WTPQ30 RJTD 081200
RSMC TROPICAL CYCLONE PROGNOSTIC REASONING
REASONING NO.17 FOR TY 2014 CHAN-HOM (2014)
1.GENERAL COMMENTS
TY CHAN-HOM IS LOCATED AT 29.5N, 133.4E. INFORMATION ON THE
CURRENT POSITION IS BASED ON ANIMATED MSI AND SURFACE
OBSERVATIONS. POSITIONAL ACCURACY IS GOOD. CENTRAL PRESSURE IS
965HPA AND MAXIMUM SUSTAINED WINDS NEAR THE CENTER ARE 70KNOTS.
THE SYSTEM IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT UNDER THE
INFLUENCE OF HIGH SSTS AND GOOD UPPER-LEVEL OUTFLOW. THIS HAS
CAUSED THE SYSTEM TO DEVELOP 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-NORTHEASTWARD ALONG THE NORTHWESTERN
PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH. ANIMATED MSI SHOWS A
BAND SPIRALING AROUND THE EYE BY AT LEAST 360 DEGREES. ANIMATED
MSI SHOWS GOOD CLOUD CHARACTERISTICS OF ANTICYCLONIC OUTFLOW.
WATER VAPOR IMAGERY SHOWS DRY AIR IN THE DIRECTION OF THE
MOVEMENT. DMSP-F17/SSMIS 89 GHZ MICROWAVE IMAGERY SHOWS THE SYSTEM
HAS A BAND WITH CURVATURE INDICATING THE CSC.
3.TRACK FORECAST
THE SYSTEM WILL GRADUALLY TURN TO THE NORTHEAST ALONG THE
PERIPHERY OF A MID-LEVEL SUB-TROPICAL HIGH UNTIL FT24. THE SYSTEM
WILL THEN GRADUALLY ACCELERATE AND MOVE EAST-NORTHEASTWARD UNDER
THE INFLUENCE OF MID-LATITUDE PREVAILING WESTERLIES UNTIL FT96.
THE TRACK FORECAST IS BASED ON GSM PREDICTIONS, AND REFERENCE TO
OTHER NWP MODELS. TRACK FORECAST CONFIDENCE IS FAIR UNTIL FT48 BUT
LOW THEREAFTER DUE TO SIGNIFICANT DIFFERENCES AMONG NWP MODEL
OUTPUTS.
4.INTENSITY FORECAST
THE SYSTEM WILL MAINTAIN ITS INTENSITY UNTIL FT24 DUE TO THE
INFLUENCE OF INTERACTION WITH GOOD UPPER LEVEL OUTFLOW AND
INCREASED VWS. THE SYSTEM WILL THEN WEAKEN UNTIL FT96 DUE TO THE
INFLUENCE OF INTERACTION WITH LOWER SSTS, REDUCED TCHP AND
INCREASED VWS. THE SYSTEM WILL TRANSFORM INTO AN EXTRATROPICAL
CYCLONE BY FT96. THE INTENSITY FORECAST IS BASED ON GSM
PREDICTIONS.
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