WDPN32 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (TWENTYFIVE) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.8N 159.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 421 NM NORTH OF POHNPEI
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A
CONSOLIDATING SYSTEM WITH FORMATIVE BANDING WRAPPING IN FROM THE
NORTH INTO A DEEPENING COLD CENTRAL COVER THAT IS OBSCURING THE LOW
LEVEL CIRCULATION (LLC). THE INITIAL POSITION AND THE INITIAL 
INTENSITY, HELD HIGHER THAN AGENCY DVORAK ESTIMATES, ARE PLACED WITH 
HIGH CONFIDENCE BASED ON A 08223OZ PARTIAL ASCAT PASS OVER THE LLC AND 
ALSO SHOWING MULTIPLE 30-KT WIND BARBS ALONG THE RIGHT HEMISPHERE OF 
THE CYCLONE. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH WARM SST, 
LOW VWS, AND ROBUST VENTILATION.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 05-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 25W WILL TRACK NORTHWESTWARD UNDER THE STR
TO THE NORTHEAST UP TO TAU 24. AFTERWARD, A SECONDARY STR BUILDING
IN FROM THE NORTHWEST WILL ASSUME STEERING AND DRIVE THE SYSTEM
WESTWARD. THE FAVORABLE ENVIRONMENT WILL PROMOTE A MODEST, STEADY
INTENSIFICATION TO A PEAK OF 50KTS BY TAU 36; AFTERWARD, DRY AIR
INTRUSION FROM THE NORTHWEST AND INCREASING VWS WILL GRADUALLY
WEAKEN THE SYSTEM DOWN TO 25KTS BY TAU 96 AS IT PASSES TO THE NORTH
OF THE NORTHERN MARIANA ISLANDS. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT,
ESPECIALLY FOR A DEVELOPING SYSTEM, WITH A GRADUAL AND EVEN SPREAD
TO 181NM AT TAU 72 THEN SIGNIFICANTLY TO 415NM AT TAU 120. GIVEN
THE FORMATIVE NATURE OF THE CYCLONE, THERE IS ONLY MEDIUM
CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 72, THEN LOW
CONFIDENCE AFTERWARD GIVEN THE WIDE SPREAD IN THE MODEL ENVELOPE.
CONSEQUENTLY, THERE IS ALSO MEDIUM CONFIDENCE IN THE INTENSITY
FORECAST UP TO TAU 72, THEN LOW CONFIDENCE AFTERWARD. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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