Although we have moved into August the changeable weather continues.
Tuesday gave us 4.47 hours of strong sunshine but showers arrived late morning and an especially heavy one just after 1pm, which produced 4.5mm of rainfall.
It was a warmer day with the maximum of 20.7C equal to the August average. As on previous nights the cloud meant a mild night, minimum of 13.4C, which was 2C above the August average.
This morning has dawned grey and breezy as the thick cloud from the approaching depression obliterates any sunshine.
Summary for July 2017
July 2017 was not a month to remember as a summer month as we had little glorious sunshine or recurring high temperatures.
The very changeable month, after the first week, was due to a succession of depressions passing over or near the UK. The barometric pressure was 2mb below the long-term average.
Although the mean temperature was just above the 33-year average (+0.27C) this figure masks the fact that the average daytime temperature was 0.2C below the long-term average. The many cloudy nights gave a contrasting picture as the average minimum was above the long-term average (+0.6C). During such nights the cloud acts as a blanket to stop heat radiating back into the atmosphere.
The month started with several very warm days, the peak being reached on the 6th with a maximum of 29.9C but from the 11th onwards the temperatures fell away during the daytime. There were two days when the thermometer only reached 17.3C (22nd and 23rd), which was a significant 5C below the 33-year average.
Low-pressure systems bring cloud that mask the sun and bring precipitation. There were many days when bands of showers, some heavy, transited the area. There were 9 dry days before the 11th, but only 6 after that date.
The wettest day occurred on the 11th when a considerable rainfall total was recorded of 26.2mm. There were two additional days, 21st and 29th, when rainfall totals were in double figures, 23.5mm and 14.8mm respectively.
The rainfall total for July came to 97.4mm, making it the wettest July since 2009. This total was 163% of the 33-year average or plus 37.6mm. It is interesting to note that the five wettest July months have occurred since 2002 (my records go back to 1984). In July 2007 I recorded a total of 127.2mm and 2009 amounted to 113.0mm.
I recorded 117 hours of strong sunshine, slightly better than the past two years since this instrument was installed. However, global sunshine, which includes reflected strong light, was 11 hours down on the average for the past 11 years.
During the periods of strong sunshine, including latter days when there were only brief bursts, the UV levels rose into the ‘Very High’ category on 19 days. The peak reading was on the 16th that was almost into the ‘Extreme’ category.
Meteorologists keep diurnal temperature records. These figures note the daily range of temperature from the maximum to the minimum. As humans we have to adapt to these ever-changing conditions. A good example occurred this month. On the 2nd, the diurnal temperature range was 23.4C (24.2C to 1.0C) and in contrast the 19th had a range of just 3.0C (19.4C to 16.4C).