000 WTPZ42 KNHC 250234 TCDEP2 TROPICAL STORM IGNACIO DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP122009 800 PM PDT MON AUG 24 2009 ALTHOUGH SOME OF THE DEEP CONVECTION WITHIN THE CURVED BAND TO THE WEST OF THE CYCLONE CENTER HAS DIMINISHED...SATELLITE INTENSITY ESTIMATES ARE NOW T3.0 FROM TAFB AND T2.5 FROM SAB. BASED ON THIS...THE DEPRESSION IS BEING UPGRADED TO TROPICAL STORM IGNACIO. THE LOW-LEVEL CENTER POSITION REMAINS A LITTLE UNCERTAIN...AND THE POSITION GIVEN HERE IS LIKELY A MEAN POSITION OF SEVERAL SWIRLS ROTATING AROUND A COMMON CENTER. A 2056 UTC AMSR-E PASS INDICATED THAT THIS MEAN CENTER IS PROBABLY A LITTLE FARTHER NORTH THAN PREVIOUSLY THOUGHT...AND THE NEW FORECAST TRACK HAS CONSEQUENTLY BEEN SHIFTED A LITTLE TO THE NORTH THROUGH THE FIRST 72 HOURS. THE INITIAL MOTION IS 290/09...BUT IGNACIO IS EXPECTED TO TURN TOWARD THE NORTHWEST BY 36 HOURS AS IT BEGINS TO MOVE AROUND THE WESTERN PERIPHERY OF A SUBTROPICAL RIDGE EXTENDING WEST OF NORTHERN MEXICO. ONCE THE CYCLONE WEAKENS BY 96 AND 120 HOURS...IT IS EXPECTED TO TURN BACK TOWARD THE WEST-NORTHWEST AS IT IS STEERED BY THE LOW-LEVEL FLOW. THE TRACK GUIDANCE IS IN REASONABLY GOOD AGREEMENT THROUGH 120 HOURS...AND VERY LITTLE CHANGE WAS MADE TO THE PREVIOUS FORECAST. IGNACIO WILL BE MOVING OVER WATER THAT IS AT LEAST 26 DEG CELSIUS FOR ANOTHER 36 HOURS OR SO. VERTICAL SHEAR IS EXPECTED TO REMAIN LIGHT...SO SOME STRENGTHENING IS ANTICIPATED UNTIL THE SEA SURFACE TEMPERATURES BEGIN TO DECREASE. THE OFFICIAL FORECAST REMAINS AT THE UPPER END OF THE INTENSITY GUIDANCE AND IS VERY CLOSE TO THE SHIPS MODEL THROUGH 36 HOURS. WHILE THE DYNAMICAL GFDL AND HWRF MODELS...AS WELL AS THE STATISTICAL LGEM...ONLY STRENGTHEN IGNACIO TO ABOUT 40-45 KT...THE PEAK INTENSITY SHOWN IN THE FORECAST IS NOT BEING LOWERED...SINCE ONLY A SLIGHT INCREASE IN ORGANIZATION WOULD SUPPORT SATELLITE INTENSITY ESTIMATES OF 55 KT. FORECAST POSITIONS AND MAX WINDS INITIAL 25/0300Z 17.0N 117.8W 35 KT 12HR VT 25/1200Z 17.4N 119.1W 40 KT 24HR VT 26/0000Z 18.1N 120.9W 50 KT 36HR VT 26/1200Z 19.2N 122.6W 55 KT 48HR VT 27/0000Z 20.8N 124.3W 50 KT 72HR VT 28/0000Z 24.0N 127.5W 40 KT 96HR VT 29/0000Z 26.5N 131.0W 25 KT...REMNANT LOW 120HR VT 30/0000Z 27.5N 134.5W 20 KT...REMNANT LOW $$ FORECASTER BERG