000 AXNT20 KNHC 180548 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT THU APR 18 2013 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W TO 03N19W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 03N19W TO 01N33W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM EITHER SIDE OF A LINE FROM 04N09W TO 02N15W. ...DISCUSSION... GULF OF MEXICO... A WEAK UPPER LEVEL TROUGH AXIS EXTENDS OVER THE EASTERN GULF FROM 30N85W TO 21N85W THAT IS GENERATING MIDDLE TO UPPER LEVEL CLOUDINESS E OF 85W...INCLUDING THE FLORIDA PENINSULA. OTHERWISE...WATER VAPOR IMAGERY INDICATES UPPER LEVEL RIDGING CONTINUE TO BUILD IN OVER PORTIONS OF THE WESTERN GULF WITH NORTHERLY FLOW ALOFT DOMINATING W OF 90W. THIS UPPER LEVEL REGIME IS SUPPORTIVE OF THE SOUTHWESTERN PERIPHERY OF A SURFACE RIDGE ANCHORED OVER THE SE CONUS BY A 1021 MB HIGH CENTERED NEAR 35N83W. EAST-SOUTHEASTERLY WINDS IN THE RANGE OF 15 TO 25 KT ARE NOTED ON SHIP OBSERVATIONS...BUOYS...AND OFFSHORE OIL PLATFORMS WITH THE STRONGEST WINDS PRIMARILY OCCURRING W OF 90W AS AN AREA OF LOW PRESSURE CONTINUES TO DEVELOP AND PRODUCE ACTIVE WEATHER OVER THE CENTRAL PLAINS. THE ASSOCIATED COLD FRONT WITH THIS LOW IS EXPECTED TO EMERGE OFF THE TEXAS AND LOUISIANA COAST LATE THURSDAY INTO EARLY FRIDAY. NORTH-NORTHEASTERLY WINDS WILL THEN SWEEP ACROSS THE BASIN OVER THE WEEKEND AS THE FRONT MOVES EAST OF THE BASIN BY LATE SATURDAY. CARIBBEAN SEA... AN UPPER LEVEL TROUGH AXIS EXTENDS FROM OVER THE NW CARIBBEAN NEAR 23N86W TO 14N89W. EAST OF THE TROUGH AXIS DRY AND SUBSIDENT WEST-NORTHWESTERLY FLOW CONTINUES TO PROVIDE OVERALL TRANQUIL CONDITIONS FOR THE A MAJORITY OF THE BASIN THIS EVENING WITH THE EXCEPTION OF AN AREA OF ISOLATED SHOWERS OCCURRING IN THE VICINITY OF THE LESSER ANTILLES FROM 14N-18N BETWEEN 57W-63W. OTHERWISE...TRADES PERSIST IN THE RANGE OF 10 TO 20 KT WITH THE HIGHEST WINDS ANTICIPATED S OF 14N BETWEEN 68W-78W...AND IN CLOSE PROXIMITY TO THE COAST OF COLOMBIA. THIS OVERALL SYNOPTIC PATTERN IS EXPECTED TO CONTINUE THROUGH EARLY THURSDAY. THEREAFTER INTO THE WEEKEND...THE TRADES WILL GRADUALLY INCREASE E OF 80W DUE TO A STRENGTHENING PRESSURE GRADIENT AND HIGH PRESSURE RIDGE ANCHORED OVER THE SW NORTH ATLC REGION. ATLANTIC OCEAN... DRY AND SUBSIDENT NW FLOW ALOFT DOMINATES OVER THE SW NORTH ATLC...HOWEVER AT THE SURFACE...A PAIR OF WEAK AND SHALLOW SURFACE LOWS CONTINUE TO PROVIDE FOCUS FOR ISOLATED LOW-TOPPED SHOWERS. A 1019 MB LOW IS CENTERED NEAR 29N76W WITH POSSIBLE SHOWERS OCCURRING WITHIN 120 NM OF CENTER AND A 1020 MB LOW IS CENTERED NEAR 30N69W WITH A SURFACE TROUGH EXTENDING NE FROM THE LOW CENTER TO 33N66W. POSSIBLE ISOLATED SHOWERS ARE GENERALLY LOCATED N OF 30N BETWEEN 63W-73W. FARTHER EAST...A MIDDLE TO UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY WITH AXIS EXTENDING FROM 35N43W TO A BASE NEAR 21N62W. THIS TROUGHING SUPPORTS A COLD FRONT ANALYZED FROM 32N40W SW TO 24N57W WITH ISOLATED SHOWERS OCCURRING WITHIN 120 NM EITHER SIDE OF THE BOUNDARY. OTHERWISE...THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF WEAK SURFACE RIDGING WITH NORTHEASTERLY TRADES IN THE RANGE OF 10 TO 20 KT. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN