000 AXNT20 KNHC 122335 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU FEB 12 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2030 UTC. ...THE ITCZ... ITCZ IS CENTERED ALONG 05N09W 03N20W 01N30W CROSSING THE EQUATOR NEAR 39W AND INTO NE BRAZIL NEAR 02S44W. SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 75 NM N AND 210 NM S OF THE ITCZ AXIS FROM 20W TO 34W. ...DISCUSSION... GULF OF MEXICO... A PROGRESSIVE MID LATITUDE PATTERN WITH STRONG MID TO UPPER-LEVEL WESTERLIES COVERS THE GULF REGION BETWEEN THE SOUTHERN EDGE THE DEEP LAYER TROUGH OVER ST LAWRENCE VALLEY/ CANADIAN MARITIMES AND THE RIDGE OVER CENTRAL AMERICA/NORTHERN CARIBBEAN. THE STATIONARY SURFACE FRONT ASSOCIATED WITH THE DEEP LAYER TROUGH CAN BE FOUND FROM THE BAY OF CAMPECHE NORTH TO NEAR 23N94W AND EAST-NORTHEASTWARD TO CENTRAL FLORIDA NORTH OF TAMPA BAY. MULTI-LEVEL CLOUDS AND SCATTERED SHOWERS ARE WITHIN 120 NM OF THE BOUNDARY E OF 88W...WITHIN 90 NM OF THE FRONT IN THE CENTRAL GULF...AND WITHIN 75 NM OF THE FRONT W OF 92W. THE STRONG WESTERLY FLOW HAS PREVENTED THE DEVELOPMENT OF DEEP CONVECTION HERE. NORTHEAST TO EAST WINDS AND A RELATIVELY DRIER AIRMASS ARE OBSERVED N OF THIS FRONT AND SOUTHERLY FLOW IS DOMINANT SOUTHEAST OF THE FRONT. ACCORDING TO THE ASCAT PASSES AROUND 1500 AND 1640 UTC...WINDS OVER THE ENTIRE GULF ARE NO STRONGER THAN 20 KT. UPPER LEVEL SUBSIDENCE AND DRY AIR ARE MAINTAINING MOSTLY CLEAR CONDITIONS IN THE SE GULF AWAY FROM THE INFLUENCE OF THE FRONTAL BOUNDARY. CARIBBEAN SEA... CONFLUENCE BETWEEN THE FLOW AROUND THE UPPER LEVEL RIDGE AXIS OVER CENTRAL AMERICA AND THE UPPER TROUGH OVER THE CENTRAL ATLC EXTENDING SOUTHWESTWARD INTO THE THE EASTERN CARIBBEAN HAS LIMITED THE DEVELOPMENT OF DEEP CONVECTION OVER MUCH OF THE CARIBBEAN TODAY. ISOLATED SHOWERS CONTINUE TO BE TRANSPORTED ACROSS THE CARIBBEAN BY STRONG TRADE WIND FLOW. THE ASCAT PASS FROM 1500 UTC SHOWS WINDS GENERALLY IN THE 20 TO 30 KT RANGE OVER MUCH OF THE CARIBBEAN E OF 79W AND S OF 18N...WITH WINDS TO GALE FORCE OFF THE COAST OF COLOMBIA. THE TRADE WINDS ARE EXPECTED TO WEAKEN OVER THE NEXT 24-48 HOURS AS HIGH PRESSURE IN THE CENTRAL ATLC NEAR 27N56W SHIFTS E. ATLANTIC OCEAN... THE SURFACE COLD FRONT ASSOCIATED WITH THE DEEP LAYER TROUGH OVER THE ST LAWRENCE VALLEY/CANADIAN MARITIMES IS SLOWLY MOVING SE THROUGH THE FAR NW ATLC FORECAST WATERS OFF THE N FL COAST...WITH THE LOW LEVEL BOUNDARY FOUND JUST S OF DAYTONA BEACH AT 1800 UTC. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE WITHIN 45 NM OF THE BOUNDARY. SW WINDS TO 25 KT AHEAD OF THE FRONT SHIFT TO WEST-NORTHWEST 15 TO 20 KT BEHIND THE BOUNDARY NEAR SHORE AND INCREASE TO THE 20 TO 30 KT RANGE OVER FORECAST WATERS E OF 75W BASED ON THE 1458 ASCAT PASS. ELSEWHERE...FAIR WEATHER COVERS MUCH OF THE W ATLC WITH CONFLUENT UPPER FLOW FOUND BETWEEN THE COLD FRONT AND A 1023 MB SFC HIGH PRESSURE CENTERED NEAR 27N56W. THE HIGH PRESSURE IS EXPECTED TO CONTINUE TO WEAKEN AS IT MOVES EASTWARD INTO THE CENTRAL ATLANTIC...ALLOWING TRADE WIND FLOW TO DECREASE ACROSS THE WESTERN ATLC. THE ASCAT PASS FROM 1320 UTC SHOWS WINDS IN THE 20 TO 25 KT RANGE WELL INTO THE CENTRAL TROPICAL ATLC W OF 45W S OF 20N. FARTHER EAST...A SURFACE TROUGH EXTENDS FROM A COLD FRONT N OF THE AREA ALONG 31N27W TO 27N29W TO 25N39W. MULTI-LEVEL CLOUDS WITH POSSIBLE EMBEDDED SHOWERS ARE WITHIN 30 NM OF THE TROUGH...WITH THE HIGH CLOUDS CENTERED FARTHER SOUTHEAST WHERE MID TO UPPER LEVEL MOISTURE IS BEING PUMPED NORTHEASTWARD ON THE LEADING EDGE OF THE UPPER LEVEL TROUGH OVER THE EASTERN ATLC FROM THE TROPICS. THIS SURFACE TROUGH IS BEGINNING TO WEAKEN AS THE AFOREMENTIONED HIGH PRESSURE SLIDES EASTWARD. FARTHER SOUTH...AN UPPER HIGH IS PRESENT NEAR 07N35W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THIS HIGH IS ENHANCING THE CONVECTION ALONG THE ITCZ. SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 75 NM N AND 210 NM S OF THE ITCZ AXIS FROM 20W TO 34W. $$ SCHAUER CLARK