Tropical Cyclone Wallace looks likely to develop either Friday night or Saturday morning North of the Kimberley in WA waters. This will make Wallace the 8th tropical cyclone of the 2018-19 season, very close to what we predicted back in September.
A large cluster of thunderstorms is continuing to develop along a weak monsoon located between Australia and Indonesia / Papua New Guinea. This cluster of thunderstorms has consolidated over the past 24-36 hours with a weak tropical low now located (Invest 97S) active. Over the next 24 hours, this tropical low is forecast to become more defined and tighten along the monsoon trough as it drifts West to South West into a more favourable environment.
Models remain in agreement that tropical cyclone formation (where Wallace will be named) seems likely either later on Friday or early on Saturday with the system at this stage located over the North East Indian Ocean. From there, models are tending to agree on the strength with the system intensifying into either a high-end Category 2 or low-end Category 3 system. The impacts of Wallace over WA will be highly reliant on what happens with a large high pressure region moving across the Southern half of AUS.
A high is expected to move across the Southern half of WA during the weekend, with another high trailing in about 3-4 days later. Wallace is likely to squeeze between these 2 high’s and ‘make landfall’ somewhere over WA, but the timing of that interaction is vital. If Wallace follows the ECMWF track which has a slower moving high, then its not expected to make landfall until its an Ex-TC which could be anywhere from Exmouth to Perth down the West Coast. If Wallace follows the GFS track which has a slightly faster moving high, then the channel between high’s which Wallace can turn towards the Coast will happen sooner and this could pose a threat for areas from Shark Bay to Karratha which would also mean Wallace should be a Category 2 or 3 system as it makes landfall, not an Ex-TC.
Other models are differing also which doesn’t make the long term tracking any easier.. but we are confined that Wallace will at least be named either Friday or Saturday, and a landfall as either an Ex-TC or TC seems probable at some stage next week.