000 AXNT20 KNHC 092340 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE OCT 09 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 09N48W TO 15N48W TO 19N46W MOVING W AT 15 KT. A 1008 MB LOW IS CENTERED AT THE SOUTHERN EXTENT OF THE WAVE AXIS NEAR 09N48W AND REMAINS EMBEDDED WITHIN THE ITCZ. TOTAL PRECIPITABLE WATER IMAGERY INDICATES MAXIMUM DEEP LAYER MOISTURE SURROUNDING THE WAVE FROM 06N-17N BETWEEN 45W-52W. SCATTERED MODERATE CONVECTION IS FROM 08N-15N BETWEEN 43W-53W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 10N14W TO 06N24W TO 08N32W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 08N32W TO 10N42W TO 06N57W. SCATTERED MODERATE CONVECTION IS FROM 03N-10N BETWEEN 19W-35W...AND FROM 09N-12N BETWEEN 54W-60W. ...DISCUSSION... GULF OF MEXICO... BROAD UPPER LEVEL TROUGHING IS OVER MUCH OF THE CENTRAL AND EASTERN CONUS WITH A BASE THAT REACHES SOUTHWARD TO 27N OVER PORTIONS OF THE NORTHERN GULF WATERS. WATER VAPOR IMAGERY INDICATES THAT A SHORTWAVE TROUGH AXIS EXTENDS FROM OVER THE NW GULF NEAR 27N97W TO 20N100W OVER CENTRAL MEXICO. THE LARGER SYNOPTIC-SCALE TROUGH OVER THE EASTERN CONUS SUPPORTS A COLD FRONT ANALYZED FROM LAKE OKEECHOBEE SW INTO THE SE GULF NEAR 24N85W. WHILE THE FRONT HAS DRIFTED SOUTHEASTWARD OVER THE PAST 24 TO 36 HOURS AND BECOME MORE AND MORE DIFFUSE...A FEW ISOLATED SHOWERS AND TSTMS ARE OCCURRING THIS EVENING OVER THE SOUTHERN FLORIDA PENINSULA AND PORTIONS OF THE FLORIDA STRAITS FROM 23N-25N BETWEEN 80W-85W. WHILE THE COLD FRONT HAS CONTINUED TO RECEIVE MORE FAVORABLE MIDDLE TO UPPER LEVEL DYNAMICS TO DRIFT EASTWARD...A DISSIPATING STATIONARY FRONT IS ANALYZED FROM 26N89W TO 25N95W. THE RESIDUAL MOISTURE AND CLOUDINESS CAN BE SEEN ON THE LAST FEW VISIBLE SATELLITE IMAGES ROUNDING A SURFACE RIDGE ANCHORED BY A 1020 MB HIGH CENTERED OVER SOUTHWESTERN LOUISIANA NEAR 30N93W. THE ONLY REMAINING BOUNDARY IS A SURFACE TROUGH ANALYZED OVER THE SW GULF FROM 18N93W N-NW TO THE MEXICO COAST NEAR 24N98W. ISOBARIC ANALYSIS INDICATES THAT WEAK LOWER PRESSURE EXTENDS NORTHWEST ALONG THE SPINE OF CENTRAL AMERICA INTO THE WESTERN GULF AND ACROSS EXTREME SOUTHERN TEXAS THIS EVENING. GLOBAL MODELS INDICATE THIS TROUGHING WILL GRADUALLY BECOME REPLACED BY A SURFACE RIDGE THAT BUILDS IN FROM THE CENTRAL PLAINS WEDNESDAY INTO THE SE CONUS BY THURSDAY. BY THE LATTER PORTION OF THE WEEK...THE SURFACE RIDGE IS FORECAST TO PROVIDE NE TO E WINDS IN THE RANGE OF 10 TO 20 KT. