Tropical Storm HINNAMNOR Advisory 8月31日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 12W (HINNAMNOR) WARNING NR
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 26.3N 131.9E
   INITIAL INTENSITY: 140 KTS
   GEOGRAPHIC REFERENCE: 221 NM EAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A WELL
DEFINED SUPER TYPHOON, WITH A SYMMETRIC CENTRAL DENSE OVERCAST
SURROUNDING A 9NM WIDE CLEAR EYE WITH EYE TEMPERATURES AROUND
18-20C. A 301315Z GMI 89GHZ MICROWAVE IMAGE SHOWED A SMALL INNER
CORE SURROUNDING THE EYE, WITH A MOAT AND A NASCENT SECONDARY
EYEWALL BEGINNING TO FORM. JAPANESE RADAR DATA AT THE 1800Z HOUR
CONFIRMS A STRONG INNER-EYEWALL WITH A RAGGED AND WEAK SECONDARY
EYEWALL CONTINUING TO DEVELOP, PARTICULARLY ON THE WESTERN SIDE OF
THE CIRCULATION, MARKING THE ONSET OF ANOTHER EYEWALL REPLACEMENT
CYCLE (ERC). THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE 9NM WIDE EYE AND THE RADAR DATA. THE INITIAL INTENSITY
IS ASSESSED AT 140 KNOTS, SLIGHTLY HIGHER THAN THE SUBJECTIVE AND
OBJECTIVE FIXES, BASED ON CONSISTENT SIX HOUR TRENDS IN THE
SUBJECTIVE FIXES AND OVERALL STEADY STRUCTURE. THE EXTENT OF THE
WIND RADII HAS BEEN SIGNIFICANTLY REDUCED BASED ON A 301240Z ASCAT
PASS AS WELL AS OBSERVATIONAL DATA FROM MINAMI DAITO, JUST
SOUTHWEST OF STY 12W, REPORTING WINDS AROUND 25 KNOTS.
INITIAL WIND RADII BASIS: 301240Z SCATTEROMETER DATA
CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T7.0 - 140 KTS
   RJTD: T7.0 - 140 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 136 KTS AT 301625Z
   CIMSS ADT: 130 KTS AT 301810Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: MODERATE EQUATORWARD OUTFLOW INTO A TROPICAL
UPPER TROPOSPHERIC TROUGH (TUTT) CELL FAR TO THE SOUTHEAST.
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: STY 12W HAS TRACKED JUST A SHADE SOUTH OF DUE
WEST OVER THE PAST SIX HOURS, AND HAS REACHED AN INFLECTION POINT
IN THE STEERING PATTERN. THE SYSTEM IS CURRENTLY BEING STEERED
ALONG THE SOUTHWESTERN SIDE OF A STR TO THE NORTHEAST, BUT THE
PASSAGE OF A SHORTWAVE TROUGH TO THE NORTH HAS BROKEN THE RIDGE,
WITH A COL REGION DEVELOPING IN THE DEEP-LAYER MEAN FLOW JUST WEST
OF KYUSHU. HENCE, THE SYSTEM WILL LIKELY SLOW A BIT BEFORE ANOTHER
STR TO THE WEST PICKS UP THE BATON AS THE PRIMARY STEERING
MECHANISM AND THE SYSTEM WILL START TO TURN MORE SOUTHWESTWARD OVER
THE NEXT FEW HOURS AS THE RIDGE TO THE WEST TAKES OVER. AN
ADDITIONAL FACTOR IN THE FORECAST TRACK OVER THE NEXT 48 HOURS IS A
POTENTIAL BINARY INTERACTION WITH TD 13W, DEVELOPING APROXIMATELY
400NM TO THE SOUTH. AS TD 13W MOVES NORTH-NORTHWESTWARD ALONG THE
EASTERN PERIPHERY OF STY 12W, IT WILL LIKELY PULL STY 12W ONTO A
SLIGHTLY MORE SOUTHWARD TRAJECTORY, THOUGH THE STRENGTH OF THIS
INTERACTION IS HIGHLY UNCERTAIN DUE TO THE RELATIVELY WEAKNESS OF
TD 13W. BY TAU 36 THE SYSTEM WILL MOVE INTO A COMPETING STEERING
ENVIRONMENT, TRAPPED BETWEEN AND STR TO THE WEST AND NORTHEAST AND
A NEAR EQUATORIAL RIDGE (NER) TO THE SOUTH, LEADING TO
QUASI-STATIONARY MOTION FROM TAU 36 TO 72. BY TAU 72 THE APPROACH
OF A MAJOR SHORTWAVE TROUGH WITH STRONG MID-LATITUDE DYNAMIC FORCING
WILL ERODE THE RIDGE TO THE WEST AND ALLOW A BUILDING STR TO THE
EAST TO EJECT 12W OUT OF ITS COCOON AND THE SYSTEM WILL BEGIN
TRANSITING NORTHWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD.
