Weekly Tropical Climate Note

Issued 25 August 2015

Continued typhoon activity in the northern Pacific region

Typhoons Atsani and Goni (Ineng) continued to affect the northwestern Pacific Ocean this week. Atsani maintained typhoon strength last week as it moved northwest before weakening and moving to the northeast. Early this week Atsani weakened to tropical storm strength as it tracked northward into higher latitudes. Goni (Ineng) moved westward and delivered torrential rainfall to the northern Philippines before moving north-northeast and intensifying over the East China Sea. Typhoon Goni (Ineng) made landfall over Kyushu, southwest Japan, and maintained typhoon strength as it moved over the Sea of Japan on 25 August.

There are also presently two tropical systems in the central north Pacific Ocean. Tropical storm Loke is forecast to track northeast before turning to the northwest, intensifying briefly to hurricane strength tomorrow. Tropical depression Kilo is forecast to move north and strengthen to hurricane intensity later this week.

Madden-Julian Oscillation remains weak

The MJO has remained weak for several weeks now and is unlikely to have contributed significantly to tropical activity over this time. Most forecasts from international models show a likely continuation of a weak or indiscernible MJO. This means the MJO is unlikely to influence tropical weather this week.

In the situation of a weak MJO, tropical activity is often concentrated in areas of warm sea surface temperatures. The current number of Pacific tropical systems would indicate this is presently the case.

See the Bureau's MJO Monitoring for current MJO information.

2015 El Niño update

The 2015 El Niño continues to be the dominant climate driver in the Pacific. The latest weekly NINO3.4 sea surface temperature anomaly is +1.9 °C and the 30-day Southern Oscillation Index (SOI) value to 23 August is −22.0. The ocean and atmosphere are reinforcing each other, with tropical Pacific Ocean temperatures well above El Niño thresholds, consistently weakened trade winds, and a strongly negative SOI. Strong coupling of the tropical Pacific Ocean and atmosphere is typical of a mature El Niño, and suggests only a small chance of the event finishing before the end of the year.

See the Bureau of Meteorology's ENSO Wrap-Up for official El Niño information.

Next update expected by 1 September 2015 | Product Code IDCKGEW000

Further information

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