000 WTPZ42 KNHC 260232 TCDEP2 TROPICAL STORM IGNACIO DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP122009 800 PM PDT TUE AUG 25 2009 IGNACIO NOW CONSISTS OF A SMALL CENTRAL DENSE OVERCAST WITH A CONVECTIVE BAND CURLING AROUND THE EASTERN PART OF THE CIRCULATION. THE WESTERN SEMICIRCLE IS MOSTLY VOID OF ANY DEEP CONVECTION...AND VISIBLE SATELLITE IMAGERY SHOWS A DECK OF LOW-LEVEL STRATUS BEING ADVECTED INTO THE CIRCULATION FROM THE NORTH. AN ASCAT PASS AT 1809 UTC INDICATES THAT THE TROPICAL-STORM-FORCE WINDS ARE PRIMARILY LIMITED TO THE EASTERN SEMICIRCLE AND THAT THE MAXIMUM WINDS AT THE TIME WERE 45 KT. THEREFORE...THE INITIAL INTENSITY IS HELD AT 45 KT FOR THIS ADVISORY AND IS IN AGREEMENT WITH DVORAK ESTIMATES OF T3.0 FROM TAFB AND SAB. THIS COULD BE GENEROUS NOW THAT THERE HAS BEEN A RECENT WARMING OF THE CONVECTIVE CLOUD TOPS. THE CENTER OF IGNACIO IS NOW MOVING OVER SEA SURFACE TEMPERATURES NEAR 26C...AND THE SSTS ARE EXPECTED TO DECREASE BY SEVERAL DEGREES CELSIUS AS THE STORM MOVES NORTHWESTWARD OVER THE NEXT 48 HOURS. COMBINED WITH THE INGESTION OF DRIER AND MORE STABLE AIR...THIS SHOULD CAUSE IGNACIO TO STEADILY WEAKEN OVER THE NEXT 2 DAYS. SOME OF THE GUIDANCE...INCLUDING THE INTENSITY CONSENSUS...HOLDS IGNACIO AT ITS CURRENT INTENSITY FOR ANOTHER 36 HOURS OR SO...BUT THIS APPEARS UNLIKELY GIVEN THE UNFAVORABLE ENVIRONMENT AHEAD OF THE CYCLONE. THE OFFICIAL FORECAST HAS BEEN ADJUSTED DOWNWARD AND SHOWS IGNACIO BECOMING A REMNANT LOW BY 72 HOURS. ALL OF THE GLOBAL MODELS THEN DISSIPATE THE SYSTEM BY 96 HOURS. THE FORWARD SPEED HAS INCREASED FOR AN INITIAL MOTION OF 305/13. IGNACIO IS MOVING AROUND THE WESTERN PERIPHERY OF A MID-LEVEL RIDGE CENTERED OVER THE SOUTHWESTERN UNITED STATES...BUT ONCE IT WEAKENS IT IS EXPECTED TO SLOW DOWN AND TURN TO THE WEST WITHIN THE LOW-LEVEL TRADE WIND FLOW. FORECAST POSITIONS AND MAX WINDS INITIAL 26/0300Z 20.4N 121.5W 45 KT 12HR VT 26/1200Z 21.5N 123.2W 40 KT 24HR VT 27/0000Z 23.1N 125.2W 40 KT 36HR VT 27/1200Z 24.8N 127.1W 35 KT 48HR VT 28/0000Z 26.3N 128.7W 30 KT 72HR VT 29/0000Z 27.5N 131.5W 20 KT...REMNANT LOW 96HR VT 30/0000Z...DISSIPATED $$ FORECASTER BERG