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| #374890 (Received by flhurricane at: 10:34 AM 09.Sep.2010) TCDAT1 TROPICAL STORM IGOR DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010 1100 AM AST THU SEP 09 2010 DEEP CONVECTION FORMED NEAR THE LOW-LEVEL CENTER OF IGOR AROUND 1030 UTC...AND HAS EXPANDED SINCE THAT TIME. HOWEVER...THIS CONVECTION REMAINS WEST OF THE CENTER DUE TO ABOUT 20 KT OF EASTERLY SHEAR ...AS SHOWN BY UW-CIMSS ANALYSES. ALTHOUGH AN ASCAT PASS AROUND 0000 UTC ONLY SHOWED MAXIMUM WINDS OF 25-30 KT...THE WINDS ARE ASSUMED TO BE A LITTLE STRONGER NOW DUE TO THE INCREASE IN CONVECTION. THEREFORE...IGOR WILL REMAIN A TROPICAL STORM WITH AN INITIAL WIND SPEED ESTIMATE OF 35 KT. THE SHIPS MODEL SHOWS THE EASTERLY SHEAR DECREASING OVER THE NEXT FEW DAYS. THIS...COMBINED WITH WARM WATERS AND A RELATIVELY MOIST ATMOSPHERE SHOULD ALLOW FOR STEADY INTENSIFICATION. THE STATISTICAL AND DYNAMICAL INTENSITY MODELS BRING IGOR TO HURRICANE STRENGTH IN ABOUT 3 DAYS AND SHOW ADDITIONAL STRENGTHENING THEREAFTER. THE NHC OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE AND IS IN CLOSEST AGREEMENT WITH THE STATISTICAL GUIDANCE. IGOR HAS BEEN GENERALLY MOVING NORTH-NORTHWESTWARD DURING THE LAST SEVERAL HOURS...AND THE 6-HOUR INITIAL MOTION ESTIMATE IS 330/5. HOWEVER...THE LAST FEW FEW VISIBLE IMAGES SUGGEST A SLIGHTLY FASTER NORTHWESTWARD MOTION. NOW THAT IGOR APPEARS TO HAVE ABSORBED THE WEAK LOW THAT HAD BEEN IN ITS VICINITY...A LOW- TO MID-LEVEL RIDGE NORTH AND NORTHEAST OF IGOR SHOULD STEER THE CYCLONE WESTWARD OR WEST-NORTHWESTWARD WITH A GRADUAL INCREASE IN FORWARD SPEED. BY THE END OF THE PERIOD...THE GLOBAL MODELS SHOW IGOR NEARING A CENTRAL ATLANTIC TROUGH WHICH SHOULD CAUSE A NORTHWESTWARD TURN. THE OFFICIAL FORECAST IS ADJUSTED TO THE NORTH IN THE SHORT-TERM DUE TO THE INITIAL POSITION AND MOTION...AND IS A LITTLE SLOWER AT THE END OF THE FORECAST PERIOD AS SUGGESTED BY THE GUIDANCE SUITE. FORECAST POSITIONS AND MAX WINDS INITIAL 09/1500Z 14.7N 24.8W 35 KT 12HR VT 10/0000Z 15.0N 26.3W 35 KT 24HR VT 10/1200Z 15.8N 29.0W 40 KT 36HR VT 11/0000Z 16.4N 32.0W 50 KT 48HR VT 11/1200Z 16.7N 35.0W 60 KT 72HR VT 12/1200Z 17.3N 40.4W 70 KT 96HR VT 13/1200Z 18.5N 44.5W 80 KT 120HR VT 14/1200Z 20.0N 48.5W 85 KT $$ FORECASTER CANGIALOSI/BRENNAN |
