BOM: Renewed warming in the tropical Pacific Ocean

BOM, 3 March 2015

The Bureau’s ENSO Tracker has been upgraded to El Niño WATCH. This is due to a combination of warmer-than-average temperatures in the tropical Pacific Ocean and models showing that further warming is likely in coming months. El Niño WATCH indicates about a 50% chance of El Niño forming in 2015.

The central to western regions of the tropical Pacific Ocean have warmed by 0.2 °C to 0.3 °C over the past fortnight, while monthly sub-surface temperatures were more than 2 °C above average over a large area for February. This is largely the result of weakened trade winds and tropical surface currents in recent weeks. Weakened trade winds are forecast to continue, and this may induce further warming.

All international models surveyed by the Bureau indicate that central tropical Pacific sea surface temperatures (SSTs) are likely to remain warmer than average, but within the neutral range, until at least May. By mid-year, six of the eight models indicate SSTs will exceed El Niño thresholds. However, accuracy of forecasts made at this time are lower than those at other times of the year, and hence some caution should be exercised.

El Niño is often associated with below-average winter–spring rainfall over eastern Australia and above-average daytime temperatures over the southern half of Australia.