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Rural Monthly Outlook:

October settles down

Issued 1 October 2019

September 2019 - Unusually cold

During the first few days of September, a Tasman Low produced warmer, wetter weather for northern New Zealand (Tauranga northwards), as well as Nelson and Marlborough. It was subsequently a wetter than usual September for parts of Northland, Auckland, Coromandel and northern Waikato, also Nelson and Marlborough. Elsewhere, cold,showery weather resulted in monthly rainfall totals that generally ranged between 60 and 100 percent of September normal.

By the 5th of the month, however,persistent cold southerlies kicked in across the country. These unseasonable cold outbreaks continued through the month,producing an extremely cold September for southern, eastern and northern parts of the South Island. Temperatures were also below average for the western South Island, as well as around Wellington and the Wairarapa. For the remainder of the North Island, monthly temperatures were closer to normal.

Sudden Stratospheric Warming (SSW) occurred in early September over the sou thern pole, but impacts have failed to penetrate down to the troposphere (where the weather occurs). Recent cooler temperatures over New Zealand have not been influenced by the SSW, but instead have been driven by frequent Southern Ocean southerlies washing up and over New Zealand, as per MetService forecast.

The Ocean

The Southern Ocean is forecast to quieten down during October, taking a break from driving stormy weather over New Zealand. Instead, a Tasman Sea rain maker is expected to develop next week and should bring a spell of wetter weather to northern and western North Island areas, maybe also Nelson and Marlborough. The second half of the month looks quieter, with a ridge of High pressure showing up over Northland, and a muted west to northwest regime across the South Island.

Sea temperatures near the North Island and upper South Island coastline remain cooler than usual. The El Nino Southern Oscillation (ENSO)continues neutral, and the tropical Pacific Ocean is predicted to remain neutral during spring.

The October 2019 Outlook

Temperatures this week run extremely cold for the time of year, before a gr adual return to near average October temperatures next week and through the rest of the month. Rainfall wise, monthly rainfall totals are predicted to run on the drier side of the ledger (normal to below normal) north of about Taupo, also Gisborne, Hawkes Bay, Nelson, Marlborough. For all other regions, near normal October totals are forecast.

Bottom Line - An extremely cold start to October, before temperatures climb back towards average. October to run a touch drier than normal north of about Taupo,also for Gisborne, Hawkes Bay, Nelson and Marlborough. Elsewhere, near normal rainfall totals are forecast.