WDPN31 PGTW 022100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.0N 158.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 1075 NM EAST-SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) TO THE NORTHEAST OF AN
AREA OF FLARING DEEP CONVECTION WITH SMALL, ISOLATED POPS OF
CONVECTION NEAR THE LLCC. A 021754Z SSMIS 91 GHZ PASS SHOWS
PREDOMINATELY DISORGANIZED BANDING WRAPPING INTO THE WELL DEFINED
LLCC. LATEST WATER VAPOR IMAGERY REVEALS TD 17W IS MOVING AWAY FROM
THE INFLUENCE OF THE TUTT CELL LOCATED TO THE SOUTHWEST. THE
INITIAL POSITION AND INTENSITY OF 30 KTS ARE ASSESSED WITH HIGH
CONFIDENCE BASED ON THE AFOREMENTIONED SATELLITE IMAGERY AND
MULTI-AGENCY DVORAK FIXES.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) LOCATED TO THE
EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 021740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: ALTERED THE END SATE OF THE FORECAST.
INSTEAD OF UNDERGOING EXTRA-TROPICAL TRANSITION AT THE END OF THE
FORECAST PERIOD, TD 17W IS NOW FORECAST TO DISSIPATE OVER WATER.

FORECAST DISCUSSION: TD 17W IS FORECAST TO TRACK NORTHWARD THROUGH
TAU 24 AS IT CONTINUES TO ROUND THE RIDGE AXIS. AFTER TAU 24, TD 17W 
WILL ACCELERATE NORTHEASTWARD AND BEGIN INTERACTING WITH THE 
BAROCLINIC ZONE. ALTHOUGH THE SYSTEM IS OVER WARM SSTS, IT HAS 
BECOME DECOUPLED AS WELL AS LOST ITS UPPER LEVEL OUTFLOW CHANNEL. BY 
TAU 36 THE SYSTEM WILL MOVE OVER COOLER SSTS AND WILL BEGIN TO FEEL 
THE INFLUENCE OF AN UPPER-LEVEL RIDGE, COMBINED WITH DRY AIR MOVING 
OVER TOP THE SYSTEM IN THE MID-LEVELS, WILL BEGIN TO DISSIPATE OVER 
WATER AT THIS TIME. BY TAU 48, THE SYSTEM WILL BE COMPLETELY 
DISSIPATED UNDER THE UPPER LEVEL RIDGE.

MODEL DISCUSSION: AS TD 17W CONTINUES TO ROUND THE STR AXIS,
OVERALL MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH A GRADUAL SPREAD
FROM 88 NM AT TAU 36 TO 125 NM AT TAU 48. THE JTWC FORECAST TRACK
IS LAID SLIGHTLY RIGHT OF MODEL CONSENSUS TO SUBTRACT THE
UNREALISTIC MOTION OF THE NAVGEM AND COAMPS TRACKERS WHICH MOVE THE
SYSTEM FAR TO THE NORTH-NORTHEAST DURING THE LATER PORTION OF THE
FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS IN AGREEMENT WITH
THE INTENSITY CONSENSUS (ICNW) DURING THE FIRST 24 HOURS, HOWEVER
IT DROPS BELOW ICNW BY TAUS 36 AND 48 AS MOST OF THE GUIDANCE
INDICATES UNREALISTIC INTENSIFICATION DURING THESE TIMES.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
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