MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (TWENTYFIVE) WARNING NR 01// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 25W (TWENTYFIVE), LOCATED APPROXIMATELY 78 NM WEST OF YAP, FSM, HAS TRACKED WEST-NORTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS THE SYSTEM HAS IMPROVED AS FORMATIVE CONVECTIVE BANDS, ALBEIT STILL SHALLOW, HAVE BECOME MORE ORGANIZED AND SYMMETRICALLY WRAPPED INTO A DEFINED LOW LEVEL CIRCULATION CENTER. THE INITIAL POSITION LINED UP WELL WITH A LOW REFLECTIVITY CIRCULATION FEATURE IN THE 150922Z SSMIS MICROWAVE PASS. THE INITIAL INTENSITY OF 25 KNOTS IS CONSISTENT WITH DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS IN AN AREA OF LOW (05-10 KNOT) VERTICAL WIND SHEAR AND MODERATE RADIAL OUTFLOW THAT IS PROVIDING ADEQUATE VENTILATION TO THE CENTRAL CONVECTION. ALONG-TRACK SEA SURFACE TEMPERATURES IN THE PHILIPPINE SEA ARE 30 DEG CELSIUS AND ALSO FAVORABLE FOR DEVELOPMENT. THE CYCLONE IS CURRENTLY TRACKING WITH THE LOW LEVEL EASTERLY TRADEWIND FLOW. 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING BULLETIN ON THIS SYSTEM AND SETS THE FORECAST PHILOSOPHY. B. NEAR TERM, TD 25W WILL GRADUALLY TRACK ON A MORE NORTHWESTWARD TRAJECTORY AS A NEAR EQUATORIAL RIDGE TO THE EAST EMERGES AS THE INITIAL STEERING MECHANISM. HOWEVER, AFTER TAU 24, A MID-LEVEL REFLECTION OF THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST WILL ASSUME STEERING AND DRIVE THE CYCLONE ON A MORE WESTWARD TRACK. AFTER TAU 36, THE STR WILL WEAKEN AND RECEDE, ALLOWING TD 25W TO TRACK MORE POLEWARD. THE FAVORABLE DYNAMICS MENTIONED IN PARA 2 WILL PERSIST AND PROMOTE A FASTER THAN NORMAL INTENSIFICATION; BY TAU 72 THE SYSTEM WILL BE A MODERATE TYPHOON AT 90 KNOTS CENTRAL WIND SPEED. C. AFTER TAU 72, TD 25W WILL CONTINUE ITS NORTHWARD TRACK UNDER THE STEERING INFLUENCE OF THE STR AND MAY LIKELY UNDERGO RAPID INTENSIFICATION AS FAVORABLE CONDITIONS FURTHER IMPROVE INCLUDING INCREASED POLEWARD OUTFLOW. THE SYSTEM IS EXPECTED TO REACH 110 KNOTS CENTRAL WIND SPEED BY END OF FORECAST, POSSIBLY HIGHER. THE AVAILABLE NUMERIC GUIDANCE, TYPICAL WITH DEVELOPING SYSTEMS, IS IN POOR AGREEMENT AS INDICATED IN THE WIDE SPREAD IN THE MODEL ENVELOPE. IN VIEW OF THIS, THERE IS LOW CONFIDENCE IN THE INITIAL JTWC TRACK FORECAST ON TD 25W.// NNNN NNNN