WDPN33 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (NEOGURI) WARNING NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.7N 151.0E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 367 NM NORTH-NORTHWEST OF MINAMI TORI
SHIMA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
A DEEP MIDLATITUDE MAJOR SHORTWAVE TROUGH IS BEGINNING TO IMPINGE ON 
THE WESTERN PERIPHERY OF THE SYSTEM, WITH DRY AIR AND WESTERLIES 
PRESSING ON THE WESTERN EDGE OF THE SYSTEM. HOWEVER, A ROBUST 
POLEWARD OUTFLOW CHANNEL HAS FORMED INTO THE LEADING EDGE OF THE 
UPPER-LEVEL TROUGH, WHICH HAS ALLOWED THE SYSTEM TO MAINTAIN A 
SYMMETRIC CORE WITH A CLOUD-FILLED EYE, WHICH SUPPORTS THE INITIAL 
POSITION WITH HIGH CONFIDENCE. A 212257Z ASCAT-B BULLSEYE IMAGE 
SUPPORTS THE INITIAL WIND RADII WITH MEDIUM CONFIDENCE. THE INITIAL 
INTENSITY IS BASED ON THE CIMSS OBJECTIVE INTENSITY ESTIMATES RANGING 
FROM 102-104 KNOTS AND THE PGTW, RCTP, KNES CURRENT INTENSITY 
ESTIMATES OF 5.5 (102 KNOTS).

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE EAST, WITH A MAJOR SHORTWAVE TROUGH DIGGING EAST
OF JAPAN.  

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T6.5 - 127 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   CIMSS ADT: 104 KTS AT 220010Z
   CIMSS AIDT: 102 KTS AT 220010Z
   CIMSS D-MINT: 104 KTS AT 212029Z
   CIMSS D-PRINT: 102 KTS AT 220110Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE JTWC TRACK FORECAST HAS CONTINUED
TO SLOW, WITH A MORE COMPLEX S-SHAPED TRACK. 

FORECAST DISCUSSION: AS THE MAJOR SHORTWAVE TROUGH PROPAGATES 
EASTWARD OVER THE NEXT 12-24 HOURS, TYPHOON 25W IS FORECAST TO SLOWLY 
TRACK EAST-NORTHEASTWARD TO NORTHEASTWARD THROUGH TAU 48. THE SLOW 
TRACK MOTION WILL LEAD TO A PERIOD OF SIGNIFICANT WEAKENING DUE TO 
COOL UPWELLING WATER AND INCREASING MODERATE (20 KNOTS) VERTICAL WIND 
SHEAR (VWS) ASSOCIATED WITH THE MIDLATITUDE TROUGH. TY 25W WILL TRACK 
ALONG THE SOUTHERN EDGE OF A STRONG FRONTAL ZONE, WHICH MAY ALSO 
CONTRIBUTE TO THE WEAKENING TREND, BUT IS NOT EXPECTED TO UNDERGO 
EXTRA-TROPICAL TRANSITION (ETT). AFTER TAU 48, THE SYSTEM WILL SLOW 
AND TURN WESTWARD TO WEST-NORTHWESTWARD AS A COMPETING STEERING 
PATTERN DOMINATES, WITH THE STR BUILDING QUICKLY TO THE NORTH 
EFFECTIVELY BLOCKING POLEWARD PROGRESSION AND THE DEEP-LAYERED STR 
MAINTAINING TO THE EAST. TRACK MOTION IS EXPECTED TO BE SLOW BUT 
COULD ALSO BE ERRATIC THROUGH TAU 72. BY TAU 96, ANOTHER DEEP 
MIDLATITUDE MAJOR SHORTWAVE TROUGH WILL DIG INTO NORTHERN JAPAN AND 
THE NORTHERN PACIFIC, WEAKENING THE STR AND ALLOWING THE SYSTEM TO 
ACCELERATE GRADUALLY POLEWARD THROUGH TAU 120. THE SYSTEM WILL 
COMMENCE ETT JUST AFTER TAU 120 WHILE INTERACTING WITH THE BAROCLINIC 
ZONE AND THE UPPER-LEVEL WESTERLIES. THEREFORE, ETT IS NOT INDICATED 
IN THIS WARNING.

MODEL DISCUSSION: JTWC TRACK FORECAST CONFIDENCE IS LOW THROUGH THE 
FORECAST PERIOD DUE TO THE COMPLEX, RAPIDLY EVOLVING STEERING PATTERN 
AND LARGE SPREAD IN DETERMINISTIC AND PROBABILISTIC GUIDANCE. THE 
211800Z EPS RUN IS A MESS WITH ALL SOLUTIONS TURNING SHARPLY WESTWARD 
FROM 23-38N THEN TURNING SHARPLY POLEWARD. THE 211800Z GEFS RUN IS 
NOT MUCH BETTER, WITH SIMILAR ISSUES. WITH THE EXCEPTION OF EEM2, THE 
DETERMINISTIC GUIDANCE IS MORE COHESIVE THAN THE PROBABILISTIC 
GUIDANCE, SUPPORTING THE JTWC TRACK SCENARIO WITH LOW CONFIDENCE. THE 
211800Z FSU CYCLONE PHASE PRODUCT FOR GFS CONTINUES TO INDICATE ETT 
WILL COMPLETE NEAR 290000Z, WITH TWO DISCRETE PERIODS OF ASYMMETRIC 
WARM-CORE CHARACTERISTICS.     

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