WDPN33 PGTW 041500 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 22W (NALGAE) WARNING NR 30// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. TROPICAL DEPRESSION (TD) 22W (NALGAE), LOCATED APPROXIMATELY 210 NM SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED WESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY INDICATES SIGNIFICANT WARMING OF THE CLOUD TOPS AND WEAKENING OF THE SYSTEM OVER THE PAST SIX HOURS. THE EFFECTS OF LAND INTERACTION WITH THE RUGGED TERRAIN OF HAINAN ARE DRAMATIC, WITH DEEP CONVECTION ALL BUT GONE AND THE LOW LEVEL CIRCULATION CENTER (LLCC) OBSCURED IN THE MOUNTAINS AND DIFFICULT TO TRACK. THE LATEST AMSU TEMPERATURE PROFILE NO LONGER INDICATES THE PRESENCE OF A WARM MID-LEVEL ANOMALY. SANYA, HAINAN, IS REPORTING 4 MB PRESSURE RISES SINCE 040600Z DESPITE THE PASSAGE OF THE SYSTEM ALONG AN ARC OF RELATIVELY EQUAL DISTANCE TO ITS NORTH. TD 22W HAS RESUMED A WESTWARD TRACK IN RESPONSE TO A STRENGTHENING LOW- TO MID-LEVEL STEERING RIDGE BUILDING ALONG THE SOUTH COAST OF CHINA. THE 040000Z UPPER AIR SOUNDING FROM HAIKOU, CHINA SHOWS STRONG EASTERLIES BEGINNING AT THE GRADIENT LEVEL, INDICATING THE RIDGE IS FIRMLY ENTRENCHED AND WILL BLOCK FURTHER POLEWARD MOVEMENT. THE PGTW 040000Z UPPER LEVEL STREAMLINE ANALYSIS REVEALS THAT TD 22W IS SOUTH OF THE SUBTROPICAL RIDGE AXIS, WHICH IS ANCHORED IN AN ANTICYCLONE JUST SOUTHEAST OF TAIWAN. DIFFLUENT FLOW ASSOCIATED WITH THE SOUTHWESTERN REGION OF THE RIDGE IS COMPENSATING FOR SOME OF THE EFFECTS OF VERTICAL WIND SHEAR. VERTICAL WIND SHEAR IS ESTIMATED AT 20 KNOTS AND SEA SURFACE TEMPERATURES BETWEEN HAINAN AND THE VIETNAMESE COAST ARE 28 TO 30 DEGREES. ANIMATED WATER VAPOR IMAGERY DEPICTS A POLEWARD OUTFLOW CHANNEL STRETCHING TO THE NORTHEAST AND WELL-DEVELOPED EQUATORWARD OUTFLOW. 3. A. THE FORECAST PHILOSOPHY HAS NOT CHANGED. B. TD 22W WILL STEER ALONG THE SOUTHWESTERN PERIMETER OF THE SUBTROPICAL RIDGE. THE RIDGE WILL CONTINUE BUILDING, FORCING THE SYSTEM TO TRACK SOUTH OF WEST. SOME RE-INTENSIFICATION IS TO BE EXPECTED AFTER TD 22W MOVES OUT OF HAINAN AND INTO OPEN WATERS, BUT VERTICAL WIND SHEAR WILL REMAIN NEAR 20 KNOTS AND THE MARGINALLY FAVORABLE UPPER LEVEL CONDITIONS COUPLED WITH THE RELATIVELY BRIEF TIME OVER WATER WILL CAP DEVELOPMENT. THERE IS SUBSTANTIAL SPREAD IN MODEL GUIDANCE AFTER TAU 12, WITH GFDN SHOWING A SHARP SOUTHWARD MOVEMENT AND ECMWF DEPICTING A COMPLETE COURSE REVERSAL BACK INTO THE SOUTH CHINA SEA. AS A RESULT, CONSENSUS IS BEING SLOWED AND PULLED SOUTH. THE JTWC TRACK FORECAST STAYS POLEWARD AND FASTER THAN CONSENSUS.// NNNN