Press Release December 2017

Meteorological data summary for December 2017 and Annual Summary for 2017, for the Blenheim Weather station located at the Grovetown Park campus of the Marlborough Research Centre.

 Weekly temperatures, rainfall and sunshine during December 2017

Mean Max

(°C)

Mean Min

(°C)

Mean

(°C)

Rainfall

(mm)

Sunshine

(hours)

1st – 7th 26.2     (+4.3) 13.0      (+1.4) 19.6    (+2.8) 0.0 98.7
8th – 14th 25.4     (+3.5) 15.8      (+4.2) 20.6    (+3.8) 15.2 66.7
15th – 21st 25.5     (+3.6) 12.1      (+0.5) 18.8    (+2.0) 0.8 63.9
22nd – 28th 21.9     (=) 12.3      (+0.7) 17.1    (+0.3) 5.6 59.3
29th – 31st    (3 days) 22.4      (+0.5)   9.9      (-1.7) 16.2    (-0.4) 0.0 30.5
1st – 31st December 24.5 (+2.6°C ) 12.9   (+1.3°C) 18.7  (+1.9°C) 21.6     45% 319.1   130%
LTA 1986-2016 21.9 11.6 16.8 47.8 246.3

Temperatures for December

Mean temperature of 18.7°C for December 2017 was 1.9°C above the long-term average of 16.8°C (1986-2016).

December 2016 mean temperature was 16.7°C.

December 2015 mean temperature was 15.9°C.

December 2014 mean temperature was 17.3°C.

December 2013 mean temperature was 18.1°C.

The Maximum temperature during December 2017 was 31.3°C recorded on Sunday 17 December

The Minimum temperature during December 2017 was 6.2°C recorded on 28 December

Despite the very warm December mean temperature, the mercury only surpassed 30.0°C in Blenheim on two days in December, (11th with 30.1°C and 17th with 31.3°C). However, there were a further 14 days that recorded maximum temperatures between 25 and 30°C.

 December 2017 with a mean temperature of 18.7°C is the second warmest December on record for Blenheim for the 86 years 1932-2017.

The warmest on record is 1969 with a mean temperature of 18.8°C.

 Sunshine

319.1 hours sunshine for December 2017 was 130% of the long-term average for December of 246.3 hours.

December 2016 recorded 253.0 hours sunshine

December 2015 recorded 294.5 hours sunshine

December 2014 recorded 222.6 hours sunshine

December 2011 recorded 167.4 hours sunshine. Lowest December sunshine hours on record

December 1974 recorded 321.2 hours sunshine. Highest December sunshine hours on record

December 2017 with 319.1 hours sunshine is the second sunniest December on record for the 88 years 1930-2017. The sunniest December on record is 1974 with 321.2 hours sunshine.

Rainfall for December

21.6 mm of rain for December 2017 was 45% of the long-term average for December of 47.8 mm.

December 2016 recorded 20.2 mm

December 2015 recorded 17.4 mm

December 2014 recorded 31.8 mm

December 2010 recorded 131.6 mm, the wettest December on record for Blenheim; 1930-2017.

December 1934 recorded 0.8 mm, the driest December on record for Blenheim; 1930-2017.

December 2017 is the sixth year in a row (2012-2017) in which December has recorded well below average rainfall.

 Wind-run

Average daily wind-run for December 2017 was 250.3 km. The long-term average for December is 290.3 km. Average daily wind speed in December was 10.4 km/hr compared to the December average of 12.1 km/hr.

Maximum wind speed of 59.8 km/hr was recorded on 19 December.

There were 24 days during December 2017 that recorded lower than the average daily wind-run of 290.3 km, and there were 7 days that recorded higher than average daily wind-run.

In each of the eight years 2010 to 2017, December has recorded below average daily wind-run.

 Evapotranspiration

Total potential evapotranspiration for December 2017 was 177.8 mm, compared to the average of 139.7 mm.  This is the highest potential evapotranspiration for December for the 22 years 1996-2017, the period over which it has been measured.

Soil Moisture for December

Average shallow soil moisture (5-35 cm depth) at the Grovetown Park weather station was 15.4% for December 2017 compared with 21% average (2002-2016).  Shallow soil moisture was close to its minimum potential value throughout December 2017.

