WDPN31 PGTW 190300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (NINETEEN) WARNING NR 001// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 19W (NINETEEN), LOCATED APPROXIMATELY 491 NM EAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 24 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS OF CONVECTION WRAPPING INTO AN OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON ANALYSIS OF THE LOW LEVEL FEATURES PRESENT IN THE MSI LOOP AS WELL AS IN A 182207Z SSMIS 37GHZ COMPOSITE IMAGE. THE INITIAL INTENSITY OF 25 KTS IS PLACED WITH HIGH CONFIDENCE BASED ON MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T1.5 (25 KTS, PGTW, RJTD AND KNES) AS WELL AS THE PRESENCE OF 20-25 KTS IN SCATTEROMETRY DATA FROM A TIMELY 182330Z ASCAT-A PASS. TD 19W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL RIDGE POSITIONED TO THE NORTHEAST AND THROUGH A REGION FAVORABLE FOR FURTHER INTENSIFICATION AS EVIDENCED BY LOW (10-15 KTS) VERTICAL WIND SHEAR, WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST) AND ROBUST POLEWARD AND FAIR EQUATORWARD OUTFLOW ALOFT. 3. FORECAST REASONING. A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE FORECAST PHILOSOPHY. B. TD 19W WILL CONTINUE TO TRACK GENERALLY WEST-NORTHWESTWARD ALONG THE PERIPHERY OF THE STEERING RIDGE OVER THE NEXT 36 HOURS AS IT APPROACHES LUZON, PHILIPPINES. DURING THIS TIME THE SYSTEM WILL CONTINUE TO INTENSIFY DUE TO CONTINUED LOW VWS AND WARM SST, RESULTING IN AN INTENSITY OF 50 KTS BY TAU 36. AT THIS TIME THE SYSTEM CENTER WILL MAKE LANDFALL OVER LUZON. AS TD 19W TRACKS OVER THE RUGGED TERRAIN OF LUZON IT WILL STEADILY WEAKEN TO 40 KTS BEFORE RETURNING OVER WATER INTO THE SOUTH CHINA SEA. DURING THIS TIME, THE SYSTEM WILL BEGIN A WESTWARD TRACK ALONG THE SOUTHERN PERIPHERY OF AN EXTENSION OF THE STR. AFTER TAU 48, THE SYSTEM WILL BEGIN TO GRADUALLY INTENSIFY ONCE AGAIN DUE TO CONTINUED WARM (28-29 CELSIUS) SST AND REACH 55 KTS BY TAU 72. THIS INTENSIFICATION WILL BE OFFSET SLIGHTLY BY MARGINAL VWS WHICH IS FORECAST TO INCREASE TO 20-25 KTS BY TAU 72. NUMERICAL MODELS TRACK GUIDANCE IS IN GOOD AGREEMENT WITH A MAXIMUM 116 NM SPREAD IN SOLUTIONS AT TAU 48. THIS TIGHT AGREEMENT IN MODEL GUIDANCE LENDS OVERALL HIGH CONFIDENCE IN THIS INITIAL PORTION OF THE JTWC FORECAST TRACK, WHICH IS LAID ON THE JTWC MULTI- MODEL CONSENSUS. C. IN THE EXTENDED PERIOD, TD 19W IS FORECAST TO CONTINUE TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STEERING RIDGE POSITIONED TO THE NORTH. THE SYSTEM WILL CONTINUE TO GRADUALLY INTENSIFY FROM 55 KTS AT TAU 72 TO 65 KTS BY TAU 120 DUE TO CONTINUED WARM SST THAT WILL REMAIN OFFSET BY UNFAVORABLE VWS WHICH WILL VARY FROM 20 TO 30 KTS DURING THIS TIME. NUMERICAL MODELS ARE IN FAIR AGREEMENT ON THE GENERALLY WESTWARD TRACK WITH A MAXIMUM SPREAD IN MODEL TRACK GUIDANCE OF 624 NM AT TAU 120. THE UKMET MODEL SOLUTION IS A NOTABLE OUTLIER AS IT BRINGS THE TRACK NORTHWARD AFTER TAU 48. REMOVING THIS SOLUTION RESULTS IN A SPREAD OF 132 NM AT TAU 120. DUE TO THIS OUTLIER, THE JTWC FORECAST TRACK IS PLACED JUST SOUTH OF THE MULTI-MODEL CONSENSUS WITH OVERALL FAIR CONFIDENCE.// NNNN