La Nina warmth expected to linger
WELLINGTON: The La Nina climate system that stoked New Zealand’s hottest recorded summer in history is finally about to fizzle out, but the warm weather looks set to linger on.
And an El Nino system could even be on the cards for the end of the year.
Niwa’s climate outlook for the next three months gives a high chance of aboveaverage temperatures right across the country.
Warm ocean waters around New Zealand, which experienced a summer marine heatwave, are forecast to persist through the next three months, but by the end of winter are expected to return to near normal west of the country.
Even though temperatures would be on the balmier side, Niwa said there would be frosts in cooler places as we moved into the end of autumn.
Rainfall levels were predicted to be above normal in the north and east of the North Island, while everywhere else rain would be near or above normal.
Soilmoisture levels and river flows would be above normal in the north and east of the North Island and the north of the South Island, near or above normal in the west of the North Island, and near normal in the west and east of the South Island.
In the background, La Nina conditions carried on last month but trends in winds and seasurface temperatures indicated its influence was coming to an end.
‘‘Even though La Nina’s influence will wane over the next threemonth period, New Zealand’s regional climate over April to June 2018 is expected to be driven by persistence of more northeasterly airflow than normal, and by the persistence of warm ocean waters that are present around the country,’’ Niwa reported.
‘‘The northern Tasman Sea will remain unsettled, with lower pressures than normal, bringing the likelihood of significant rainfall events to the North Island and the upper South Island.’’
International models suggested the tropical Pacific would also move into an Ensoneutral state over the next three months.
But perhaps not for long — towards the end of the year there was an equal chance of it staying that way or shifting towards an El Nino system over spring.
In New Zealand, El Nino systems typically bring cooler, wetter conditions, higher rainfall to regions that are normally wet, and often drought to areas that are usually dry. — NZME