WDPN31 PGTW 120900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (NAKRI) WARNING NR 
017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.9N 135.2E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 257 NM SOUTHEAST OF IWAKUNI, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 29W (NAKRI) WITH A WRAPPED LOW-LEVEL CIRCULATION (LLCC)
AND DEEP CONVECTION. THE SYSTEM SHOWS SIGNS OF STRENGTHENING AS IT
CONTINUES ON ITS NORTHEASTWARD TRACK UNDER THE INFLUENCE OF THE
SUBTROPICAL RIDGE TO THE SOUTHEAST. CONDITIONS REMAIN FAVORABLE
WITH LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS), WARM (28-29 C) SEA 
SURFACE TEMPERATURES (SST), AND GOOD OUTFLOW. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE AS TECHNICAL DIFFICULTIES WITH THE
HIMAWARI-9 SATELLITE LIMITED POSITIONING DATA TO STILL SATELLITE 
IMAGERY AND RADAR FIXES. THE INITIAL INTENSITY IS BASED ON THE AGENCY 
FIXES LISTED BELOW AND IS ASSESSED WITH MEDIUM CONFIDENCE, DUE TO THE 
LACK OF AVAILABLE OBJECTIVE INTENSITY AIDS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.5 - 55 KTS
   CIMSS SATCON: 56 KTS AT 120110Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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 NAKRI IS FORECAST TO CONTINUE ON ITS
NORTHEASTWARD TRACK UNDER THE INFLUENCE OF A STR TO THE SOUTHEAST FOR 
THE REST OF THE FORECAST WITH A BRIEF PERIOD OF RE-STRENGTHENING, 
WHICH HAS ALREADY BEGUN. THE SYSTEM WILL CONTINUE TO TRACK THROUGH 
WARM (28-29 C) WATERS WITH LOW 5-10 KTS VWS, OFFSET BY SURROUNDING BY 
DRY AIR, WHICH IS EXPECTED TO EVENTUALLY START WRAPPING INTO THE 
CORE. AT THE SAME TIME, AROUND TAU 48, TS NAKRI WILL ENCOUNTER COOLER 
(27-28 C) SSTS AND UNFAVORABLE WIND SHEAR (30-40 KTS). DEGRADING 
ENVIRONMENTAL CONDITIONS WILL RESULT IN A WEAKENING TREND. 
SIMULTANEOUSLY, THE SYSTEM IS EXPECTED TO BEGIN ITS EXTRATROPICAL
TRANSITION (ETT), WHICH IS EXPECTED TO CONCLUDE BY TAU 72.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN TIGHT 
AGREEMENT WITH A CROSS-TRACK SPREAD UNDER 40 NM THROUGH TAU 48, 
EXPANDING JUST SLIGHTLY AFTERWARDS. THE JTWC FORECAST TRACK IS PLACED 
CLOSE TO THE MULTI-MODEL CONSENSUS, WITH HIGH CONFIDENCE. INTENSITY 
GUIDANCE HAS DECREASED SLIGHTLY FROM THE PREVIOUS RUNS, WITH THE JTWC 
PREDICTION SLIGHTLY HIGHER THAN HAFS-A GUIDANCE AND ASSESSED WITH A 
PEAK INTENSITY OF 75 KTS AT TAUS 24 AND 36. AS TS NAKRI BEGINS TO 
TRANSITION INTO AN EXTRATROPICAL CYCLONE AROUND TAU 36, IT IS 
EXPECTED TO WEAKEN, AS INDICATED BY ALL OF THE AVAILABLE CONSENSUS 
MEMBERS. SOME UNCERTAINTY REMAINS, PARTICULARLY BETWEEN TAUS 24 AND 
36, AS COAMPS-TC AND HAFS PROJECT A SHORT-TERM STABILIZATION OF THE 
MAXIMUM WIND SPEEDS, WHILE MAJORITY OF THE OTHER MODELS INDICATE A 
WEAKENING TREND, LIKELY DRIVEN BY INCREASING VWS AND DRY AIR 
ENTRAINMENT.

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