Tropical Storm IN-FA Advisory 7月20日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 24.2N 131.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 230 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SUBSTANTIAL
DRY AIR ENTRAINMENT WRAPPING INTO THE WESTERN SEMICIRCLE OF TS 09W
AND RETARDING DEVELOPMENT. THE SYSTEM HAS MAINTAINED GOOD
ORGANIZATION AND THERE REMAINS A STRONG CORE. THE
SUBTROPICAL RIDGE (STR) HAS SETTLED OVER JAPAN, STRENGTHENED, AND
IS NOW PUSHING THE SYSTEM SLOWLY AND STEADILY TO THE
WEST-NORTHWEST. THE SLOW MOVEMENT OF THE SYSTEM IS CHURNING UP
COOLER WATERS, ALSO LIMITING INTENSIFICATION. THE SYSTEM IS
ASSESSED AT 55 KNOTS BASED ON A SATCON MEMBER CONSENSUS OF 53KTS.
INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK
CURRENT STEERING MECHANISM: THE SUBTROPICAL RIDGE, WHICH IS
BUILDING AND SETTLING OVER MAINLAND JAPAN AND EXTENDING SOUTHWARD
AS FAR AS THE RYUKUS.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 37 KTS AT 191740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: THE SLOW MOVEMENT OF TS 09W IS CHURNING UP COOLER
WATERS FROM BELOW, ALSO ACTING TO IMPEDE DEVELOPMENT.
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: THE SUB TROPICAL RIDGE WILL CONTINUE TO DRIVE
TS 09W STEADILY WEST-NORTHWESTWARD THROUGH TAU 72. ANIMATED WATER
VAPOR IMAGERY REVEALS A DEEPING TROUGH MOVING OFF OF SHANGHAI THAT
IS INCREASING UPPER LEVEL CONVERGENCE ALONG TRACK. AFTER TAU 72, TS
09W WILL DRIFT POLEWARD AS IT TRACKS ALONG THE SOUTHWESTERN
PERIPHERY OF THE STR. TS 09W SHOULD STEADILY INTENSIFY TO ITS PEAK
OF NEAR 90 KTS, REACHING ITS MAXIMUM INTENSITY OVER AND JUST WEST
OF THE SOUTHERN RYUKUS.
MODEL DISCUSSION: CONFIDENCE IN THE MID-TO-LONG RANGE OF THE
FORECAST IS INCREASING AS THE STR ENTRENCHES ITSELF OVER JAPAN AND
AN UPPER LEVEL COLD CORE LOW OVER THE WEST SEA THAT WAS PREVIOUSLY
MUDDLING THE FORECAST DRIFTS FURTHER OUT OF INCLUENCE. MODEL
GUIDANCE DIVERGES IN THE LATER TAUS, WITH A LARGE SPREAD AND SOME
MEMBERS OF CONSENSUS STEERING THE SYSTEM CLOSER TO TAIWAN.
CONFIDENCE IN THE INTENSITY FORECAST IS IMPROVING, HOWEVER, AS EACH
CONSECUTIVE FIX CYCLES VERIFY THE EFFICACY OF THE PREDICTIONS AND
THE UPSTREAM ENVIRONMENT IS BECOMING LESS COMPLEX.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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