WDPN31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.1N 158.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 1186 NM SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH FLARING DEEP
CONVECTION DISPLACED TO THE WEST-SOUTHWEST OF THE LLCC. WATER VAPOR
IMAGERY INDICATES TD 17W IS LOCATED TO THE NORTHEAST OF AN
ELONGATED TUTT CELL WHICH HAS AIDED IN DEEPENING THE SYSTEM OVER
THE PAST 24 HOURS. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON A 020541Z SSMIS MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
MULTIPLE DVORAK FIXES.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE LOCATED TO THE
EAST-NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 30 KTS AT 020540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TD 17W IS FORECAST TO TRACK TO THE NORTHWEST
THROUGH TAU 12 BEFORE SLOWLY AND STEADILY TURNING NORTHWARD AS IT
ROUNDS THE RIDGE AXIS THROUGH TAU 36. AFTER ROUNDING THE RIDGE
AXIS, TD 17W WILL ACCELERATE NORTHEASTWARD AND BEGIN INTERACTING
WITH THE BAROCLINIC ZONE. AS THE SYSTEM MOVES NORTHWARD, THE TUTT
CELL WILL MOVE FURTHER AWAY TOWARDS THE SOUTHWEST, EASING THE
UPPER-LEVEL GRADIENT AND DECREASING SHEAR, WHICH COMBINED WITH WARM
SSTS ABOVE 29C, WILL SUPPORT A PERIOD OF SLIGHT INTENSIFICATION
THROUGH TAU 24 TO A PEAK OF 35 KNOTS. BY TAU 36 THE SYSTEM MOVES
UNDER AN UPPER-LEVEL RIDGE, WHICH WILL DECREASE NET OUTFLOW ALOFT,
LEADING TO GRADUAL WEAKENING BEGINNING AT TAU 36. BY TAU 48, THE
SYSTEM WILL BEGIN TO FEEL THE EFFECTS OF RAPIDLY INCREASING
VERTICAL WIND SHEAR (VWS) AND DECREASING SEA SURFACE TEMPERATURES
(UNDER 26 DEGREES CELSIUS) AS IT MOVES UNDER THE UPPER-LEVEL
WESTERLIES, AND SIMULTANEOUSLY BEGIN EXTRA-TROPICAL TRANSITION
(ETT). THE SYSTEM IS EXPECTED TO COMPLETE ETT NO LATER THAN TAU 72
AND POSSIBLY AS EARLY AS TAU 60.  

MODEL DISCUSSION: OVERALL MODEL CONSENSUS IS IN TIGHT AGREEMENT
THAT TD 17W IS ON TRACK FOR A RECURVE SCENARIO AS THE SYSTEM ROUNDS
THE STR AXIS BY TAU 36. THE JTWC FORECAST TRACK IS PLACED SLIGHTLY
TO THE RIGHT OF THE MODEL CONSENSUS, TO SUBTRACT THE UNREALISTIC
MOTION OF THE AFUM TRACKER WHICH MOVES THE SYSTEM FAR TO THE WEST
OF THE REMAINING GUIDANCE. INTENSITY AIDS ARE IN RELATIVELY FAIR
AGREEMENT WITH COAMPS BEING THE OUTLIER INDICATING A WEAKENING
TREND EARLY IN THE FORECAST PERIOD. THE JTWC INTENSITY FORECAST IS
PLACED SLIGHTLY ABOVE INTENSITY CONSENSUS (ICNW) DURING THE FIRST 24 
HOURS, THEN SLIGHTLY BELOW AFTERWARDS AS THE SYSTEM ROUNDS THE STR 
AND BEGINS TO UNDERGO ETT.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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