Tropical Storm NORU Advisory 9月27日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (NORU) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 15.9N 113.9E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 418 NM WEST-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 37 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
INDICATES IMPROVING DEEP CONVECTIVE BANDING WRAPPING IN FROM THE
SOUTH AND WEST QUADRANTS, WITH A SMALL EYE FEATURE THAT IS PARTLY
CLOUD-FILLED. AN EARLIER 261654Z GMI 89GHZ MICROWAVE IMAGE REVEALS
CONVECTIVE BANDING WRAPPING INTO WITH APPEARS TO BE A MICROWAVE
EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
EIR IMAGERY AND THE GMI MICROWAVE IMAGERY. THE INITIAL INTENSITY OF
90 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE CURRENT
IMPROVED CONVECTIVE STRUCTURE AS WELL AS A COMBINATION OF AGENCY
OBJECTIVE AND SUBJECTIVE DVORAK INTENSITY ESTIMATES, PGTW T5.5,
RJTD T4.5, ALONG WITH CMISS ADT UP TO 90 KTS.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE TO THE
NORTH
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T5.5 - 102 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T5.0 - 90 KTS
   CIMSS SATCON: 73 KTS AT 261803Z
   CIMSS ADT: 90 KTS AT 261740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG 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 18W (NORU) IS BEGINNING TO RAPIDLY
INTENSIFY AS ENVIRONMENTAL CONDITIONS ARE FAVORABLE WITH LOW
VERTICAL WIND SHEAR, WARM SEA SURFACE TEMPERATURES, AND STRONG
RADIAL OUTFLOW. TY 18W IS FORECAST TO TRACK WESTWARD THROUGH THE
FORECAST PERIOD UNDER THE STEERING INFLUENCE OF THE STR POSITIONED
TO THE NORTH, BEFORE MAKING LANDFALL INTO CENTRAL VIETNAM WITHIN
THE NEXT 24-36 HOURS. DUE TO FAVORABLE ENVIRONMENTAL CONDITIONS THE
SYSTEM HAS A SHORT DURATION OVER WARM WATER BEFORE REACHING A
MAXIMUM PEAK OF 110 KNOTS BY TAU 12. AFTER TAU 24, THE SYSTEM WILL
BEGIN TO WEAKEN AS VERTICAL WIND SHEAR INCREASES AND THE SYSTEM
TRACKS OVER SOUTHEAST ASIA WITH DISSIPATION EXPECTED BY TAU 72.
MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT
REGARDING THE TRACK FORECAST, WITH THE EXCEPTION OF THE NAVGEM
TRACKER. THIS LENDS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST
THROUGH OUT THE FORECAST. THE OVERALL CONFIDENCE IN THE JTWC INTENSITY
FORECAST IS MEDIUM DUETO UNCERTAINTY IN THE MODEL GUIDANCE MAX
INTENSITY OVER THE NEXT 24 HOURS. THE BULK OF THE INTENSITY GUIDANCE
INDICATES A RE-INTENSIFICATION PHASE WITH HWRF INDICATING A PEAK OF
110 KNOTS AT TAU 12 AND COAMPS-TC A PEAK OF 100 KNOTS. AS WELL AS THE
UNCERTAINLY DUE TO LAND INTERACTION AFTER TAU 24.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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