El Nino hot on trail of new record

A bushfire glows in the Blue Mountains region of Washington State in the US yesterday. Photo / AP

The present El Nino event, on the cusp of attaining "strong" intensity, has a chance to become the most powerful on record.

The event - defined by the expanding, deepening pool of warmer-than-normal ocean water in the tropical Pacific - has grown stronger since the northern spring.

The presence of a strong El Nino almost ensures 2015 will become the warmest on record and will have ripple effects on weather patterns all over the world.

In the Northern Hemisphere a strong El Nino would likely lead to enhanced rainfall in California, a quieter than normal Atlantic hurricane season, a warmer than normal winter over large parts of the US, and a very active hurricane and typhoon season in the Pacific.

Some of these effects have already manifested and will become particularly apparent in the second half of the year.

Frequent and persistent bursts of wind from the west, counter to the prevailing easterly direction, have helped this year's El Nino sustain itself and grow. Warm water from the western Pacific has sloshed eastward, piling up in the central and eastern basin.

The sprawling area of warm waters has proven a boon for Pacific tropical cyclone activity, causing near-record levels through the mid-northern summer. Through a positive feedback mechanism, these cyclones have likely helped reinforce the westerly push of warm waters, Slate's Eric Holthaus reported.

The 2015 El Nino event is now neck-and-neck with the record-setting event of 1997-1998 in terms of its mid-summer intensity.

That 1997-1998 event was notorious for its winter flash floods and mudslides in California.

Michael Ventrice, a Weather Company meteorologist, said the atmospheric footprint of this year's event - given the time of year - is statistically rare, with a less than one in 1000 chance of occurring.

Although the El Nino is still officially a "moderate" strength event, Tony Barnston, one of the world's leading El Nino experts, explained it could well become a "strong" event by the month's end.

"The strength of the departure from normal sea surface temperatures was enough to call it a strong event for just last week," Barnston, of Columbia's International Research Institute for Climate and Society (IRI), said. "But to call it an officially strong event, we need for it to stay at that level or higher for a full month. And the average for July could make it."

The large group of El Nino models, both dynamic (based on physical processes) and statistical (based on historical data), mostly forecast at least a strong event - likely to peak in the northern autumn. Collectively, the IRI described the model simulations as "off-the-charts". "[El Nino] is growing and the prediction models say it's going to get stronger," Barnston said. "And that's our prediction, that it will become a strong event, most likely."

A few models, notably the European model and the National Weather Service CFS model, point to the possibility of a near-record event in which a very strong or "super" El Nino develops.

The only two super (or very strong) El Ninos occurred in 1982-83 and 1997-98.

However, NOAA climate analyst Michelle L'Heureux expressed some scepticism to Mashable's Andrew Freedman.

"L'Heureux noted that none of the major forecasting centres responsible for monitoring El Nino are predicting a record event at this time," Freedman reported. NOAA says the "forecaster consensus" is for a strong event but doesn't specify how strong.