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JTWC/04W/#39/04-16 12Z Prognostic Reasoning
WDPN31 PGTW 181500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (SINLAKU) WARNING NR
039//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
INITIAL POSITION: 24.3N 147.5E
INITIAL INTENSITY: 60 KTS
GEOGRAPHIC REFERENCE: 340 NM EAST OF IWO TO
MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 12 KTS
SIGNIFICANT WAVE HEIGHT: 30 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) O4W (SINLAKU) CONTINUES TO DETERIORATE WHILE
TRAVERSING POLEWARD. ANIMATED SHORTWAVE INFRARED (SWIR) SATELLITE
IMAGERY DEPICTS A SYMMETRIC LOW LEVEL CIRCULATION CENTER (LLCC), WITH
THE WESTERN SEMICIRCLE FULLY EXPOSED, CONSTRAINING WEAK CONVECTION
AND MID-LEVEL CLOUD COVER TO THE EASTERN SEMICIRCLE. SWIR AND
ANIMATED WATER VAPOR IMAGERY INDICATE DIFFLUENT UPPER-LEVEL OUTFLOW
DIRECTED INTO THE ENTRANCE REGION OF A 130KT MID-LATITUDE JET STREAM
TO THE NORTHEAST. THE DISTAL END OF A WEAKENING FRONTAL BOUNDARY IS
ALSO EVIDENT TO THE EAST-NORTHEAST OF THE LLCC. LOW-LEVEL
STRATOCUMULUS IS ADVECTING SOUTHWARD ALONG THE WESTERN FLANK AND
RECURVING INTO THE SOUTHERN PERIMETER, INDICATING ENTRAINMENT OF A
SUBSIDENT, STABLE AIR MASS. COINCIDENT ASCAT-B AND ASCAT-C PASSES AT
181021Z AND 181056Z REVEALED A WELL-DEFINED LLCC, WITH 55 KNOT WINDS
OBSERVED IN THE NORTHWEST AND SOUTHEAST QUADRANTS, CONSTITUTING A
TYPICAL BOWTIE SIGNATURE, SURROUNDED BY AN EXTENSIVE REGION OF GALE-
FORCE WINDS. THIS MULTI-PLATFORM SCATTEROMETRY DATA LENDS HIGH
CONFIDENCE TO BOTH THE INITIAL POSITION AND INTENSITY. ENVIRONMENTAL
CONDITIONS REMAIN UNFAVORABLE; VERTICAL WIND SHEAR (VWS) HAS INCREASED
BEYOND 25 KNOTS, SEA SURFACE TEMPERATURES (SST) ARE DECLINING RAPIDLY,
AND DRY MID-LEVEL AIR IS EXPANDING INTO THE VORTEX CORE. WHILE
POLEWARD OUTFLOW REMAINS ROBUST, IT IS INSUFFICIENT TO MITIGATE THESE
DETRIMENTAL ENVIRONMENTAL FACTORS.
INITIAL WIND RADII BASIS: SCATTEROMETER DATA
CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
PGTW: T3.0 - 45 KTS
RJTD: T3.0 - 45 KTS
RCTP: T3.0 - 45 KTS
KNES: T3.0 - 45 KTS
CIMSS ADT: 35 KTS AT 181140Z
CIMSS AIDT: 36 KTS AT 181140Z
CIMSS D-PRINT: 53 KTS AT 181140Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
VWS: 25-30 KTS
SST: 24-25 CELSIUS
OUTFLOW: STRONG POLEWARD
OTHER FACTORS: DRY AIR ENTRAINMENT ALONG THE WESTERN FLANK.
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: TS 04W IS COMMENCING A NORTHEASTWARD
ACCELERATION AS A TRANSIENT MID-LATITUDE ANTICYCLONE MOVES EASTWARD,
RE-ESTABLISHING THE STR TO THE SOUTHEAST AS THE DOMINANT STEERING
INFLUENCE. OVER THE NEXT 48 HOURS, THE STR WILL REPOSITION
SOUTHWESTWARD TOWARDS GUAM. THE REMNANT FRONTAL BOUNDARY LOCATED
NORTHEAST OF TS 04W WILL SIMULTANEOUSLY MIGRATE NORTHWARD WHILE
ELONGATING ZONALLY. TS 04W WILL UNDERGO RAPID RECURVATURE TO AN
EASTWARD TRAJECTORY BY THE END OF THE PERIOD, INFLUENCED BY THE STR
TO THE SOUTHEAST AND FLOW ALONG THE FRONTAL INTERFACE. FORWARD SPEED
IS ANTICIPATED TO STEADILY INCREASE. THE SYSTEM WILL COMMENCE
EXTRATROPICAL TRANSITION (ETT) WITHIN THE NEXT 24 HOURS, EVOLVING
INTO A STRONG GALE-FORCE POST-TROPICAL LOW BETWEEN TAU 36 AND TAU 48.
DESPITE MARGINAL SSTS AND INTENSE WESTERLY SHEAR, TS 04W HAS
MAINTAINED INTENSITY THROUGH MOMENTUM CONSERVATION. SUBSEQUENTLY, THE
SYSTEM WILL GRADUALLY DECAY THROUGH TAU 36. POST-TAU 36, BAROCLINIC
FORCING IS EXPECTED TO FACILITATE INTENSITY MAINTENANCE THROUGH THE
COMPLETION OF ETT.
MODEL DISCUSSION: TRACK GUIDANCE REMAINS STABLE AND EXHIBITS MINIMAL
CROSS-TRACK UNCERTAINTY, WITH CONSENSUS SPREAD CONFINED TO A 100NM
ENVELOPE AT TAU 48. ALONG-TRACK UNCERTAINTY IS ELEVATED (190NM
SPREAD), TYPICAL OF RECURVATURE SCENARIOS. GFS-INITIALIZED AI
GUIDANCE PERSISTS AS THE POLEWARD AND FASTEST EXTREME, WHILE EGRR
REMAINS THE EQUATORWARD AND SLOWEST OUTLIER. THE JTWC FORECAST IS
ALIGNED WITH THE ECMWF AND EXPERIMENTAL AI TRACKERS WITH HIGH
CONFIDENCE. INTENSITY GUIDANCE REMAINS MIXED; SHIPS INDICATES RAPID
DISSIPATION, WHEREAS GFS, HAFS-A, HWRF, AND AI-BASED MODELS DEPICT A
MORE GRADUAL DECAY. NOTABLY, SEVERAL DYNAMICAL MODELS SUGGEST SLIGHT
RE-INTENSIFICATION AFTER TAU 36 AS THE VORTEX INTERACTS WITH THE
BAROCLINIC ZONE. THE JTWC FORECAST IS POSITIONED NEAR THE HAFS-A
SOLUTIONS WITH HIGH CONFIDENCE.
FORECAST CONFIDENCE:
TRACK 00-72 HR: HIGH
INTENSITY 00-72 HR: HIGH//
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楼主: ygsj24
发表于 2026-4-18 21:30
