000 AXNT20 KNHC 271800 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT OCT 27 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. ...SPECIAL FEATURES... HURRICANE SANDY IS CENTERED NEAR 29.7N 75.6W AT 27/1800 UTC OR ABOUT 210 NM NNE OF GREAT ABACO ISLAND...AND ABOUT 290 NM SE OF CHARLESTON SOUTH CAROLINA MOVING NE AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 961 MB. MAXIMUM SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT3/WTNT33 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. SCATTERED MODERATE CONVECTION IS NEAR THE STORM CENTER FROM 29N-31N BETWEEN 75W-77W. SCATTERED MODERATE CONVECTION SPREADS WESTWARD TO 81W BEGINNING TO IMPACT COASTAL SOUTH CAROLINA...NORTH CAROLINA...AND APPROACHING THE MID-ATLANTIC STATES. AN OUTER BAND TO THE EAST IS PRODUCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 22N-30N BETWEEN 63W-67W. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 16N40W TO 10N41W STAYING MAINLY STATIONARY. THE WAVE STILL ALIGNS WITH AN AREA OF MAXIMUM MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY THAT IS BEING ENHANCED BY AN UPPER LEVEL TROUGH. DUE TO ITS STATIONARY NATURE...THE WAVE WILL LIKELY DISSIPATE SHORTLY. ISOLATED MODERATE CONVECTION IS FROM 7N-14N BETWEEN 38W-43W. TROPICAL WAVE PREVIOUSLY ALONG 52W HAS NOW DISSIPATED INTO A WEAK SURFACE TROUGH ALONG 15N52W TO 13N48W. THE WAVE HAS DISSIPATED DUE TO A LACK OF WESTWARD MOTION AND A LOSS OF ITS INTENSE MOISTURE SIGNAL. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF SENEGAL AT 14N17W TO 10N24W. THE ITCZ BEGINS AT 10N24W AND CONTINUES ALONG 9N32W 7N38W 9N46W. VERY ISOLATED MODERATE CONVECTION IS FROM 3N-7N BETWEEN 29W-35W. ...DISCUSSION... GULF OF MEXICO... A TIGHT PRESSURE GRADIENT IS ACROSS THE GULF OF MEXICO TODAY BETWEEN HURRICANE SANDY IN THE WEST ATLC AND A HIGH PRESSURE SYSTEM BUILDING OVER THE CENTRAL CONUS PROVIDING WINDY CONDITIONS. MAINLY NORTHERLY FLOW RANGING FROM 15-25 KT IS PRESENT ACROSS THE BASIN AROUND BOTH AROUND THE CIRCULATION OF SANDY AS WELL AS BEHIND A COLD FRONT THAT IS MOVING THROUGH THE AREA. THE COLD FRONT EXTENDS FROM THE FLORIDA PANHANDLE AT 31N86W TO MEXICO ALONG 27N92W 20N97W CONTINUING INLAND INTO MEXICO. A DRY AND COOLER AIRMASS WAS ALREADY BEING DRAWN SOUTHWARD AROUND THE WEST SIDE OF SANDY PROVIDING FAIR WEATHER ACROSS FLORIDA AND THE EASTERN GULF. TEMPERATURES WILL LOWER AS THE FRONT PASSES. FROM RADAR IMAGERY IT APPEARS THAT NO SHOWER ACTIVITY IS ASSOCIATED WITH THE FRONT EXCEPT FOR A FEW SHOWERS IN THE SW GULF NEAR MEXICO. OVERCAST SKIES ARE BEHIND THE FRONT ELSEWHERE AS WELL AS ACROSS NORTHERN FLORIDA ASSOCIATED WITH SANDY. ALOFT...DRY AIR COVERS THE BASIN AROUND A BROAD UPPER LEVEL TROUGH OVER THE AREA WITH A NARROWER AXIS NEAR FLORIDA AS THE OUTFLOW OF SANDY PUSHES OVER NORTHERN FLORIDA. SANDY WILL CONTINUE TO MOVE NORTHWARD AWAY FROM FLORIDA. THE FRONT WILL CONTINUE TO MOVE SOUTHWARD ACROSS THE BASIN WITH A COOLER AIRMASS BEHIND IT. WINDY CONDITIONS WILL REMAIN THROUGHOUT THE