Weekly Tropical Climate Note

Issued 4 August 2015

Tropical Cyclones

It has been an active week for tropical cyclones, with activity in Bay of Bengal, the Philippine Sea, and both sides of the equator in the central Pacific region. Cyclonic storm Komen formed over the Bay of Bengal last week, impacting Bangladesh and later India, with widespread heavy rainfall causing flooding, damage to property and loss of life. Tropical storm Guillermo developed in the central Pacific Ocean last week and has moved steadily west-northwest in recent days. Guillermo is forecast to weaken as it approaches Hawaii in the coming days and is not expected to make landfall. Typhoon Soudelor, which developed rapidly north of Guam on 2 August, is currently moving west-northwest over the Philippine Sea and is forecast to maintain its category five strength until later in the week. A southern hemisphere tropical depression, about 1000 km northwest of Fiji, weakened yesterday and has a low chance of further development.

El Niño well established

The 2015 El Niño event is well established. The latest weekly NINO3.4 sea surface temperature anomaly is +1.7 °C and the 30-day SOI value to 2 August is −14.4. The weakened trade winds remain and contribute to the continued warming of the tropical Pacific Ocean. Cloudiness near the date line in the tropical Pacific Ocean is also consistent with El Niño. International climate models surveyed by the Bureau of Meteorology all indicate the El Niño will likely strengthen further, and persist into early 2016.

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

Madden-Julian Oscillation weak

During the last week, the Madden-Julian Oscillation (MJO) weakened over Africa&emdash;hence is unlikely to have contributed significantly to tropical activity this past week. International climate models suggest a weak to moderate MJO signal will reappear over the western tropical Pacific Ocean this week. However, it is possible that climate models are detecting an El Niño signal, rather than the MJO. If the MJO does reappear over the western Pacific Ocean, typical impacts at this time of year would include suppressed convection over the Indian Ocean and an increased chance of tropical activity over the northwest Pacific Ocean.

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

Next update expected by 11 August 2015 | Product Code IDCKGEW000

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