WDPN31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (NAKRI) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.9N 135.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 482 NM EAST-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 29W CONTINUES TO STRUGGLE TO CONSOLIDATE DUE TO 
DRY AIR ENTRAINMENT AND PERSISTENT NORTHEASTERLY VERTICAL WIND SHEAR 
(VWS) FROM THE EXTENSIVE EQUATORWARD OUTFLOW OF TYPHOON 28W (LOCATED 
APPROXIMATELY 670NM NORTH-NORTHEAST). ANIMATED MULTISPECTRAL 
SATELLITE IMAGERY (MSI) DEPICTS A WELL-DEFINED EXPOSED LOW-LEVEL 
CIRCULATION, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH 
CONFIDENCE, WITH DEEP CONVECTION SHEARED TO THE SOUTHWEST. A 082123Z 
WSFM 37GHZ COLOR COMPOSITE MICROWAVE IMAGE INDICATES LIMITED SHALLOW 
BANDING HOOKING INTO A WEAKLY DEFINED LOW-LEVEL CIRCULATION CENTER. A 
082349Z ASCAT-B IMAGE SHOWS A WELL-DEFINED CENTER, WITH A SWATH OF 
35-40 KNOT WINDS OVER THE SOUTHEASTERN QUADRANT. THE INITIAL 
INTENSITY OF 40 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
ASCAT-B IMAGE, WITH SUBJECTIVE ESTIMATES AND CIMSS OBJECTIVE 
ESTIMATES RANGING FROM 32-36 KNOTS. THE 34-KNOT WIND RADII HAVE BEEN 
ADJUSTED BASED ON THE ASCAT IMAGE AS WELL.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 082030Z
   CIMSS AIDT: 36 KTS AT 082030Z
   CIMSS D-MINT: 32 KTS AT 082134Z
   CIMSS D-PRINT: 33 KTS AT 090040Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

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 36 
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 PERSISTENT NORTHEASTERLY VWS THROUGH TAU 36. AFTER 
TAU 36, THE SYSTEM WILL TURN POLEWARD AND SLOW WHILE FURTHER 
INTENSIFYING NEAR THE RYUKYU ISLANDS. AFTER TAU 48, POLEWARD OUTFLOW 
WILL IMPROVE AND THE SYSTEM WILL BEGIN TO CONSOLIDATE AS IT TRACKS 
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 80 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 160 TO 190NM CROSS-TRACK SPREAD IN THE 
GUIDANCE FROM TAU 24 TO TAU 36. THE 081800Z GEFS AND EPS RUNS 
INDICATE A FAIRLY LARGE SPREAD OF SOLUTIONS EXTENDING FROM 126E TO 
ABOUT 134E LONGITUDE, WITH THE BULK OF SOLUTIONS NOW OVER AND TO THE 
EAST OF OKINAWA. 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 95-105 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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