000
AXNT20 KNHC 071750
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
105 PM EST MON DEC 07 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER 
OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1700 UTC.

...ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 7N12W 5N21W 4N34W 3N44W 1N51W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-8N BETWEEN 
17W-25W...AND FROM 4N-7N BETWEEN 36W-42W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A STATIONARY FRONT LINES THE NW GULF OF MEXICO 
EXTENDING ACROSS ERN LOUISIANA TO THE COAST NEAR 30N92W ALONG 
28N94W TO THE SRN TIP OF TEXAS NEAR 26N97W. RADAR IMAGERY INDICATES 
A LINE OF SHOWERS/THUNDERSTORMS ALONG THE FRONT AXIS...AND ISOLATED 
SHOWERS WITHIN 50 NM OF THE FRONT WITH A LARGER WIDTH OF SHOWERS 
INLAND OVER MISSISSIPPI AND ALABAMA. RECENT LIGHTNING DATA SHOWS 
THAT THE MOST ACTIVE THUNDERSTORMS ARE AHEAD OF THE FRONT S OF THE 
CENTRAL LOUISIANA COAST. THE FRONTAL BOUNDARY IS SUPPORTED BY A 
SHORTWAVE UPPER LEVEL TROUGH WITH AXIS OVER THE ERN TEXAS/MEXICO 
COASTLINE. A WEAK SURFACE RIDGE EXTENDS ACROSS THE CENTRAL/E GULF 
BETWEEN THE FRONTAL BOUNDARY IN THE NW GULF AND A SURFACE TROUGH 
EXTENDING DOWN THE ERN SIDE OF THE FLORIDA PENINSULA. FLORIDA RADAR 
IMAGERY INDICATES ISOLATED SHOWERS ACROSS CENTRAL FLORIDA BETWEEN 
27N-28N EXTENDING INTO THE ERN GULF MOST LIKELY DUE TO A COMBINATION 
OF SURFACE CONVERGENCE NEAR THE TROUGH OVER E FLORIDA...AND SWLY 
FLOW ALOFT WHICH CONTINUES TO DRAW MOISTURE ACROSS THE BASIN. EXPECT 
THE STATIONARY BOUNDARY IN THE NW GULF TO LIFT N AND DISSIPATE AS 
SLY RETURN FLOW BUILDS IN ADVANCE OF A STRONGER COLD FRONT EXPECTED 
TO MOVE OFF THE TEXAS COAST EARLY WED.

CARIBBEAN SEA...
STRONG SUBSIDENCE AND DRY AIR ALOFT ACROSS THE CARIBBEAN CONTINUES 
TO BRING GENERALLY FAIR WEATHER ACROSS THE BASIN. ISOLATED SHOWERS 
ARE POSSIBLE ALONG A LINE FROM JAMAICA TO CENTRAL HONDURAS. MODERATE 
TO FRESH TRADEWINDS ARE ACROSS MUCH OF THE AREA WITH THE 
STRONGEST WINDS OFF THE COAST OF COLOMBIA SUPPORTED BY THE PRESSURE 
GRADIENT BETWEEN LOWER PRESSURE OVER COLOMBIA AND SUB-TROPICAL 
RIDGING OVER THE W AND CENTRAL ATLC. ZONAL ELY FLOW ALOFT COVERS 
MUCH OF THE BASIN. EXPECT LITTLE CHANGE OVER THE NEXT 24 HRS. 

ATLANTIC OCEAN...
A COLD FRONT EXTENDS ACROSS THE SW N ATLC ENTERING THE DISCUSSION 
AREA NEAR 32N53W CONTINUING ALONG 29N64W...AND AS OF 1500 UTC 
BECOMING STATIONARY ALONG 29N73W TO THE NW BAHAMAS NEAR 27N79W. 
RECENT LIGHTNING DATA INDICATES SCATTERED SHOWERS/THUNDERSTORMS FROM 
27N-29N BETWEEN 69W-74W. ISOLATED SHOWERS ARE ELSEWHERE WITHIN 30 NM 
AHEAD AND 90 NM BEHIND THE FRONT. THE FRONT IS SUPPORTED BY A 
SHORTWAVE UPPER TROUGH WITH AXIS ALONG 70W. MOIST SWLY FLOW ALOFT TO 
THE E OF THE TROUGH AXIS IS ENHANCING SHOWER ACTIVITY ALONG THE 
FRONT. A SURFACE TROUGH EXTENDS DOWN THE ERN SEABOARD ENTERING THE 
DISCUSSION AREA NEAR 32N80W TO CENTRAL FLORIDA NEAR 27N81W. MOSAIC 
RADAR IMAGERY ACROSS FLORIDA INDICATES ISOLATED SHOWERS WITHIN 90 NM 
OF THE TROUGH AXIS. A BROAD SURFACE RIDGE DOMINATES THE REMAINDER OF 
THE W AND CENTRAL ATLC ANCHORED BY A 1023 MB HIGH NEAR 28N41W. THE 
SURFACE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE EXTENDING FROM N 
OF PUERTO RICO ACROSS THE CENTRAL ATLC TO SE OF THE AZORES ISLANDS. 
A NARROW UPPER LEVEL TROUGH EXTENDS FROM PORTUGAL ACROSS THE CANARY 
ISLANDS TO THE CAPE VERDE ISLANDS SUPPORTING A STATIONARY FRONT THAT 
EXTENDS FROM PORTUGAL TO NEAR 29N26W. ISOLATED SHOWERS ARE POSSIBLE 
ALONG THE FRONT. THE AFOREMENTIONED UPPER LEVEL TROUGH IS ALSO 
SUPPORTING A SURFACE TROUGH THAT EXTENDS DOWN THE W AFRICA COAST 
FROM 9N17W TO 21N14W. A STRONG UPPER LEVEL JET AROUND THE BASE OF 
THE UPPER TROUGH IS ENHANCING CONVECTION ALONG THE ITCZ...AS WELL AS 
DRAWING MOISTURE FROM THE ITCZ TO THE NE ENHANCING WIDESPREAD CLOUDS 
ACROSS THE TROPICAL E ATLC AND AFRICA. 

$$
WALTON