WTPQ30 RJTD 061200
RSMC TROPICAL CYCLONE PROGNOSTIC REASONING
REASONING NO. 9 FOR STS 2014 CHAN-HOM (2014)
1.GENERAL COMMENTS
STS CHAN-HOM IS LOCATED AT 24.3N, 137.6E. INFORMATION ON THE
CURRENT POSITION IS BASED ON ANIMATED MSI. POSITIONAL ACCURACY IS
FAIR. CENTRAL PRESSURE IS 990HPA AND MAXIMUM SUSTAINED WINDS NEAR
THE CENTER ARE 50KNOTS. THE SYSTEM IS IN A FAVORABLE ENVIRONMENT
FOR DEVELOPMENT UNDER THE INFLUENCE OF HIGH SSTS, HIGH TCHP, WEAK
VWS AND GOOD UPPER-LEVEL OUTFLOW. THIS HAS CAUSED THE SYSTEM TO
DEVELOP OVER THE LAST SIX HOURS. HOWEVER, THE INFLUENCE OF DRY AIR
IS UNFAVORABLE FOR SYSTEM DEVELOPMENT. INFORMATION ON THE CURRENT
INTENSITY IS BASED ON SURFACE WINDS DATA ESTIMATED FROM SATELLITE
SCATTEROMETERS AND DVORAK INTENSITY ANALYSES.
2.SYNOPTIC SITUATION
THE SYSTEM IS MOVING SLOWLY WEST-NORTHWESTWARD DUE TO WEAK
STEERING FLOW. ANIMATED MSI SHOWS THE SYSTEM HAS A BAND WITH A
CURVATURE SUGGESTING THE CSC. ANIMATED MSI SHOWS GOOD CLOUD
CHARACTERISTICS OF ANTICYCLONIC OUTFLOW. WATER VAPOR IMAGERY SHOWS
DRY AIR IN THE DIRECTION OF THE MOVEMENT.
3.TRACK FORECAST
THE SYSTEM WILL MOVE WEST-NORTHWESTWARD ALONG THE PERIPHERY OF A
MID-LEVEL SUB-TROPICAL HIGH UNTIL FT24. THE SYSTEM WILL THEN
GRADUALLY DECELERATE AND MOVE NORTHWARD BETWEEN TWO MID-LEVEL
SUB-TROPICAL HIGHS UNTIL FT72. THE SYSTEM WILL THEN GRADUALLY
ACCELERATE AND MOVE EAST-NORTHEASTWARD ALONG THE PERIPHERY OF A
MID-LEVEL SUB-TROPICAL HIGH UNTIL FT120. 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 FT60 DUE TO THE INFLUENCE OF
INTERACTION WITH HIGH SSTS, HIGH TCHP, WEAK VWS AND GOOD UPPER
LEVEL OUTFLOW. THE SYSTEM WILL THEN WEAKEN UNTIL FT120 DUE TO THE
INFLUENCE OF INTERACTION WITH LOWER SSTS, REDUCED TCHP AND
INCREASED VWS. THE INTENSITY FORECAST IS BASED ON GUIDANCE DATA.
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