Early May cold snap will ease

Time to put another blanket on the bed: May looks set to get off to a colder-than-usual start, but long-range forecasters believe “milder conditions” will follow in June and July.

Niwa National Climate Center senior forecast scientist Chris Brandolino said the El Niño climate phenomenon, currently bringing much of our weather in from the west, was dissipating and expected to decline to ENSO-neutral by The end of this month.

El Niño-Southern Oscillation (ENSO) is a recurring climate pattern that involves changes in water temperatures in the central and eastern tropical Pacific Ocean, which impact our climate.

“However, global atmospheric patterns favor the continuation of higher than normal atmospheric pressure around New Zealand, particularly near the North Island.

“That means May is expected to feature rounds of cold southerly winds before a transition to milder westerly winds from the end of the month through June and July.”

On the west coast, the Southern Alps and foothills, inland Otago and Southland, temperatures were equally likely to be near average or above average over the next three months, and total rainfall was most likely were close to normal, he said.

“However, May appears drier than normal. The region may be exposed to strong fronts and lows at times, especially late in the season.

“Soil moisture levels and river flows will most likely be close to normal.”

Otago coast temperatures were also equally likely to be above or near average.

“However, during the first half of May, cold air masses from the south are expected.

“More frequent westerly winds in June and July can lead to milder temperatures.

“Precipitation totals will most likely be below normal and May has a high chance of being drier than normal.

“Soil moisture levels and river flows are very likely to be below normal, so soil moisture deficits will take time to alleviate.”

He said oceanic La Nina conditions (which bring weather from the east) could develop in late winter at the earliest, but were more likely to arrive later in the spring.

“There is expected to be a significant delay between the development of La Niña in the ocean and the atmosphere responding similarly to La Niña, particularly in the New Zealand context.

“In other words, moist northeasterly winds are not expected to be a dominant flavor of New Zealand weather patterns for at least the next 3 to 6 months.”

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