MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT) WARNING NR 02// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 28W (TWENTYEIGHT), LOCATED APPROXIMATELY 75 NM NORTHWEST OF ANDERSEN AFB, HAS TRACKED NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) WHICH DEPICTS A CONSOLIDATING CYCLONE WITH DEEP CONVECTION OVER THE LOW LEVEL CIRCULATION CENTER (LLCC) AND BANDING FROM ALL QUADRANTS, PARTICULARLY TO THE EAST, WRAPPING IN TO THE LLCC. THE INITIAL INTENSITY IS CONSISTENT WITH THE PGTW DVORAK CURRENT INTENSITY ESTIMATE OF T2.0 (30 KNOTS). LOW (5-15 KTS) VERTICAL WIND SHEAR (VWS), EXCELLENT EQUATORWARD AND POLEWARD OUTFLOW, AND WARM SEA SURFACE TEMPERATURES (28-29 CELSIUS) MAKE FOR A PRIME ENVIRONMENT FOR INTENSIFICATION. TD 28W IS CURRENTLY TRACKING ALONG THE PERIPHERY OF A SOUTHERN EXTENSION OF AN OTHERWISE EAST-WEST ORIENTED SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 28W IS FORECASTED TO BEGIN A GRADUAL TURN TOWARD A WESTWARD TRACK AS IT MOVES AWAY FROM THE SOUTHERN EXTENSION OF THE STR. AN APPROACHING MID-LATITUDE TROUGH IS EXPECTED TO CREATE A WEAKNESS IN THE STR AND, BY TAU 72, TD 28W IS EXPECTED TO BEGIN A POLEWARD TURN AS IT ROUNDS THE STR AXIS. FOR THIS PERIOD, THE FORECAST INTENSITY CLOSELY FOLLOWS THE HIGH END OF THE INTENSITY GUIDANCE, WHICH HAS COME INTO BETTER AGREEMENT THIS CYCLE. THE JTWC FORECAST TRACK FOLLOWS THE CONSENSUS TRACK WITH FAIR CONFIDENCE BASED ON 140 NM OF SPREAD AMONG THE MODELS AT TAU 72. C. AFTER TAU 72, TD 28W IS EXPECTED TO CONTINUE ROUNDING THE STR AXIS. AS IS OFTEN THE CASE, UNCERTAINTY IN THE MODEL GUIDANCE INCREASES AS DIFFERENCES IN HOW THE MEMBERS RESOLVE THE INTERACTION BETWEEN THE STR AND THE MID-LATITUDE TROUGH TRANSLATE INTO DIFFERENCES IN DIRECTION OF MOTION AND ALONG TRACK SPEED. THE INTENSITY IS FORECASTED TO CONTINUE TO GRADUALLY INCREASE, DESPITE A DOWNWARD TREND IN THE MODEL GUIDANCE, BECAUSE THE ORIENTATION OF THE MID-LATITUDE TROUGH IS EXPECTED TO AID POLEWARD OUTFLOW BEFORE INCREASING VWS SHOULD CAUSE WEAKENING. BY TAU 120, SPREAD IN THE MODEL TRACK GUIDANCE BECOMES QUITE LARGE, THEREFORE CONFIDENCE IS LOW IN THE EXTENDED FORECAST TRACK.// NNNN NNNN