WDPN33 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (NEOGURI) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.3N 152.6E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 374 NM NORTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A HIGHLY
ASYMMETRIC TYPHOON (TY) WITH DEEP CONVECTION STRUGGLING TO REBUILD
AGAINST 20-25KT SOUTHWESTERLY VERTICAL WIND SHEAR. AN EYE IS NO
LONGER EVIDENT AND IS CONTINUING ON A WEAKENING TREND DUE TO THE
SHEAR AND UPWELLING. AN UPPER-LEVEL TROUGH TO THE NORTHWEST IS BOTH
ENHANCING POLEWARD OUTFLOW AND UNFAVORABLY OVERWHELMING THE SYSTEM.
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
AFOREMENTIONED DISORGANIZED NATURE OF THE TYPHOON AND THE TILTED
VERTICAL STRUCTURE. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED
WITH LOW CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED
BELOW.

INITIAL WIND RADII BASIS: 221013Z METOP-B ASCAT SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT
BETWEEN TWO SUBTROPICAL RIDGES

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 82 KTS AT 221140Z
   CIMSS AIDT: 82 KTS AT 221140Z
   CIMSS D-MINT: 87 KTS AT 220745Z
   CIMSS D-PRINT: 92 KTS AT 221240Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 25W WILL CONTINUE TO TRACK ERRATICALLY
WHILE IN A COMPLEX AND COMPETING STEERING ENVIRONMENT BETWEEN TWO
SUBTROPICAL RIDGES TO THE EAST AND WEST. THE TRACK FORECAST IS SLOW
AND EAST-NORTHEASTWARD FOR THE NEXT 36 HOURS, BUT UNUSUAL MOVEMENT
SUCH AS LOOPING OR DOUBLING BACK MAY OCCUR BETWEEN TAUS AND IS NOT
CAPTURED IN THE WARNING GRAPHIC. AFTER TAU 48, A DEEP-LAYER TROUGH
WILL WEAKEN THE RIDGE TO THE EAST, CAUSING TY 25W TO COMPLETE A
NEAR U-TURN WHILE COMING UNDER THE STEERING INFLUENCE OVER THE
RIDGE TO THE WEST. AFTER TAU 96, BOTH RIDGES WILL STRONGLY CONTINUE
TO COMPETE WITH ONE ANOTHER. THE SLOW TRACK MOTION WILL RESULT IN
SIGNIFICANT UPWELLING OF COOL WATER THROUGHOUT THE FORECAST PERIOD.
THE LACK OF HEAT WILL PRIMARILY DRIVE WEAKENING, BUT THE ELEVATED
VERTICAL WIND SHEAR WILL ALSO SUPPORT THE WEAKENING. GIVEN THE SLOW
MOTION, THE THERMAL BOUNDARY REMAINS TO THE NORTH OF THE TYPHOON,
AND TRANSITION IS NOT EXPECTED DURING THE FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC MODEL SOLUTIONS CONSISTENTLY
INDICATE A ZIG-ZAGGING TRACK MOTION IN THE GAME OF TUG-OF-WAR THAT
THESE TWO SUBTROPICAL RIDGES ARE PLAYING, HOWEVER, THE OUTCOMES
VARY GREATLY AND THERE IS STILL GREAT TRACK UNCERTAINTY IN THE
LONG-TERM. THIS IS DUE TO VARIED INTERPRETATIONS OF HOW MUCH THE
TROUGH WEAKENS THE RIDGE AND HOW STRONG THE RIDGES ARE. THE
INTENSITY GUIDANCE IS CONSISTENT AND FORECASTS WEAKENING, BUT THE
TRACK VARIATION CAN MEAN MORE OR LESS EXPOSURE TO SUPPORTIVE WARM
WATER, SO THE RATE OF WEAKENING WILL VARY BASED ON THE TRACK. 

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