000 AXNT20 KNHC 201813 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST THU DEC 20 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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 1745 UTC ...THE ITCZ... FROM NORTHERN COASTAL LIBERIA TO 4N20W 5N37W INTO NORTHEASTERN BRAZIL NEAR 2N52W. SCATTERED STRONG SHOWERS/THUNDERSTORMS FROM 3N TO 5N BETWEEN 31W AND 34W...FROM 2N TO 5N BETWEEN 39W AND 41W...FROM 4N TO 6N BETWEEN 42W AND 46W...FROM 5N TO 6N BETWEEN 47W AND 48W...AND FROM 3N TO 4N BETWEEN 47W AND 49W. ISOLATED MODERATE SHOWERS TO POSSIBLE THUNDERSTORMS ARE ELSEWHERE WITHIN 120 NM ON EITHER SIDE OF 4N15W 5N34W 4N52W. ...DISCUSSION... THE GULF OF MEXICO... A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM NORTHEASTERN TEXAS INTO THE DEEP SOUTH TEXAS/NORTHEASTERN MEXICO. THIS TROUGH SUPPORTS THE NORTHEAST TEXAS-TO-SOUTH TEXAS FRONTAL BOUNDARY AND SURFACE TROUGH IN THAT AREA. ISOLATED MODERATE SHOWERS AND POSSIBLE THUNDERSTORMS ARE NORTH OF 26N BETWEEN 89W AND 95W... REACHING COASTAL SECTIONS OF LOUISIANA...AND STAYING OFFSHORE WITH RESPECT TO TEXAS. UPPER LEVEL WESTERLY WIND FLOW COVERS THE REST OF THE GULF OF MEXICO. MIDDLE TO UPPER LEVEL DRY AIR/ SUBSIDENCE IS SOUTH OF 27N. A WEAK SURFACE PRESSURE GRADIENT EXISTS IN THE GULF OF MEXICO. THE WIND FLOW FOR THIS SITUATION IS SUGGESTING A RETURN FLOW SCENARIO...SOUTHERLY WIND FLOW TO THE EAST OF THE TEXAS FRONT AS THIS FRONT TRAVERSES THE AREA DURING THE NEXT FEW DAYS. NORTHERLY TO NORTHWESTERLY WIND FLOW WILL BE ON THE WESTERN SIDE OF THE FRONT. THE CARIBBEAN SEA... A MIDDLE LEVEL TROUGH...NOW LESS WELL-DEFINED THAN IT WAS 24 HOURS AGO...CONTINUES FROM THE NORTHEASTERN CORNER OF THE AREA TO 16N66W TO THE NORTHERN COASTAL PLAINS/COASTAL WATERS OF VENEZUELA AND COLOMBIA...INTO THE EASTERN PACIFIC OCEAN NEAR 7N83W. MIDDLE TO UPPER LEVEL ANTICYCLONIC FLOW AND DRY AIR/ SUBSIDENCE ARE WEST OF THE TROUGH. THE CLOUD PATTERN ON VISIBLE IMAGERY MAY LEAD ONE TO BELIEVE THAT A CYCLONIC CIRCULATION CENTER AT SOME LEVEL OF THE ATMOSPHERE IS IN THE AREA OF THE GULF OF HONDURAS/BELIZE/THE SOUTHEASTERN YUCATAN PENINSULA. IT IS ONLY A LOCALIZED SITUATION IN AN AREA OF WEAK SURFACE WIND SPEEDS. NO SURFACE LOW PRESSURE CENTER IS PRESENT. NOTHING SHOWS UP ON WATER VAPOR IMAGERY. THE 500 MB GFS MODEL SHOWS NO CYCLONIC CIRCULATION CENTER. THE ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL TROUGH PASSES THROUGH 32N70W TO 24N72W. THIS TROUGH SUPPORTS THE COLD FRONT THAT PASSES THROUGH 32N74W TO 31N79W. BROKEN TO OVERCAST LOW TO MIDDLE LEVEL CLOUDS AND POSSIBLE SHOWERS ARE WITHIN 30 NM TO 60 NM ON EITHER SIDE OF 31N80W 31N76W BEYOND 33N70W. A SURFACE TROUGH DEVELOPED ALONG 28N66W 26N67W 22N68W. A STATIONARY FRONT IS ALONG 32N41W TO 30N50W TO 29N60W. BROKEN TO OVERCAST MULTILAYERED CLOUDS AND MODERATE SHOWERS ARE WITHIN 100 NM ON EITHER SIDE OF 27N59W 30N54W BEYOND 33N50W. THE MIDDLE TO UPPER LEVEL TROUGH SUPPORTING THIS FRONT IS ALONG 32N59W TO 26N62W TO 20N64W. UPPER LEVEL ANTICYCLONIC WIND FLOW IS NORTH OF 16N BETWEEN THE 32N59W 20N64W TROUGH AND THE MOROCCO COAST TO 19N19W TROUGH. A DEEP LAYER TROUGH REMAINS...PASSING THROUGH THE MOROCCO COAST NEAR 31N...ACROSS THE CANARY ISLANDS TO 24N18W TO 19N19W. A COLD FRONT PASSES THROUGH 32N11W TO THE COAST OF MOROCCO/ WESTERN SAHARA NEAR 22N17W. CLOUDS AND POSSIBLE PRECIPITATION ARE WITHIN 30 NM TO 60 NM ON EITHER SIDE OF THE FRONT. UPPER LEVEL WESTERLY TO SOUTHWESTERLY WIND FLOW IS SOUTH OF 16N EAST OF 50W. $$ MT