Tropical Storm MERBOK Advisory 15 Σεπ.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (MERBOK) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 33.9N 162.4E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 729 NM NORTHEAST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 20 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP
CONVECTION WRAPPING AROUND THE NORTHERN SEMICIRCLE OF TY 15W. A
141531Z AMSR2 PASS INDICATES TYPHOON FORCE WINDS ARE PRIMARILY
RESTRICTED TO THE NORTHEAST QUADRANT, AND THE RAPID IMPINGEMENT OF
MID-LATITUDE FORCING SUGGESTS THAT EXTRATROPICAL TRANSITION SHOULD
COMMENCE SHORTLY. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON MSI IMAGERY. THE INITIAL INTENSITY IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THE AMSR2 PASS AND IS CORROBORATED BY
AGENCY DVORAK ESTIMATES.
INITIAL WIND RADII BASIS: SCATTEROMETER DATA
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 71 KTS AT 141500Z
   CIMSS ADT: 51 KTS AT 141740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TY 15W CONTINUES TO TRACK NORTH-NORTHEASTWARD
AROUND THE PERIPHERY OF THE STR TO THE EAST. AS A MID-LATITUDE
TROUGH RAPIDLY APPROACHES THE SYSTEM, EXTRATROPICAL TRANSITION
SHOULD COMMENCE SHORTLY. TY 15W IS FORECAST TO ACCELERATE TOWARD
THE NORTHEAST. GIVEN THE STRONG BAROCLINIC DYNAMICS FORECAST TO
AFFECT THE SYSTEM, TY 15W WILL UNDERGO A RAPID EXTRATROPICAL
TRANSITION PROCESS, LIKELY COMPLETING THE TRANSITION BY TAU 24
PRIOR TO REACHING THE ALEUTIAN ISLANDS.
MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT, AND THE
JTWC FORECAST TRACK HAS BEEN PLACED WITH HIGH CONFIDENCE. SOME
UNCERTAINTY EXISTS WITH RESPECT TO THE SPREAD OF INTENSITY GUIDANCE
AS 15W UNDERGOES EXTRATROPICAL TRANSITION, WITH HWRF AND COAMPS-TC
SUGGESTING THE POSSIBILITY OF A BRIEF BURST OF INTENSIFICATION
THROUGH TAU 12, BUT THAT IS LIKELY ASSOCIATED WITH BAROCLINIC
INTERACTION. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE
MULTIMODEL CONSENSUS WITH MEDIUM CONFIDENCE.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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