A contrasting end to this week for the South Island

December 10, 2017

The record number of dry days* in a row recorded at Christchurch Airport was 45 days and this was seen during September/October 1954. In the 24 hours leading up to 9am this morning, once again Christchurch Airport recorded no rainfall, making 2017 equal to the 1954 dry spell record. Should little or no rain be reported at the Airport by Monday at 9am then the record will be broken. The average rainfall for Christchurch Airport for the month of December is 47mm (this is a similar amount to November with 46mm). There is some relief to hand, as MetService forecasters are expecting a southerly change to move through Christchurch, overnight Monday/Tuesday bringing a period of rain to the region.

“Temperatures have also been well above normal this past week in centres around the country” said MetService meteorologist Andy Best. “Many places recorded maximum temperatures in the low 30’s.” Christchurch Airport reached 33 C, Wanaka 31 C and Timaru 30 C on the 8th December, while Reefton reached 30 C on the 6th. Over the North Island, Hastings and Napier reached 30 C on the 9th December, Masterton climbed to 31 C on the 5th, Lower Hutt reached 31.4 on the 7th and Taumaranui 31.6 C on the 6th.

In contrast, the West Coast of the South Island has seen a dramatic change to rainfall conditions this week as the ridge of high pressure which has dominated our weather pattern for so long during November and early December moved away to the northeast. This has allowed active fronts to move up the South Island this weekend bringing significant amount of rainfall about and west of the South Island ranges. The rainfall in the west was enough to reach warning criteria in many places. Franz Josef weather station recorded 90mm in the 24 hours leading up to 9am this morning, Milford Sound 96mm, and several places in the ranges reported more than 100mm with the West Coast Regional Council’s Cropp River Gorge station recording 242mm.

(*A dry day is defined as <1mm of rainfall recorded at the station).

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MetService issues Warnings, Watches and Outlooks for severe weather over New Zealand.

Warnings are about taking action when severe weather is imminent or is occurring. They are issued only when required.
Recommendation: ACT 

Watches are about being alert when severe weather is possible, but not sufficiently imminent or certain for a Warning to be issued. They are issued only when required.
Recommendation: BE READY 

Outlooks are about looking ahead, providing advance information on possible future Watches and/or Warnings. They are issued routinely once or twice a day.
Recommendation: PLAN