Tropical Storm IN-FA Advisory 7月23日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (IN-FA) WARNING NR 027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 23.7N 125.5E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 209 NM SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
SHOWS THE EYE OF TY 09W EXPANDING EVEN FURTHER. THE LATEST JTWC FIX
MEASURED THE EYE DIAMETER AT 60NM. CORE CONVECTION OVER THE
POLEWARD SEMICIRCLE HAS WANED SUBSTANTIALLY DURING THE PAST 12
HOURS BUT VIGOROUS DEEP CONVECTION PERSISTS AROUND THE ENTIRETY OF
THE EQUATORWARD EYEWALL. THE CURRENT INTENSITY ASSESSMENT IS BASED
ON A COMBINATION OF DVORAK ESTIMATES FROM PGTW AND RJTD AND MATCHES
THE SATCON MEMBER CONSENSUS. THE EXPANSIVE EYE INDICATES SYSTEMIC
WEAKENING BUT ANIMATED WATER VAPOR IMAGERY DOES NOT SHOW ANY MAJOR
SUPPRESSION OF OUTFLOW. THE SYSTEM IS TRACKING THROUGH AN AREA OF
VERY LOW VERTICAL WINDSHEAR. DURING THE PAST 12 HOURS THE SYSTEM
HAS RESUMED TRACKING TO THE NORTH OF WEST AND ALONG TRACK SPEEDS
ARE INCREASING. THE SLOW MOVEMENT OF THE SYSTEM PREVIOUSLY WAS
CHURNING UP COOLING WATERS AND ACTING AS A BRAKING MECHANISM ON
INTENSIFICATION.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: THE DEEP-LAYERED SUBTROPICAL RIDGE
(STR) ANCHORED TO THE NORTH.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 80 KTS AT 221742Z
   CIMSS ADT: 87 KTS AT 221740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TY 09W HAS SETTLED INTO ITS NORTHWESTERLY LEG
AND WILL ROAR OVER THE SOUTHERN SENKAKUS DURING THE NEXT 24 HOURS.
THE SYSTEM WILL ALSO PEAK IN THE NEXT 24 HOURS. TY 09W WILL
ACCELERATE ALONG TRACK AS A MIDLATITUDE TROUGH MOVES INTO EASTERN
CHINA, DRAWING THE SYSTEM TOWARDS SHANGHAI. COOLER WATERS AND
INCRESING VERTICAL WIND SHEAR OVER THE EAST CHINA SEA WILL PUT THE
SYSTEM ON A WEAKENING TREND FOR THE REMAINDER OF ITS TRACK INTO
LANDFALL, WHERE IT IS EXPECTED TO COME ASHORE SOUTH OF SHANGHAI AT
HIGH TROPICAL STORM STRENGTH.
MODEL DISCUSSION: THE MAJORITY OF GUIDANCE SUPPORTS THE JTWC
FORECAST TRACK REGARDING THE LANDFALL SCENARIO. THE ECMWF ENSEMBLE
MEAN HAS BEEN LOCKED IN ON THE LANDFALL SCENARIO FOR SEVERAL DAYS.
THE GFS DETERMINISTIC MODEL, HOWEVER, COMES CLOSER TO THE COAST
AND RUNS OVER SHANGHAI AND RETURNS TO SEA. MANY--BUT NOT THE
MAJORITY--OF MEMBERS OF THE GEFS ENSEMBLE DEPICT A SEAWARD TRACK
TRACK TOWARD THE KOREAN PENINSULA. ALTHOUGH GFS HAS BEEN AN
OUTSTANDING PERFORMER THUS FAR THIS SEASON, THE EROSION OF THE
SUBTROPICAL RIDGE THAT SCENARIO IS PREDICATED UPON IS LESS LIKELY
THAN THE STABLE STR RIDGE DRIVING THE WESTWARD TRACK. THERE REMAINS
LOW CONFIDENCE IN THE POST TAU 72 FORECAST TRACK BUT INCREASING
CONFIDENCE THROUGH TAU 72, AND THERE IS INCREASING CONVICTION IN
THE LANDFALL SCENARIO WITH EACH FIX CYCLE. THE INTENSITY GUIDANCE
REMAINS IN EXCELLENT AGREEMENT AND ALTHOUGH IT HAS BEEN A LITTLE
HIGH THROUGHOUT THE FORECAST, IT HAS BEEN CONSISTENT AND IN TIGHT
AGREEMENT THROUGHOUT THE STORMS HISTORY.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
NNNN
NNNN