Tropical activity has recently increased over the western Indian Ocean, near Africa, and is likely to be linked to a Madden Julian Oscillation (MJO) event which has recently developed in the region. This past week has seen a steady continuation of the seasonal advance of the monsoon towards India, with the monsoon trough entering the southern Arabian Sea and moving further into the Bay of Bengal this week.
The arrival of the monsoon at Kerala indicates the official start of the monsoon over the Indian subcontinent. Based on the recent observations of monsoonal flow, the India Meteorological Department expects onset at Kerala in the next three to four days. The normal date of monsoon onset over Kerala is 1 June.
Climate models indicate the MJO event currently observed over the western Indian Ocean will move slowly eastwards across the tropical Indian Ocean this week and weaken. Some models indicate a weakened MJO will continue eastwards over southern Asia and Papua New Guinea next week, while others indicate the MJO will have weakened to the extent it becomes indiscernible by the time it reaches these longitudes. As the MJO moves across the Indian Ocean it is likely to enhance tropical activity, including increasing the likelihood of monsoon onset over the Indian subcontinent. It will also increase the likelihood of tropical cyclone development in the northern Indian Ocean this week.
The tropical Pacific Ocean remains on track for El Niño in 2014, with just over half of the climate models surveyed by the Bureau suggesting El Niño will become established by August. An El Niño ALERT remains in place, indicating at least a 70% chance of an El Niño developing in 2014.
Sea surface temperature (SST) anomalies in the tropical Pacific Ocean have increased steadily since February, and are now greater than +0.5 °C in the key NINO regions. However, above-average SSTs also extend into the western tropical Pacific, meaning strong west to east gradients in tropical Pacific SSTs are yet to become established. As a result, atmospheric indicators—such as the Southern Oscillation Index and trade winds—have only shown a weak response.
For Australia, El Niño is often associated with below-average rainfall over southern and eastern inland areas and above-normal daytime temperatures over southern parts of the continent. It is not uncommon to see some impacts prior to an event becoming fully established. May rainfall was below normal across parts of eastern Australia and maximum temperatures were above normal across much of the south and east. The Indian Ocean Dipole (IOD) is currently neutral. Model outlooks suggest the IOD is most likely to remain neutral through winter, with two of the five models surveyed suggesting a positive IOD may develop during spring. Positive IOD events often coincide with El Niño and are typically associated with large parts of southern and central Australia experiencing lower rainfall than usual.
Our ENSO Tracker provides up-to-date information on the likelihood of an El Niño or La Niña developing.
The status remains El Niño ALERT.
Next update expected on 17 June 2014 (Courtesy of Bureau of Metereology).