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El Nino behind our wintry summer

WHAT some scientists are now describing as the strongest El Nino on record is the culprit behind a chilly and disappointing summer for the Gisborne-East Coast region.

The current El Nino has built gradually from as long ago as March last year and in the critical area of the tropical Pacific, latest measurements show the heat soaked up by the ocean is still building.

For the East Coast, an El Nino usually delivers a cool, dry summer and the statistics show that is what is happening, despite the occasional heavy but brief downpour.

December had less than half its usual rainfall (26mm against the December running average of 64mm) and 2015 ended well behind the usual yearly rainfall average.

Last year saw just 893mm put in the tank — almost 300mm short of what fell in 2014.

National Institute of Water and Atmospheric Research (Niwa) data going back over 75 years show the number of dry years closely matching the El Nino/Southern Oscillation (ENSO) climate pattern.

The driest year on record for Gisborne was 1998, the last strong El Nino, with just 638mm of rain.

Farmers and crop growers need to know that the latest forecast from the US National Oceanic and Atmospheric Administration’s Climate Centre is for this El Nino to last into the June/July/August quarter.

For locals and holidaymakers looking for a decent dose of hot, sunny weather, the outlook is not that bright — cool changeable weather likely until El Nino relents and the high and low pressure zones track further north.

Poor weather for ChristmasThose who thought it was a pretty poor Christmas/New Year for weather were right. The figures show it was cold and miserable most of the time.

Over the 15 days from Christmas Eve to the return to work, the daily mean temperature was just 15.6 degrees, a whole 3 degrees colder than the 30-year average for that period.

On only one day did the mercury get to a decent 28.2 degrees, while there was a string of cold nights and mornings with the air temperature plummeting to 4.8 on December 29, with a frosty grass minimum of just 0.7 of a degree that morning.

The days’ highs over those 15 days averaged just 20.4 degrees. This time of year we normally enjoy about 24 degrees. Overnight temperatures averaged a cool 15.6, where we could normally expect over 18.6.

One unexpected result from the El Nino-driven weather is that it has been consistently a lot sunnier than usual, even if it has not delivered the expected warmth.

This month continues the pattern, with sunshine hours currently running at 110-120 percent of normal.

Niwa’s daily climate charts show temperatures overall running 2 degrees below average, and the lack of any decent rain for a while is seeing soil moisture deficits build to the 120mm mark.

Niwa’s charts clearly show the El Nino drying effect, with soil moisture deficits from the Tolaga Bay and Poverty Bay flats to Mahia, the Wairarapa and all of the east coast of the South Island.

The last big El Niño, in 1997. Wikipedia picture