000 AXNT20 KNHC 121158 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT WED SEP 12 2012 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... TROPICAL STORM NADINE IS CENTERED NEAR 18.6N 46.6W 12/0900 UTC OR ABOUT 865 NM ENE OF THE LESSER ANTILLES MOVING WNW AT 15 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1001 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 15N-22N BETWEEN 43W-49W. CLUSTER OF SCATTERED MODERATE/ ISOLATED STRONG CONVECTION ARE 13N-15N BETWEEN 44W-49W AND FROM 22N-25N BETWEEN 44W-49W. ...TROPICAL WAVES... TROPICAL WAVE IS SW OF THE CAPE VERDE ISLANDS EXTENDING FROM 14N31W TO 5N25W MOVING W NEAR 20 KT. WAVE IS ALONG THE LEADING EDGE OF AN AREA OF DEEP MOISTURE WITH A SWATH OF DRIER AIR UNDERCUTTING THE WAVE NEAR 8N AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 60/75 NM EITHER SIDE OF THE WAVE N OF 8N. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL ATLC NEAR 15N17W TO 16N19W BEING DISRUPTED BY THE PRESENCE OF TROPICAL STORM NADINE. THE ITCZ EXTENDS FROM 10N52W TO SOUTH AMERICA NEAR 8N60W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 10-16N E OF 20W TO INLAND OVER W AFRICA. ...DISCUSSION... GULF OF MEXICO... THE CUTOFF UPPER LOW REMAINS OVER THE LOWER MISSISSIPPI VALLEY WITH THE UPPER TROUGH EXTENDING S OVER THE NW GULF OF MEXICO. AN UPPER TROUGH COVERS THE FAR E U.S. INTO THE NW ATLC SUPPORTING A COLD FRONT IN THE W ATLC AND ENTERING THE GULF OF MEXICO AT 12/0900 UTC OVER THE UPPER FLORIDA KEYS AS A WEAKENING STATIONARY FRONT ALONG 26N87W TO INLAND ALONG THE COAST OF LOUISIANA NEAR ATCHAFALAYA BAY. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE N OF 26N BETWEEN 87W-95W. AN UPPER RIDGE ANCHORED OVER SW MEXICO EXTENDS OVER THE SW GULF IS ENHANCING CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90 NM ALONG THE COAST OF MEXICO S OF 23N W OF 93W TO INLAND OVER MEXICO. THE REMAINDER OF THE GULF IS UNDER FAIR WEATHER THIS MORNING. THE WEAKENING FRONTAL BOUNDARY WILL GRADUALLY DISSIPATE THROUGH THU E OF 85W AND CONTINUE TO LIFT NORTHWARD INLAND W OF 85W. HIGH PRESSURE WILL BUILD IN FROM THE NE THROUGH THU NIGHT. A WEAK COLD FRONT IS EXPECTED TO ENTER THE FAR NW GULF SAT AND SUN. CARIBBEAN SEA... A BROAD UPPER RIDGE OVER THE W ATLC DOMINATES THE N CARIBBEAN WHILE A SECOND UPPER RIDGE DOMINATES THE SW WATERS. CLUSTERS OF ISOLATED SHOWERS/THUNDERSTORMS DOT THE NW CARIBBEAN N OF 15N W OF 76W. THE MONSOON TROUGH EXTENDS FROM COLOMBIA ALONG 10N ACROSS COSTA RICA INTO THE E PACIFIC REGION GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 10N BETWEEN 79W-84W. A CUTOFF UPPER LOW IS CENTERED NE OF THE VIRGIN ISLANDS EXTENDING AN UPPER TROUGH OVER THE E CARIBBEAN E OF 70W. MODERATE TO FRESH TRADE WINDS ARE ACROSS THE S CENTRAL CARIBBEAN WATERS WITH LIGHT TO MODERATE TRADE WINDS ELSEWHERE. THESE TRADE WINDS ARE USHERING IN SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ACROSS THE E CARIBBEAN N OF 14N E OF 70W AND S OF 13N E OF 66W. OTHERWISE THE REMAINDER OF THE CARIBBEAN IS UNDER FAIR WEATHER THIS MORNING. HIGH PRESSURE N OF THE AREA WILL MAINTAIN THE TRADE WINDS ACROSS THE CARIBBEAN THROUGH THU. ATLANTIC OCEAN... THE PRIMARY CONCERN THIS MORNING IS TROPICAL STORM NADINE IN THE CENTRAL TROPICAL ATLC. SEE SPECIAL FEATURES ABOVE. AN UPPER TROUGH COVERS THE FAR E U.S. INTO THE NW ATLC SUPPORTING A COLD FRONT THAT EXTENDS INTO THE CENTRAL ATLC NEAR 32N56W EXTENDING ALONG 27N61W TO 25N65W WHERE IT BECOMES A WEAKENING STATIONARY FRONT THROUGH THE N BAHAMA ISLANDS INTO THE GULF OF MEXICO OVER THE UPPER FLORIDA KEYS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 120 NM W OF THE COLD FRONT WITH CLUSTERS OF SIMILAR ACTIVITY WITHIN 60 NM S AND WITHIN 120/150 NM N OF THE STATIONARY FRONT. A SURFACE RIDGE CONTINUES TO BUILD S OVER THE W ATLC W OF THE ABOVE FRONTAL BOUNDARY ANCHORED BY A 1026 MB HIGH OFF THE NEW ENGLAND COAST. A CUTOFF UPPER LOW IS CENTERED IN THE W TROPICAL ATLC NE OF THE VIRGIN ISLANDS NEAR 20N61W EXTENDING AN UPPER TROUGH OVER THE E CARIBBEAN AND NNE TO NEAR 26N56W PRECEDING TROPICAL STORM NADINE. BROAD UPPER LOW IS OVER THE NE ATLC SUPPORTING A COLD FRONT THAT ENTERS THE E ATLC NEAR 32N20W EXTENDING ALONG 20N27W TO 31N35W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 60 NM S OF THE FRONT. SATELLITE IMAGES INDICATES SAHARAN DUST COVERS THE E TROPICAL ATLC FROM 14N-26N E OF 40W AND TO THE NORTH OF TROPICAL STORM NADINE. WEAKENING COLD FRONT WILL GRADUALLY DISSIPATE THROUGH THU. HIGH PRESSURE WILL CONTINUE TO BUILD IN ACROSS THE AREA BEHIND THE FRONT. TROPICAL STORM NADINE IN THE CENTRAL TROPICAL ATLC IS FORECAST TO MOVE IN A GENERAL NW DIRECTION THROUGH THU AS IT SLOWLY INTENSIFIES INTO A HURRICANE BEFORE IT TURNS IN A NE DIRECTION. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ PAW