Tropical Storm MERBOK Advisory Wed Sep 14

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (MERBOK) WARNING
NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 31.9N 161.9E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 623 NM NORTHEAST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 20 KTS
   SIGNIFICANT WAVE HEIGHT: 31 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SINGLE
SLIGHTLY FRAGMENTED BANDING FEATURE AND FLARING CENTRAL CONVECTION
THAT RECENTLY ACHIEVED A SHORT-LIVED EYE FEATURE. A FORTUITOUS
141049Z ASCAT-B SCATTEROMETERY PASS SHOWS THAT WHILE 15W HAS A
SMALL SYMMETRIC LOW LEVEL CIRCULATION CENTER (LLCC), ALL OF THE
STORM FORCE WINDS ARE RESTRICTED TO THE EASTERN SEMICIRCLE. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EIR IMAGERY
AND SCATTEROMETERY DATA. THE INITIAL INTENSITY OF 70 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON AGENCY DVORAK INTENSITY ESTIMATES
INDICATING T4.0-T4.5 WHILE CIMSS ADT AND SATCON REMAIN SLIGHTLY
LOWER.
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: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   PHFO: T4.5 - 77 KTS
   CIMSS SATCON: 60 KTS AT 140719Z
   CIMSS ADT: 51 KTS AT 141140Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TY 15W (MERBOK) CONTINUES TO TRACK GENERALLY
NORTHWARD AROUND THE PERIPHERY OF THE STR TO THE EAST. OVER THE
NEXT 12 HOURS, TRACK SPEEDS WILL INCREASE AND THE SYSTEM WILL
TRANSITION TO A NORTH-NORTHEASTWARD HEADING. AS 15W CONTINUES
POLEWARD, IT WILL BEGIN TO RAPIDLY INTERACT WITH A PASSING UPPER-
LEVEL TROUGH PASSING SOUTH OF THE KAMCHATKA PENINSULA. AFTER
TAU 12 AND THROUGH TAU 24 AS THE SYSTEM RAPIDLY PROGRESSES THROUGH
EXTRA-TROPICAL TRANSITION, INTENSITIES WILL CONTINUE TO INCREASE TO
A POSSIBLE MAXIMUM OF 80KTS AS 15W BECOMES INCREASINGLY FRONTAL IN
NATURE. BY TAU 36, ETT WILL COMPLETE AS THE REMAINING TROPICAL
CHARACTERISTICS ARE EXTINGUISHED, AND THE NOW FRONTAL SYSTEM
CONTINUES TOWARDS THE ALEUTIAN ISLANDS WITH A MAJORITY OF ITS
FORMER INTENSITY.
MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH THE
JTWC FORECAST TRACK AND IT HAS THEREFOR BEEN PLACED WITH HIGH
CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE IS IN GOOD AGREEMENT,
WITH A NOTABLE SPREAD TAKING PLACE AFTER TAU 24 WITH COAMPS-TC AND
HWRF CONTINUING TO RAPIDLY INTENSIFY AND THE REAMING GUIDANCE
REMAINING NEAR THE MULTI-MODEL CONSENSUS. THEREFORE THE JTWC FORECAST
INTENSITY HAS BEEN PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH
MEDIUM CONFIDENCE.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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