WDPN31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (NAKRI) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.8N 136.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 544 NM EAST-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 29W IS STRUGGLING TO CONSOLIDATE DUE TO DRY AIR
ENTRAINMENT AND PERSISTENT NORTHEASTERLY VERTICAL WIND SHEAR (VWS) 
FROM THE EXTENSIVE EQUATORWARD OUTFLOW OF TYPHOON 28W (LOCATED 
APPROXIMATELY 663NM NORTH-NORTHEAST). ANIMATED ENHANCED INFRARED 
(EIR) SATELLITE IMAGERY DEPICTS A WELL-DEFINED, EXPOSED LOW-LEVEL 
CIRCULATION CENTER (LLCC), WITH LIMITED DEEP CONVECTION SHEARED TO 
THE SOUTHWEST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON THE EIR SATELLITE IMAGERY. A PARTIAL 081714Z AMSR2 36GHZ 
MICROWAVE IMAGE REVEALS CONVECTIVE BANDING OVER THE WESTERN QUADRANT 
WRAPPING INTO THE SOUTHERN QUADRANT, WITH A WEAKLY DEFINED CORE. THE 
INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON 
RECENT ASCAT DATA, WITH SUBJECTIVE ESTIMATES AND CIMSS OBJECTIVE 
ESTIMATES RANGING FROM 28-36 KNOTS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: LOW-LEVEL SUBTROPICAL RIDGE (STR) TO
THE EAST AND NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 081740Z
   CIMSS AIDT: 36 KTS AT 081740Z
   CIMSS D-MINT: 28 KTS AT 081620Z
   CIMSS D-PRINT: 31 KTS AT 081800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TS 29W WILL TRACK NORTHWESTWARD THROUGH TAU 48 
UNDER THE STEERING INFLUENCE OF THE LOW- TO MID-LEVEL STR POSITIONED 
TO THE NORTHEAST. THE SYSTEM WILL INTENSIFY SLOWLY DUE TO DRY AIR 
ENTRAINMENT AND NORTHEASTERLY VWS THROUGH TAU 36. AS TYPHOON 28W 
ACCELERATES EASTWARD AND TRANSITIONS TO AN EXTRA-TROPICAL CYCLONE, 
ENVIRONMENTAL CONDITIONS OVER TS 29W ARE EXPECTED TO GRADUALLY 
IMPROVE. AFTER TAU 36, POLEWARD OUTFLOW WILL IMPROVE AND THE SYSTEM 
WILL BEGIN TO CONSOLIDATE AS IT TRACKS EAST AND NORTHEAST OF THE 
RYUKYU ISLANDS. ENVIRONMENTAL CONDITIONS WILL BE OPTIMAL FROM TAU 48 
TO TAU 96 AS THE SYSTEM RECURVES AROUND THE NORTHWEST PERIPHERY OF 
THE STR, WITH A PEAK INTENSITY OF 70 KNOTS EXPECTED BY TAU 96. SST 
VALUES WILL COOL SLIGHTLY BY TAU 96 TO 26-27C BUT ARE STILL 
CONDUCIVE, IN CONJUNCTION WITH STRONG POLEWARD OUTFLOW INTO THE 
MIDLATITUDE WESTERLIES. AFTER TAU 96, TS 29W WILL COMMENCE EXTRA-
TROPICAL TRANSITION, WITH INCREASING VWS (35-45 KNOTS).          

MODEL DISCUSSION: WITH THE EXCEPTION OF JGSM, WHICH IS THE SOLE 
OUTLIER ON THE WESTERN EDGE OF THE AIDS ENVELOPE, DETERMINISTIC TRACK 
GUIDANCE IS IN FAIR AGREEMENT. THERE IS INCREASING UNCERTAINTY NEAR 
THE RECURVATURE POINT, WITH A 90 TO 100NM CROSS-TRACK SPREAD IN THE 
GUIDANCE FROM TAU 24 TO TAU 36. THE 081200Z GEFS AND EPS RUNS 
INDICATE A FAIRLY LARGE SPREAD OF SOLUTIONS EXTENDING FROM OKINAWA TO 
ABOUT 135E LONGITUDE, WITH THE BULK OF SOLUTIONS EAST OF OKINAWA FROM 
APPROXIMATELY 130E-133E. DURING THE RECURVATURE PHASE SOUTH OF 
MAINLAND JAPAN, THE GEFS AND EPS ENSMBLES SHOW ALL SOLUTIONS WELL 
SOUTH OF THE KANTO PLAIN. DURING THIS TIMEFRAME, THERE IS 
CONSIDERABLE UNCERTAINTY IN THE JTWC INTENSITY FORECAST WITH HAFS-A 
AND COAMPS-TC (GFS) INDICATING A PEAK INTENSITY RANGING FROM 88-100 
KNOTS.        

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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