WDPN31 PGTW 171500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (ONE) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION (TD) 01W (ONE), LOCATED APPROXIMATELY 402 NM 
EAST OF DAVAO, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 07 
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED (EIR) SATELLITE 
IMAGERY SHOWS THE SYSTEM CONTINUED TO CONSOLIDATE AS FORMATIVE RAIN 
BANDS WRAPPED TIGHTER INTO A PARTLY EXPOSED LOW LEVEL CIRCULATION 
(LLC) AS THE CENTRAL CONVECTION IS OFFSET NORTHWESTWARD. THE INITIAL 
POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON LOW CLOUD TRACING 
IN THE EIR LOOP AND LINED UP WITH A RAGGED BUT DISCERNIBLE LLC 
FEATURE IN THE 171157Z AMSU-B MICROWAVE IMAGE. THE INITIAL INTENSITY 
OF 30KTS IS HEDGED HIGHER THAN THE DVORAK ESTIMATES OF T1.5/25KTS 
FROM PGTW AND RJTD AND MORE IN LINE WITH THE ADT ESTIMATE OF 
T2.0/30KTS TO REFLECT THE IMPROVED 6-HR EIR STRUCTURE. ANALYSIS 
INDICATES A FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (10-20KT) 
VERTICAL WIND SHEAR (VWS), ROBUST WESTWARD AND POLEWARD UPPER LEVEL 
OUTFLOW THAT IS PROVIDING AMPLE VENTILATION TO THE CONVECTION, AND 
WARM (29-30C) ALONG-TRACK SST IN THE PHILIPPINE SEA. THE CYCLONE IS 
TRACKING ALONG THE SOUTHWEST PERIPHERY OF A DEEP-LAYERED SUBTROPICAL 
RIDGE (STR) TO THE NORTHEAST. 
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE IN THE FORECAST PHILOSOPHY FROM 
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 01W WILL TRACK MORE NORTHWESTWARD FOR THE DURATION OF THE 
FORECAST UNDER THE STEERING INFLUENCE OF THE AFOREMENTIONED STR. 
THE FAVORABLE ENVIRONMENT WILL PROMOTE STEADY INTENSIFICATION TO A 
PEAK OF 60KTS BY TAU 72 AS THE SYSTEM APPROACHES NORTHERN MINDANAO. 
   C. AFTER TAU 72, TD 01W WILL TRACK ACROSS THE PHILIPPINE 
ARCHIPELAGO, AND BY TAU 120, WILL REACH THE SOUTH CHINA SEA OFF THE 
ISLAND OF MINDORO. INTERACTION WITH THE ISLANDS AND INCREASED VWS 
WILL ERODE THE SYSTEM DOWN TO 35KTS BY TAU 120. NUMERICAL MODELS ARE 
IN OVERALL GOOD AGREEMENT WITH UKMET THE SOLE RIGHT OF TRACK 
OUTLIER, LENDING FAIR CONFIDENCE IN THE JTWC TRACK FORECAST.//
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