WDPN33 PGTW 050300 MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 19W (PARMA) WARNING NR 30// RMKS/ 1. FOR METEOROLOGISTS. 2. 12 HOUR SUMMARY AND ANALYSIS. A. FOLLOWING THE PASSAGE OF A MID- TO UPPER LEVEL SHORTWAVE TROUGH, TROPICAL STORM (TS) PARMA HAS BEGUN TO REDEVELOP DEEP CONVECTION AROUND ITS LOW LEVEL CIRCULATION CENTER (LLCC) AND IN THE BANDING TO THE NORTH OF THE LLCC. DVORAK ESTIMATES FROM PGTW HAVE REMAINED AT A 3.0/4.0. THE FINAL-T NUMBER IS BASED ON THE PATTERN-T, VICE A WRAP, BECAUSE THE CONVECTION IS TOO WEAK. THE SYSTEM HAS ALSO BECOME LARGELY QUASI-STATIONARY WITHIN A WEAK STEERING ENVIRONMENT, HAVING ONLY MOVED 30NM OVER THE PAST 12 HOURS. 3. FORECAST REASONING A. THE FORECAST PHILOSOPHY HAS NOT CHANGED SINCE THE LAST PROGNOSTIC REASONING BULLETIN. B. THE SYSTEM IS STILL EXPECTED TO MEANDER TO THE NORTHWEST OF LUZON IN THE SOUTH CHINA SEA FOR THE NEXT 4 DAYS. THE POTENTIAL FOR MILD RE-INTENSIFICATION EXISTS NOW THAT THE TROUGH MENTIONED IN PARA 2.A. HAS PASSED TO THE EAST. HOWEVER, UPWELLING OF COOLER WATER WILL BEGIN TO STALL INTENSIFICATION OR EVEN BEGIN TO WEAKEN THE SYSTEM. THERE IS STILL SOME UNCERTAINTY IN THE TRACK OF TS 19W GIVEN THAT IT IS IN A WEAK AND ILL-DEFINED STEERING ENVIRONMENT. IF RIDGING BUILDS TO THE WEST OF THE SYSTEM, THEN THE STORM WILL GRADUALLY BEGIN TO PULL OUT TO THE SOUTHWEST, AS THE MAJORITY OF THE DYNAMIC AIDS INDICATE. ON THE OTHER HAND, IF THE RIDGE TO THE EAST REBUILDS FASTER (AND STRONGER) THAN THE RIDGE TO THE WEST THEN THAT WILL BECOME THE PREDOMINANT STEERING MECHANISM FOR PARMA. C. IN THE LATER PERIOD THE SYSTEM SHOULD START TO ACCELERATE ALONG THE FAVORED TRACK TO THE SOUTHWEST ALONG THE SOUTHEASTERN PERIPHERY OF THE SUBTROPICAL RIDGE LOCATED OVER SOUTHERN CHINA. 19W WILL MOVE INTO LOWER AMOUNTS OF FAVORABLE OCEAN HEAT CONTENT AND INCREASING VERTICAL WIND SHEAR ALONG THIS TRACK AND START TO SLOWLY WEAKEN.// NNNN