7 August 2017
Warmer, Windier - and Wetter on Wednesday
Forget about frosts – this week is looking warm and windy. Warm northerlies pick up through the first part of the week
as a slab of warm air from the tropics sidles up to New Zealand. On Wednesday, this warm air crosses the country,
trailed by a low pressure system which crosses the South Island on Thursday. The week ends with westerlies, so unlike
other recent weather systems, there is no southerly bite to follow these northerly winds.
The worst of the rain will be on Wednesday, when the warm air will bring rain to much of the upper North Island and also
the Nelson and Buller regions, with some areas getting heavy falls. A Severe Weather Watch has already been issued for
heavy rain for these areas and is likely to be upgraded to a Warning closer to the event, so people in these regions are
advised to keep up to date with the latest weather information.
“The Bay of Plenty and Nelson regions are often hit quite hard in moist northerlies,” said meteorologist Tom Adams, “and
our expert meteorologists will be watching them closely to ensure emergency managers and the public are kept well
informed.”
Overnight Wednesday the persistent rain eases, but there is still a chance of some heavy falls with possible
thunderstorms for much of the country on Thursday. The wind will also play a part, with northerlies rising to gale on
Tuesday night in the Cook Strait, and peaking on Wednesday ahead of the back edge of the warm air.
“Warm air higher in the atmosphere will increase wind speeds at the surface,” explained Mr Adams. “We call these ‘stable
northerlies’ – and where those winds get funnelled through gaps in the hills, they can end up being surprisingly
strong.”
On a more positive note, the upside with moist northerlies is warmer temperatures, and parts of the north and east could
get close to 20 degrees on Tuesday.
ends