Moisture Deficit for December

The water deficit for December 2017 was -156.2 mm

Rainfall 21.6 mm minus Evapotranspiration 177.8 mm = Moisture Deficit -156.2 mm

Moisture deficit is the amount of water that would need to be applied as irrigation to keep a grass pasture actively growing.

Annual Statistics for Blenheim in 2017, compared to the long term average

 Sunshine

Total sunshine for Blenheim in 2017 was 2604.5 hours. This is 106% of the long-term average of 2462 hours (1930-2016) (142.5 hours above the long-term average).

2017 is the 10th sunniest year on record for the 88 years 1930-2017. The sunniest year on record is 2015 with 2813.8 hours sunshine.

Sunniest town in New Zealand for 2017 (NIWA will confirm sunshine totals in the next week)

Richmond is the sunniest town in New Zealand for 2017 with a provisional total of 2632 hours.

Blenheim is in second place with 2604.5 hours, 28.3 hours behind Richmond.

However, there is one days sunshine missing from Richmond’s total in the NIWA database on 25 August. If total sunshine hours from the nearby Appleby station are added to Richmond’s total for 25 August, then the Richmond total would be 2641.7 hours; 37.2 hours ahead of Blenheim.

Richmond installed their sunshine recorder part way through 2015. For both years they have been in the race (2016 and 2017) they have won.

Rainfall

Total Rainfall for 2017 was 591.4 mm; 92.4% of the long term average (1930-2016) of 639.7 mm.  The 2017 rainfall was almost identical to the 2016 rainfall.

2016 rainfall was 591.2 mm.

2015 rainfall was 381.6 mm.  2015 is the driest year on record in Blenheim.

2014 rainfall was 519.3 mm.

2013 rainfall was 700.1 mm.

Monthly rainfall recorded in Blenheim for 2017

Month Rainfall (mm) % of long

term average

Long-term

average (mm)

1930-2016

January 27.2 56% 48.4
February 61.8 144% 42.8
March 47 108% 43.4
April 131.4 249% 52.9
May 57.2 90% 63.6
June 18.4 30% 60.6
July 62.4 99% 63.0
August 65.8 105% 62.5
September 49.8 98% 50.9
October 32.4 57% 56.6
November 16.4 35% 47.3
December 21.6 45% 47.8
 
Total (Jan-Dec) 591.4 92.4% 639.7

Two months recorded well above average rainfall (February and April). Five months recorded close to average rainfall (March, May, July, August and September). Five months recorded well below average rainfall (January, June, October, November and December).

Temperature

Mean temperature for 2017 was 13.67°C; 0.53°C above the long term average for the 31 years 1986-2016, of 13.14°C.

11 months in 2017 recorded above average mean temperatures.

The only month to record a below average mean temperature was May.

The hottest day of 2017 was 17 December with 31.3°C.

The coldest day of 2017 was 31 July with an air frost of -2.0°C and a ground frost of -6.8°C.

Frosts

39 ground frosts were recorded in 2017; 13 less than the long term average of 52 (1986-2016).

12 air frosts were recorded in 2017; 7 less than the long-term average of 19.3.

45 ground frosts and 9 air frosts in 2016

62 ground frosts and 25 air frosts in 2015

40 ground frosts and 16 air frosts in 2014

Wind-run

Average daily wind-run for 2017 was 224.6 km compared to the long-term average of 256.9 km (1996-2016).

Total daily wind-run for 2017 was 81,967 km compared to the long-term average of 94,076 km (1996-2016).

Total and Average daily wind-run for 2017 were the lowest on record for the 22 years 1996 to 2017; i.e. 2017 was a very calm year.

For ten years in a row (2008-2017) Blenheim has recorded lower than average total and daily wind-run.

January was the only month in 2017 to record above average daily wind-run and it was by far the windiest month of the year. All 11 months from February to December 2017 recorded well below average wind-run.

Plant & Food Research / Marlborough Research Centre

rob.agnew@plantandfood.co.nz

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Filed under Blenheim Weather Data, Weather Press Releases.

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