Tropical Storm NORU Advisory Di, 27.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (NORU) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 15.5N 112.2E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 513 NM WEST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SYSTEM
THAT CONTINUES TO RAPIDLY INTENSIFY, WITH DEEP CONVECTIVE FEEDER
BANDS ON THE EASTERN PERIPHERY WRAPPING AROUND AN EYE FEATURE THAT
IS PARTLY CLOUD-FILLED. AN EARLIER 261652Z GMI 89 GHZ MICROWAVE
IMAGE DEPICTS A 40 NM DEEP CONVECTIVE CURVED BAND FULLY SURROUNDING
A 5NM MICROWAVE EYE, INDICATING THE SYSTEM HAS CONTINUED TO RAPIDLY
INTENSIFY OVER THE PAST 6 HOURS. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE CLOUD-FILLED EYE FEATURE IN
ANIMATED VISIBLE IMAGERY ALONG WITH THE EXTRAPOLATED GMI MICROWAVE
IMAGE. THE INITIAL INTENSITY IS ALSO PLACED WITH MEDIUM CONFIDENCE
BASED ON SUBJECTIVE  DVORAK INTENSITIES FROM PGTW T6.5, RJTD T5.5,
AND KNES T6.0. OBJECTIVE AUTOMATED DVORAK ESTIMATES INTENSITIES
SEEM TO BE UNDER ESTIMATING THE MAXIMUM INTENSITY AND THEREFORE THE
INITIAL INTENSITY IS PLACED CLOSER TO SUBJECTIVE AGENCY DVORAK
ESTIMATES.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE TO THE
NORTH DEEP-LAYER SUBTROPICAL RIDGE TO THE
NORTH
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T6.5 - 127 KTS
   RJTD: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 90 KTS AT 262340Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 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) CONTINUES TO RAPIDLY INTENSIFY OVER
THE PAST 12 HOURS AS ENVIRONMENTAL CONDITIONS ARE FAVORABLE WITH
MODERATE VERTICAL WIND SHEAR (VWS) (10-15KTS), OFFSET BY WARM SEA
SURFACE TEMPERATURES (29-30C), 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 HOURS. DUE
TO THE CURRENT FAVORABLE ENVIRONMENTAL CONDITIONS THE SYSTEM HAS
LIKELY REACHED ITS PEAK INTENSITY OF 125 KTS, HOWEVER AS THE SYSTEM
CONTINUES TO TRACK WESTWARD OVER THE NEXT 12-24 HOURS, TY 18W WILL
BEGIN TO BE INFLUENCED BY INCREASING VWS AND LAND INTERACTION,
WHICH WILL RESULT IN THE SYSTEM GRADUALLY DECREASING IN INTENSITY.
AFTER TAU 24, TY 18W WILL MAKE LANDFALL INTO CENTRAL VIETNAM, AS LAND
INTERACTION AS WELL AS AN INCREASE IN VWS WILL DECREASE THE SYSTEMS
INTENSITY EVEN FURTHER. BY TAU 48, THE SYSTEM TRACKS FURTHER INLAND
OVER SOUTHEAST ASIA WITH DISSIPATION EXPECTED.
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 DUE TO SOME UNCERTAINTY IN THE MODEL
GUIDANCE INTENSITY OVER THE NEXT 24 HOURS, AS GFS DECAY SHIPS
(DSHA) SHOWS A MORE GRADUAL DECREASE IN INTENSITY FROM THE OTHER
MODEL GUIDANCE. HOWEVER, AFTER LANDFALL, THE BULK OF THE INTENSITY
GUIDANCE IS IN OVERALL GOOD AGREEMENT OF A RAPID DECREASE THROUGH
TAU 48.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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