A SECONDARY CPA TO OKINAWA OF APPROXIMATELY 185NM IS ANTICIPATED
AROUND 041600Z AS THE SYSTEM MOVES NORTH IN THE EAST CHINA SEA.
WHILE ENVIRONMENTAL CONDITIONS REMAIN VERY FAVORABLE, INTENSITY HAS
LIKELY PEAKED OVERNIGHT, WITH THE ANTICIPATED ERC EXPECTED TO
WEAKEN THE SYSTEM DOWN TO 130 KNOTS WITHIN THE NEXT 12 HOURS. AS
THE SYSTEM STALLS SOUTH OF THE RYUKUS, SIGNIFICANT UPWELLING IS
ANTICPATED, COUPLED WITH AN INCREASE IN VWS IN FORECAST TO RESULT
IN A SHARP DECREASE IN INTENSITY, DOWN TO 95 KNOTS BY TAU 72.
HOWEVER, REINTENSIFICATION IS FORECAST AFTER THE SYSTEM KICKS OUT
TO THE NORTH AND MOVES BACK OVER WARMER WATERS, SHEAR DECREASES AND
IT BEGINS TO TAP INTO STRONG POLEWARD OUTFLOW AHEAD OF THE
APPROACHING TROUGH.
MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINS IN
VERY GOOD AGREEMENT IN THE SHORT-TERM, WITH MINIMAL SPREAD ACROSS
THE GUIDANCE THROUGH TAU 36. A DIFFERENT STORY TAKES HOLD AFTER
THIS POINT HOWEVER, WITH SIGNIFICANT DISAGREEMENT BETWEEN THE
CONSENSUS MEMBERS, WITH TWO DISTINCT GROUPINGS. THE FIRST GROUP
CONSISTING OF GFS, ECMWF AND THEIR ENSEMBLE MEANS, HWRF AND THE
JGSM, TURN THE SYSTEM SHARPLY NORTH TO NORTH-NORTHEASTWARD AFTER
TAU 72, WITH THE ECMWF SHOWING THE SHARPEST INSIDE CURVE. MEANWHILE
THE SECOND GROUPING CONSISTING OF NAVGEM, EGRR, UKMET ENSEMBLE AND
THE GALWEM TAKE THE SYSTEM FURTHER SOUTH BEFORE TAKING A GRADUAL
POLEWARD TURN, TAKING THE SYSTEM OVER TAIWAN. THE JTWC TRACK
REMAINS CONSISTENT WITH THE PREVIOUS FORECAST, AND LIES ON THE
NORTHERN EDGE OF THE ENVELOPE WITH HIGH CONFIDENCE IN THE
SHORT-TERM FORECAST. THE LONGER RANGE FORECAST LIES NORTH AND EAST
OF THE CONSENSUS MEAN, AS IT IS PULLED TO FAR SOUTH AND WEST BY THE
SECOND GROUPING OF MODELS ABOVE, HEDGED MORE TOWARDS THE GFS AND
ECMWF, WITH LOW CONFIDENCE. INTENSITY GUIDANCE IS IN FAIRLY GOOD
AGREEMENT THROUGH THE FORECAST PERIOD, THOUGH THE ULTIMATE
SECONDARY PEAK IS DEPENDENT UPON THE AMOUNT OF WEAKENING
EXPERIENCED IN THE MID-TERM, THUS CONFIDENCE IS MEDIUM, TRENDING
LOW.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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