000 AXNT20 KNHC 011737 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT SEP 01 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 1500 UTC. ...SPECIAL FEATURES... TROPICAL STORM KIRK IS CENTERED NEAR 37.4N 46.5W AT 01/1500 UTC OR ABOUT 630 NM SSE OF CAPE RACE NEWFOUNDLAND AND ABOUT 925 NM W OF THE AZORES MOVING NE AT 22 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM OF CENTER EXCEPT 240 NM NE QUADRANT. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. TROPICAL STORM LESLIE IS CENTERED NEAR 18.3N 55.7W AT 01/1500 UTC OR ABOUT 355 NM E OF THE LEEWARD ISLANDS MOVING W-NW AT 16 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. NUMEROUS MODERATE AND SCATTERED STRONG CONVECTION IS WITHIN 270 NM SE SEMICIRCLE OF CENTER WHILE SCATTERED MODERATE CONVECTION CAN ALSO BE FOUND NW OF LESLIE FROM 18N-23N BETWEEN 55W AND 59W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 12N27W TO 19N24W AND IS MOVING W AT 10 KT. A 1011 MB SURFACE LOW IS CENTERED AT THE SOUTHERN EXTENT OF THE WAVE AXIS NEAR 12N27W. THE 01/1104 UTC ASCAT PASS INDICATES THAT THIS BROAD LOW CENTER IS MOST LIKELY EMBEDDED IN THE MONSOON TROUGH. GLOBAL MODEL GUIDANCE SHOWS THE WAVE WILL BE SLOW TO MOVE WESTWARD OVER THE NEXT DAY OR SO. NO SIGNIFICANT CONVECTION IS NOTED IN THE VICINITY OF THE WAVE. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM THE BORDER OF WESTERN SAHARA AND MAURITANIA NEAR 21N17W TO THE AFOREMENTIONED LOW PRES SYSTEM NEAR 12N27W TO 06N34W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 06N34W TO 05N40W TO 06N48W. NO SIGNIFICANT DEEP CONVECTION IS NOTED ON SATELLITE IMAGERY NEAR THE AXIS AT THIS TIME. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 29N94W. A BELT OF 20-30 KT NE TO E WINDS ALOFT LIES S OF THE ANTICYCLONE FROM 21N-27N. DESPITE THE SHEAR ALOFT...SCATTERED MODERATE CONVECTION LIES WITHIN 120 NM OF THE COAST OF MEXICO FROM 19N-25N. PRECIPITABLE WATER IMAGERY SHOWS LOW LEVEL MOISTURE IS POOLED HERE ALONG THE WESTERN GULF COAST AND EXTENDS N-NE INTO THE MISSISSIPPI VALLEY TOWARD THE REMNANTS OF ISAAC LOCATED NEAR 38.6N 93.6W AT 01/1500 UTC. AT THE SURFACE...HIGH PRES IS CENTERED NEAR THE ALABAMA/GEORGIA BORDER. LOW LEVEL WINDS ARE SOUTHEASTERLY ACROSS MUCH OF THE GULF W OF 85W...WITH MODERATE TO FRESH FLOW FOUND PRIMARILY W OF 90W. A LIGHT TO GENTLE NORTHEASTERLY BREEZE IS PRIMARILY FOUND E OF 85W ACCORDING TO THE 01/0552 UTC OSCAT PASS AND OBSERVATIONS. THE SURFACE HIGH IS FORECAST TO DRIFT W-SW INTO THE NORTHERN GULF OVER THE NEXT FEW DAYS. THIS WILL WEAKEN THE WINDS OVER THE WESTERN GULF. CARIBBEAN SEA... AN UPPER LEVEL TROUGH EXTENDING SOUTHWESTWARD FROM A LOW ALOFT OVER THE SW N ATLC IS DIPPING SOUTHWARD INTO CUBA. FAST MOVING MID TO UPPER LEVEL CLOUDS ARE RACING OVER THE NE CARIBBEAN...CAUGHT IN THE 25-30 KT NE FLOW ALOFT W OF THE UPPER TROUGH. PRECIPITABLE WATER IMAGERY AT THE SURFACE SHOWS ANY POOLING OF LOW LEVEL MOISTURE ASSOCIATED WITH THIS TROUGH IS STILL N OF