Weekly Tropical Climate Note

ENSO neutral, but 50% chance of El Niño developing

The El Niño–Southern Oscillation (ENSO) remains neutral—neither El Niño nor La Niña. However, warming in the tropical Pacific Ocean and recent model outlooks suggest an increased likelihood of El Niño developing during the Australian spring. As a result, the Bureau's ENSO Outlook is at El Niño WATCH, meaning there is roughly a 50% chance of El Niño developing later in the year (double the climatological average). Much of Queensland and the Northern Territory typically experiences drier than average conditions in the lead up to, and early part of, the northern wet season (October to April) during El Niño.

See the Bureau's current ENSO Wrap-Up for more information.

Madden–Julian Oscillation likely to move over western Pacific Ocean and weaken

Cloudiness and rainfall has been enhanced over parts of South-East Asia and the north western tropical Pacific Ocean this past week. This is likely associated with a moderate to strong eastward moving pulse of the Madden–Julian Oscillation (MJO) which has been detected over these regions during this period.

Most international climate models indicate the MJO will continue its eastward progression into the Western Pacific and weaken. Before weakening, it could increase the likelihood of cloudiness and rainfall over the northwestern tropical Pacific Ocean and increase the risk of tropical cyclone development in this region.

The MJO generally has little effect on Australian climate at this time of year. See the Bureau's current MJO monitoring for more information.

An increase in cloudiness over the Indian subcontinent this past week indicated that some regions experienced an active monsoon this past week. Check the India Meteorological Department website for information about the Indian Monsoon.

Tropical cyclone activity continues over western north Pacific region

The Madden–Julian Oscillation also contributed to ongoing tropical cyclone activity across the western north Pacific Ocean this past week. The very intense typhoon Maria formed in the northwest Pacific on the 8 July and peaked at a maximum intensity equivalent to a category 5 tropical cyclone in Australia. Maria later weakened as it moved north westward, and made landfall on the eastern Chinese coast on 11 July at a strength comparable to an Australia category 3 system. Maria weakened rapidly to below tropical cyclone strength after crossing the Chinese coast, but generated heavy rainfall across Japan's southern Ryukyu Islands, northern Taiwan and parts of eastern China during its passage. Maria was an especially notable tropical typhoon due to its rapid intensification. Analysis by the United States Joint Typhoon Warning Centre indicated Maria strengthened from a category 1 to a category 5 hurricane (or equivalent tropical cyclone intensity at http://www.bom.gov.au/cyclone/about/intensity.shtml) in the space of just 24 hours on 5 July—one of the fastest developing systems ever recorded.

Tropical cyclone Son-Tinh, which reached tropical cyclone strength in the northwest Pacific Ocean on 17 July, is expected to impact parts of the Philippines, the Chinese island of Hainan, and Vietnam in the coming days. See the Japanese Meteorological Agency for more information.