Weekly Tropical Climate Note
Negative Indian Ocean Dipole and La Niña-like pattern continues
In the Indian Ocean, the negative Indian Ocean Dipole (IOD) has weakened from its peak but continues to influence the climate of northern Australia. Models predict the IOD will return to neutral by November or December. During a negative IOD event rainfall across northern Australia is typically above average from September to November, with warmer daytime and night-time temperatures usually observed.
In the tropical Pacific Ocean, although the El Niño–Southern Oscillation (ENSO) remains neutral, the ocean and atmospheric display some patterns typically associated with La Niña. In particular, the ocean to the north and east of Australia is warmer than usual. The majority of international climate models monitored by the Bureau indicate the tropical Pacific is likely to remain at ENSO-neutral levels in the coming months. However, two models indicate weak La Niña levels will be reached, hence, the ENSO Outlook remains at La Niña WATCH. Even if La Niña thresholds are not met, the warmer water to the north of Australia means La Niña-like impacts are possible. During La Niña, northern Australia typically experiences above-average wet season rainfall, with the first rains of the season typically arriving earlier than normal.
See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and IOD information.
Average to above-average tropical activity for 2016-17 in Australian region
The 2016-17 tropical cyclone outlook for Australia predicts an average to above-average number of cyclones for the Australian tropical cyclone season (November–April). La Niña years are typically associated with above-average tropical cyclone numbers, and an earlier-than-normal date for the first cyclone to impact Australia.
Tropical activity continues in northwest Pacific Ocean
After two powerful typhoons affected the northwest Pacific region last week, a further two typhoons have developed in the area, typhoons Sarika (Karen) and Haima (Lawin).
Typhoon Sarika (Karen) is expected to make landfall at Hainan today, before a second landfall near the Vietnam-China border in the next 48 hours. Prior to these encounters, Sarika (Karen) caused significant damage and disruption to the northern and central Philippines where it made landfall on 16 October. Sarika (Karen) is expected to impact Hainan as a ‘strong’ typhoon with estimated wind speeds near the storm’s centre in excess of 135 km/h.
To the east of the Philippines is typhoon Haima (Lawin). It is tracking to the west and is expected to impact the northern Philippines in the next 48 to 72 hours with winds near the storm’s centre in excess of 200 km/h. Warnings and information on these systems can be found at the Japan Meteorological Agency website.
The recent tropical activity in the northwest Pacific Ocean brings the number of tropical storms or typhoons since the start of September to eleven (average number for September to October is between eight and nine). The tropical activity is occurring without the influence of a discernible Madden–Julian Oscillation (MJO) signal in the last week. Other tropical wave activity and the very warm waters in the region, combined with a persistent monsoon trough, are likely to be the main climate drivers responsible for the recent activity.
Most international climate models predict that the MJO will remain weak or indiscernible in the coming week, although one or two of the models surveyed by the Bureau of Meteorology predict the MJO will move into the western Pacific Ocean and strengthen slightly.
See the Bureau's MJO Monitoring for current MJO information.
Product code: IDCKGEW000