Tropical Cyclone Eighteen (18S) in Weak Steering Environment15S 101.9E
Tropical Cyclone Eighteen (18S), located approximately 1000 nm west-northwest of Learmonth, Australia, has tracked south-southeastward at 04 knots over the past six hours.
Animated multispectral satellite imagery shows the main convection remains detached from a fully exposed low level circulation that has become more elongated and irregular, making it difficult to pinpoint the center. The initial position is based on the above animation with poor confidence. The initial intensity, assessed higher than multi-agency subjective Dvorak estimates, is extrapolated from recent scatterometer data. Upper level analysis indicates the system is in an area of strong (30-40 knot) easterly vertical wind shear (VWS).
The cyclone is currently in a weak steering environment between the near-equatorial ridge (NER) to the north and a subtropical ridge (STR) to the south resulting in a very slow eastward drift. It is expected to remain in this state over the next 48 hours until the STR recedes to the east. At that stage, the NER will rebuild and resume steering and track the cyclone faster eastward.