An El Nino may form this winter as tropical Pacific Ocean sea surface temperatures continue to climb, the Bureau of Meteorology says.

The bureau examines sea surface temperatures and atmospheric conditions in monitoring the El Nino Southern Oscillation.

“All models, including the bureau’s, forecast the tropical Pacific to continue warming in the coming months, reaching El Nino thresholds later in the year,” it says in an update.

“There is some variation across models in the rate at which El Nino thresholds may be reached, with some suggesting development as early as May while others show a slower warming with thresholds not being met until July.”

Forecasts range from a weak-to-moderate event to a strong El Nino, based on central tropical Pacific warming.

The bureau says a strong El Nino does not necessarily mean significant Australian climate impacts, and it is just one of many factors that can influence seasonal conditions.

The update adds that most models indicate the Indian Ocean Dipole (IOD) is likely to remain neutral until the end of autumn but may turn positive during winter to spring.

“Some models suggest it could develop earlier, in late autumn. However, forecast uncertainty associated with the IOD is currently high, with models showing a large spread of possible outcomes.”

An El Nino and positive IOD are historically associated with an increased chance of drier weather in eastern Australia.