Category: Commentary

The nearby anticyclone really began to dominate our weather on Friday that brought heat and humidity and saw the temperature rise to a maximum of 26.8C being 6.2C above my long-term average. The UV level of 7.9 for the second consecutive day was well into the ‘Very High’ category. Cloud cover overnight persisted and looking at the track on radar it indicated that it began to thicken around 05.00, which is why the minimum of 18.4C was a significant 8.2C above average and made it the warmest night since 13th August 2020 when a low of 19.4C was logged.

The heat factor, using the data of temperature, wind speed, humidity and solar activity, calculated that outside it felt more like 31.5C when the thermometer read 26.6C.

Saturday revealed low, thick cloud and thus no sunshine to greet the new day. The anticyclone has continued to build and dominant our weather with the barometric pressure reading of 1023.7mb at 08.00, up 10mb since Wednesday.

The forecast is for the heat to continue to build and peak on Monday, with Tuesday down a few degrees and the rest of the week much closer to July temperatures. It is likely that we will technically be experiencing a heatwave over the next three consecutive days as maxima are likely to equal or exceed 27C, which is the heatwave threshold for Wiltshire.

The image taken in 2015 is from St Peters Church tower in Marlborough, looking south with Savernake Forest in the background.

The variable cloud on Thursday, especially in the afternoon, combined with the very brisk westerly breeze, muted the temperature a few degrees with a maximum of 22.3C logged at 13.15, being the lowest for three days but still 1.7C above average. A narrow band of rain arrived at 10.25 that produced just 1mm in a very sharp shower, but within an hour all evidence of the rain had disappeared as the sun returned. More rain was observed starting at 22.30, light at first and a little heavier just before midnight, that amounted to 2.0mm. Although it was a cloudy night the thermometer sank to its lowest for eight days bottoming out at 11.6C logged at 05.29, being 1.4C above average.

Friday began with strong sunshine that lifted the temperature to 17.5C by 08.00. However by 08.30 variable cloud began to obstruct the sunshine.

The rainfall total for June to date is 37.1mm compared with my 41-year average of 52.9mm. However, the equivalent loss of rainfall through evaporation from the ground and plant life this month is triple the rainfall total with 96.7mm of moisture lost due to the heat and brisk winds that occurred on many days.

There are a few days left in June but both the average maximum and average minimum are currently a significant 2C or higher above my long-term average. An Amber Heat Health Alert has been issued for today and the next four days, which is one step up from a Yellow warning.

The high pressure to the south has begun to assert itself as it gets closer and currently extends from mid-atlantic to the east of the Continent. The forecast track of the Jet Stream indicates that the very hot weather will build today and last until at least Tuesday. There are indications our area will be influenced by a heatwave that has been developing across western Europe.

The image was taken from St Peter’s Church tower in Marlborough in 2015 looking across part of Marlborough College.

Wednesday was the sixteenth consecutive day with the maximum above my long-term average with a peak of 24.3C logged at 14.56, which was +3.7C. Mid-afternoon brought variable cloud before the temperature picked up again late afternoon but not surpassing the earlier high. The wind was very light, after a few breezy days, with a maximum gust of 11mph continuing from the west. The UV level fell back to ‘High’ after three consecutive days when it soared into the ‘Very High’ category. The minimum of 16.1C was also well above average at +5.9C logged at 04.27 early Thursday.

Thursday arrived revealing a cloudy sky after some initial brightness, which was due to a cold front passing over our area bringing thicker cloud. A few light spots of precipitation were observed at 06.40. The cloud from the second weather front, currently over the West Country, appears to be fragmenting so probably little or no precipitation when it arrives over our area around midday. The cloud will limit sunshine today so a cooler day is in prospect.

The anticyclone just to the south of the UK will begin to assert itself from Friday that will see temperatures by day soar again with a possible short-lived heatwave that will last through the weekend reaching a peak on Monday.

Summer temperatures usually rise due to day-on-day heating known as homegrown warmth, as high pressure takes charge. This was the case through the middle of last week, which will be repeated over the next four days as a plume of hot air surges north over the UK. The soil temperature at a depth of 5cm has risen over the past three days with 17.3C, 19.7C and 20.0C respectively today.

The image is looking north from St Peter’s Church tower in Marlborough over the sports ground that was taken in 2015.

Tuesday saw temperatures rise again, both by day and night. Although the breeze was from the west, the very strong sunshine after a cloudy morning, boosted the temperature to a high of 24.7C at 16.33 being 4.1C above my long-term average and the warmest day since Saturday. Overnight cloud minimised loss of warmth into the atmosphere thus it has been a mild night with a minimum of 15.2C just before sunrise at 04.24 being 5.0C above average.

The clearer air from the Atlantic saw the peak solar radiation reach 1172W/m2 at 12.58, some 35% higher than last week when we had the polluted air from the Continent.

Wednesday morning brought total cloud cover that has been edging up from a larger bank of thick cloud over the Channel. However, there are signs that it might begin to thin and break up as the morning progresses. The temperature at 08.00 had risen to 17.6C.

We are still under the influence of the Atlantic and sandwiched between the low pressure to the northwest and high pressure to the south thus the wind will continue to come from the west but be less strong than of late as the pressure gradient has decreased. There is currently an area of disturbance over the Bay of Biscay that is likely to move northeastwards and clip the southeast of the UK but not likely to produce much rain over our area.

The Atlantic air has brought much more humid air having travelled over the sea rather than land from the Continent as last week. The humidity at 08.00 for the last two days has been in the mid-80’s compared to the mid-70’s last week. The pattern is the same in the afternoon with mid 70% recently when last week the humidity dropped exceptionally low to the mid 40%.

The total rainfall for June so far is just 34.1mm compared to my 41-year average of 52.9mm with little rain likely in the next few days.

The forecast track of the Jet Stream is for it to begin to move northwards again so allowing hotter air to return for the next few days, likely peaking over the weekend or possibly next Monday.

The image was taken from St Peter’s Church tower in Marlborough looking east over the high street

Now that we are under the influence of Atlantic weather it was not surprising to see the temperature by day on Monday much lower than last week with a maximum of 20.2C at 17.01, which was 0.4C below my long-term average. It was also the coolest day since the 9th June. The cloud cover overnight meant a mild night with a low of 12.9C at 00.24 just after midnight early Tuesday which was 2.7C above average.

Tuesday revealed a cloudy start to the new day with a couple of light drizzle showers that amounted to just 0.2mm. The temperature had recovered to 15.7C by 08.00. Another weather front is the reason for the overcast conditions, which is crossing our area during daylight hours brought by a brisk southwesterly breeze. As the depression mainly over Scandinavia edges further east, the wind will veer into the west later in the morning, the air stream travelling around the southern flank of the low pressure system.

The clearer air on Monday from the Atlantic again showed a 25% increase in peak solar activity compared to the polluted air from the Continent during the previous week.

Tomorrow will see the high pressure to the south edge a little closer that will result in a brighter day with the temperature rising again to well above normal before the possibility of disturbed conditions arriving, possibly in the evening.

The images this week were taken from St Peter’s Church tower. This picture is of the very wide high street looking east.