Tropical Storm NEPARTAK Advisory 7月26日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NEPARTAK) WARNING
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 32.9N 150.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 546 NM EAST-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A CLASSIC
SUBTROPICAL CYCLONE WITH A BROAD SWATH OF CONVECTION CURLING INTO A
WIDE AND ELONGATED CIRCULATION WITH AT LEAST THREE EMBEDDED
VORTICES. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE ON THE
CENTROID OF THESE VORTICES. THE INITIAL INTENSITY OF 35KTS IS BASED
ON PATCHES OF 35-KT WIND BARBS DEPICTED IN RECENT SCATTEROMETRY
PASSES OVER 100NM AWAY FROM THE CENTROID AND UNDER THE SWATH OF
CONVECTION. ALTHOUGH NOT REPRESENTATIVE OF THE STORM POSITION, THE
INITIAL INTENSITY IS SUPPORTED BY THE PGTW DVORAK AND THE ADT
AUTOMATED FIXES.
INITIAL WIND RADII BASIS: PERSISTENCE, ADJUSTED FROM RECENT
SCATTEROMETER DATA.
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 251740Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 30+ KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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.
FORECAST DISCUSSION: SUBTROPICAL CYCLONE 11W WILL TRACK
NORTHWESTWARD UNDER THE STEERING STR ON A PINWHEEL PATTERN AROUND
AN UPPER LEVEL LOW TO THE SOUTHWEST, MAKING LANDFALL OVER NORTHERN
HONSHU NEAR KASENNUMA, JAPAN, AROUND TAU 48. THE MARGINAL
ENVIRONMENT - STRONG VWS OFFSET BY STRONG POLEWARD OUTFLOW AND WARM
SST - WILL FUEL A SLIGHT INTENSIFICATION TO 40KTS AT TAUS 24-36.
AFTERWARD, THE UPPER LEVEL WILL COME INTO PROXIMITY AND PROMOTE
SUBSIDENCE ALOFT AND INDUCE THE INFLOW OF COLD DRY AIR IN THE LOWER
LEVELS. THESE AND THE TOPOGRAPHICAL EFFECTS AFTER LANDFALL WILL
ERODE THE SYSTEM DOWN TO 30KTS AFTER IT EXITS INTO THE SEA OF JAPAN
(SOJ). THE COOLER SSTS IN THE SOJ PLUS A SECONDARY LANDFALL INTO
HOKKAIDO AFTER THE SYSTEM RECURVES NORTHEASTWARD AROUND THE STR
AXIS WILL FURTHER ERODE 11W TO DISSIPATION BY TAU 120.
MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL GOOD AGREEMENT
WITH AEMN THE LEFT OUTLIER IN THE EXTENDED PERIOD CURLING THE
VORTEX SOUTHWARD IN THE SOJ. GIVEN THE BROAD COMPLEXITY OF A
SUBTROPICAL CYCLONE AND THE UNCERTAINTY OF A LAND PASSAGE, THERE IS
MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS UP TO
TAU 72, THEN LOW CONFIDENCE AFTERWARD.
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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