Tropical Storm MERBOK Advisory Mi, 14.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (MERBOK) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 28.3N 162.2E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 505 NM EAST-NORTHEAST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAGGED
INNER CORE WITH TIGHTLY-CURVING CONVECTIVE BANDS WRAPPING INTO AN
OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). A PROPER EYE HAS NOT
BEEN APPARENT DURING THE PAST SIX HOURS, THOUGH ONE MAY BE STARTING
TO FORM WITHIN THE PAST HOUR OR SO. VISIBLE IMAGERY AND A 132000Z
SSMIS MICROWAVE PASS SHOW MULTIPLE CONCENTRIC BANDS AROUND THE
LLCC, SUGGESTING THAT THE INNER CORE WIND FIELD IS NOT PARTICULARLY
COMPACT. UPPER-LEVEL OUTFLOW IS PROMINENT IN ALL QUADRANTS AS THE
SYSTEM ENJOYS A LOW-SHEAR ENVIRONMENT. THE INITIAL INTENSITY IS
HELD AT 65 KTS, A BLEND BETWEEN SUBJECTIVE DVORAK ESTIMATES OF 77 KTS
FROM PGTW AND RJTD, MUCH LOWER SATCON ESTIMATES OF 53 KTS, AND AN
EARLIER 131843Z SMOS PASS SHOWING MAX WINDS OF 63 KTS IN THE EASTERN
SEMICIRCLE.
INITIAL WIND RADII BASIS: SMOS DATA
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE EAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T4.5 - 77 KTS
   RJTD: T4.5 - 77 KTS
   CIMSS SATCON: 56 KTS AT 132000Z
   CIMSS ADT: 49 KTS AT 132340Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TYPHOON 15W (MERBOK) CONTINUES TO TRACK AROUND
THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE TO ITS EAST, AND
WILL ACCELERATE AS IT BEGINS TO INTERACT WITH AN UPPER-LEVEL TROUGH
PASSING SOUTH OF THE KAMCHATKA PENINSULA DURING THE NEXT 24 HOURS.
THIS INTERACTION WILL BE FAVORABLE FOR RAPID EXTRATROPICAL
TRANSITION AND INTENSIFICATION INTO A LARGER AND DEEPER CYCLONE AS
MERBOK RACES TOWARD THE ALEUTIAN ISLANDS. THIS TRANSITION IS
EXPECTED TO OCCUR BY 36 HOURS, AS MERBOK WILL CROSS OVER THE 26
DEGREE CELSIUS SEA SURFACE TEMPERATURE ISOTHERM IN 18-24 HOURS, AND
VERTICAL SHEAR WILL INCREASE DRAMATICALLY AFTER 24 HOURS,
UNDERMINING THE CONVECTIVE CORE AND RESULTING IN A FULLY FRONTAL
STRUCTURE AS THE DISTANCE BETWEEN THE CYCLONE AND THE UPPER-LEVEL
TROUGH TO ITS NORTHWEST CLOSES. THE MAXIMUM WINDS WITHIN THE
CIRCULATION MAY IN FACT INCREASE DURING THIS PROCESS, AS THE
BAROCLINIC INTERACTION IS FAVORABLE FOR RAPID DEVELOPMENT VIA
NON-TROPICAL PROCESSES. BASED ON THE MULTI-MODEL CONSENSUS, THE
INTENSITY IS FORECAST TO REACH 80 KTS BY THE TIME EXTRATROPICAL
TRANSITION COMPLETES AT TAU 36.
MODEL DISCUSSION: THE JTWC TRACK AND INTENSITY FORECASTS ARE BOTH
CLOSE TO THE MULTI-MODEL CONSENSUS, WITH NO SIGNIFICANT SPREAD
NOTED.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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