WDPN31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (YUN-YEUNG)    
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.8N 134.8E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 515 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXYVIS SATELLITE IMAGERY (PSI) DEPICTS A PARTIALLY EXPOSED, 
DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) POSITIONED ALONG THE 
NORTHERN EDGE OF AN AREA OF EXPANDING DEEP CONVECTION. A 060912Z SSMIS 
91 GHZ MICROWAVE IMAGE REVEALS TIGHTLY CURVED, SHALLOW BANDING 
WRAPPING INTO A DEFINED LLCC WITH A LINEAR BAND OF DEEP CONVECTION 
SHEARED TOWARD THE SOUTH-SOUTHWEST. THE INITIAL POSITION IS PLACED 
WITH MEDIUM CONFIDENCE BASED ON THE PSI. THE INITIAL INTENSITY OF 40 
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN AVERAGE OF THE PGTW 
AND KNES DVORAK ESTIMATES, CONSISTENT WITH THE CIMSS DMINT, AIDT, AND 
SATCON ESTIMATES. THE REMNANTS OF 11W (KIROGI), WHICH ARE CURRENTLY 
CENTERED ABOUT 230 NM NORTH-NORTHWEST OF 12W'S INITIAL POSITION, ARE 
UNDERGOING BINARY INTERACTION WITH 12W. PSI INDICATES THE REMNANTS OF 
11W ARE WEAKENING SIGNIFICANTLY AS THEY INTERACT WITH AND ROTATE 
CYCLONICALLY AROUND THE OUTER PERIPHERY OF 12W.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: PRIMARY: LOW- TO MID-LEVEL SUBTROPICAL
RIDGE (STR) POSITIONED TO THE EAST. SECONDARY (THROUGH TAU 24):
BINARY INTERACTION WITH THE REMNANTS OF 11W (KIROGI). 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 40 KTS AT 060800Z
   CIMSS ADT: 34 KTS AT 061130Z
   CIMSS AIDT: 37 KTS AT 061240Z
   CIMSS DMINT: 39 KTS AT 060912Z
   CIMSS DPRINT: 33 KTS AT 061200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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) 12W'S RECENT TRACK MOTION IS 
CLEARLY BEING AFFECTED BY ITS BINARY INTERACTION WITH THE MUCH WEAKER 
REMNANTS OF 11W (KIROGI). AS 11W ROTATES CYCLONICALLY AROUND THE 
NORTHWESTERN AND WESTERN PERIPHERY OF TS 12W OVER THE NEXT 12 HOURS 
AND EVENTUALLY GETS ABSORBED, THE BINARY INTERACTION OR FUJIWARA 
INTERACTION WILL CONTINUE TO CREATE SOME UNCERTAINTY IN THE EXACT 
TRACK OF TS 12W WITH A SHORT DURATION NORTHWARD TRACK POSSIBLE BEFORE 
12W RESUMES A STEADY NORTH-NORTHEASTWARD TRACK CLOSE TO THE KANTO 
PLAIN. POLEWARD OUTFLOW HAS IMPROVED SLIGHTLY IN RESPONSE TO A 
MIDLATITUDE SHORTWAVE TROUGH CURRENTLY DIGGING OVER SOUTH KOREA AND 
WESTERN JAPAN. THE IMPROVED ENVIRONMENTAL CONDITIONS WILL SUPPORT A 
SHORT (24 HOUR) PERIOD OF INTENSIFICATION WITH A PEAK OF 45-50 KNOTS 
BY TAU 24. AFTER TAU 24, VERTICAL WIND SHEAR IS FORECAST TO INCREASE 
TO 30+ KNOTS WITH INCREASING DRY AIR ENTRAINMENT AND FRICTIONAL 
EFFECTS LEADING TO A STEADY WEAKENING TREND AS THE SYSTEM APPROACHES 
AND PASSES THE KANTO PLAIN. THE MIDLATITUDE SHORTWAVE TROUGH IS 
EXPECTED TO QUICKLY PROPAGATE NORTHEASTWARD WITH THE STR REBUILDING, 
WHICH WILL TURN THE SYSTEM EAST-NORTHEASTWARD AFTER TAU 72 WITH 
DISSIPATION ANTICIPATED BY TAU 96. DUE TO THE LACK OF A RECURVE 
MECHANISM AND BAROCLINIC ZONE, A TYPICAL RECURVE SCENARIO WITH EXTRA-
TROPICAL TRANSITION IS UNLIKELY. 

MODEL DISCUSSION: DETERMINISTIC AND PROBABILISTIC GUIDANCE SUPPORTS
THIS SCENARIO WITH A DISTINCT SLOW DOWN AND WEAKENING TREND
REFLECTED IN THE 060600Z GFS AND 060000Z ECMWF ENSEMBLES. 
ADDITIONALLY, THERE ARE NO RECURVING SOLUTIONS, REINFORCING THE LACK 
OF A RECURVE MECHANISM. OVERALL, THERE IS MEDIUM CONFIDENCE IN THE 
JTWC FORECAST TRACK WITH MODEL GUIDANCE SHOWING SOME POTENTIAL FOR THE 
SYSTEM TO TRACK CLOSER TO THE KANTO PLAIN REGION. THE 060600Z COAMPS-
TC ENSEMBLE SUPPORTS THE JTWC INTENSITY FORECAST OVER THE NEXT 24 
HOURS WITH MODERATE INTENSIFICATION PROBABILITIES INCREASING TO 80
TO 90 PERCENT.

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