WDPN32 PGTW 180300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (PULASAN) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.4N 131.9E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 290 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM (TS) 15W AS A MONSOON DEPRESSION, WITH AN EXTENSIVE CLOUD
BAND EXTENDING FROM THE NORTHERN QUADRANT, AROUND THE EASTERN
FLANK, AND BECOMING INCREASINGLY FRAGMENTED EQUATORWARD TOWARD A
SOUTHWEST TO NORTHEAST ORIENTED MONSOON TROUGH. THE LOW-LEVEL
CIRCULATION CENTER (LLCC) OF THE MONSOON DEPRESSION HAS REMAINED
BROAD AND PARTIALLY TO FULLY EXPOSED OVER THE LAST FEW HOURS, AS
DRY AIR CONTINUES TO WRAP AROUND THE SOUTHERN SEMICIRCLE. ALTHOUGH
ISOLATED AREAS OF FLARING CONVECTION HAVE BEEN OBSERVED, THEY HAVE
BEEN SHORT-LIVED AND QUICK TO DISSIPATE DUE TO INCREASING
INFLUENCES FROM DRY AIR DRIVEN BY A TROPICAL UPPER TROPOSPHERIC
TROUGH (TUTT) ALOFT. UPPER-LEVEL OUTFLOW REMAINS MODERATE AS
ANIMATED WATER VAPOR IMAGERY HAS REVEALED A CONTINUOUS EQUATORWARD
CHANNEL AND NEWLY OBSERVED CIRRIFORM STRIATIONS ALONG THE WESTERN
EDGES OF THE REMAINING CONVECTIVE STRUCTURES. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE BROAD AND EXPOSED
LLCC ON ANIMATED VISIBLE IMAGERY. THE INITIAL INTENSITY IS ASSESSED
WITH LOW CONFIDENCE BASED ON THE BROAD NATURE OF THE MONSOON
DEPRESSION, THE WIDE SWATH OF ENHANCED WINDS ALONG THE EASTERN
SEMICIRCLE OF THE SYSTEM, AND AN EARLIER 171239Z METOP-B ASCAT PASS.
OF NOTE, THE ASSOCIATED WIND FIELD FOR THE SYSTEM REMAINS GREATER
THAN 120 NM FROM THE ASSESSED INITIAL POSITION, WHILE MAXIMUM
INTENSITIES WERE OBSERVED EARLIER WITHIN THE NORTHERN QUADRANT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) OVER JAPAN AND
THE KOREAN PENINSULA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 30-32 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: INITIAL INTENSITY WAS ADJUSTED TO 55
KTS BASED ON A REANALYSIS OF THE 170857Z RCM-2 SAR PASS. 

FORECAST DISCUSSION: TS 15W IS FORECASTED TO TRACK NORTHWESTWARD AS
A MONSOON DEPRESSION ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL
RIDGE LOCATED TO THE NORTH. THE MONSOON DEPRESSION IS EXPECTED TO
MAINTAIN ITS BROAD CHARACTERISTICS, WITH A BAND OF INTENSE WINDS
WRAPPED FROM THE NORTHERN QUADRANT, ALONG THE EASTERN PERIPHERY,
AND MAINTAIN A 130 NM TO 250 NM DISTANCE FROM THE FORECASTED TRACK.
DURING THE SYSTEMS NORTHWESTWARD TRACK, THE WELL-ESTABLISHED STR
WILL DRIVE THE MONSOON DEPRESSION 15 NM SOUTH OF OKINAWA. AFTER THE
PASSAGE SOUTH OF OKINAWA, 15W WILL CONTINUE NORTHWESTWARD,
POTENTIALLY ENHANCING WINDS A SECOND TIME WITH THE TAIL-END OF THE
SOUTHWARD EXTENDING WIND BAND THROUGHOUT THE ISLAND OF OKINAWA
BETWEEN TAU 12 AND TAU 24. THE SYSTEM IS FORECASTED TO MAKE
LANDFALL JUST BEFORE TAU 36 ALONG THE NORTHWESTWARD TRACK. AFTER
TAU 36, A WEAKENING SURFACE PRESSURE GRADIENT, INCREASED INFLUENCES
FROM DRY AIR ASSOCIATED WITH THE TUTT ALOFT, AND TOPOGRAPHIC
INTERACTION WILL RAPIDLY WEAKEN TS 15W THROUGH TAU 72 TO 25 KTS.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN TIGHT
AGREEMENT THAT THE MONSOON DEPRESSION WILL CONTINUE TO TRACK
NORTHWESTWARD, WITH A MAXIMUM CROSS-TRACK SPREAD OF 112 NM JUST
PRIOR TO LANDFALL NEAR TAU 36. AFTER LANDFALL, THE MEMBERS OF THE
JTWC CONSENSUS (CONW) CONTINUE TO ILLUSTRATE A SIGNIFICANT
DIVERGENCE IN SOLUTIONS UNTIL THE END OF THE FORECAST PERIOD (TAU
72). THE JTWC FORECAST IS VERY MUCH ALIGNED WITH THE MULTI-MODEL
CONSENSUS, LENDING HIGH CONFIDENCE TO THE FORECASTED TRACK UNTIL
TAU 72. THE MODEL INTENSITY GUIDANCE IS IN MODERATE AGREEMENT, WITH
ALL MEMBERS OF THE JTWC INTENSITY GUIDANCE TRENDING DOWNWARD
THROUGH THE END OF THE FORECAST, WITH THE EXCEPTION OF TWO
MESOSCALE INTENSITY MODELS, ILLUSTRATING A SLIGHT INCREASE IN
INTENSITY BETWEEN TAU 24 AND TAU 36. GFS CONTINUES TO SHOW A
SIGNIFICANT WEAKENING TREND AS THE SINGLE LOWER-THAN-CONSENSUS
SOLUTION. THE JTWC INTENSITY FORECAST REMAINS CLOSELY ALIGNED WITH
THE MULTI-MODEL CONSENSUS, WHILE SHOWING AN INCREASED WEAKENING
PHASE AFTER LANDFALL DUE TO ENVIRONMENTAL INFLUENCES OUTLINED IN THE 
FORECAST DISCUSSION.

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