By PDC’s Senior Weather
Specialist Glenn James
Tropical cyclone 21S (Charlotte), is located approximately 412 NM west-northwest of Learmonth, Australia – Final Warning
According to the JTWC Warning number 15 sustained winds were 35 knots with gusts to near 45 knots.
Satellite imagery shows a weakening system as evidenced by a warming central convection and
unraveling feeder bands.
Analysis indicates an unfavorable environment with strong poleward outflow and warm sea surface temperatures offset by moderate to strong westerly vertical wind shear. The cyclone is tracking along the northwest periphery of the deep layer ridge to the southeast.
TC Charlotte will continue southwestward under the steering influence of the ridge. After 24 hours, it will round the ridge axis and track more southward then southeastward on the poleward side of the ridge.
The environment is expected to become more unfavorable with increasing vertical wind shear, influx of low level dry air, and cooling sea surface temperatures, continuing the gradual deterioration.
Concurrently, by 48 hours, the system will begin subtropical transition and by 72 hours will transform into a gale-force, 40-knot subtropical system with an expanding wind field.