CUBA. ELSEWHERE...WATER VAPOR IMAGERY INDICATES DRY AIR IS ALOFT OVER MUCH OF THE CARIBBEAN BASIN. MIDDLE TO UPPER LEVEL MOISTURE INCREASES S OF 15N. THE ONLY AREA OF SIGNIFICANT DEEP CONVECTION IN THE BASIN LIES WITHIN 120 NM OF THE COAST W OF 77W AND S OF 13N WHERE SCATTERED MODERATE AND ISOLATED STRONG CONVECTION CAN BE FOUND. WITH TROPICAL STORM LESLIE LOCATED EAST OF THE LESSER ANTILLES...MOSTLY NORTHEAST WINDS PREVAIL ACROSS THE CARIBBEAN SHIFTING MORE EASTERLY W OF 70W. TYPICAL OF THIS TYPE OF SYNOPTIC PATTERN...THE STRONGEST WINDS ARE NOTED NORTH OF THE COAST OF COLOMBIA WITH CONFIRMATION BY A 01/1426 UTC ASCAT PASS. LESLIE IS FORECAST TO LIFT AWAY FROM THE CARIBBEAN OVER THE NEXT FEW DAYS AND WINDS WILL VERE MORE SOUTHERLY OVER THE LESSER ANTILLES AND FAR EASTERN CARIBBEAN. ATLANTIC OCEAN... THE UPPER LEVEL LOW NEAR 29N70W EXTENDS A TROUGH SOUTHWESTWARD THROUGH THE SOUTHEASTERN BAHAMAS INTO EASTERN CUBA. WATER VAPOR IMAGERY SHOWS DRY AIR ALOFT BEHIND THIS TROUGH IS MOVING OVER THE EASTERN FLORIDA PENINSULA AND THE NORTHERN AND CENTRAL BAHAMAS. WINDS ARE A LIGHT TO GENTLE BREEZE OVER THE SW N ATLC UNDER THE INFLUENCE OF A 1022 MB HIGH PRES SYSTEM N OF THE AREA NEAR 33N76W. A WEAKENING STATIONARY FRONT ASSOCIATED WITH THE TROUGH ALOFT WAS ANALYZED FROM 29N72W TO 31N61W WITH A TROUGH ANALYZED FROM 29N66W TO 26N71W. ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE STATIONARY FRONT AND TROUGH. THE UPPER LOW IS FORECAST TO PINCH OFF FROM THE MEAN NORTHERN STREAM TROUGH OVER THE NEXT FEW DAYS AND RETROGRADE SOUTHWESTWARD THROUGH THE BAHAMAS. A SECONDARY UPPER TROUGH AXIS ASSOCIATED WITH THE NORTHERN STREAM MEAN TROUGH EXTENDS ALONG 58W N OF 27N. THIS TROUGH IS HELPING TO STEER T.S. LESLIE NORTHWARD. AN ANTICYCLONE CENTERED NEAR 19N60W LIES OVER LESLIE AT THE MOMENT. THIS ANTICYCLONE IS FORECAST TO MOVE AWAY FROM LESLIE OVER THE NEXT FEW DAYS AS IT PASSES W-SW THROUGH PUERTO RICO AND INTO THE NORTHERN CARIBBEAN. TROPICAL STORM KIRK IS LOCATED WELL N OF THE DISCUSSION AREA. IT IS BEING STEERED NORTHEASTWARD ON THE LEADING EDGE OF THE AFOREMENTIONED NORTHERN STREAM MEAN TROUGH. FARTHER E... A SURFACE RIDGE AXIS EXTENDS FROM A 1030 MB HIGH CENTERED NEAR 43N20W TO BETWEEN KIRK AND LESLIE NEAR 29N51W. FAIR CONDITIONS ARE ASSOCIATED WITH THE RIDGING. HOWEVER...A MIDDLE TO UPPER LEVEL LOW CENTERED NEAR 29N35W CONTINUES TO PROVIDE FOCUS FOR ISOLATED SHOWERS AND THUNDERSTORMS OVER THE FORECAST AREA N OF 25N BETWEEN 34W-40W AND ISOLATED SHOWERS WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH ANALYZED FROM 31N31W TO 26N31W. THE GOES-R PG DUST PRODUCT SHOWS A LARGE AREA OF SAHARAN DUST TO THE S OF THIS TROUGH WITHIN ABOUT 300 NM EITHER SIDE OF A LINE FROM 30N16W TO 10N35W. THE TROPICAL WAVE FROM 12N27W TO 19N24W DISCUSSED ABOVE LIES ON THE EASTERN SIDE OF THIS SAHARAN AIR MASS WHICH IS INHIBITING THE DEVELOPMENT OF ANY DEEP CONVECTION. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ SCHAUER