[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 100531
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST FRI 10 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0515 UTC.

...ITCZ...

AXIS OF ITCZ IS CENTERED ALONG 7N12W 5N20W 8N36W 7N41W 9N52W
9N62W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS WITHIN
60 NM OF THE AXIS FROM 30W-37W AND WITHIN 60 NM OF LINE 4N24W
7N27W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF THE
AXIS FROM 27W-29W...39W-42W...AND 48W-53W.

...DISCUSSION...

GULF OF MEXICO...
A POTENT SHORTWAVE TROUGH CONTINUES TO PUSH THROUGH THE CENTRAL
UNITED STATES AND REMAINS THE BIGGEST WEATHER MAKER ACROSS THE
AREA. GOOD UPPER LEVEL DYNAMICS/LIFT AND AMPLE LOW LEVEL
MOISTURE ASSOCIATED WITH THIS SYSTEM IS PRODUCING SCATTERED
SHOWERS OVER THE SE UNITED STATES. A LINE OF
SHOWERS/THUNDERSTORMS EXTENDS SW INTO THE GULF OF MEXICO FROM
THE WESTERN FLORIDA PANHANDLE TO THE CENTRAL GULF NEAR 26N90W.
THIS LINE IS ALONG A SURFACE TROUGH AHEAD OF A COLD FRONT. THE
FRONT STRETCHES FROM THE TENNESSEE VALLEY SWD OVER SE LOUISIANA
TO THE COAST OF MEXICO NEAR TAMPICO THEN AS A STATIONARY FRONT
OVER INTERIOR MEXICO ALONG THE E SLOPES OF THE SIERRA MADRE
ORIENTAL MOUNTAINS. THE FRONT IS MOVING VERY SLOWLY AT THIS
TIME...BUT A SECOND SHORTWAVE TROUGH IS CONTINUING TO DROP SWD
FROM THE SOUTHERN PLAINS AND WILL FURTHER AMPLIFY THE PATTERN
SETTING UP A LARGE-SCALE TROUGH REGIME OVER THE E UNITED STATES
DURING THE NEXT 24-36 HOURS. THIS WILL ALLOW THE COLD FRONT TO
MOVE MUCH FASTER SE LATER TODAY. THE FRONT IS FORECAST TO REACH
FROM CENTRAL FLORIDA TO THE YUCATAN PENINSULA BY NIGHT...THEN
WILL CLEAR THE GULF OF MEXICO EARLY SAT. STRONG HIGH PRESSURE IS
EXPECTED TO BUILD IN BEHIND THE FRONT SUPPORTING BRISK NLY FLOW
AND MODERATE COLD AIR ADVECTION.  IN FACT...THIS AIRMASS LOOKS
TO BE ONE OF THE COOLEST THUS FAR IN THE SEASON.

CARIBBEAN...
THE CARIBBEAN REMAINS UNDER THE INFLUENCE OF STRONG MIDDLE TO
UPPER LEVEL RIDGING AND SUBSIDENCE.  A MIDDLE TO UPPER CYCLONIC
CIRCULATION OVER THE E PACIFIC ABOUT 150 NM SW OF THE NW COAST
OF COSTA RICA IS HELPING TO PRODUCE WIDELY SCATTERED ITCZ
CONVECTION OVER PANAMA AND COSTA RICA.  OTHERWISE...DRY/STABLE
CONDITIONS PREVAIL IN THE MIDDLE TO UPPER LEVELS...ESPECIALLY E
OF 70W.  AREAS OF LOW LEVEL MOISTURE ARE PRODUCING SCATTERED
CLOUDS AND ISOLATED SHOWERS OVER THE CARIBBEAN S OF 17N BETWEEN
70W-84W. MIDDLE TO UPPER LEVEL RIDGING WILL GRADUALLY WEAKEN
OVER THE NEXT COUPLE DAYS IN ADVANCE OF THE AMPLIFYING TROUGH
OVER THE E UNITED STATES AND GULF OF MEXICO.

ATLANTIC OCEAN...
LARGE SCALE ANTICYCLONE CENTERED OVER THE SE BAHAMAS DOMINATES
THE W ATLC WITH ASSOCIATED RIDGE EXTENDING NEWD INTO THE CENTRAL
ATLC ALONG 28N50W 28N40W.  THE RIDGE IS BEING PARTIALLY ERODED
BY A WEAK SHORTWAVE TROUGH DROPPING SWD ALONG 32N48W TO 29N54W.
THE RIDGE IS KEEPING THE W ATLC UNDER DRY/TRANQUIL CONDITIONS.

OVER THE CENTRAL ATLC...WATER VAPOR IMAGERY SUGGESTS THAT A
CUT-OFF UPPER LOW HAS FORMED NEAR 20N49W. A TROUGH EXTENDS SW
FROM THE CIRCULATION TO 12N54W...JUST SE OF THE WINDWARD ISLANDS.
MODERATE/STRONG SUBSIDENCE/DRY AIR IS LOCATED ALONG AND WEST
OF THE CYCLONIC CIRCULATION AND TROUGH. OVER THE EASTERN ATLC A
LARGE MID/UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NEAR
7N22W. BROAD ANTICYCLONIC FLOW COVERS THE EASTERN ATLC S OF 24N
E OF THE UPPER LOW. THIS PATTERN IS PRODUCING DIFFLUENT MIDDLE
TO UPPER LEVEL FLOW TO THE EAST OF THE UPPER LOW AND SUPPORTING
WIDESPREAD CLOUDINESS AND SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS FROM THE ITCZ NWD TO 22N BETWEEN THE CAPE
VERDE ISLANDS AND 48W.  THE STRONGEST AND MOST NUMEROUS
SHOWER/THUNDERSTORM ACTIVITY IS LOCATED FROM 10N-20N BETWEEN
33W-45W.  THIS AREA SHOULD REMAIN UNSETTLED OVER THE NEXT DAY OR
SO AS THE UPPER LOW REMAINS NEARLY STATIONARY. OVER THE FAR NE
PORTION OF THE AREA...A FAST-MOVING SHORTWAVE TROUGH IS MOVING
SE TOWARDS THE AZORES AND THE COAST OF AFRICA.

$$
JP/HC




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