WDPN31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W WARNING NR 04//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 26W, LOCATED APPROXIMATELY 265 NM
SOUTHEAST OF CHUUK, FSM, HAS TRACKED WEST-NORTHWESTWARD AT 06 KNOTS
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY
SHOWS THE SYSTEM HAS MAINTAINED A BROAD LOW-LEVEL CIRCULATION CENTER
(LLCC) WITH CURVED BUT FRAGMENTED CONVECTIVE BANDS. THE INITIAL
POSITION IS BASED ON THE ABOVE ANIMATION AND EXTRAPOLATED FROM A 26
1038Z AMSU-B MICROWAVE IMAGE WITH LOW CONFIDENCE. THE INITIAL
INTENSITY IS BASED ON CONGRUENT DVORAK ESTIMATES FROM PGTW, RJTD, AND
KNES. BOTH INITIAL POSITION AND INTENSITY ARE SUPPORTED BY A 261038Z
DIRECT ASCAT PASS OVER THE LLCC. UPPER LEVEL ANALYSIS INDICATES THE
SYSTEM IS ABOUT 07 DEGREES SOUTH OF THE RIDGE AXIS IN AN AREA OF
LIGHT (05-10 KNOT) VERTICAL WIND SHEAR. ANIMATED WATER VAPOR IMAGERY
SHOWS GOOD RADIAL OUTFLOW WITH A STRONG BIAS ON THE POLEWARD SIDE.
THE CYCLONE IS TRACKING WESTWARD UNDER THE EASTERN EXTENSION OF THE
DEEP-LAYERED SUBTROPICAL RIDGE (STR) STRETCHED ACROSS LUZON,
PHILIPPINES.     
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TD 26W IS EXPECTED TO BE STEERED BY THE STR THROUGHOUT THIS
FORECAST. DUE TO THE FAVORABLE ENVIRONMENT, IT WILL GRADUALLY
INTENSIFY, BECOMING A TYPHOON BY TAU 72. 
   C. IN THE EXTENDED PERIOD, TD 26W WILL DRIFT INTO THE WARM
PHILIPPINE SEA AND CONTINUE TO STRENGTHEN, REACHING 90 KNOTS BY END
OF FORECAST IN THE VICINITY OF YAP, FSM. THE AVAILABLE DYNAMIC AIDS
ARE IN FAIR AGREEMENT AND SUPPORT THE JTWC FORECAST, WHICH IS FASTER
AND SLIGHTLY NORTH OF THE MULTI-MODEL CONSENSUS TO OFFSET SLOW AND
LEFT OUTLYING TRACKERS. THERE IS LOW CONFIDENCE IN THE TRACK FORECAST
DUE TO THE ILL-DEFINED INITIAL POSITION.    //
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