WEEKEND. CARIBBEAN SEA... LOW-LEVEL CYCLONIC FLOW REMAINS ACROSS THE CARIBBEAN ASSOCIATED WITH HURRICANE SANDY WELL TO THE NORTH. DRY AIR IS SINKING SOUTH AROUND A BROAD UPPER TROUGH ACROSS THE GULF OF MEXICO AND THE WESTERN ATLC PROVIDING FAIR CONDITIONS ACROSS THE CARIBBEAN. HISPANIOLA IS FINALLY GAINING SOME RELIEF FROM THE HEAVY RAINFALL THAT HAS IMPACTED THE ISLAND OVER THE PAST FEW DAYS. ONLY A FEW ISOLATED SHOWERS ARE EMBEDDED WITHIN THE CYCLONIC FLOW. WINDS HAVE BEGUN TO DECREASE AS SANDY HAS MOVED NORTH. ONLY A SMALL AREA OF 15 KT WINDS ARE PRESENT IN THE FAR NW CARIBBEAN AND SOUTH OF CUBA. THE EASTERN CARIBBEAN IS COVERED BY AN UPPER LEVEL RIDGE THAT IS CENTERED NEAR 19N64W. DRY AIR IS WRAPPING AROUND THE EAST SIDE OF THE RIDGE PROVIDING FAIR CONDITIONS ACROSS THE EASTERN CARIBBEAN AS WELL. CYCLONIC FLOW WILL REMAIN ACROSS THE BASIN FOR THE NEXT SEVERAL DAYS UNTIL SANDY IS WELL TO THE NORTH AND TRADEWIND FLOW CAN RE-ESTABLISH ACROSS THE AREA IN THE MIDDLE OF THE WEEK. ATLANTIC OCEAN... HURRICANE SANDY REMAINS THE FOCUS OF THE WEST ATLANTIC TODAY AS IT CONTINUES TO THREATEN THE EASTERN SEABOARD. WIND AND RAIN ARE ALREADY BEGINNING TO IMPACT THE COASTLINE FROM SE VIRGINIA TO SOUTH CAROLINA. ALL INTERESTS IN THE EASTERN UNITED STATES COAST SHOULD MONITOR THE PROGRESS OF HURRICANE SANDY CLOSELY. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. DRY AIR ALOFT IS WRAPPING AROUND THE SOUTHERN EXTENT OF SANDY AROUND AN UPPER LEVEL TROUGH IN THE GULF AND PROVIDING FAIR CONDITIONS ACROSS THE NW CARIBBEAN ISLANDS AND THE MAJORITY OF THE BAHAMAS. UPPER LEVEL MOISTURE IS BEING DRAW AROUND THE NORTHERN SIDE OF SANDY AND AROUND AN UPPER LEVEL RIDGE TO THE EAST ALONG 65W. THIS COINCIDES WITH AN OUTER RAINBAND OF SANDY THAT BEGINS WELL NORTH OF THE NE CARIBBEAN AND WRAPS AROUND THE NW SIDE AND AROUND THE NE TO THE CENTER OF SANDY. A FRONTAL BOUNDARY IS ALSO BEGINNING TO MERGE WITH THIS RAIN BAND AS A FORMING WARM FRONT IS ALONG 29N58W TO 31N65W. THE WARM FRONT IS AN EXTENSION OF A FRONTAL BOUNDARY TO THE EAST. A COLD FRONT ENTERS THE AREA NEAR 32N39W TO 28N44W 28N51W TRANSITIONING INTO A STATIONARY FRONT TO 29N58W WHERE THE WARM FRONT BEGINS. SCATTERED SHOWERS ARE 90 NM EITHER SIDE THE AXIS. THIS FRONTAL SYSTEM IS ASSOCIATED WITH A LARGE AND ELONGATED UPPER LEVEL LOW IN THE NORTH ATLC NEAR 41N49W WITH A TROUGH AXIS EXTENDING WELL INTO THE TROPICS TO NEAR 13N43W. THIS SAME UPPER TROUGH IS SUPPORTING A FEW SHOWERS NEAR A TROPICAL WAVE NEAR 41W. A SWATH OF SHOWERS/THUNDERSTORMS IS ALSO SOUTH OF THE FRONT FROM NEAR 30N28W TO 21N42W. A WEAK 1009 MB SURFACE LOW IS ALONG THE DISCUSSION AREA BORDER NEAR 31N23W WITH A DISSIPATING COLD FRONT EXTENDING TO THE SW TO NEAR 25N32W CONTRIBUTING TO THE SWATCH OF SHOWERS/THUNDERSTORMS. A WEAK 1015 MB HIGH IS SOUTH OF THIS SYSTEM NEAR 24N23W PROVIDING FAIR WEATHER ACROSS THE EASTERN TROPICAL ATLC. ALL EYES WILL REMAIN ON SANDY AS IT CONTINUES IT PATH NORTHWARD. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON