Tropical Storm CEMPAKA Advisory 7月20日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (CEMPAKA) WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 21.2N 112.5E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 115 NM SOUTHWEST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
REVEALS TY 10W HAS DEVELOPED A RAGGED 15NM EYE. THE INITIAL
INTENSITY ASSESSMENT IS BASED ON A PGTW DVORAK ESTIMATE OF T4.0. A
19752Z AMSR2 PASS CONFIRMS A CONCENTRIC AND VERTICALLY STACKED EYE.
TY CEMPAKA IS A COMPACT AND TIGHTLY ORGANIZED SYSTEM, ALTHOUGH IT
IS BECOMING INCREASINGLY ASYMMETRICAL AS IT FEELS THE EFFECTS OF
LAND INTERACTION. THE IMBALANCE IS ALSO BEING EXACERBATED BY THE
SURGING SOUTHWESTERLIES STEMMING FROM THE MONSOONAL FLOW OVER THE
SOUTH CHINA SEA ON THE EQUTORWARD SIDE OF THE SYSTEM, WITH WEAKER AND
SLIGHTLY LESS SATURATED FLOW OFF-SHORE FLOW OVER THE NORTHEASTERN
SEMICIRCLE. TYPHOON 10W EXISTS IN A HIGHLY FAVORABLE ENVIRONMENT
UNDERNEATH VERY LITTLE WINDSHEAR AND RADIAL OUTFLOW.
INITIAL WIND RADII BASIS: PERSISTENCE AND NEARBY SHIP REPORTS.
CURRENT STEERING MECHANISM: THE SUBTROPICAL RIDGE POSTIONED TO THE
NORTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T4.0 - 65 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 70 KTS AT 191432Z
   CIMSS ADT: 53 KTS AT 191740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: LAND INTERACTION IS BEGINNING TO SLOW
DEVELOPMENT.
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 10W WILL TRACK SLOWLY NORTHWESTWARD AND
MOVE ASHORE NEAR TAU 18. AFTER LANDFALL, A LOOPING OVERLAND TRACK
WILL WEAKEN THE SYTEM SUBSTANTIALLY BUT NOT COMPLETELY KILL IT.
TRACK GUIDANCE IS SURPRISINGLY CONSISTENT IN CARRYING THE VORTEX
BACK OUT TO SEA OVER THE GULF OF TONKIN IN THE TAU 48-72 HOUR
PERIOD, WHERE THE SYSTEM WILL RE-INTENSIFY AND BE PUSHED POLEWARD
AS IT ENCOUNTERS THE MONSOONAL SOUTHWESTERLIES. THERE IS GREAT
UNCERTAINTY IN THE INTENSITY FORECAST DURING THE LATER PERIODS DUE
TO THE VARIABILITY IN WHERE THE SYSTEM ENTERS THE GULF OF TONKIN AND
WHAT TRACK IT TAKES OVER HAINAN, AS WELL AS CONDITIONS OVER THE
SOUTH CHINA SEA.
MODEL DISCUSSION: AFTER LANDFALL, MODEL GUIDANCE SHOWS SUBSTANTIAL
VARIABILITY IN HOW AND WHERE IT RE-ENTERS THE GULF OF TONKIN AND
TRAVERSES HAINAN ISLAND. THEREFORE THERE IS VERY LOW CONFIDENCE IN
THE INTENSITY IN THE TAU 72-120HR PERIOD.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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