Tropical Storm MUIFA Advisory Mon Sep 12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (MUIFA) WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 25.0N 124.0E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 224 NM WEST-SOUTHWEST OF KADENA AB,
OKINAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A
MEDIUM-SIZED TYPHOON WITH A SYMMETRICAL DEEP CENTRAL CONVECTION THAT
APPEARS TO BE UNDERGOING A SECOND EYEWALL REPLACEMENT CYCLE AS
EVIDENCED BY THE ONSET OF A SECONDARY EYEWALL THAT IS SURROUNDING THE
CURRENT EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON THE 24-NM EYE IN THE EIR LOOP THAT WAS CONCENTRIC WITH A
WELL-DEFINED CIRCULATION FEATURE IN THE COMPOSITE RADAR LOOP FROM
JMA. THE INITIAL INTENSITY IS ALSO PLACED WITH HIGH CONFIDENCE BASED
ON OVERALL ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND
REFLECTS THE SLIGHT 6-HR IMPROVEMENT. ANALYSIS INDICATES A MARGINAL
ENVIRONMENT WITH MEDIUM RADIAL OUTFLOW AND LIGHT TO MODERATE VWS
OFFSET BY COOLING LOCALIZED SST DUE TO UPWELLING BROUGHT ON BY THE
CURRENT SLOW STORM MOTION.
INITIAL WIND RADII BASIS: SCATTEROMETER DATA.
CURRENT STEERING MECHANISM: EXTENSION OF A DEEP-LAYERED SUBTROPICAL
RIDGE (STR) TO THE NORTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T5.0 - 90 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 94 KTS AT 121130Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL
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: A MIDLATITUDE SHORTWAVE TROUGH EXITING CHINA
VIA THE YELLOW SEA HAS WEAKENED THE STEERING STR AND ALLOWED THE
SYSTEM TO TRACK MORE NORTHWARD. BEHIND THE TROUGH, A SECONDARY,
ALBEIT WEAK, STR TO THE WEST IS COMPETING FOR STEERING CAUSING THE
SLOW STORM MOTION. AFTER TAU 12, THE STR TO THE NORTHEAST WILL
BUILD ANEW AND REGAIN FULL STEERING AND ACCELERATE TY 14W
NORTH-NORTHWESTWARD. THE MARGINAL ENVIRONMENT WILL VERY SLOWLY
WEAKEN THE SYSTEM DOWN TO 65KTS BY TAU 48. AFTERWARD, COOLING SST
IN THE EAST CHINA SEA, INCREASING VWS, AND LANDFALL INTO NORTHEAST
CHINA VIA SHANGHAI WILL RAPIDLY ERODE THE SYSTEM AND BY TAU 96 WILL
DISSIPATE JUST SOUTH OF SHANDONG BANDAO PENINSULA.
MODEL DISCUSSION: THE MAIN PACK OF NUMERICAL MODELS ARE IN TIGHT
AGREEMENT, EVENLY SPREADING OUT TO JUST 82NM BY TAU 72 THEN TO
400NM+ BY TAU 96 AS THE MODELS LOSE A DISSIPATING VORTEX. NVGM AND
JGSM ARE THE EXTREME LEFT OUTLIERS OUTSIDE THE MAIN PACK. IN VIEW
OF THIS, THERE IS MEDIUM CONFIDENCE IN THE JTWC TRACK LAID JUST TO
THE RIGHT OF THE MODEL CONSENSUS TO OFFSET NVGM AND JGSM, THEN LOW
CONFIDENCE AFTER TAU 72. THERE IS ALSO MEDIUM CONFIDENCE IN THE
INTENSITY FORECAST UP TO TAU 72 THEN LOW CONFIDENCE AFTERWARD.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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