WDPN31 PGTW 1901500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W 
(NINETEEN) WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 
(TD) 19W (NINETEEN), LOCATED APPROXIMATELY 356 NM 
EAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD 
AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A BROAD 
SYSTEM WITH CONVECTIVE BANDS SPIRALING INTO A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER. DEEP CONVECTION 
APPEARS TO BE LIMITED TO THE WESTERN HALF OF THE 
CIRCULATION, WITH THE BANDING FEATURES ON THE WEST 
SIDE BECOMING INCREASINGLY WELL ORGANIZED OVER THE PAST 
COUPLE OF HOURS, WHILE THE EASTERN HALF OF THE SYSTEM 
REMAINS RELATIVELY FREE OF DEEP CONVECTION AND THE 
SPIRAL BANDS ARE SOMEWHAT MORE ILL-DEFINED. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANALYSIS 
OF THE EXPOSED OUTER BANDS EVIDENT IN ANIMATED INFRARED 
IMAGERY. THE INITIAL INTENSITY OF 30 KNOTS IS ASSESSED 
WITH HIGH CONFIDENCE BASED ON ANALYSIS OF MULTI-AGENCY 
DVORAK CURRENT INTENSITY ESTIMATES OF T2.0 (30 KNOTS) 
FROM PGTW, T2.5 (35 KNOTS) FROM KNES AND T1.5 (25 KNOTS) 
FROM RJTD, AS WELL AS AN ADVANCED DVORAK TECHNIQUE 
ESTIMATE OF T2.3 (32 KNOTS). TD 19W CONTINUES TO TRACK 
ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE 
EXTENDING SOUTHWESTWARD FROM A CENTER NEAR 30N 155E TO 
NORTHERN VIETNAM. THE SYSTEM IS TRACKING THROUGH A 
GENERALLY FAVORABLE ENVIRONMENT WITH WARM SSTS (29-30 
DEG CELSIUS), LOW (10-15 KNOTS) VWS AND MODERATE UPPER-
LEVEL OUTFLOW ON THE DIVERGENT SOUTHWEST QUADRANT OF 
AN UPPER LEVEL ANTICYCLONE.  
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 19W WILL TRACK WEST-NORTHWESTWARD THROUGH TAU 
72 UNDER THE STEERING INFLUENCE OF THE DEEP-LAYER STR TO 
THE NORTH. THE SYSTEM IS EXPECTED TO MAKE LANDFALL ALONG 
THE EAST COAST OF CENTRAL LUZON SHORTLY AFTER TAU 24, THEN 
REEMERGE INTO THE SOUTH CHINA SEA BY TAU 36. WHILE A 
WEAKNESS IS STILL EXPECTED TO DEVELOP IN THE STEERING 
RIDGE AROUND TAU 48, THE VAST MAJORITY OF THE MODEL 
GUIDANCE INDICATES THAT THE MAIN IMPACT ON THE TRACK OF 
TD 19W WILL BE TO SLOW ITS FORWARD SPEED, WITH ONLY A 
VERY SMALL JOG TO A MORE NORTHWESTWARD TRACK BETWEEN TAUS 
48 AND 72. THE SYSTEM IS CURRENTLY EXPERIENCING A BIT OF 
EASTERLY SHEAR, PUSHING THE MAJORITY OF THE CONVECTION 
OFF TO THE WEST OF THE CENTER, AND THIS PATTERN IS 
EXPECTED TO CONTINUE THROUGH TAU 72, ALLOWING FOR ONLY 
SLOW BUT STEADY INTENSIFICATION. AFTER MAKING LANDFALL 
ON LUZON, THE SYSTEM MAY WEAKEN SLIGHTLY BUT ONCE BACK 
OVER WATER WILL QUICKLY REGAIN INTENSITY AND THEREAFTER 
RESUME SLOW BUT STEADY INTENSIFICATION, REACHING A PEAK OF 
55 KNOTS BY TAU 72. NUMERICAL TRACK GUIDANCE HAS COME INTO 
MUCH BETTER AGREEMENT SINCE THE PREVIOUS RUN, WITH ALL 
CONSENSUS MEMBERS WITHIN THE EXCEPTION OF NAVGEM AND THE 
UKMET ENSEMBLE FORMING A VERY TIGHT ENVELOPE WITH LESS 
THAN 60 NM AT TAU 72. HOWEVER THIS SPREAD INCREASES TO 
195 NM IF THE NAVGEM IS INCLUDED. THE ALTERNATE SCENARIO 
OF A MORE NORTHWARD TRACK INTO THE STR WEAKNESS IS STILL 
A POSSIBILITY, IF AN INCREASINGLY LESS LIKELY ONE, WITH 
ONLY THE TWO PREVIOUSLY MENTIONED MODELS SUPPORTING THAT 
SCENARIO AND EVEN THE HWRF NOW SIGNIFICANTLY CHANGING AND 
COMING IN LINE WITH THE REMAINDER OF THE TRACKERS. THE 
JTWC TRACK LIES JUST SOUTH OF THE MULTI-MODEL CONSENSUS 
TRACK THROUGH TAU 72 WITH HIGH CONFIDENCE.   
   C. IN THE EXTENDED FORECAST, TD 19W IS EXPECTED TO TRACK 
WESTWARD THROUGH TAU 120 UNDER THE STEERING INFLUENCE OF A 
REFORMED AND STRENGTHENED STR IN THE NORTHERN SOUTH CHINA 
SEA. AS THE SYSTEM MOVES WEST IT WILL INCREASINGLY COME 
UNDER CONFLUENT UPPER-LEVEL FLOW, CHOKING OFF THE OUTFLOW, 
WHICH COMBINED WITH INCREASING VWS WILL LEAD TO A SLOW 
WEAKENING TREND THROUGH TAU 120. NUMERICAL GUIDANCE IS IN 
GOOD AGREEMENT WITH THE EXCEPTION OF NAVGEM, WITH ONLY A 
65 NM SPREAD AT TAU 120 IF NAVGEM IS DISCOUNTED, AND 190 NM 
IF IT IS INCLUDED. THE JTWC FORECAST LIES TO THE SOUTH OF 
THE MULTI-MODEL CONSENSUS WITH FAIR CONFIDENCE IN LIGHT OF 
THE ALTERNATE SCENARIO AS REPRESENTED BY THE NAVGEM TRACKER.//

NNNN