WDPN32 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (LEEPI)        
WARNING NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 37.9N 151.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 484 NM EAST-SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE SYSTEM HAS ALL BUT FALLEN APART WHEN VIEWED ON ANIMATED ENHANCED 
INFRARED (EIR) SATELLITE IMAGERY, BUT A CAREFUL ANALYSIS REVEALS A 
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) STILL INTACT. A 
061051Z AMSU-B 89 GHZ MICROWAVE IMAGE ALSO HINTS AT SHALLOW, CURVED 
BANDS WRAPPING AROUND THE FULLY CLOSED LLCC POSITION, SUPPORTING THE 
ASSESSED POSITION WITH HIGH CONFIDENCE. AT 061200Z, EIR IMAGERY SHOWS 
A SINGLE CONVECTIVE BURST ORIGINATING IN THE SOUTHEAST QUADRANT WITH 
ASSOCIATED OUTFLOW SHEARING IN THE EQUATORWARD DIRECTION. ASIDE FROM 
THIS, GENERALLY SPARSE OUTFLOW IS NOTED DUE TO THE BULK OF THE UPPER 
LEVEL CLOUDS HAVING ALREADY DEPARTED EQUATORWARD OR DISSIPATED IN 
RECENT TAUS. A 061133Z ASCAT PARTIAL PASS IMAGE SHOWS WINDS OF 20-25 
KTS ALONG THE SOUTHWESTERN PERIPHERY, BUT RECENT SCATTEROMETRY IS NOT 
AVAILABLE NEAR THE LLCC OR ALONG THE EASTERN SIDE OF THE SYSTEM WHERE 
THE STRONGER WINDS ARE PRESUMED TO BE. THE BEST OBJECTIVE-ESTIMATED 
VALUE USING A COMBINED ADT (27 KTS) AND AIDT (38 KTS) IS 35 KTS, 
SUPPORTING THE ASSESSED INTENSITY WITH MEDIUM CONFIDENCE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP LAYER STR TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T1.5 - 25 KTS
   CIMSS ADT: 27 KTS AT 1200Z
   CIMSS AIDT: 38 KTS AT 1200Z
   CIMSS SATCON: 42 KTS AT 1300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 30+ KTS
   SST: 26-27 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: ALTHOUGH ANIMATED EIR SATELLITE IMAGERY HAS
REVEALED A FADING APPEARANCE OF TS 13W, THE LLCC WILL CONTINUE
WRAPPING INTO ITSELF OVER THE NEXT 24 HOURS IN THE LOWER LEVELS OF
THE TROPOSPHERE DUE TO CONSERVATION OF ANGULAR MOMENTUM. THE UPPER
PORTIONS OF THE SYSTEM WILL CONTINUE TO SHEAR AWAY FROM THE LLCC AS
TS LEEPI APPROACHES THE EQUATORWARD BOUNDS OF THE JETSTREAM.
VERTICAL WIND SHEAR (VWS) VALUES WILL REMAIN AT UNFAVORABLE LEVELS
AND CONTINUE TO WORSEN, WHILE SEA SURFACE TEMPERATURES (SSTS) COOL
FROM APPROXIMATELY 27C AT TAU 0 TO 22C BY TAU 24. INTERACTION WITH
A THERMAL RIBBON IS IMMINENT, WITH EXTRATROPICAL TRANSITION (ETT)
BEGINNING NEAR TAU 12. BY TAU 24, A COLD FRONT APPROACHING FROM THE
NORTHWEST WILL COLLIDE WITH THE SYSTEM, AT WHICH POINT IT WILL
COMPLETE ETT. NO FURTHER DEVELOPMENT IS EXPECTED WITHIN THE
FORECAST PERIOD, HOWEVER, THE SYSTEM IS FORECAST TO MAINTAIN AN
INTENSITY OF 35 KTS DUE TO A COMBINATION OF FACTORS THAT INCLUDE
ITS PROXIMITY TO STRONG RIDGING TO THE EAST, LEADING TO
GRADIENT-INDUCED WINDS ALONG THE EAST SIDE, AND COMPOUNDED BY THE
ACCELERATING FORWARD SPEEDS (APPROXIMATELY 17-23 KTS).

MODEL DISCUSSION: GFS ENSEMBLE MODEL (GEFS) GUIDANCE CONTINUES TO
DEMONSTRATE A VERY TIGHT AGREEMENT AMONG MEMBERS, WITH A STRAIGHT
AND ACCELERATING NORTHEASTWARD TRACK DEPICTED. OTHER MODELS ARE
STARTING TO LOSE TRACK OF THE SYSTEM AS THE SIGNAL BECOMES
CONTAMINATED BY MID-LATITUDE INFLUENCES, BUT ALL RELIABLE NUMERICAL
MODEL GUIDANCE HAS SHOWN CONSISTENTLY VERY GOOD AGREEMENT
CONCERNING THE TRACK AND INTENSITY. THE INTENSITY CONSENSUS (ICNW)
PREDICTS A GRADUAL DECLINE, BUT NOT ENOUGH OF A WEAKENING TO DROP
BELOW THE CURRENT INTENSITY. CONFIDENCE REMAINS HIGH FOR BOTH THE
JTWC TRACK AND INTENSITY FORECASTS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
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