WTPQ30 RJTD 081800
RSMC TROPICAL CYCLONE PROGNOSTIC REASONING
REASONING NO. 4 FOR TS 2021 ETAU (2021)
1.GENERAL COMMENTS
A TD PREVIOUSLY LOCATED AT 12.7N, 118.2E HAS BEEN UPGRADED TO TS
(ETAU) STATUS. TS ETAU IS LOCATED AT 13.0N, 115.4E. INFORMATION ON
THE CURRENT POSITION IS BASED ON ANIMATED MSI. POSITIONAL ACCURACY
IS FAIR. CENTRAL PRESSURE IS 998HPA AND MAXIMUM SUSTAINED WINDS
NEAR THE CENTER ARE 35KNOTS. THE SYSTEM IS IN A FAVORABLE
ENVIRONMENT FOR DEVELOPMENT UNDER THE INFLUENCE OF HIGH SSTS AND
WEAK VWS. THIS HAS CAUSED THE SYSTEM TO DEVELOP OVER THE LAST SIX
HOURS. INFORMATION ON THE CURRENT INTENSITY IS BASED ON DVORAK
INTENSITY ANALYSES.
2.SYNOPTIC SITUATION
THE SYSTEM IS MOVING WESTWARD ALONG THE SOUTHERN PERIPHERY OF A
MID-LEVEL SUB-TROPICAL HIGH. ANIMATED MSI SHOWS CB CLUSTERS
GATHERING AROUND THE CSC AND STARTING TO FORM A CURVED BAND.
ANIMATED MSI SHOWS THE CLOUD CHARACTERISTICS OF ANTICYCLONIC
OUTFLOW ARE NOW DISTINCT.
3.TRACK FORECAST
THE SYSTEM WILL MOVE WESTWARD ALONG THE PERIPHERY OF A MID-LEVEL
SUB-TROPICAL HIGH UNTIL FT48. THE SYSTEM WILL HIT VIET-NAM BY
FT48. THE TRACK FORECAST IS BASED ON GSM PREDICTIONS, AND
REFERENCE TO OTHER NWP MODELS. TRACK FORECAST CONFIDENCE IS FAIR
UNTIL FT24 BUT LOW THEREAFTER DUE TO SIGNIFICANT DIFFERENCES AMONG
NWP MODEL OUTPUTS.
4.INTENSITY FORECAST
THE SYSTEM WILL DEVELOP UNTIL FT24 DUE TO THE INFLUENCE OF
INTERACTION WITH WEAK VWS AND GOOD UPPER LEVEL OUTFLOW. THE SYSTEM
WILL THEN WEAKEN UNTIL FT48 DUE TO ITS LANDFALL. THE SYSTEM WILL
WEAKEN TO TD INTENSITY BY FT48. THE INTENSITY FORECAST IS BASED ON
GUIDANCE DATA.
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