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老農民版夜神月|2021-9-2 10:32
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JTWC短暫的上望TS
WDPN31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 26.9N 159.7E
INITIAL INTENSITY: 30 KTS
GEOGRAPHIC REFERENCE: 1141 NM EAST-SOUTHEAST OF YOKOSUKA, JAPAN
MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
SIGNIFICANT WAVE HEIGHT: 9 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH FLARING DEEP
CONVECTION, WITH EVIDENT OVERSHOOTING TOPS, TO THE WEST-SOUTHWEST
AND EAST OF THE LLCC. WATER VAPOR IMAGERY INDICATES TD 17W IS
LOCATED TO THE NORTHEAST OF AN ELONGATED TUTT CELL WHICH HAS AIDED
IN DEEPENING THE SYSTEM OVER THE PAST 24 HOURS. A 012335Z ASCAT-B
BULLSEYE PASS SHOWS A WELL-DEFINED, SLIGHTLY ELONGATED LLCC WITH
25-30 KT WINDS IN THE NORTHEAST QUADRANT AND 20-25 KT WINDS
ELSEWHERE. THE INITIAL POSITION AND INTENSITY ARE BOTH ASSESSED
WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED MULTISPECTRAL
IMAGERY AND ASCAT-B PASS. TD 17W IS A HIGH LATITUDE CYCLONE WHICH
HAS FORMED BY CONSOLIDATION OF A LOW LEVEL CIRCULATION MOVING IN
PHASE WITH THE FAVORABLE POSITION RELATIVE TO THE TUTT CELL TO THE
SOUTHWEST. THE SYSTEM LIES IN AN OVERALL MARGINALLY FAVORABLE
ENVIRONMENT, WITH EASTERLY WIND SHEAR BEING THE MOST CONSTRAINING
FACTOR.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL
WIND
RADII).
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE
EAST-NORTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
KNES: T2.0 - 30 KTS
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
VWS: 15-20 KTS
SST: 29-30 CELSIUS
OUTFLOW: STRONG EQUATORWARD
ANALYSIS CONFIDENCE:
INITIAL POSITION: HIGH
INITIAL INTENSITY: HIGH
INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.
FORECAST DISCUSSION: TD 17W IS FORECAST TO TRACK TO THE NORTHWEST
THROUGH TAU 12 BEFORE SLOWLY AND STEADILY TURNING NORTHWARD AS IT
ROUNDS THE RIDGE AXIS THROUGH TAU 36. AFTER ROUNDING THE RIDGE
AXIS, TD 17W WILL ACCELERATE NORTHEASTWARD AND BEGIN INTERACTING
WITH THE BAROCLINIC ZONE. AS THE SYSTEM MOVES NORTHWARD, THE TUTT
CELL WILL MOVE FURTHER AWAY TOWARDS THE SOUTHWEST, EASING THE
UPPER-LEVEL GRADIENT AND DECREASING SHEAR, WHICH COMBINED WITH
WARM SSTS ABOVE 29C, WILL SUPPORT A PERIOD OF INTENSIFICATION THROUGH
TAU 24 TO A PEAK OF 35 KNOTS. BY TAU 36 THE SYSTEM MOVES UNDER AN
UPPER-LEVEL RIDGE, WHICH WILL DECREASE NET OUTFLOW ALOFT, AND
COMBINED WITH DRY AIR MOVING OVER TOP THE SYSTEM IN THE MID-
LEVELS, WILL LEAD TO SLOW WEAKENING BEGINNING AT TAU 36. BY TAU 48,
THE SYSTEM WILL BEGIN TO FEEL THE EFFECTS OF RAPIDLY INCREASING VWS
AS IT MOVES UNDER THE UPPER-LEVEL WESTERLIES, AND SIMULTANEOUSLY
BEGIN EXTRA-TROPICAL TRANSITION (ETT). THE SYSTEM IS EXPECTED TO
COMPLETE EXTRA-TROPICAL TRANSITION NO LATER THAN TAU 72 AND
POSSIBLY AS EARLY AS TAU 60.
MODEL DISCUSSION: OVERALL MODEL CONSENSUS IS IN TIGHT AGREEMENT
THAT TD 17W IS ON TRACK FOR A RECURVE SCENARIO AS THE SYSTEM
ROUNDS STR AXIS BY TAU 30. THE JTWC FORECAST TRACK IS PLACED
SLIGHTLY TO THE RIGHT OF THE MODEL CONSENSUS, TO SUBTRACT THE
UNREALISTIC MOTION OF THE GALWEM AND ECMWF TRACKERS WHICH MOVE THE
SYSTEM FAR TO THE WEST OF THE REMAINING GUIDANCE. INTENSITY AIDS ARE
IN RELATIVELY FAIR AGREEMENT WITH COAMPS BEING THE OUTLIER INDICATING
A WEAKENING TREND EARLY IN THE FORECAST PERIOD. THE JTWC INTENSITY
FORECAST IS PLACED SLIGHTLY ABOVE INTENSITY CONSENSUS (ICNW)
DURING THE FIRST 24 HOURS, THEN SLIGHTLY BELOW AFTERWARDS AS THE
SYSTEM ROUNDS THE STR AND BEGINS TO UNDERGO EXTRA-TROPICAL
TRANSITION.
FORECAST CONFIDENCE:
TRACK 0 - 72 HR: HIGH
INTENSITY 0 - 72 HR: HIGH//
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