Sept/Oct summary NZ 2016

 

GENERAL FOR SEPTEMBER

The North Island is drier than average and the South Island wetter, with below average rain for the southern hydrolakes. Both islands are sunnier than the norm, with average temperatures. In the second half of September, it is sunny and continuing to be very dry in the east, also dry in the north of the North Island but wet in the south of the South Island.  Temperatures are remaining mild. 

Northland, Auckland, Coromandel Peninsula, Bay of Plenty, Rotorua, Hamilton

Drier than average except Coromandel, average to sunnier, average temperatures except cooler Taumaranui.

Rain likely: 4th-6th, 9th, 13th, 16th-18th, 21st, 24th-27th (heavier 6th, 16th, 26th)

Western & central NI not including Taupo 

Average to wetter, average sunshine, average to cooler temperatures. 

Rain likely: 3rd, 5th-6th, 8th, 11th-13th, 15th-17th, 24th-27th (heavier 13th, 26th)

Taupo

Drier than average, sunnier, average temperatures.

Rain likely: 6th, 8th-9th, 16th, 25th-27th (heavier 26th)

Gisborne, Hawkes Bay 

Drier than average, sunnier, average temperatures.

Rain likely: 6th-9th, 13th, 16th, 21st, (heavier 6th, 16th)

Lower NI

Wetter than average, average to sunnier, average-to-cooler.

Rain likely: 3rd-6th, 8th, 13th-16th, 24th-27th, 30th, and 1 October  (heavier 13th, 26th)  

Nelson and Marlborough

Average to wetter, average sun, average temperatures. 

Rain likely: 3rd-5th, 8th, 13th-15th, 24th-27th (heavier 5th, 25th)

Canterbury

Average to drier, average sun, average temperatures.

Rain likely: 3rd-5th, 8th, 12th-15th, 25th-27th, 30th (heavier 4th, 13th)

Inland Otago

Average to wetter, average sun, average temperatures. 

Rain likely: 2nd-6th, 8th, 12th, 15th, 25th, 30th (heavier 2nd, 13th, 25th)

Coastal Otago, Dunedin 

Average to drier, average to sunnier, above average temperatures.

Rain likely: 5th, 8th, 12th-18th, 25th, 30th (heavier 13th-15th)

Southland 

Average rain, wetter Invercargill, average sun, average to cooler.

Rain likely: 2nd, 5th, 8th-12th, 15th-20th, 25th, 30th (heavier 2nd, 8th, 15th, 25th)

Buller/West Coast/Fiordland

Wetter than average (except drier Bruce Bay), average to cloudier, average to cooler. 

Rain likely: 2nd-5th, 8th, 11th-21st, 24th-30th, and 1 October (heavier 2nd, 4th, 17th, 25th)

SEPTEMBER SUMMARY

5th: High rainfall in Northland and Nelson regions.

6th: Westerly change in the south with a trough over the North Island.

7th: Change to cold southwesterlies.

10th: Ridge of high pressure develops.  

11th: Westerlies.  Low temperature at the Chateau, possibly -5C.  

12th : Over the next four weeks weather patterns are more typical of mid, rather than early spring with more frequent westerly or southwesterly flows over much of the country.  These may be caused by frequent anticyclones tracking across northern New Zealand with depressions passing to the south of the country.  Rainfall may be low in Gisborne and Hawkes Bay, dry in the east of the  South Island from Kaikoura to north Otago and dry in the north of the North Island.  In the previous 11 months, there has been below average rain in the east from Wairarapa to north Otago, lowering soil moisture levels.  This will start to get more severe in coming months.  In contrast, changeable wet conditions persist in the far south of the South Island.  Daytime maximum temperatures may be a degree or two above average and night time minimums a degree or two below average in the east of both Islands.  Sunshine totals may be above average in most regions, especially Gisborne and Hawkes Bay but near average in Northland and Auckland.  Westerlies bring frequent clear skies in the east of both Islands.  

13th: Change to cold southerlies.

15th: Northwesterly change ahead of a trough.

16th: Change to southwesterlies with showers mainly in the south and west.

17th: Low temperature at Twizel.

22nd: Anticyclonic conditions.

24th: Strong northwesterlies precede an active frontal band.  Low temperature at Fairley.

27th: Frontal band passes over New Zealand.

28th-29th: Settled weather with high pressures.

30th : Southwesterlies.

OCTOBER

1st-3rd: Anticyclonic conditions.

1st: Low temperatures in central North Island

Allow 1-2 days error in all forecasting. Skewing may occur around 1st(New moon), 7th (apogee), 17th (full moon) and 19th (perigee), 1 October: New moon.