Press Release April 2018

Weather Data summary for April 2018 for the Blenheim Meteorological station located at Grovetown Park Campus of the Marlborough Research Centre.

April 2018 was a very average month. Mean temperature, sunshine hours, rainfall and wind-run were all close to average. Soil moisture was well above average.

Table 1: Weekly temperatures, rainfall and sunshine during April 2018

  Mean Max

(°C)

Mean Min

(°C)

Mean

(°C)

Rainfall

(mm)

Sunshine

(hours)

1st – 7th 22.7      (+3.9) 12.0     (+4.0) 17.4    (+3.9) 0.0 59.7
8th – 14th 15.3       (-3.5) 6.7       (-1.3) 11.0    (-2.5) 24.2 24.2
15th – 21st 20.4       (+1.6) 8.9       (+0.9) 14.6    (+1.1) 17.2 49.0
22nd – 28th 18.1       (-0.7) 5.4       (-2.6) 11.7    (-1.8) 8.6 55.0
29th – 30th 15.0       (-3.8) 12.7      (+4.7) 13.9    (+0.4) 2.2 0.0
           
1 – 30 April 18.9    (+0.1°C ) 8.5   (+0.5°C) 13.7  (+0.2°C) 52.2   (103%) 187.9   (98.5%)
LTA 1986-2017 18.8 8.0 13.5 50.8 189.8

Sunshine

188.0 hours sunshine for April was 99% of the long-term average for April of 189.8 hours (1986-2017)

April 2017 recorded 169.2 hours sunshine.

April 2016 recorded 238.3 hours sunshine.

April 2015 recorded 162.5 hours sunshine.

April 2014 recorded 123.7 hours sunshine.

There were some very sunny days during April. Five days recorded 10 or more hour’s sunshine. The average daily sunshine for April is 6.3 hours. However, there were also five days when no sunshine was recorded. The last three days of April all recorded zero hour’s sunshine.

Total sunshine for Blenheim from January to April 2018 is 896.4 hours, 98.5% of the long-term average of 910.2 hours (1986-2017).

Rainfall

52.2 mm of rain in April was 103% of the long-term average for April of 50.8 mm (1986-2017).

April 2017 rainfall was 131.4 mm.

April 2016 rainfall was 25.6 mm.

April 2015 rainfall was 52.0 mm.

April 2014 rainfall was 149.8 mm. 4th highest rainfall total for April

Total rainfall for Blenheim from January to April 2018 is 367.6 mm, 205% of the long-term average of 179.6 mm (1986-2017).  January and February rainfall totals were well above average whereas March and April totals have been close to average.

Soil moisture (5-35 cm depth)

Average shallow soil moisture for April 2018 was 34.2%. This was 10.1% above the April average (15 year average 2003-2017).

The average soil moisture for the four months January to April 2018 was 30.6%, exactly 10% above the long-term average. This is by far the wettest that the topsoil has been in the 16 years 2003 to 2018. This also helps to explain why Marlborough has been so green so far in 2018, with abundant grass growth.

Temperature

Mean temperature of 13.7°C was 0.2°C above the long-term average temperature for April of 13.5°C (1986-2017).

April 2017 mean temperature was 14.0°C.

April 2016 mean temperature was 13.9°C.

April 2015 mean temperature was 14.2°C.

April 2014 mean temperature was 14.5°C.

 The data in Table 1 indicate that the weekly temperatures during April 2018 oscillated from warm to cool throughout the month.

Ground Frosts and Coldest and Hottest days during April

Two ground frosts were recorded during April 2018 on the 11th and 12th.  In contrast no ground frost were recorded in April 2017.

There were a further five cold mornings during April when the ground temperature was between 0 and -1.0°C, but not recorded as a ground frost. Only temperatures below -1.0 classify as ground frosts.

No air frosts were recorded during April.

The coldest temperatures were recorded on the morning of 12 April, with a grass minimum (ground frost) of -3.3°C and an air minimum of +0.3°C.

The hottest day was 4 April with a maximum temperature of 25.4°C.

Wind Run

April 2018 recorded slightly above average daily wind-run of 223.3 km compared to the long-term average of 220.4 km.  What is somewhat remarkable is that April 2018, has recorded the highest daily wind-run since April 2010. All seven years 2011 to 2017 recorded below average wind-run in April.

 Daily wind-run totals during April 2018 varied quite markedly. Six days during the month were quite windy, recording greater than 300 km wind-run. The windiest day was 16 April with 439 km wind-run.

However, there were also eight days that were fairly calm, recording less than 150 km wind-run. The calmest day was 13 April with only 95 km wind-run. The final three days of April were all very calm associated with the overcast wet weather.

Rob Agnew

Plant & Food Research / Marlborough Research Centre

 

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