WDPN33 PGTW 040300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 19W (PARMA) WARNING NR 26// 
RMKS/
1. FOR METEOROLOGISTS. 
2. 12 HOUR SUMMARY AND ANALYSIS. 
    A. TYPHOON 19W (PARMA), LOCATED APPROXIMATELY 250 NM NORTH OF 
MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 07 KNOTS OVER 
THE PAST SIX HOURS. THE SYSTEM HAS MOVED BACK OVER WATER IN THE 
STRAIT OF LUZON AND HAS STARTED TO REGAIN ORGANIZATION AS SEEN IN 
RECENT ANIMATED MULTISPECTRAL IMAGERY. A 032224Z SSMI 37GHZ IMAGE 
SHOWS THE LOW LEVEL WITH GOOD STRUCTURE AND AN EYE-LIKE FEATURE OVER 
WATER TO THE NORTHWEST OF LUZON. THE SYSTEM IS LOCATED UNDER AN 
UPPER-LEVEL RIDGE AXIS THAT IS PROVIDING EXCELLENT WESTWARD AND 
EQUATORWARD OUTFLOW. THE SYSTEM IS IN A RELATIVELY WEAK STEERING 
ENVIRONMENT UNDER THE INFLUENCES OF THE SUBTROPICAL RIDGE (STR) 
CENTER LOCATED TO THE NORTHEAST.
3.   FORECAST REASONING 
    A. THE FORECAST PHILOSOPHY HAS CHANGED SIGNIFICANTLY SINCE THE 
PREVIOUS PROGNOSTIC REASONING BULLETIN. THE FORECAST HAS THE STR 
OVER SOUTHERN CHINA BECOMING THE PREDOMINATE STEERING INFLUENCE ON 
THE SYSTEM AFTER TAU 72 AND TRACKING THE 19W INTO THE SOUTH CHINA 
SEA.
    B. THE SYSTEM WILL SLOWLY DRIFT NORTHWESTWARD INTO THE LUZON 
STRAIT AS THE STR TO THE NORTHEAST, LOCATED SOUTH OF JAPAN, ERODES 
IN ADVANCE OF A MIDLATITUDE TROUGH. THIS WILL LEAVE TY 19W IN A VERY 
WEAK STEERING ENVIRONMENT, REMOVED FROM THE INFLUENCES OF THE STR TO 
THE NORTHEAST AND THE STR LOCATED TO THE NORTHWEST OVER SOUTHERN 
CHINA. DUE TO THE LACK OF STEERING FLOW, THE SYSTEM WILL REMAIN 
QUASI-STATIONARY THROUGH TAU 72 AND THE GENERALLY FAVORABLE 
ENVIRONMENTAL CONDITIONS WILL FACILITATE FURTHER INTENSIFICATION. 
HOWEVER, INTENSIFICATION WILL BE LIMITED DUE TO UPWELLING OF COOLER 
WATER, WHICH IS TYPICAL OF SLOW-MOVING SYSTEMS. MODEL GUIDANCE SHOWS 
VERY ERRATIC MOVEMENT OF THE SYSTEM THROUGH TAU 72.  THIS IS 
INDICATIVE OF A SYSTEM WITH WEAK STEERING INFLUENCES THAT IS 
EXPECTED TO MEANDER AIMLESSLY. THE ONLY MODEL THAT DOES NOT SHOW 
THIS MOTION IS GFS, WHICH SUPPORTS STRENGTHENING OF THE STR TO THE 
EAST AND A SHARP TURN AND ACCELERATION TO THE NORTHEAST BEHIND TY 
20W. A TURN TO THE NORTHEAST IS STILL A VIABLE ALTERNATIVE TRACK, 
ESPECIALLY IF THERE IS BINARY INTERACTION WITH THE APPROACHING TY 
20W FROM THE EAST, BUT BECOMING MORE UNLIKELY AS 19W CONTINUES TO 
TRACK NORTHWESTWARD.
    C. AFTER TAU 72, THE STR OVER CHINA IS EXPECTED TO BUILD AFTER 
THE PASSAGE OF A ZONAL TROUGH IN THE MIDLATITUDES. AS IT BUILDS, IT 
WILL IMPART A WEAK INFLUENCE ON 19W THAT WILL SLOWLY DRAG THE SYSTEM 
TO THE WEST INTO THE SOUTH CHINA SEA. AS THE SYSTEM MOVES TO THE 
WEST, AVAILABLE OCEAN HEAT CONTENT WILL DECREASE AND NOT BE ABLE TO 
SUPPORT A SLOW MOVING TYPHOON, AND INTENSITY WILL START TO SLOWLY 
DECREASE IN THE LATE PERIOD. MODEL GUIDANCE IS IN POOR AGREEMENT 
AFTER TAU 72 AS TO THE ACTUAL TRACK OF THE SYSTEM. ECMWF, TCLPS AND 
JGSM  TAKE THE SYSTEM ON A MORE SOUTHWESTERLY TRACK AND EGRR AND 
GFDN TAKE THE STORM ON A WESTERLY TRACK. NOGAPS KEEPS THE SYSTEM 
QUASI-STATIONARY THROUGH THE FORECAST PERIOD.//
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