ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM IGNACIO DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP122009 800 AM PDT TUE AUG 25 2009 THE CLOUD PATTERN OF IGNACIO APPEARS DISORGANIZED...WITH THE CENTER LOCATED NEAR THE NORTHERN EDGE OF AN AMORPHOUS MASS OF VERY DEEP CONVECTION. WHILE THE UPPER-LEVEL OUTFLOW IS FAIRLY WELL-ESTABLISHED IN THE SOUTHERN SEMICIRCLE...IT REMAINS SOMEWHAT RESTRICTED TO THE NORTH. DVORAK T-NUMBERS HAVE INCREASED TO T3.0 FROM TAFB AND SAB AND THE OFFICIAL INTENSITY IS SET AT 45 KT. IGNACIO STILL HAS AN OPPORTUNITY TO STRENGTHEN DURING THE NEXT 12-24 HOURS WHILE IT TRACKS OVER WARM WATERS AND ENCOUNTERS RELATIVELY WEAK SHEAR. THEREAFTER...THE CYCLONE SHOULD REACH SIGNIFICANTLY COOLER WATERS AND QUICKLY WEAKEN TO A REMNANT LOW BY 72 HOURS. A 1158 UTC TRMM PASS WAS HELPFUL IN LOCATING THE CENTER. WHILE STILL UNCERTAIN...THE INITIAL MOTION ESTIMATE IS 295/10. THE FORECAST TRACK PHILOSOPHY HAS NOT CHANGED. IGNACIO IS ON THE SOUTHWEST SIDE OF A DEEP-LAYER ANTICYCLONE EXTENDING FROM THE SOUTHERN UNITED STATES INTO THE EAST PACIFIC TO NEAR 130W. A WEAK SHORTWAVE TROUGH SHOULD LIFT NORTHEAST AHEAD OF A DEEPENING EAST PACIFIC/GULF OF ALASKA LONGWAVE TROUGH...KEEPING A WEAKNESS IN THE SUBTROPICAL RIDGE IN PLACE ALONG 130W. THIS SHOULD HELP STEER IGNACIO ON A NORTHWESTERLY COURSE DURING THE NEXT FEW DAYS. TOWARD THE END OF THE PERIOD...THE CYCLONE SHOULD ASSUME A MORE WESTERLY TRACK ONCE IGNACIO WEAKENS AND BECOMES MORE SHALLOW. THE OFFICIAL TRACK DIFFERS LITTLE FROM THE PREVIOUS ADVISORY AND IS IN GOOD AGREEMENT WITH THE MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 25/1500Z 18.6N 119.3W 45 KT 12HR VT 26/0000Z 19.4N 120.8W 50 KT 24HR VT 26/1200Z 20.8N 122.8W 50 KT 36HR VT 27/0000Z 22.3N 124.6W 45 KT 48HR VT 27/1200Z 24.0N 126.5W 35 KT 72HR VT 28/1200Z 26.5N 129.5W 25 KT...REMNANT LOW 96HR VT 29/1200Z 27.0N 133.0W 20 KT...REMNANT LOW 120HR VT 30/1200Z...DISSIPATED $$ FORECASTER KIMBERLAIN/WALTON NNNN
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Page last modified: Thursday, 31-Dec-2009 12:09:23 UTC