Tropical Storm MERBOK Advisory Di, 13.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (MERBOK) WARNING NR
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 23.9N 163.3E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 332 NM NORTH-NORTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEPENING
CONVECTIVE BANDING WRAPPING TIGHTLY AROUND A CONSOLIDATING
LOW-LEVEL CIRCULATION CENTER. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON RECENT SATELLITE FIXES FROM PGTW, KNES AND
RJTD, AS WELL AS 122012Z SSMIS 37 GHZ IMAGERY SHOWING AN UPSTREAM
LOW-LEVEL EYE FEATURE. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON RECENT AUTOMATED AND SUBJECTIVE
DVORAK INTENSITY ESTIMATES AS WELL AS RECENT ASCAT PASSES COVERING
THE EASTERN PORTION OF THE CIRCULATION.
INITIAL WIND RADII BASIS: SCATTEROMETER DATA (METOP-B ASCAT FROM
122215Z) FOR THE EASTERN PORTION OF THE CIRCULATION AND OBJECTIVE
BEST TRACK DATA FOR THE WESTERN PORTION.
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) EXTENSION TO
THE EAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T4.0 - 65 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 55 KTS AT 122014Z
   CIMSS ADT: 55 KTS AT 122330Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL
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: TS 15W WILL TRACK POLEWARD THROUGH TAU 36 AND
TURN TOWARD THE NORTH-NORTHEAST FOR THE REMAINDER OF THE FORECAST
PERIOD FOLLOWING THE FLOW ASSOCIATED WITH SUBTROPICAL RIDGING TO
THE EAST AND NORTHEAST. STEADY INTENSIFICATION WILL LIKELY CONTINUE
FOR THE NEXT 36 HOURS AS THE SYSTEM PASSES OVER WARM WATER,
VERTICAL WIND SHEAR REMAINS LOW AND THE OUTFLOW PATTERN IS
GENERALLY SUPPORTIVE. THEREAFTER, COOLING ALONG-TRACK SEA SURFACE
TEMPERATURES AND INCREASING VERTICAL WIND ASSOCIATED WITH A
MID-LATITUDE TROUGH APPROACHING FROM THE NORTHWEST WILL INDUCE
WEAKENING. BETWEEN TAU 48 AND TAU 72, TS 15W WILL BECOME EMBEDDED
IN THE AFOREMENTIONED TROUGH AND COMPLETE EXTRATROPICAL TRANSITION.
FAVORABLE BAROCLINIC INTERACTION BETWEEN THE SYSTEM AND THE TROUGH
WILL ENABLE 15W TO TRANSITION INTO A VERY STRONG EXTRATROPICAL LOW
BY TAU 72.
MODEL DISCUSSION: NUMERICAL MODEL TRACK FORECASTS REMAIN IN
EXCELLENT AGREEMENT THROUGH THE ENTIRETY OF THE FORECAST PERIOD.
INTENSITY GUIDANCE IS IN FAIR AGREEMENT AS WELL, PARTICULARLY
REGARDING THE OVERALL TREND, TIMING OF PEAK INTENSITY AND HIGH
POST-EXTRATROPICAL TRANSITION INTENSITY.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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