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Prepare for a hot summer

FRIDAY DECEMBER 06, 2013

pic: Kaikoura coastline, photographer Susan Alesbury

 

 

December
This summer starts with a wet first week of December for all, but the second and third weeks of December are mostly dry except for the west and south of the South Island. From 8-22 December may be the longest dry spell of the season particularly for the North Island and top of the South Island, so early holidaying then may be prudent. Around the middle of December temperatures may soar to the 30s in places, a precursor of more intense heat to come. Heavy rain comes just before Christmas for most of the South island but largely misses Canterbury, then in the North Island after 23 December for a handful of days, lasting over Xmas and Boxing Days, which may affect campers. (Allow 1-2 days error in all forecasting)

January
New Years day may be wet for all, clearing by 5 January for the North Island but lingering until the 8th for the lower North Island and much of the South Island. In the upper half of the North Island the 6th-20th may be the driest interval. Although January may be the summer’s wettest month, heat waves are likely between the 11th-19th due to the northern declination full moon in apogee, with temperatures in the 25C-30C range. Rain in the South Island around mid January may bring relief but the North Island may have to wait until 21st-25th for any soaking. For BoP and Marlborough only 1st-2nd and 22nd-24th may deliver January rain. For BoP it may be enough in two short windows to put their month's total above the average but Marlborough may not be so lucky. For the North Island from BoP southwards the last 4-5 days of January may be dry. High temperatures should persist into February and hang around until the first week in March.

February
February brings the second heat wave and may be the hottest month of this summer, with most days reaching well over 25C for Auckland and perhaps approaching 35C for Christchurch at either the start of February or near midmonth.. Despite the heat, dumps of heavy rain around 10th, 18th and 28th in Northland may avert possibility of drought. The driest parts of February in the top half of the North Island may be 1st-9th and 19th-27th. In the South Island the 3rd-10th may be the driest. Canterbury is dry for the first half of February but may be wet in the third week. For Auckland dumps of heavy rain come 13-18 February and it may be wet 16th-18th for much of the South Island.

March
March brings good rain in the first five days and around midmonth, clearing for all between 5th-12h. Both islands are again mostly dry 14th-25th except for a rainband crossing the South Island 20th-21st. March brings a wet final week to the country. Although there may be isolated hot days 25C-28C over the first week in March, there should be no temperatures too extreme for the rest of the month.

Cyclones
The cyclone season will get under way in December, with an early depression moving through Fiji, Tonga and Samoa and the Cooks, followed by another depression about the 10th. Another system between 17-24 December affects the Solomons and Vanuatu, and may bring rain to Christchurch about 22 December. The New Year brings rain to NZ from the remnants of a tropical depression in Samoa. The 16-20 January is active for unsettled weather in the Pacific, with another system affecting Tonga and the Cook Islands around the end of January. February is also active in the Pacific in the third and fourth weeks

Why the warmer temperatures?
It has nothing whatever to do with global warming or climate change. Two decades, or close to 19 years on average is the lunar cycle seasonal repeat. Some remember the summers of 20 and 40 years ago. 1994-95 was a long dry summer with an Auckland drought and the city running out of water, and the 1974-5 summer was also warm and dry. Then as now, perigees (moon closer to earth) were closer over initial summer months. In 1975 February’s perigee was closest for the year, and in 1994 the December perigee was the third closest. This December’s perigee is fifth closest, with second and third closest perigees during January and February. Close summer perigees correlate with hotter temperatures.
Some will recall how the close perigee in December 2012 brought an extra warm month, with more frequent northerly and northwest winds. Temperatures greater than 1.2°C above average affected much of the North Island, as well as Nelson and parts of eastern South Island, resulting in temperature records or near-records. For example the air was warm enough on 6 December to generate a tornado in west Auckland and the North Shore. Wind gusts brought down trees and flung them over the motorway, along with panels ripped from a construction site with three fatalities from falling slabs of concrete.
It does not mean that a tornado comes with every close summer perigee, but we should at least plan for the possibility of temperature hikes.

 

You tube clips
Guiding you through sobaric maps for all December
http://www.youtube.com/watch?v=op9Gqc9SM00

Explaining why both the UK and Wellington had extreme winds
and why there were earthquakes last Friday in South island.
http://www.youtube.com/watch?v=Nv5R5hrogBQ

For enquiries please email ken@predictweather.co.nz


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