Tuesday returned to the pattern of a dry day with sunshine, brought on the brisk north easterly winds, gusting to 18mph. The thermometer peaked at 17.1C, just above the average for early May. We enjoyed 6 hours of strong sunshine that felt warm out of the wind. Overnight the cloud cover stopped the temperature from dropping very low with a minimum of 6.1C just after 5am. However, the cool, brisk wind meant that wind chill made this feel like 4C.
Summary for April 2017
The outstanding feature of April was the lack of precipitation, which totalled just 8.2mm from the light rain showers and wet snow that fell during the late afternoon of the 25th.
The record for the driest April was in 1984, when this station started recording, with just 2.0mm, followed by 5.4mm in 2011 and 6.7mm in 2007.
There were 20 dry days in the month with the wettest on the 25th producing 2.2mm and 2.1mm on the 30th.
There just 4 ‘wet’ days in the whole month, which the Meteorological Office class as daily precipitation equal to or above 1mm.
The 33-year average for April was 59.7mm making a deficit of 51mm for April. When an overview of the past few months is reviewed the situation is even more severe. The winter months of December to February produced a deficit of 99mm and March was 9mm below the long-term average.
The precipitation over the past five months was 159mm below the 33-year average or over 6 inches in old money. The slight falls this last month, in both the River Og and River Kennet levels, can be traced not only to the lack of rainfall but also that in April, 69mm of equivalent rainfall evaporated into the atmosphere from ground sources and plant life.
There is a contrast when analysing the temperatures over the past month comparing day and night. The daytime average was +1.5C but the cold nights meant the average was -0.9C. This gives a mean of +0.3C for the complete month.
Looking back over the years the coldest April occurred in 1986 being 2.9C below the average and the warmest in 2011, which was 3.7C above the average.
There were 7 air frosts; the most severe occurring at the end of the month during the night of the 26th/27th when the thermometer fell below zero for eight hours giving a minimum of -3.0C at dawn. This resulted in much damage to new growth and existing spring flowers, sadly, such as my rhododendrons and apple blossom.
There were several windy days towards the end of the month with gusts to 30mph on the 30th.
We enjoyed 150 hours of strong sunshine with the solar energy 4% above the seven-year average.
The dry weather with cold nights was mainly due to the consistent high pressure and winds predominantly from a northerly quarter. The barometric pressure for April was a significant 7mb above the long-term average at 1023mb.
The quotation form Ralph Josselin, a Puritan minister and diarist from Essex who wrote the following in 1649, might be applicable to the past month with its dry weather and frosty nights – “Dry, windie, indifferently cleare in the nights very cold, and much given to frosts … good to purge the aire, and to prevent infection. Oh Lord watch over me and mine”.