Tropical Storm HINNAMNOR Advisory 8月30日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (HINNAMNOR) WARNING NR
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 27.1N 139.3E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 155 NM WEST OF CHICHI JIMA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TY 12W HAS CONTINUED ITS RAPID INTENSIFICATION, WITH 125 KNOT MAXIMUM
WINDS NOW ESTIMATED AT 291800Z. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS A COMPACT SYSTEM, WITH A 140 NM DIAMETER
CENTRAL DENSE OVERCAST FEATURE. A PINHOLE EYE MEASURED AT 8 NM HAD
CENTER TEMPERATURES BETWEEN 10 TO 12 DEG C. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EIR IMAGERY. THE EARLY
MORNING DMSP AND AMSR-2 PASSES DID NOT PROVIDE COVERAGE OVER THE
SYSTEM. A LOW RESOLUTION ATMS PASS SUPPORTS THE POSITIONING, AND
DEPICTS A BANDING ASYMMETRY IN THE SOUTHEAST QUADRANT. THE INITIAL
INTENSITY OF 125 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
THE PGTW DVORAK T6.5 ESTIMATE (127 KNOTS), WHICH IS ON THE HIGH END
OF THE ENVELOPE OF ESTIMATES. KNES FINAL-T WAS 6.0, WITH A DATA-T
OF 6.5, WHILE RJTD FINAL-T CAME IN AT T5.5. OBJECTIVE ESTIMATES
RANGED FROM 105 TO 110 KNOTS. ENVIRONMENTAL CONDITIONS ARE HIGHLY
FAVORABLE WITH RADIAL OUTFLOW, LOW VERTICAL WIND SHEAR AND VERY
WARM (29-30 DEGREE C) SST VALUES.
INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK
CURRENT STEERING MECHANISM: DEEP-LAYERED EXTENSION OF THE
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T6.5 - 127 KTS
   RJTD: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 106 KTS AT 291217Z
   CIMSS ADT: 109 KTS AT 291740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: OUTFLOW IS ENHANCED BY A TUTT CELL TO THE
SOUTHEAST
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, HOWEVER, A BI-FURCATION IN
GUIDANCE AFTER TAU 72 IS RESULTING IN A POSSIBLE ALTERNATE
LONG-RANGE FORECAST SCENARIO.
FORECAST DISCUSSION: TY 12W IS FORECAST TO TRACK QUICKLY WESTWARD
TO WEST-SOUTHWESTWARD OVER THE NEXT 24 HOURS AS IT TRACKS ALONG
THE SOUTHERN PERIPHERY OF THE STR TO THE NORTH. FORECAST TRACKS
WERE ADJUSTED SLIGHTLY FASTER BASED ON THE CURRENT SPEED OF ADVANCE
AND LATEST ROUND OF GUIDANCE. AFTER TAU 24, THE TRACK IS THEN
EXPECTED TO DEFLECT MORE EQUATORWARD AS A WESTERN STR GRADUALLY
TAKES OVER AS THE PREDOMINANT STEERING MECHANISM. BINARY
INTERACTION WITH INVEST 98W MAY ALSO PLAY A PART IN THIS SHIFT.
