000 AXNT20 KNHC 131750 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN MAY 13 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W TO 07N19W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N19W TO 04N22W TO 03N46W TO 02N50W. NO SIGNIFICANT CONVECTION IS NOTED ON SATELLITE IMAGERY AT THIS TIME. THIS IS LIKELY DUE TO THE SAHARAN AIR LAYER AND SUSPENDED DUST THAT ENCOMPASSES MUCH OF THE EASTERN ATLC S OF 25N E OF 35W...AND S OF 15N E OF 55W. ...DISCUSSION... GULF OF MEXICO... SOUTHWESTERLY UPPER LEVEL FLOW DOMINATES ALOFT OVER THE GULF THIS AFTERNOON AS AN UPPER LEVEL SHORTWAVE TROUGH PROGRESSES NORTHEASTWARD ACROSS THE SE CONUS. THIS MIDDLE TO UPPER LEVEL TROUGHING SUPPORTS A 1016 MB LOW CENTERED OVER NORTHERN MISSISSIPPI NEAR 35N89W THAT EXTENDS A STATIONARY FRONT SOUTHWARD TO THE GULF COAST NEAR 30N89W THEN ALONG 28N89W TO 27N90W THEN DISSIPATING SOUTHWESTWARD TO 23N97W. SURFACE WINDS EAST OF THIS FRONTAL BOUNDARY ARE PRIMARILY EAST-SOUTHEAST IN THE RANGE OF 10 TO 15 KT WITH LOW-LEVEL MOISTURE CONVERGENCE MAXIMIZED ALONG A SURFACE TROUGH ANALYZED FROM 25N96W TO 21N96W TO 18N93W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE STATIONARY FRONT AND S OF 26N W OF 89W OVER PORTIONS OF THE WESTERN GULF IN THE VICINITY OF THE SURFACE TROUGH AXIS. AS THE LOW DRIFTS NORTHEAST OVER THE NEXT COUPLE OF DAYS...SURFACE TROUGHING WILL BE SLOW TO LIFT NORTH OF THE GULF BASIN AS WINDS FORECAST TO REMAIN LIGHT AND BECOME NORTHERLY BY MID-WEEK. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER WESTERN GUATEMALA NEAR 15N92W AND IS PROVIDING THE WESTERN CARIBBEAN W OF 68W WITH DRY AND SUBSIDENT WEST TO NORTHWEST FLOW ALOFT. WHILE EASTERLY TRADES CONTINUE AT THE SURFACE...SATELLITE IMAGERY INDICATES MOSTLY CLEAR SKIES. A FEW ISOLATED SHOWERS HOWEVER ARE BEGINNING TO INITIATE ACROSS THE GULF OF HONDURAS AND INLAND HONDURAS SOUTHWARD INTO NICARAGUA THIS AFTERNOON. E OF 68W...AN UPPER LEVEL LOW IS CENTERED NORTHEAST OF THE LESSER ANTILLES NEAR 20N60W AND EXTENDS UPPER LEVEL TROUGHING ACROSS THE EASTERN PORTION OF THE BASIN. WEAKER NORTHWEST TO WEST FLOW IS NOTED WEST OF THE UPPER LEVEL TROUGH AXIS...HOWEVER WATER VAPOR IMAGERY INDICATES THE PRESENCE OF INCREASED UPPER LEVEL MOISTURE. AT THE SURFACE...EASTERLY TRADES DOMINATE UNDER A MOSTLY SUBSIDENT ATMOSPHERE ALOFT. EXAMINING THE SAN JUAN PUERTO RICO 13/1200 UTC UPPER AIR SOUNDING...THE 650-850 MB LAYER CONTAINS THE SAHARAN AIR LAYER THAT HAS BEEN PROGRESSING WESTWARD ACROSS THE TROPICAL ATLC THE PAST SEVERAL DAYS. THIS IS ALSO LENDING TO THE OVERALL STABILITY OF THE CARIBBEAN SEA BASIN THIS AFTERNOON. ATLANTIC OCEAN... AN UPPER LEVEL TROUGH IS OVER THE WESTERN NORTH ATLC WITH AXIS EXTENDING ALONG 55W TO 30N THEN SOUTH-SOUTHWESTWARD TO 24N60W AND INTO AN UPPER LEVEL LOW CENTERED NEAR 20N60W. THIS TROUGHING SUPPORTS A COLD FRONT ANALYZED FROM 32N57W TO 30N60W THEN STATIONARY TO 27N63W AND CONTINUING W-SW AS A SHEAR LINE TO 25N71W. ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE FRONTAL BOUNDARY. A PRE-FRONTAL TROUGH IS ANALYZED SE OF THE FRONT FROM 28N62W TO 22N61W. ISOLATED SHOWERS ARE OCCURRING OVER THE AREA FROM 21N-26N BETWEEN 53W-62W. THE REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF SURFACE RIDGING ANCHORED BY A 1028 MB HIGH CENTERED NEAR 35N70W. THE FRONT IS FORECAST TO WEAKEN OVER THE NEXT FEW DAYS AS THE SURFACE RIDGE BUILDS EASTWARD THROUGH TUESDAY. FARTHER EAST...A CUT-OFF UPPER LEVEL LOW IS CENTERED NEAR 34N33W THAT SUPPORTS A NEARLY COLLOCATED 1012 MB SURFACE LOW CENTERED NEAR 35N33W. THIS LOW MAINTAINS ISOLATED CONVECTION VERY NEAR THE CENTER...HOWEVER THE POTENTIAL FOR SUBTROPICAL OR TROPICAL CYCLONE DEVELOPMENT HAS DECREASED. THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE WITH AXIS EXTENDING FROM 30N50W TO 18N30W. AS NOTED ABOVE IN THE ITCZ/MONSOON TROUGH SECTION...A LARGE AREA OF SAHARAN DUST REMAINS OVER MUCH OF THE TROPICAL ATLC S OF 25N E OF 35W...AND S OF 15N E OF 55W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN