ZCZC MIATCDAT1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM OPHELIA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL162011 1100 PM AST THU SEP 22 2011 ALTHOUGH THE LOW-LEVEL CENTER OF OPHELIA HAS BECOME BETTER DEFINED AS COMPARED TO EARLIER TODAY...THE DEEP CONVECTION HAS BECOME FURTHER REMOVED FROM THE CENTER DUE TO STRONG SOUTHWESTERLY SHEAR. SATELLITE CURRENT INTENSITY ESTIMATES FROM TAFB AND SAB ONLY SUPPORT A 35-KT TROPICAL STORM. SINCE THE WINDS FROM THIS STORM HAVE HISTORICALLY BEEN HIGHER THAN THE SATELLITE PRESENTATION WOULD SUGGEST...THE INITIAL INTENSITY IS BEING CONSERVATIVELY REDUCED TO 45 KT ON THIS ADVISORY. IT APPEARS THAT OPHELIA MAY BE MAKING A LITTLE MORE NORTHWARD PROGRESS AND IS NOW MOVING TO THE WEST-NORTHWEST AT 10 KT. THE TRACK MODEL GUIDANCE IS IN GENERALLY GOOD AGREEMENT ON TURNING OPHELIA NORTHWESTWARD WITHIN THE NEXT 24 HOURS AND THEN MAINTAINING THAT HEADING THROUGH DAY 5. HOWEVER...THERE ARE SOME SPEED DIFFERENCES THAT APPEAR TO BE RELATED TO THE ORIENTATION OF THE MID-LEVEL HIGH RELATIVE TO THE CYCLONE. MOST NOTABLY...THE ECMWF SHOWS THE HIGH WEAKENING AND SLIDING SOUTHEASTWARD MORE THAN THE OTHER MODELS BY DAYS 4 AND 5 AND THEREFORE HAS OPHELIA MAKING MORE NORTHWESTWARD PROGRESS DURING THAT TIME. THE NEW OFFICIAL FORECAST IS JUST A LITTLE SLOWER THAN THE PREVIOUS ONE BUT IS STILL FASTER THAN THE VARIOUS CONSENSUS MODELS. AS FAR AS INTENSITY...OPHELIA HAS A TOUGH ROAD AHEAD OF IT...AND THE CYCLONE IS ALREADY WEAKENING DUE TO ABOUT 25 KT OF SOUTHWESTERLY SHEAR. THE UPPER-LEVEL TROUGH RESPONSIBLE FOR THIS SHEAR IS EXPECTED TO CUT-OFF AND MOVE WESTWARD IN TANDEM WITH OPHELIA...REMAINING ABOUT 600 N MI NORTHWEST OF THE STORM AT LEAST FOR THE NEXT 3 DAYS. YOU WOULD THINK THAT OPHELIA WOULD NOT SURVIVE AN ENVIRONMENT LIKE THIS...BUT IT IS OFTEN HARD TO TELL IF SYSTEMS LIKE THIS WILL HANG BY A THREAD DESPITE THE CONDITIONS. DUE TO THE HIGH UNCERTAINTY...THE OFFICIAL INTENSITY FORECAST SHOWS VERY LITTLE CHANGE FOR THE NEXT 5 DAYS. IT WOULD NOT BE SURPRISING...HOWEVER...IF OPHELIA DEGENERATED INTO A REMNANT LOW OVER THE NEXT DAY OR TWO. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 14.1N 49.9W 45 KT 50 MPH 12H 23/1200Z 14.8N 51.6W 45 KT 50 MPH 24H 24/0000Z 16.2N 53.8W 40 KT 45 MPH 36H 24/1200Z 17.5N 55.8W 40 KT 45 MPH 48H 25/0000Z 18.8N 57.6W 40 KT 45 MPH 72H 26/0000Z 21.0N 61.0W 40 KT 45 MPH 96H 27/0000Z 22.5N 63.0W 40 KT 45 MPH 120H 28/0000Z 25.0N 65.0W 40 KT 45 MPH $$ FORECASTER BERG NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:06 UTC