ENVIRONMENTAL FACTORS WILL REMAIN FAVORABLE, AND HINNAMNORS TRACK
WILL TAKE IT OVER EVEN WARMER WATERS, ALLOWING ADDITIONAL
INTENSIFICATION UP TO A PEAK OF 145 KNOTS. PEAK INTENSITY COULD BE
EVEN HIGHER GIVEN THE POSITIVE ENVIRONMENT, BUT LIKELY EYEWALL
REPLACEMENT CYCLES COULD CAUSE SHORT-LIVED MODIFICATIONS TO THE
INTENSITY. ALL BUT ONE MEMBER OF THE COAMPS-TC ENSEMBLE REACH
SUPER-TYPHOON INTENSITY. THE GENERAL TREND IN MODELS THROUGH TAU 72
HAS BEEN FOR A MORE PRONOUNCED SOUTHERLY SHIFT, KEEPING THE
STRONGEST CORE WINDS OFF OF OKINAWA. OVERALL MODEL AGREEMENT IS
GOOD IN THE SHORT TERM. HOWEVER, HWRF REMAINS A NOTABLE OUTLIER,
BOTTOMING OUT AS A 910 MB LOW AS THE CENTER PASSES JUST 30 NM OFF THE
SOUTHERN TIP OF THE ISLAND PRIOR TO TAU 48. BEYOND TAU 72, THE
OUTLOOK BECOMES VERY COMPLEX. A MIDLATITUDE SHORTWAVE TROUGH
IS EXPECTED TO DIG OVER THE KOREAN PENINSULA NEAR 311200Z AND SHOULD
PASS QUICKILY TO THE NORTH, ERODING THE CURRENT STR AND CREATING A
COMPETING STEERING SYNOPTIC PATTERN, WITH A STR TO THE NORTHEAST AND
WEST, AND A NEAR-EQUATORIAL RIDGE TO THE SOUTH. THE SCENARIO RESULTS
IN A PERIOD OF SLOW, QUASI-STATIONARY (QS) MOTION. DURING THIS TIME,
THE WIND FIELD IS EXPECTED TO GROW SUBSTANTIALLY, WITH HWRF
PREDICTING SIGNIFICANT UPWELLING OF COOLER 24-25 DEGREE C WATER.
MODELS DIVERGE SHARPLY IN THE 96-120 TAU RANGE. THE PRIMARY GROUPING
OF MODELS TURNS 12W BACK TO THE NORTH TO NORTHWEST ACROSS
THE RYUKUS. THE AMOUNT OF TIME SPENT QS OVER COOLER WATERS WILL
HAVE A STRONG IMPACT ON LONG-RANGE INTENSITY FORECAST.
ADDITIONALLY, IF HINNAMNOR TURNS BACK ON A NORTHWARD TRAJECTORY
OVER ITS COLD WAKE, TY 12W COULD WEAKEN SUBSTANTIALLY BY TAU 120.
THE SECONDARY MODEL GROUPING, ACCOUNTING FOR APPROXIMATELY 15
PERCENT OF THE TOTAL SPREAD, TAKES TYPHOON 12W ON A MORE WESTERLY
TRAJECTORY WITH POSSIBLE LANDFALL OVER TAIWAN OR SOUTHEASTERN
CHINA. DUE TO THE COMPETING STEERING, THERE IS HIGH UNCERTAINTY IN
THE EXACT TRACK OF THE CENTER. REGARDLESS, THE SYSTEM IS EXPECTED
TO TRANSITION INTO A LARGE SYSTEM WITH A 400-500NM DIAMETER.
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 72 WITH APPROXIMATELY 140NM SPREAD IN SOLUTIONS AT THAT
TIME. AFTER TAU 72, HOWEVER, DETERMINISTIC GUIDANCE DIVERGES AND IS
IN POOR AGREEMENT. ALL THE MODELS INDICATE THE SYSTEM WILL SLOW AND
BECOME QUASI-STATIONARY BUT DISAGREE ON WHERE THE SYSTEM WILL
STALL, AND WHERE THE SYSTEM WILL TRACK ONCE FORWARD MOTION RESUMES.
THE BULK OF THE DETERMINISTIC AND PROBABILISTIC GUIDANCE (ECMWF
ENSEMBLE AND GEFS) INDICATES THE SYSTEM WILL STALL SOUTH TO
SOUTH-SOUTHWEST OF OKINAWA FOR ABOUT 24 HOURS, AND THEN TURN BACK
TO THE NORTH LEADING TO AN EVENTUAL RE-CURVATURE SCENARIO. THE
SECONDARY GROUPING CONSISTING PRIMARILY OF UKMET OFFICE-BASED MODEL
GUIDANCE TRACKS HINNAMNOR WESTWARD.
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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