WDPN31 PGTW 110300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (NAKRI) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.2N 130.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 140 NM EAST-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY
DECAPITATED LOW-LEVEL CIRCULATION CENTER WHICH HAS BECOME EXPOSED
OVER THE LAST SIX HOURS. DEEP CONVECTION HAS BEEN SHEARED TO THE
SOUTH-SOUTHWEST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). WHILE
VERTICAL WIND SHEAR IS LOW BY NORMAL STANDARDS, THE SMALL RADIUS OF
THE SYSTEM IS NOT HANDLING THE 10KT (CIMSS ESTIMATE) NORTHERLY 
VERTICAL WIND SHEAR WELL. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE AFOREMENTIONED EXPOSED LLCC IDENTIFIED IN
ANIMATED MSI AND THE LOW TO MID-LEVEL CLOUD BANDS IDENTIFIABLE ON
ANIMATED DOPPLER RADAR LOOP. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE
FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN
TWO SUBTROPICAL RIDGES

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 37 KTS AT 102030Z
   CIMSS AIDT: 38 KTS AT 102030Z
   CIMSS D-MINT: 30 KTS AT 102001Z
   CIMSS D-PRINT: 36 KTS AT 110030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TROPICAL STORM (TS) 29W WILL BREAK OUT OF THE
CURRENT COMPETING STEERING ENVIRONMENT AS THE SUBTROPICAL RIDGE
POSITIONED OVER THE EAST CHINA SEA WEAKENS AND THE PRIMARY STEERING
INFLUENCE BECOMES THE SUBTROPICAL RIDGE TO THE EAST. THE SYSTEM
WILL GRADUALLY CURVE FROM A NORTH-NORTHEASTWARD TRACK TO A
NORTHEASTWARD TRACK BETWEEN TAU 0-48. AFTER TAU 48, THE SYSTEM WILL
INCREASE TRACK SPEED AND TRACK ALONG THE NORTHERN PERIPHERY OF THE
SUBTROPICAL RIDGE. INTERACTION WITH THE SUBTROPICAL JET WILL ALLOW
EXTRATROPICAL TRANSITION TO START BY TAU 72, AND COMPLETE BY TAU
50. WHILE THE SYSTEM INTENSIFIES, VERTICAL WIND SHEAR WILL BE
MODERATE (10-15KTS) DURING THE FIRST 12-24 HOURS, THEN DROP FAVORABLY
TO LOW (0-5KTS). VERTICAL WIND SHEAR WILL GRADUALLY INCREASE AS
THE SYSTEM BECOMES INFLUENCED BY THE JET, BUT WILL NOT BECOME
UNFAVORABLE ABOVE 20KTS UNTIL TAU 48. SEA SURFACE TEMPERATURES WILL
SUPPORT INTENSIFICATION AS WELL AS THE TRACK REMAINS ALONG THE WARM
KUROSHIO CURRENT UNTIL TAU 48. BETWEEN TAU 48-72, THE SYSTEM BEGINS
TO BECOME INFLUENCED BY UPWELLING AND EVENTUALLY PASSES INTO WATERS
BELOW 26C. UPPER-LEVEL DIVERGENCE WILL REMAIN FAVORABLE UNTIL TS
29W BEGINS TO INTERACT CLOSELY TO THE SUBTROPICAL JET, RESULTING IN
THE AFOREMENTIONED VERTICAL WIND SHEAR. THE ENVIRONMENTAL EFFECTS
WILL RESULT IN A PEAK INTENSITY OF 75KTS AT TAU 48, FOLLOWED BY A
PERIOD OF WEAKENING AS THE SYSTEM BECOMES A FULLY EXTRATROPICAL
CYCLONE WITH AN INTENSITY OF 50KTS BY TAU 96.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE HAS COME INTO
STRONGER AGREEMENT THAT TS 29W WILL CURVE ALONG THE NORTHERN
PERIPHERY OF THE SUBTROPICAL RIDGE TO THE EAST, AND INCREASE TRACK
SPEED AS ENHANCED DUE THE NORTHERLY JET. THE TRACK CONFIDENCE IS
SUPPORTED BY A CROSS-TRACK SPREAD OF 114NM. THE INTENSITY GUIDANCE
HAS VEERED AWAY FROM A RAPID INTENSIFICATION SCENARIO, WHICH IS
REFLECTIVE OF THE CURRENT ENVIRONMENT. THE CURRENT STRUGGLING
STRUCTURE WAS NOT WELL CAPTURED IN THE MODEL GUIDANCE PREVIOUSLY,
AND NOW IT SEEMS THAT THE MODERATE SHEAR IS BETTER REFLECTED IN THE
EARLY-TERM FORECAST AS AN INHIBITOR TO RAPID INTENSIFICATION.
NEVERTHELESS, THE GUIDANCE STILL CALLS FOR STRONG INTENSIFICATION
GIVEN THE OTHERWISE FAVORABLE FEATURES OF STRONG POLEWARD OUTFLOW
AND UNSEASONABLY HIGH SEA SURFACE TEMPERATURES.

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