Pacific's 'hot blob' to hang around for summer

A sprawling patch of unusually warm water in the Pacific Ocean - dubbed the "hot blob" - is expected to hang around for summer. Image / ClimateReanalyzer.org

A sprawling patch of unusually warm water in the Pacific Ocean – dubbed the "hot blob" – is expected to hang around for summer, the latest forecast shows.

But a Niwa climatologist doesn't expect the balmy blot, four times bigger than New Zealand itself, to have any noticeable influence on our own waters.

The blob, spanning around a million square kilometres, had been set apart on sea surface temperature maps by its huge anomaly of 6C above average.

The European Centre for Medium-Range Weather Forecasts (ECMRWF) projected it to last over summer.

That was despite some low-pressure systems that were forecast to track through it, causing mixing in the ocean that had otherwise been settled amid high pressure and drove its formation.

"It's still there at the moment, and remains the biggest sea temperature anomaly out there," Niwa's Nava Fedaeff said.

"But I don't think it's really going to have any influence on our weather patterns, as it's so well to the east of us."

In any case, she added, it was drifting in the direction of South America.

"If it was to our west, and in the Tasman, I'd expect some of it to drift over and affect our weather."

Source / European Centre for Medium-Range Weather

Rather, temperatures around the country were generally subdued at the moment, she said.

"I think we're still watching how this season plays out. We had a spike in sea surface temperatures at the end of November, but it's been a lot more unsettled in our region since then.

"And because sea temperatures don't peak until late February or early March in our part of the world, we're still just seeing a natural rise."

The quick jump at the start of summer raised the possibility of another "marine heatwave" – but that wasn't likely unless conditions around the Southern Ocean changed and flipped an indicator called the Southern Annular Mode from negative to positive.