WDPN31 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.0N 131.7E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 259 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TIGHTLY-
CURVED BANDING WRAPPING INTO A PARTIALLY-EXPOSED, WELL-DEFINED LOW-
LEVEL CIRCULATION CENTER (LLCC), WHICH SUPPORTS THE INITIAL POSITION 
AND RECENT TRACK MOTION WITH HIGH CONFIDENCE. THE 190000Z 500MB 
ANALYSIS CHART INDICATES THAT THE SUBTROPICAL RIDGE (STR) HAS BUILT 
TO THE NORTH OF THE SYSTEM AS PREDICTED BY THE NUMERICAL MODELS. 
SPECIFICALLY, THE NAZE SOUNDING (47909) NOW SHOWS DEEP EASTERLY FLOW 
FROM THE SURFACE TO 400MB. AS A CONSEQUENCE, TS 09W HAS SLOWED AND 
TURNED NORTHWESTWARD THROUGH 0600Z AND WESTWARD FROM 0600-0800Z. THE 
INITIAL INTENSITY IS ASSESSED AT 50 KNOTS BASED ON AN AVERAGE OF 
DVORAK ESTIMATES FROM PGTW, RJTD AND KNES RANGING FROM T3.0-3.5. A 
190404Z AMSR2 36GHZ MICROWAVE IMAGE REVEALS IMPROVED CENTRAL 
CONVECTION WITH A MICROWAVE EYE FEATURE, WHICH IS CONSISTENT WITH 
THE INITIAL INTENSITY OF 50 KTS. ENVIRONMENTAL ANALYSIS INDICATES 
FAVORABLE CONDITIONS WITH ROBUST POLEWARD AND EQUATORWARD OUTFLOW 
ENHANCED BY THE TUTT TO THE EAST, LOW VERTICAL WIND SHEAR (VWS) AND 
WARM SST VALUES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: STR CENTERED OVER HONSHU EXTENDING
SOUTHWARD OVER THE NORTHERN AND NORTHWESTERN PERIPHERY OF THE
SYSTEM.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 47 KTS AT 190540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 09W IS EXPECTED TO TRACK WEST-NORTHWESTWARD
TO WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STR THROUGH TAU 72.
AFTER TAU 72, TS 09W SHOULD TURN WEST-NORTHWESTWARD AS IT TRACKS
ALONG THE SOUTHWESTERN PERIPHERY OF THE STR. TS 09W SHOULD STEADILY
INTENSIFY THROUGH TAU 72 TO A PEAK INTENSITY OF 90 KNOTS. AFTER TAU
72, TS 09W WILL WEAKEN SLIGHTLY AS IT PASSES TO THE NORTH OF TAIWAN
AND APPROACHES THE COAST OF CHINA.

MODEL DISCUSSION: THERE IS INCREASING CONFIDENCE IN THE TRACK
FORECAST THROUGH TAU 72 WITH MEDIUM CONFIDENCE; AT TAU 48 THERE IS
A 46NM SPREAD IN NUMERICAL MODEL GUIDANCE AND AT TAU 72 THERE IS A
120NM SPREAD IN SOLUTIONS. AFTER TAU 72, MODEL GUIDANCE DIVERGES 
WITH A LARGE SPREAD AND LOW CONFIDENCE. THERE IS MEDIUM CONFIDENCE 
IN THE JTWC INTENSITY FORECAST THROUGH THE FORECAST PERIOD.

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