MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W WARNING NR 01// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 22W (TWENTY-TWO), LOCATED APPROXIMATELY 327 NM NORTH-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST- NORTHWESTWARD AT 21 KNOTS OVER THE PAST SIX HOURS. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 051200Z IS 9 FEET. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH FORMATIVE BANDING AND FLARING CENTRAL CONVECTION. THE INITIAL POSITION IS BASED ON SATELLITE FIXES FROM PGTW AND RJTD WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT 25 KNOTS AND IS BASED ON DVORAK ESTIMATES FROM ALL AGENCIES RANGING FROM T1.0 TO T2.0 (25 TO 30 KNOTS RESPECTIVELY) AND A PARTIAL 051226Z METOP-B ASCAT IMAGE SHOWING SEVERAL 25 KNOT BARBS ON THE NORTHEASTERN PERIPHERY. UPPER-LEVEL ANALYSIS INDICATES MODEST OUTFLOW AND MARGINAL VERTICAL WIND SHEAR VALUES (15 TO 20 KNOTS). SEA SURFACE TEMPERATURES ARE VERY WARM NEAR 30 CELSIUS. CURRENTLY TD 22 IS TRACKING WESTWARD ALONG THE PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE TO THE NORTHEAST. 3. FORECAST REASONING. A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE FORECAST PHILOSOPHY. B. TD 22W WILL CONTINUE TO TRACK WESTWARD ALONG THE CURRENT STEERING RIDGE FOR THE NEXT 24 TO 36 HOURS. BY TAU 36 TD 22 WILL ENTER A WEAK STEERING ENVIRONMENT AS A COMPETING RIDGE BUILDS IN FROM THE WEST OVER INDOCHINA. THIS WILL INTRODUCE A SOUTHERLY COMPONENT TO THE TRACK AFTER TAU 48. ENVIRONMENTAL CONDITIONS WILL REMAIN MARGINAL LIMITING DEVELOPMENT TO A WEAK TROPICAL STORM BY TAU 36, LARGELY DUE TO LESS THAN FAVORABLE OUTFLOW. C. IN THE EXTENDED FORECAST BOTH STEERING RIDGES WILL EXERT SOME INFLUENCE ON TD 22W CAUSING THE SYSTEM TO TRACK SLOWLY TO THE SOUTHWEST AS THE RIDGE OVER INDOCHINA RETROGRADES BACK TO THE WEST. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO IMPROVE SLIGHTLY DURING THIS TIME TO SUPPORT LIMITED INTENSIFICATION. DYNAMIC MODEL GUIDANCE IS GOOD AGREEMENT FOR THE FIRST 24 HOURS, BUT SHOW CONSIDERABLE DIVERGENCE IN TRACK THEREAFTER DUE TO THE WEAK STEERING ENVIRONMENT. IN GENERAL ALL SOLUTIONS SHOW THE SYSTEM MOVING WESTWARD, BUT DUE TO THE UNCERTAINTY THERE IS LOW CONFIDENCE IN THE FORECAST TRACK.// NNNN NNNN