April 2017 - Wetter and warmer than normal for most
Issued 3 April 2017
Highs often maintained a southern position during March, favouring the south of
the South Island. It was much drier and warmer than usual in the south and west of the South Island. In contrast, easterlies frequented the North Island, with low pressures repeatedly sitting over the north Tasman Sea. The month saw extremes of rainfall and humidity over the northeast of the North Island.Rainfall was more than double March norm from Bay of Plenty right up to Northland, while the remainder of the North Island, as well as Nelson, also Rangitata on the warmer and wetter side. Auckland was particularly impacted by a trio of downpours 7-12 March, and recorded around 350% of normal March rainfall.Auckland Airport observed its third wettest month, of any month, in observations since 1962. It was a wetter and cooler than usual March in the east of the South Island, due to frequent onshore winds.
Sea temperatures around the New Zealand coastline are generally above average,
excluding around Cook Strait. The Tasman Sea and the tropical oceans to the north of the country are also warmer than normal. Equatorial sea temperatures continue to increase, and most models forecast an El Nino event during the second half of the year. However, forecast accuracy is relatively low at this time of year, and there is no indication as yet of how strong any future El Nino might be. During winter, other influences, such as what happens in the Southern Ocean and Tasman Sea, will likely either add or subtract from any developing El Nino influence back here in New Zealand.
The April Outlook
Tropical moisture over the Tasman Sea is ear-marked to move onto New Zealand
this week. There is considerable potential for extreme rainfall and unusual warmth for many regions of the country this week, with low pressure coming out of the north Tasman Sea and rolling across New Zealand. Keep up to date at
http://www.metservice.com/warnings/severe-weather-warnings as the week progresses. Next week shows a continued signal for blocking High pressure to the south and east of the country,with low pressure again prevailing over the north Tasman Sea. The first two weeks of the month undoubtedly dominate the monthly forecast, but we may see a return to more typical, mobile weather systems during the second half of April.
Well above normal April rainfall totals are signalled for most regions of the
country, mostly due to the extremely large rainfall accumulations forecast this week. The exceptions are Southland and Fiordland (with near normal April rainfall forecast).
Well above average April temperatures are predicted north of Taupo. Elsewhere,
expect above average April temperatures, with the notable exception of the eastern South Island (where things should end up close to the April norm,overall).
An extremely wet April is on the cards for most regions. April temperatures are
forecast to run unusually mild for most regions of the country.