Weekly Tropical Climate Note
Ex-tropical cyclone Alfred briefly in the Gulf of Carpentaria
Tropical cyclone Alfred became only the second named storm in the Australian region so far this season. In the lead up to Alfred's formation, a monsoon trough was active across Australia, with heavy rainfall affecting northwestern Australia ahead of the focus moving to the Gulf of Carpentaria region in the last week. Alfred began as a tropical low over the Carpentaria region of the Northern Territory about a week ago and reached tropical cyclone strength on the 20th after moving over water. By the morning of the 21st Alfred had weakened to a tropical low as it moved towards the coast near the Queensland-Northern Territory border. At its peak, tropical cyclone Alfred sustained winds near its centre of at least 85 km/h, with gusts to 120 km/h. The rain bands associated with the storm caused heavy rainfall and strong winds in the Gulf coast region, including over 460 mm at Centre Island and over 300 mm at Borroloola, both in the Northern Territory. Ex-tropical cyclone Alfred is expected to continue to weaken and track westward over the Northern Territory over the next few days.
So far, this tropical cyclone season has been surprisingly quiet. The Australian region typically sees around 11 named storms in an average season. A quiet season so far is no reason to become complacent. Tropical cyclones present a real risk for tropical northern Australia. The tropical cyclone season runs through the end of April and usually peaks near the end of February and early March.
Madden-Julian Oscillation weakens to moderate strength
After maintaining relatively high amplitude for nearly all of February, the Madden-Julian Oscillation (MJO) signal has recently weakened towards more moderate values. An MJO pulse is currently tracking eastward over the tropical western hemisphere and Africa region at moderate strength. Usually when the MJO is in that part of the world at this time of year, northern Australia and the Maritime Continent sees suppressed tropical convection, below average rainfall, and a decreased risk in tropical cyclone development. Tropical cyclone Alfred is an example of a tropical cyclone forming despite a less favourable broadscale environment.
The MJO is expected to continue its eastward progress over the next two weeks. However, models do not agree on the strength of the MJO as it crosses the Indian Ocean. Some models predict the signal to weaken completely before reaching Australian longitudes, while other models maintain a weak to moderate signal for the next two weeks while over the Indian Ocean.
For more information on the MJO, see the Bureau's current MJO monitoring information.
El Niño–Southern Oscillation remains neutral
The El Niño–Southern Oscillation (ENSO) remains neutral, with virtually all indicators close to their average values. In recent weeks, the central and eastern tropical Pacific Ocean has warmed at the surface, with most climate models suggesting this warming is likely to continue during the southern autumn.
However, this is the time of year when both ENSO and climate models have greatest variability. Some caution must be taken when using recent conditions, such as central Pacific warming, to determine likely conditions later in the year. This means either neutral or El Niño are the most likely ENSO state for the southern winter/spring.
See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and Indian Ocean Dipole information.
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