PRESSURE HAS BUILT SWD
FROM THE CENTRAL UNITED STATES OVER INTERIOR MEXICO SUPPORTING
ONE OF THE COOLEST SURGES OF CONTINENTAL AIR THIS SEASON.
HOWEVER...THIS HIGH IS EXPECTED TO WEAKEN AND SLIDE EWD INTO THE
E GLFMEX ALLOWING RETURN FLOW TO DEVELOP OVER THE W GLFMEX BY
SUNDAY IN ADVANCE OF THE NEXT COLD FRONT WHICH IS FORECAST TO
MOVE INTO THE NW GLFMEX EARLY MONDAY.   THIS NEXT FRONT WILL BE
PRIMARILY MOISTURE STARVED AND ONLY ABLE TO PRODUCE WIDELY
SCATTERED LIGHT SHOWERS.  ALSO...MIDDLE TO UPPER LEVEL DYNAMICS
WILL BE ABSENT AS A MORE ZONAL PATTERN EVOLVES MONDAY AND TUE.

CARIBBEAN...
THE BIGGEST WEATHER MAKER OVER THE CARIBBEAN IS A COLD FRONT
PENETRATING SWD FROM THE W ATLC ENTERING THE CARIBBEAN OVER W
CUBA TO CENTRAL AMERICA NEAR BELIZE/GUATEMALA. A NARROW BAND OF
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ACCOMPANIES THE FRONT.
CLOUDINESS AND SHOWERS EXTEND INLAND OVER CENTRAL AMERICA
AFFECTING BELIZE AND MUCH OF GUATEMALA PRIMARILY ALONG WINDWARD
FACING SLOPES.  ELSEWHERE...MUCH OF THE CARIBBEAN REMAINS UNDER
MIDDLE TO UPPER LEVEL SUBSIDENCE AND DRY AIR. POCKETS OF LOW
LEVEL MOISTURE ARE SUPPORTING WIDELY SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ESPECIALLY S OF 16N.

ATLANTIC...
A LARGE SCALE TROUGH-RIDGE-TROUGH PATTERN IS PRESENT OVER THE
SUBTROPICAL ATLC WITH A PROGRESSIVE TROUGH OVER THE E UNITED
STATES...HIGH OVER LOW PATTERN IN THE CENTRAL AND W ATLC BETWEEN
35W-70W...AND A FLAT TROUGH OVER THE E ATLC E OF 35W.  A
DEVELOPING SUBTROPICAL JET TO 110 KT FLANKS THE E UNITED STATES
TROUGH EXTENDING FROM FLORIDA NEWD BETWEEN BERMUDA AND THE
MID-ATLANTIC COAST.  THE JET IS PROVIDING MIDDLE TO UPPER LEVEL
SUPPORT FOR A 100 NM WIDE LINE OF SCATTERED
SHOWERS/THUNDERSTORMS ALONG OF A STRONG COLD FRONT FROM 32N72W
TO W CUBA NEAR 23N82W.  WHILE WELL BELOW GALE FORCE...STRONG NLY
WINDS TO 25 KT BEHIND THE FRONT ARE USHERING IN ONE OF THE
COOLEST/DRIEST SURGES THUS FAR THIS SEASON.  MUCH OF THE
MOISTURE ASSOCIATED WITH THE FRONT RIDES UP AND OVER THE CENTRAL
ATLC RIDGE LEAVING VERY DRY AIR AND TRANQUIL WEATHER BETWEEN
50-70W.  THIS DRY AIR IS BEING ENHANCED BY STRONG SUBSIDENCE ON
THE CONFLUENT SIDE OF OF A CUTOFF UPPER LOW NEAR 20N50W.  A
TROUGH AXIS EXTENDS EWD FROM THE UPPER LOW ALONG 25N40W 24N20W
WITH A 50-80 KT ELY JET TO THE SOUTH. THIS SETUP IS PRODUCING A
BROAD AREA OF DIFFLUENT FLOW IN THE UPPER LEVELS ON THE S SIDE
OF THE TROUGH AXIS WITH OVERCAST MULTILEVEL CLOUDS AND
SCATTERED SHOWERS/THUNDERSTORMS FROM THE ITCZ NWD TO 20N BETWEEN
30W-53W. ENHANCED ITCZ CONVECTION CONTINUES EWD TO 20W. OVER THE
E SUBTROPICAL ATLC...MIDDLE/UPPER LEVEL TROUGH COVERS THE FAR NE
PART OF THE DISCUSSION AREA WITH ITS AXIS LOCATED ALONG 29W N OF
29N...MOVING ESE ABOUT 30 KNOTS. ASSOCIATED COLD FRONT IS NOW
DISSIPATING FROM THE CANARY ISLANDS SWD TO 23N23W. WIDELY
SCATTERED SHOWERS ARE LOCATED WITH 60 NM OR SO EITHER SIDE OF
THE FRONT. A SECOND...MUCH STRONGER...COLD FRONT IS EMERGING
INTO THE AREA FROM THE AZORES SWD THROUGH 30N30W 28N40W 29N48W.
HOWEVER...THIS FRONT IS ALSO FAIRLY DRY WITH ONLY A NARROW BAND
OF SCATTERED SHOWERS ALONG THE LEADING EDGE.

$$
RHOME




This weather bulletin was brought to you by:
www.nashvilleweather.net