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE GULF OF HONDURAS NEAR 17N87W AND EXTENDS AN UPPER LEVEL RIDGE AXIS NORTHEASTWARD INTO THE SW NORTH ATLC BEYOND 22N76W. WHILE AREAS OVER THE NW CARIBBEAN AREA ARE RELATIVELY CONVECTION-FREE THIS EVENING...A FEW ISOLATED SHOWERS AND TSTMS ARE OCCURRING ACROSS INLAND PORTIONS OF THE EASTERN YUCATAN PENINSULA AND ACROSS CUBA. ON THE SOUTHEASTERN PERIPHERY OF THE UPPER LEVEL RIDGE...A 1011 MB LOW IS CENTERED NEAR 12N81W AND IS PROVIDING FOCUS FOR SCATTERED SHOWERS AND TSTMS S OF 18N BETWEEN 76W-86W. IT IS LIKELY THAT MOST OF THIS CONVECTION IS ENHANCED BY MAXIMUM UPPER LEVEL DIFFLUENT NORTHEASTERLY FLOW ALOFT. FARTHER EAST... PEAK DAYTIME HEATING AND INSTABILITY IS GENERATING SCATTERED SHOWERS AND TSTMS ACROSS PORTIONS OF HISPANIOLA WITH THIS ACTIVITY EXPECTED TO GRADUALLY DIMINISH THROUGH THE LATE EVENING AND OVERNIGHT HOURS. ELSEWHERE E OF 70W...AN UPPER LEVEL LOW IS CENTERED E-NE OF THE LESSER ANTILLES NEAR 20N56W AND EXTENDS A TROUGH AXIS SOUTHWESTWARD TO 12N67W. MOSTLY DRY AIR ACCOMPANIES THIS UPPER LEVEL FEATURE...HOWEVER A FEW ISOLATED LOW-TOPPED SHOWERS ARE OCCURRING BETWEEN 60W-68W...INCLUDING THE LESSER ANTILLES AND PUERTO RICO. ATLANTIC OCEAN... SOUTHWESTERLY UPPER LEVEL FLOW DOMINATES ACROSS THE SW NORTH ATLC THIS EVENING BETWEEN BROAD UPPER LEVEL TROUGHING OVER THE EASTERN CONUS AND AN UPPER LEVEL ANTICYCLONE CENTERED NEAR 26N66W. THE UPPER LEVEL TROUGHING SUPPORTS A COLD FRONT ANALYZED INTO THE DISCUSSION AREA NEAR 32N76W SW TO 27N80W. WHILE ONLY POSSIBLE ISOLATED SHOWERS ARE OCCURRING WITHIN 30 NM EITHER SIDE OF THE FRONT...MOST OF THE ISOLATED SHOWERS AND TSTMS ARE S OF 26N BETWEEN 77W-82W SE OF THE FRONT WHERE DAYTIME HEATING AND INSTABILITY ARE MAXIMIZED. TO THE EAST OF THE FRONT...A 1012 MB LOW IS CENTERED NEAR 28N74W WITH SURFACE TROUGHS EXTENDING S-SW TO 22N76W AND N-NE TO 33N71W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 300 NM EAST OF THE SURFACE TROUGH AXIS. THIS SYSTEM CONTINUES TO BE HEAVILY SHEARED BY THE UPPER LEVEL WINDS ASSOCIATED WITH THE TROUGHING THUS LIMITING THE OVERALL CONVECTIVE ORGANIZATION. E OF 65W...THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY TWO SURFACE HIGHS...A 1021 MB HIGH CENTERED OVER THE MADEIRA ISLANDS NEAR 33N18W AND THE OTHER A STRONGER 1029 MB HIGH CENTERED NEAR 39N44W. THE ONLY ACTIVE WEATHER EMBEDDED WITHIN THE SURFACE RIDGE ARE SCATTERED SHOWERS AND TSTMS OCCURRING WITHIN 120 NM EITHER SIDE OF A LINE FROM 25N34W TO 22N50W TO 17N59W IN ASSOCIATION WITH AN UPPER LEVEL LOW CENTERED NEAR 20N55W AND UPPER LEVEL DIFFLUENT FLOW STRETCHING EASTWARD FROM THE LOW TO 25N34W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN