WDPN32 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (PULASAN) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.1N 130.0E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 187 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CLOUD
BANDING WRAPPING INTO A LOW-LEVEL CIRCULATION CENTER (LLCC) WITH
SUBSIDENT DRY AIR CLEARING THE CENTER TO FULLY EXPOSE THE LLCC.
DEEP CONVECTIVE BANDING WRAPS AROUND THE NORTHERN PERIPHERY OF THE
CIRCULATION FROM THE EAST. TROPICAL STORM 15W CONTINUES TO MAINTAIN
THE QUALITIES OF A MONSOON DEPRESSION WITH A WIND RADII BEING
115-300NM FROM THE CIRCULATION CENTER. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON THE FULLY EXPOSED NATURE OF
THE MONSOON DEPRESSION, BUT THE DIFFICULTY IN PLACING A POSITION
WITHIN THE LARGE SYSTEM. THE INITIAL INTENSITY OF 55 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON AN EARLIER 180106Z METOP-B
ASCAT IMAGE INDICATING WIND SPEEDS UPWARDS OF 50KTS IN THE
NORTHEASTERN PERIPHERY OF THE SYSTEM.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) TO THE NORTH

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

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 15W WILL CONTINUE TO TRACK NORTHWESTWARD
WHILE DRIVEN BY THE STR TO THE NORTH. THE CHARACTERISTICS OF THE
MONSOON DEPRESSION WILL PERSIST THROUGHOUT THE FORECAST, WITH AN
ELEVATED WIND FIELD DISPLACED AT LEAST 130 NM FROM CENTER. DRY AIR
ENTRAINMENT WILL CONTINUALLY WEAKEN THE SYSTEM ALONGSIDE THE
LESSENING SURFACE PRESSURE GRADIENT AS THE SYSTEM PASSES SOUTH OF
OKINAWA. IT IS LIKELY THAT ENHANCED WINDS UP TO 50KTS ON THE EAST
SIDE OF THE MONSOON DEPRESSION TO IMPACT OKINAWA SECONDARILY WITHIN
THE NEXT TWELVE HOURS. RAPID WEAKENING WILL OCCUR JUST AFTER TAU 24
DUE TO TOPOGRAPHIC INTERACTION WITH MAINLAND CHINA, ULTIMATELY
REACHING FULL DISSIPATION BY TAU 72.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG
AGREEMENT REGARDING THE TRACK FOR THE FIRST 36 HOURS BUT BEGINS TO
BIFURCATE BY TAU 48 AS THE MODELS STRUGGLE TO TRACK THE WEAK SYSTEM
VORTEX. THE INTENSITY GUIDANCE IS ALSO CONSISTENT, FORECASTING
GRADUAL WEAKENING AS THE SYSTEM TRACKS SOUTH OF OKINAWA AND
APPROACHES LANDFALL. THE ONLY OUTLIER IS HWRF, WHICH FORECASTS
UNREALISTIC INTENSIFICATION BETWEEN TAU 24-48 WHICH CAN LIKELY BE
ATTRIBUTED TO THE DIFFICULTY OF THE MESOSCALE MODELS TO ASSESS
LARGE MONSOON DEPRESSIONS. 

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