WDPN31 PGTW 131500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (RAI) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 6.0N 139.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 233 NM SOUTH-SOUTHEAST OF YAP
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
SYMMETRIC CENTRAL DENSE OVERCAST FEATURE OBSCURING THE LOW-LEVEL
CIRCULATION CENTER (LLCC). DUE TO THE LACK OF SCATTEROMETER IMAGERY
AND MICROWAVE IMAGERY, THERE IS LOW CONFIDENCE IN THE INITIAL
POSITION. THE LLCC IS EXPECTED TO CONSOLIDATE OVER THE NEXT 12
HOURS, HOWEVER, THERE MAY BE SOME UNCERTAINTY AND JUMPS IN THE
EXACT CENTER LOCATION. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON THE PGTW AND KNES DVORAK ESTIMATES
AS WELL AS THE CIMSS ADT ESTIMATE. ENVIRONMENTAL CONDITIONS ARE
FAVORABLE WITH IMPROVED POLEWARD AND EQUATORWARD OUTFLOW OFFSET
SOMEWHAT BY MODERATE VERTICAL WIND SHEAR. SEA SURFACE TEMPERATURES
REMAIN CONDUCIVE AT 29-30C.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 34 KTS AT 131140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM (TS) 28W IS EXPECTED TO TRACK
WEST-NORTHWESTWARD THROUGH THE DURATION OF THE FORECAST PERIOD
ALONG THE SOUTHERN SIDE OF A STR POSITIONED TO THE NORTH. TS 28W IS
EXPECTED TO CROSS THROUGH THE SOUTHERN PHILIPPINE ISLANDS AFTER TAU
72, AND ULTIMATELY EMERGE INTO THE SULU SEA AND TRACK WEST OF
PALAWAN BY TAU 120. OVER THE NEXT 12 HOURS, THE LLCC IS EXPECTED TO
FURTHER CONSOLIDATE WHILE MOVING UNDER THE DEEP CONVECTION,
ESTABLISHING A WELL DEFINED CORE. THIS WILL MARK THE START OF A
PERIOD OF STEADY INTENSIFICATION TO A PEAK OF 90 KNOTS BY TAU 72.
AFTER TAU 72, TS 28W WILL WEAKEN AS IT TRACKS ACROSS THE SOUTHERN 
PHILIPPINES BUT A SLIGHT REINTENSIFICATION IS EXPECTED BY TAU 120 AS 
THE SYSTEM TRACKS INTO THE SOUTH CHINA SEA AND POLEWARD OUTFLOW 
IMPROVES.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH IS THE
NORTHERN OUTLIER, NUMERICAL MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT THROUGH TAU 96 WITH A 105NM SPREAD IN SOLUTIONS AT TAU
96. THE 130000Z ECMWF ENSEMBLE (EPS), HOWEVER, INDICATES A LARGER
SPREAD OF SOLUTIONS RANGING FROM NORTHERN MINDANAO TO SOUTHERN
LUZON WITH A WIDER SPREAD OF SOLUTIONS IN THE SOUTH CHINA SEA,
ESPECIALLY AFTER TAU 96. MUCH OF THE SPREAD IN THE EPS OVER THE
PHILIPPINES IS LIKELY DUE TO POSITIONAL UNCERTAINTY IN THE EARLY
FORECAST PERIOD RELATED TO THE COMPLEX, BROAD NATURE OF THE LLCC.
IN GENERAL, RELIABLE INTENSITY GUIDANCE SUPPORTS THE JTWC INTENSITY 
FORECAST THROUGH TAU 72 WITH MEDIUM CONFIDENCE. AFTER TAU 72, THERE 
IS LOW CONFIDENCE IN THE JTWC INTENSITY FORECAST WITH GREATER SPREAD 
DUE TO A NORTHEAST SURGE EVENT EXPECTED TO BUILD INTO THE SOUTH 
CHINA SEA IN THE EXTENDED PERIOD. 

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