Tropical Cyclone Eighteen (18S) Becoming Better Organized15.7S 101.2E
Tropical Cyclone Eighteen (18S), located approximately 120 nm southeast of Cocos Island, Australia, has tracked south-southeastward at 06 knots over the past six hours. Maximum significant wave height is 11 feet.
Animated multispectral satellite imagery depicts an exposed but well-defined low-level circulation center with deep convection sheared about 45 nm west of the center due to strong easterly vertical wind shear (VWS).
TC 18S has continued to struggle due to the poor upper-level environment, however, an AMSU image indicates better organized shallow banding wrapping into a well-defined LLCC. An ASCAT image showed 40 to 45 knot winds over the north quadrant and surface observations from Cocos Island have remained steady at 30 to 35 knots sustained with gusts to 40 to 50 knots.
The initial intensity is assessed at 40 knots, slightly higher than Ddvorak intensity estimates of 35 knots, based on the ASCAT image. There is good confidence in the initial position based on the exposed center in visible imagery.
TC 18S is forecast to track eastward under the steering influence of the near- equatorial ridge through the forecast period. Dynamic model guidance is in fair agreement, therefore, the JTWC forecast is positioned close to the multi-model consensus. TC 18S is expected to slowly intensify through TAU 120 due to persistent moderate to strong VWS. Due to the marginal environment, there is uncertainty in the extended intensity forecast, which may be significantly lower than the 60 knots currently forecast to occur near TAU 120. There is low confidence in the JTWC forecast track due to the sheared nature of the system and large differences in model track speed throughout the forecast.