Table 3: Blenheim Weather Data – January 2018 January January 2018 2018 compared to LTA GDD’s for: Month - Max/Min¹ 331.3 134% Month – Mean² 322.2 135% Growing Degree Days Total Jul 17 – Jan 18 – Max/Min1 984.7 125% Jul 17 - Jan 18 – Mean2 1018 122% Mean Maximum (°C) 25.4 +2.0°C Mean Minimum (°C) 16.0 +3.3°C Mean Temp (°C) 20.7 +2.6°C Ground Frosts (<= -1.0°C) 0 Equal Air Frosts (0.0°C) 0 Equal Sunshine hours 243.6 93% Sunshine hours – lowest Sunshine hours – highest Sunshine hours total – 2018 243.6 93% Rainfall (mm) 80.4 180% Rainfall (mm) – lowest Rainfall (mm) – highest Rainfall total (mm) – 2018 80.4 180% Evapotranspiration – mm 135.6 95% Avg. Daily Windrun (km) 190.6 69% Mean soil temp – 10cm 21.0 +2.0°C Mean soil temp – 30cm 22.3 +1.5°C
January LTA
Period of LTA
January 2017
248.1 239.5
(1996-2017) (1996-2017)
260.5 258.0
790.8 (1996-2017) 831.4 (1996-2017) 23.4 (1986-2017) 12.7 (1986-2017) 18.1 (1986-2017) 0 (1986-2017) 0 (1986-2017) 262.5 (1930-2017) 165.2 1971 335.3 1957 262.5 (1930-2017) 44.6 (1930-2017) 0 1978 167.0 1985 44.6 (1930-2017) 142.2 (1997-2017) 277.1 (1996-2017) 19.0 (1986-2017) 20.8 (1986-2017)
836.4 866.6 23.9 12.9 18.4 0 0 282.0
282.0 27.2
27.2 181.5 336.3 19.1 20.9
¹GDD’s Max/Min are calculated from absolute daily maximum and minimum temperatures ²GDD’s Mean are calculated from average hourly temperatures of 32.5°C on 30 January 2018 in Blenheim was the hottest day since 6 February 2011, which recorded 33.4°C. Blenheim’s hottest day on record for the 70 years 1948-2017 is 11 January 1979 with 36.0°C. If you think January 2018 was hot in Marlborough, spare a thought for Central Otago. Cromwell recorded 21 days during January 2018 when the maximum temperature exceeded 30.0°C. The average daily maximum temperature for January 2018 was 30.0°C, which was 4.6°C warmer than Blenheim’s average maximum temperature. Growing degree days The growing degree day (GDD) graph (Figure 2) is a regular feature in Met Report. It presents the difference between the accumulating GDDs in any season and the long-term average.
8 / Winepress February 2018
It is an easy way to visualise when temperatures have been above or below average at any point during the season, i.e. an upwards sloping line means above average GDDs and a downwards sloping line means below average GDDs (temperatures). GDDs have been well above average in the 2017/18 season to the end of January 2018. In order to put the current season into perspective, other very warm seasons are also included on the graph. The 1988/89 season was previously the warmest season for the five months September to January, of any season in the past 30 years. However, the 2017/18 has now surpassed the 1988/89 season. Of interest is that the 1988/89 season recorded below average GDDs in February and only average GDDs in March and April 1989.
The 1997/98 season is also recognised as a very warm season. However, the warm temperatures in 1997/98 didn’t begin until the third week of January 1998. The period from late January through until early April 1998 was exceptionally warm while the grapes were ripening. The 2013/14 season was very warm from September to December 2013, but only average to below average from January to April 2014. The 2015/16 season was average from September 2015 to mid-January 2016 and then very warm from mid-January to early April 2016. December 2017 was 1.9°C and January 2018 was 2.6°C above the LTA. Current climate projections are that temperatures will continue to be above average in February and March 2018. In Figure 2, projected GDD lines have been added for the period 1 February to 30 April 2018. These lines assume temperatures either equal to or 1.0°C above the long-term average. The +1.0°C line indicates that temperatures from February to April 2018 do not need to be too far above average, to push the 2017/18 season into the position of being remembered as the warmest season that the Marlborough wine industry has ever experienced. Rainfall Blenheim received only 70.4 mm rain for the three months October, November and December 2017; 46% of the LTA. At the beginning of January 2018 Marlborough was greatly in need of rainfall with very dry conditions and low river levels. Fortunately much needed rainfall was received on a number of days between the 4th and 12th January and again on the 17th. Total rainfall for January of 80.4 mm was 180% of the LTA and more than in the previous three months combined. Wind-run Average daily wind-run in January 2018 was 190.6 km, well below the LTA of 274.3 km (average wind speed of 7.94 km/hr, compared to LTA of 11.43 km/hr). January 2018 wind-run is by