Weekly Tropical Climate Note
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Dry start to northern wet season likely
The Bureau's climate outlook indicates October to December rainfall is likely to be below average across much of northern Queensland and the Northern Territory. While the El Niño–Southern Oscillation (ENSO) is currently neutral, recent observations and model outlooks indicate a weak and short-lived El Niño remains possible in 2018. The Bureau's ENSO Outlook remains at El Niño WATCH, meaning there is approximately a 50% chance of El Niño forming in the coming months; double the normal chance.
The Indian Ocean Dipole (IOD) index has been above the positive IOD threshold of +0.4C for the last three weeks. Model outlooks suggest positive IOD index values are likely to continue through to late November or early December.
Reduced rainfall across northern Queensland and the Northern Territory in the early months of the wet season, which officially runs from October to April, is a typical response to both El Niño and a positive IOD. If a positive IOD occurs concurrently with El Niño, rainfall deficiencies typically associated with El Niño are generally exacerbated and more widespread.
See the Bureau's current ENSO Wrap-Up for more information.
Madden–Julian Oscillation strengthens over western hemisphere
A pulse of the Madden–Julian Oscillation (MJO) over the western hemisphere strengthened in recent days. Most international models forecast the MJO to remain close to its current strength for the coming week and track eastwards over American and African longitudes. This MJO pulse has coincided with reduced cloudiness and rainfall over a large area of the northern hemisphere, extending from India to the western North Pacific Ocean, and further weakening of the monsoon over the Indian subcontinent. Stronger-than-usual westerly winds have also developed over the tropical Pacific Ocean, something that could potentially assist El Niño development.
See the Bureau's current MJO monitoring for more information on the MJO.
Out-of-season southern hemisphere tropical cyclone
A tropical cyclone briefly developed near the Solomon Islands, well outside the normal tropical cyclone season for that region which runs from 1 November to 30 April. Tropical cyclone Liua was named by the Fijian Meteorological Service on 27 September, while just east of the Australian area of responsibility. It was downgraded to below tropical cyclone intensity on 29 September, before entering the Australian region. A tropical cyclone in this region is extremely rare at this time of the year, with just one instance of a possible cyclone in October 1952 being the closest candidate (a pre-satellite era storm without direct wind or pressure observations).
Tropical cyclone activity in the northern hemisphere
Typhoon Trami (Paeng) passed over Japan's Ryukyu Islands prior to making landfall on Japan's southern coast on 30 September at an intensity comparable to an Australian category 3 tropical cyclone. Wind gusts to 213 km/h were recorded as it moved over the Okinawa Islands. Heavy rainfall and storm surges were a feature over Japan's main southern islands, where significant flooding and major disruption to transport infrastructure occurred. A site in southern Japan reported rainfall in excess of 430 mm.
Typhoon Kong-rey currently lies to the east of the northern Philippines and is following a track similar to that of Trami (Paeng), moving in a north to northwesterly direction towards Japan's southern islands. The latest forecast indicates Kong-rey is comparable in strength to an Australian high-end category 4 tropical cyclone, but should weaken slightly before it passes over the Ryukyu Islands.
For tropical cyclones in the western North Pacific, warnings and information are issued by the Japanese Meteorological Agency.
Product code: IDCKGEW000