MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (CHAN-HOM) WARNING NR 11// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 09W (CHAN-HOM), LOCATED APPROXIMATELY 282 NM SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WESTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LOW LEVEL CIRCULATION CENTER WITH THE RECENT ASSOCIATED CONVECTION WEAKENING AND SHEARING TO THE WEST. WATER VAPOR IMAGERY SHOWS A TUTT CELL THAT WAS LOCATED FAR NORTHEAST OF THE SYSTEM BEGAN TO TRACK SOUTHWEST OVER THE PAST 3 TO 4 HOURS, POSITIONING ITSELF JUST UPSTREAM OF TS 09W. THIS HAS INCREASED THE VERTICAL WIND SHEAR (VWS) AND CREATED CONVERGENCE ALOFT. THESE IMPACTS ARE SUPPRESSING AND WEAKENING THE CONVECTION. THE INITIAL POSITION IS BASED ON THE MSI LOOP WITH HIGH CONFIDENCE. THE CURRENT INTENSITY HAS BEEN LOWERED TO 55 KNOTS BASED ON THE LACK OF A CONVECTIVE STRUCTURE; HOWEVER, DUE TO THE CURRENT STATE OF THE SYSTEM, THE INTENSITY COULD BE LOWER. TS CHAN-HOM IS DRIFTING SLOWLY WESTWARD. 3. FORECAST REASONING. A. THE CURRENT INTENSITY AND FORECASTED INTENSITY THROUGH TAU 24 HAS BEEN LOWERED DUE TO THE UNFORESEEN POSITIONING AND RELATED IMPACTS OF THE TUTT CELL JUST NORTHEAST OF THE CIRCULATION. THE TUTT CELL IS EXPECTED TO REMAIN IN PLACE OVER THE NEXT 12 TO 24 HOURS BEFORE IT GETS ABSORBED INTO THE LONGWAVE PATTERN. B. TS 09W WILL CONTINUE TO DRIFT SLOWLY WESTWARD TO WEST- NORTHWESTWARD OVER THE NEXT 12 HOURS DUE TO THE TUTT CELL POSITIONING NORTH OF THE SYSTEM. TS CHAN-HOM WILL TURN TO THE PREVIOUSLY FORECASTED NORTHWESTWARD TRAJECTORY AS THE TUTT CELL RETROGRADES TO THE EAST AND GETS REABSORBED INTO THE LONGWAVE PATTERN. THE SYSTEM WILL CONTINUE TO WEAKEN OVER THE NEXT 24 HOURS DUE TO THE IMPACTS OF THE TUTT CELL. BEYOND TAU 24, TS 09W WILL BEGIN TO REINTENSIFY DUE TO FAVORABLE DIVERGENT OUTFLOW AND DECREASED VWS AS IT ACCELERATES NORTHWESTWARD. C. IN THE EXTENDED TAUS, TS CHAN-HOM WILL CONTINUE TO TRACK NORTHWESTWARD AND FURTHER INTENSIFY AS VWS DECREASES AND THE REMAINING ENVIRONMENTAL CONDITIONS STAY FAVORABLE. DYNAMIC MODEL GUIDANCE REMAINS UNCHANGED; HOWEVER, THEY TEND TO STRUGGLE WITH TUTT CELL INTERACTION. DUE TO THE AFOREMENTIONED MODEL ISSUES AND THE COMPLEXITY OF THE STEERING ENVIRONMENT, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST.// NNNN NNNN