Author: Eric Gilbert

Wednesday was the coolest day this month with a maximum of 21.2C just 1.3C above average. Overnight, although just above average (+0.2C), the thermometer fell away to 11.7C at 05.50 making it the second coldest night in August.

There was a heavy dew overnight because of the recent rainfall and low temperature so the ground and surfaces were covered with much moisture.

A short lived ridge of high pressure will give a better day today before the rain and wind arrive from the deep depression slowly closing in on the UK from the Atlantic. The current barometric pressure at the centre of this unseasonably deep depression over the eastern Atlantic is 979mb and still falling, a pressure usually associated with autumn or winter storms.

Rainfall for July currently stands at 7.7mm and evaporation totals 18mm.

With a maximum of 21.9C (+1.1C) on Tuesday it was the coolest day this month, but still above average, with rain arriving late afternoon that, with a brief shower overnight, amounted to 5.7mm.

The sixth above average night followed with the thermometer not sinking below 13.1C (+1.6C).

Wednesday morning was overcast with drizzle between 07.15 and 08.00 but by 09.00 the sky was breaking with intermittent sunshine.

For most of the daylight hours on Monday it was dry with 7.2 hours of sunshine that just after midday lifted the maximum to 22.7C being 1.9C above average. However, spots of rain began to fall just before 19.30 that developed into a light shower for half an hour amounting to 1.1mm from a slow moving, narrow band of cloud moving in a north easterly direction over this area.

Another mild night followed with a minimum 14.6C being 3.1C above average.

Tuesday arrived with much sunshine, between variable cloud, so that by 08.00 the thermometer read 17.3C and the ground temperature, at a depth of 5cm, the warmest this month at that time of 18.3C.

As the depression off the north west of Scotland edges near the barometric pressure is currently reading 1007.8mb, the lowest this month.

Update on Monday at 18.15: reduced sunshine due to increasing cloud in the afternoon limited the temperature to a maximum of 21.9C at 13.20 before very heavy rain arrived 16.30, amounting to 5.5mm, before the sun broke out again early evening.

Sunday gave us the warmest day of the month as the thermometer rose to 25.4C being 1.5C above average. Around 16.15 ad 17.15 there were a few spots of rain, but not measurable.

The humidity on Sunday afternoon was very high, 63% mid-afternoon when usually nearer 40%, that combined with the very warm air, meant it felt rather uncomfortable.

A very mild was to follow with the thermometer not sinking below 15.2C, 3.7C above average, due to a band of thick cloud over the central part of the UK. This produced low cloud, misty conditions and drizzle on Monday morning, which by 08.00 amounted to just 0.1mm.

The barometric pressure is currently at its lowest in August due to a depression off the west coast of Ireland that is producing the thick cloud.

With less sunshine on Saturday (6.6 hours) it is not surprising to find that it was less warm than Friday with a maximum of 22.6C, still 1.7C above average.

The past night was also above average (+1.7C) with a minimum of 13.2C due to cloud cover.

Sunday arrived with brief, hazy sunshine. The barometric pressure has been slowly falling for the past two days as another Atlantic depression approaches the country.

Update on Sunday at 16.50: very warm Atlantic air with high humidity (over 60%)and a maximum of 25.4C at 15.10, made it rather uncomfortable this afternoon.

July 2019 summary

July was a month of two halves. During the first 16 days of the month we had just 0.3mm of rainfall, which fell on the 6th with the remaining 15 days totally dry.

However, with the wind then backing predominantly into the southwest the rains arrived, especially on three particular days. The daily rainfall on the 19th, 23rd and 30th was 12.9mm, 12.2 mm and 15.3mm respectively. These three days accounted for 67% of the monthly total, which at 50.8mm was 9.1mm below the 35-year average.

The rainfall extremes for July reveal that in 1999 just 10.1mm of rainfall was recorded and the year 2007 was very wet with no less than 127.2mm, which was more than twice the average.

Taking a broader look at the rainfall statistics I find that the rainfall for the period January to July was 402mm whereas the 35-year average for these seven months is 450mm, a difference of 48mm.

It was not surprising to find that evaporation from ground sources and plant life was very high during the month. We lost the equivalent rainfall of 108.1mm with eleven daily totals exceeding 4mm, the peak being 5.04mm on the 23rd.

Looking at the temperature statistics I find that the mean temperature was 1.2C above average. It is interesting to note that the mean was 3C below the very hot July in 2018.

There were 19 days when the maximum temperature rose above the 35-year average with several days notable for very hot weather. At the end of the month there were five days with exceptional heat from the 22nd to the 26th with 25.6C, 32.0C, 29.0C, 32.6C and 25.2C respectively.

At the beginning of the month there was also a short hot spell with daily maximum exceeding 25C. At that period the soil at a depth of 5cm, when read at 08.00, was at its warmest with a reading of 22.9C. With an average monthly temperature at that time of day of 19.2C, this was 2C down on the hot, dry month in 2018.

There were 276 hours of sunshine during the month with the sunniest occurring on the 4th with 13.77 hours.

Fog occurred in the early hours of the 23rd and 29th that reduced visibility to 100m but quickly dispersed as the sun got to work.

The UV level on 24 days rose up to the ‘very high’ category with on the cloudy, wet day of the 19th only ‘moderate’.