The month started with a blast of Arctic air that produced a hard frost as the thermometer dropped to -2.8C following a cold day with a maximum of just 8.8C that was 5.3C below average.
The first four days in April continued the dry theme after the previous period in March that saw twelve consecutive dry days. However, the wind then changed direction significantly from the north into the west and then south to bring warmer days and nights. High pressure to the east and low pressure to the west brought warm air from Iberia that lifted daytime temperatures above average.
The first substantial rain in eighteen days fell on the 5th with 2.3mm that refreshed the gardens.
From the 6th another dry period arrived with a further ten, consecutive dry days with temperatures rising well above the average. Over the previous 28 days we received just 3mm of rainfall and the equivalent rainfall of 44mm was lost through evaporation from ground sources and plant life.
From the 9th to the 11th the thermometer rose above 24C with the warmest day of the month on the 11th that gave a maximum of 24.4C, which was 10.3C above the 36-year average.
The long, dry spell was broken with a vengeance on the 17th as a rain band in the shape of an arc, slowly rotated anticlockwise continuously over this area producing 15.4mm of rain. After a few dry hours in the evening another intense rain band moved north in the early morning producing another 17.8mm. This brought the daily total to 33.2mm breaking the previous record for the wettest April day set in 1991 with 28.7mm. It was welcome refreshment for the very dry gardens.
On the 18th an anticyclone developed over Scandinavia that produced a ‘blocking high’, which kept weather fronts advancing from the Atlantic. This high-pressure system, circling clockwise combined with a low-pressure system circling anticlockwise over southern Europe, continued the run of strong north easterlies. It was especially strong from the 20th to the 22nd with gusts up to 33mph, only very slowly decreasing.
There was a dramatic change in our weather on the 27th. The anticyclone had been declining for several days having lost over 20mb since its peak. This allowed depressions, with accompanying rain bands, to sweep in from the Atlantic with four wet days after the eight consecutive days without rain. The strong north easterly winds and very warm conditions had meant that evaporation from ground sources also plant life was equivalent daily to rainfall of 4mm and a loss of 32mm through that period.
Tuesday 28th was an exceptionally cold day with a strong north easterly wind producing a wind chill so that the maximum of just 7.8C, being 6.3C below average, felt more like 5.7C. It was the coldest day since 5th March.
There were 23 days without measurable rainfall during April but the four days at the end of the month added another 44.5mm bringing the monthly total to 82.9mm. This was 24.4mm above the 36-year average and the wettest April since 2014. The extreme April rainfall years were in 1984 with only 2.0mm and the wettest in 2000 that produced 175.2mm. The period January to April gave us 382mm of precipitation that was 104mm above the 36-year average.
Set against the above monthly precipitation of 82.9mm is the figure of 85.4mm of equivalent rainfall that was lost to the atmosphere due to evaporation from ground sources and plant life during the very warm dry spells also the strong northeasterly winds that prevailed for 15 days during the month. So in fact there was a deficit of 2.5mm of rainfall.
Due to the many warm days it was not surprising to find that the mean temperature for April was a significant 2.0C above the average and the third warmest I have recorded since my station began in 1984.
There were only two days during the month without sunshine that totalled a considerable 237 hours.