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JTWC/18W/#03/08-19 18Z Prognostic Reasoning
WDPN32 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (EIGHTEEN)
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 28.6N 126.8E
INITIAL INTENSITY: 25 KTS
GEOGRAPHIC REFERENCE: 137 NM NORTH-NORTHWEST OF KADENA AB
MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
SIGNIFICANT WAVE HEIGHT: 12 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FULLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH FLARING DEEP
CONVECTION. MODERATE POLEWARD AND EQUATORWARD OUTFLOW IS EVIDENT ON
WATER VAPOR IMAGERY. AN UPPER-LEVEL CYCLONE IS POSITIONED OVER THE
SOUTH CHINA SEA ENHANCING THE EQUATORWARD OUTFLOW, AND THE POLEWARD
OUTFLOW COMPONENT WEAKLY DRIFTS TO THE NORTHEAST. DRY AIR DIRECTLY
SOUTH OF TROPICAL DEPRESSION (TD) 18W HAS CURTAILED DEEP CONVECTION
AND HAS IMPOSED UPON THE VERTICAL STRUCTURE, CAUSING SLIGHT
WEAKENING TO 25KTS OVER THE LAST SIX HOURS. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED ANIMATED
EIR, AND DOPPLER RADAR IMAGERY HIGHLIGHTING THE CLOUD BANDING
SURROUNDING THE CORE OF THE CIRCULATION. THE INITIAL INTENSITY OF
25 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY AND
OBJECTIVE FIXES LISTED BELOW.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE TO THE EAST.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T2.0 - 30 KTS
RJTD: T1.5 - 25 KTS
KNES: T1.5 - 25 KTS
CIMSS SATCON: 34 KTS AT 191900Z
CIMSS ADT: 32 KTS AT 191730Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
VWS: 10-15 KTS
SST: 28-29 CELSIUS
OUTFLOW: MODERATE DUAL-CHANNEL
ANALYSIS CONFIDENCE:
INITIAL POSITION: MEDIUM
INITIAL INTENSITY: MEDIUM
INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TD 18W WILL TRACK NORTH-NORTHEASTWARD DURING
THE NEXT 24 HOURS. AFTER TAU 24, THE SYSTEM WILL CURVE TO A
NORTHEASTWARD TRACK WHILE ROUNDING THE SUBTROPICAL RIDGE. IN THE
EARLY-TERM FORECAST, DRY AIR WILL BE THE PRIMARY INHIBITOR FOR
DEVELOPMENT. VERTICAL WIND SHEAR WILL BE LOW DURING THE FIRST 24
HOURS, ALLOWING FOR INTENSIFICATION TO 30KTS. AFTER TAU 24,
VERTICAL WIND SHEAR WILL INCREASE TO 20-25KTS, CAPPING
INTENSIFICATION HAVING REACHED A PEAK OF 30KTS. VERTICAL WIND SHEAR
WILL CONTINUE TO INCREASE AS THE SYSTEM TRACKS NORTHWARD TOWARD THE
UPPER-LEVEL JET, RESULTING IN A WEAKENING PERIOD STARTING AT TAU
48. TD 18W WILL FULLY DISSIPATE BY TAU 72.
MODEL DISCUSSION: THE JTWC MULTI-MODEL CONSENSUS MEMBERS ARE IN
GOOD AGREEMENT IN THE FIRST 24 HOURS OF THE FORECAST
PERIOD WITH A CROSS-TRACK SPREAD OF 50NM. HOWEVER, THE SPREAD
INCREASES SIGNIFICANTLY AFTER TAU 24 TO 350NM BY TAU 72.
BIFURCATION BY THE END OF THE FORECAST CONTRIBUTES TO LOW CONFIDENCE
IN THE JTWC TRACK FORECAST. THE UKMET AND ECMWF ENSEMBLE TRACKERS
CURVE TO THE NORTHWEST AFTER TAU 24, WHILE GFS, GEFS, NAVGEM, AND
ECMWF ALL CURVE TO THE NORTHEAST. THE JTWC TRACK CURVES
NORTHEASTWARD BASED ON THE CURRENT DEEP-LAYER RIDGE TO THE EAST
DRIVING THE STORM NORTHWARD AND THEN NORTHEASTWARD. THE JTWC
INTENSITY GUIDANCE IS IN GOOD AGREEMENT, REPRESENTING PEAK
INTENSITIES BETWEEN 25-35KTS BETWEEN TAU 24-36. AFTERWARDS, THE
INTENSITY GUIDANCE MEMBERS CONSISTENTLY REPRESENT WEAKENING,
LENDING TO HIGH CONFIDENCE IN THE INTENSITY FORECAST.
FORECAST CONFIDENCE:
TRACK 0 - 72 HR: LOW
INTENSITY 0 - 72 HR: HIGH//
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楼主: yhh
发表于 2025-8-20 04:10
