WDPN31 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX)     
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.4N 141.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 605 NM SOUTH OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: EASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 
DEVELOPING CENTRAL DENSE OVERCAST FEATURE WITH IMPROVED CONVECTIVE 
BANDING OVER THE SOUTHERN SEMICIRCLE. THE INITIAL POSITION IS PLACED 
WITH HIGH CONFIDENCE BASED ON A PARTIAL 071150Z ASCAT-B IMAGE AS WELL 
AS ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED 
WITH HIGH CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES AS WELL AS 
RECENT IWO-TO SURFACE OBSERVATIONS, SHOWING SUSTAINED WINDS OF 20-25 
KNOTS WITH GUSTS AS HIGH AS 37 KNOTS (10-MINUTE AVERAGE). UPPER-LEVEL 
ANALYSIS INDICATES A ROBUST POLEWARD OUTFLOW CHANNEL INTO AN UPPER-
LEVEL LOW OVER NORTHERN HONSHU, WITH STRONG EQUATORWARD OUTFLOW AND 
LOW VERTICAL WIND SHEAR. 

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN, WITH LOW- TO
MID-LEVEL SUBTROPICAL RIDGE (STR) DISRUPTED BY A BROAD AREA OF
CYCLONIC TURNING TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 1200Z
   CIMSS AIDT: 37 KTS AT 1200Z
   CIMSS DPRINT: 30 KTS AT 1200Z
   CIMSS DMINT: 29 KTS AT 0848Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 06W IS FORECAST TO TURN 
SHARPLY NORTHEASTWARD THEN GRADUALLY ACCELERATE NORTHWARD AS THE STR 
BUILDS TO THE EAST THROUGH TAU 36. AFTER TAU 12, THE SYSTEM WILL 
TRACK NORTHWARD ALONG A NORTH-SOUTH ORIENTED STR AND INTENSIFY 
QUICKLY TO A PEAK INTENSITY OF 55 KNOTS BY TAU 48. THERE IS A 
POSSIBILITY THAT THE PEAK INTENSITY COULD REACH MINIMAL TYPHOON 
STRENGTH. AFTER TAU 72, THE SYSTEM WILL TURN NORTH-NORTHEASTWARD 
WHILE SLOWING AS IT ROUNDS THE NORTHWEST PERIPHERY OF THE STR. THE 
POLAR FRONT AND ITS ASSOCIATED BAROCLINIC ZONE IS LOCATED NORTH OF 
45N, WITH NO DEEP MAJOR SHORTWAVE TROUGH INDICATED IN THE MODELS TO 
INDUCE A RECURVATURE TRACK. THEREFORE, EXTRA-TROPICAL TRANSITION IS 
ASSESSED AS VERY UNLIKELY THROUGH THE FORECAST PERIOD. HOWEVER, 
INTERACTION WITH A SUBTROPICAL TROUGH AND UPPER-LEVEL CONVERGENCE IS 
ANTICIPATED, WHICH WILL SERVE TO WEAKEN THE SYSTEM AFTER TAU 72. 
ADDITIONALLY, SST VALUES WILL DECREASE NORTH OF 40N TO LESS THAN 24 C 
AND DRY AIR ENTRAINMENT WILL COMMENCE, WHICH WILL AID IN THE EVENTUAL 
DISSIPATION OF THE SYSTEM.       

MODEL DISCUSSION: WITH THE EXCEPTION OF THE SOLE OUTLIER, GFS, 
DETERMINISTIC GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH A 120 
NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 72. GFS CONTINUES TO BUILD 
A STRONG STR TO THE NORTH, WHICH DRIVES THE SYSTEM INTO CENTRAL 
HONSHU. THE REMAINDER OF THE DETERMINISTIC GUIDANCE SUPPORTS A 
POLEWARD TRACK. AFTER TAU 72, THERE IS INCREASING UNCERTAINTY IN THE 
FORECAST TRACK WITH BOTH THE 070600Z EPS AND GEFS ENSEMBLES DIVERGING 
SIGNIFICANTLY. EPS INDICATES ABOUT 30 PERCENT OF THE SOLUTIONS 
TRACKING WESTWARD TO WEST-NORTHWESTWARD AND THE MAJORITY OF SOLUTIONS 
(70 PERCENT) TRACKING POLEWARD. THE MAJORITY OF THE GEFS SOLUTIONS 
NOW TRACK THE SYSTEM WESTWARD OVER HONSHU OR JUST SOUTH OF HONSHU. 
DUE TO THIS INCREASING UNCERTAINTY AFTER TAU 72, THE TRACK CONFIDENCE 
HAS BEEN DECREASED TO LOW.

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