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WTPQ31 RJTD 290600

RSMC TROPICAL CYCLONE PROGNOSTIC REASONING

REASONING NO.13 FOR TS 2417 JEBI (2417)

1.GENERAL COMMENTS

  TS JEBI IS LOCATED AT 23.8N, 141.5E. INFORMATION ON THE CURRENT

  POSITION IS BASED ON ANIMATED MSI AND SURFACE OBSERVATIONS.

  POSITIONAL ACCURACY IS FAIR. CENTRAL PRESSURE IS 1000HPA AND

  MAXIMUM SUSTAINED WINDS NEAR THE CENTER ARE 40KNOTS. THE SYSTEM IS

  IN A NEUTRAL ENVIRONMENT FOR DEVELOPMENT UNDER THE INFLUENCE OF

  HIGH SSTS, HIGH TCHP, WEAK VWS AND DRY AIR. THIS HAS CAUSED THE

  SYSTEM TO MAINTAIN ITS INTENSITY OVER THE LAST SIX HOURS.

  INFORMATION ON THE CURRENT INTENSITY IS BASED ON DVORAK INTENSITY

  ANALYSES AND SURFACE OBSERVATIONS.

2.SYNOPTIC SITUATION

  THE SYSTEM IS MOVING NORTH-NORTHWESTWARD ALONG THE SOUTHWESTERN

  PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH. ANIMATED MSI SHOWS CB

  CLUSTERS HAVE GATHERED AROUND THE CSC. ANIMATED MSI SHOWS THE

  CLOUD CHARACTERISTICS OF ANTICYCLONIC OUTFLOW ARE NOW DISTINCT.

  WATER VAPOR IMAGERY SHOWS DRY AIR IN THE DIRECTION OF THE

  MOVEMENT. NOAA-20/ATMS 85 GHZ MICROWAVE IMAGERY SHOWS THE SYSTEM

  HAS ACTIVE CONVECTIVE CLOUD CLUSTERS AROUND THE CSC.

3.TRACK FORECAST

  THE SYSTEM WILL MOVE NORTHWARD ALONG THE PERIPHERY OF A MID-LEVEL

  SUB-TROPICAL HIGH UNTIL FT24. THE SYSTEM WILL THEN MOVE NORTHWARD

  UNDER THE INFLUENCE OF A MID-LATITUDE TROUGH UNTIL FT48. THE

  SYSTEM WILL THEN GRADUALLY ACCELERATE AND MOVE NORTH-NORTHEASTWARD

  UNDER THE INFLUENCE OF MID-LATITUDE PREVAILING WESTERLIES UNTIL

  FT72. THE TRACK FORECAST IS BASED ON GSM PREDICTIONS, AND

  REFERENCE TO OTHER NWP MODELS. TRACK FORECAST CONFIDENCE IS LOW

  DUE TO SIGNIFICANT DIFFERENCES AMONG NWP MODEL OUTPUTS.

4.INTENSITY FORECAST

  THE SYSTEM WILL DEVELOP UNTIL FT48 DUE TO THE INFLUENCE OF

  INTERACTION WITH HIGH SSTS, HIGH TCHP AND WEAK VWS. THE SYSTEM

  WILL THEN WEAKEN UNTIL FT72 DUE TO THE INFLUENCE OF INTERACTION

  WITH LOWER SSTS AND REDUCED TCHP. THE SYSTEM WILL TRANSFORM INTO

  AN EXTRATROPICAL CYCLONE BY FT72. THE INTENSITY FORECAST IS BASED

  ON A CONSENSUS OF GUIDANCE DATA INCLUDING GSM.

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