Category: Commentary

Monday was a pleasant sunny day without the extreme heat of recent weeks under the heatwave conditions, after the morning cloud moved on. The thermometer steadily rose to a peak of 22.2C at 16.31 being 0.5C below average whilst the past night was cool, and also below average at -1.2C, with a minimum of 10.6C logged at 05.10 early Tuesday just after sunrise in Marlborough at 05.00. The early morning light precipitation soon evaporated as the sun got to work and the gusty northerly wind picked up speed, peaking at 19mph.

Tuesday brought a bright and sunny day with the wind still strong, however, from a more north-northwest direction.

The Azores High is currently elongated in shape ridging across the country with the airstream circulating clockwise around the anticyclone, as they do. This is bringing the warmth from the Azores region around the northerly edge of the high before turning south across the UK, which will mean a more northwesterly breeze today.

There is a possibility that the heat will increase significantly on Wednesday and then be the start of another heatwave, that could last in excess of a week. It is chastening to realise that the extreme heat can produce excess deaths. During the intense heatwave of 2022 there were in excess of 4,000 additional deaths. Research shows that with maxima in excess of 25C there is an increase of 30% of deaths in England and 60% increase in Wales. The outlook is for the maxima to be well above that temperature for a week or more.

The cool northwesterly breeze and variable sunshine on Sunday afternoon limited the rise in temperature to a maximum of 21.4C at 12.29 being 1.3C below average. The afternoon was marked by a rash of showers developing to the north of our area with the occasional one producing brief light rain and drizzle over our area at 13.00 and later at 13.35. The past night was again mild with a low of 12.2C at 06.57 due to the thick cloud cover. A longer shower of very light rain and drizzle arrived just before 07.30 that the precipitation in total for the twenty-four hours amounted to 3.6mm.

The start to Monday was overcast with the drizzly rain that stopped just after 08.00. Both major forecasters gave a 90% confidence forecast of four hours of significant rain after 02.00 early on Monday over our area, however, they were both wrong as the heavy rain once again was to the east. At least the minimal precipitation has refreshed the plant life but only dampened the surface, which will soon evaporate.

Today will be the last of the cool days with the breeze coming from the north. By Tuesday temperatures will begin to climb with some certainty that another heatwave will arrive later this week that could last much longer than the two heatwaves in June. The Jet Stream track by tomorrow will be to the north of the UK allowing a feed of hot air to arrive from the south that will build as the week progresses. This is due to the Azores High beginning to build a ridge of high pressure over the UK on Tuesday that could last into next week.

The thick cloud on Saturday produced occasional light drizzle in the morning and just after 13.00 with a more sustained fall of light rain and drizzle starting at 15.00 that in total amounted to 2.6mm. This precipitation refreshed the plants but so little it did not sink far into the ground. In fact, just after 15.30 the sun came out as the back edge of the cloud eased away eastwards, that saw the late sunshine lift the temperature to a maximum of 21.9C at 17.27 being 0.8C below average, the first below average this month. The UV level of 3.9 placed it at the top end of the ‘Moderate’ level, the lowest for a month.

The cloud cover overnight meant a mild night with a low of 14.9C logged at 03.47 early Sunday.

The new day on Sunday revealed total cloud cover, which is due to a cold front passing over the UK, which will be closely followed by another around midday, so little expectation of much, if any, sunshine today. The barometric pressure has dropped to its lowest for a month with a reading of 1007.4mb at 08.00, down a significant 22mb since Friday.

The Azores High has now fully retreated to mid-Atlantic with the result our weather is influenced by the low pressure system to the north and northeast, in fact there are three of them, but none have a deep centre pressure. The realignment of the pressure systems will see the breeze come from the northwest today thus a cooler day combined with the cloud cover, and this wind direction will likely continue until Wednesday.

The Jet Stream forecast sees it begin to loop north of the UK on Tuesday that will result in the hot dry weather becoming increasingly prevalent from Wednesday.

Although the peak solar activity on Friday was the lowest this month, peaking at 909W/m2, the strong, almost continuous sunshine pushed the temperature to a peak of 25.9C at 14.37 being 3.2C above my long-term average. The air was very dry after so many dry and hot days, I recorded a minimum humidity of just 33.9% at 15.17 before light, variable cloud arrived limiting the sun’s strength. At 14.00, when the thermometer read 24.8C, the heat index meant it felt more like 28.3C outside, taking into account the air temperature, wind strength and direction, humidity and solar strength.

Looking at the back track of cloud and rain radar in the early hours of Saturday, there was evidence of a small cloud that brought very light and brief precipitation around 04.30, which was not measurable, hence recorded as a ‘trace’. There was just a little residual moisture seen first thing on Saturday on non-porous and previously very dry surfaces. The cloud cover gave us a mild night that saw the thermometer not sink below 14.6C at 05.20 being 2.7C above average.

The start to Saturday revealed total cloud cover and a brisk wind from the west-southwest. The cloud and rain radar indicates that by mid-morning a cluster of clouds might pass our way, preceded by light drizzle, and might bring brief precipitation, but not persistent steady rain over a considerable period to quench the dry gardens. These very different weather conditions are thanks to the depression to the north edging down across the country producing a weather front that will have left the south coast later today.

The weekend will bring us much cooler and cloudier conditions. However, by Tuesday the Jet Stream track is forecast to once again loop north of the UK that will see the Azores High begin to build and ridge back over the UK, which will mean the following days are likely to become very hot again.

Thursday gave us another fine, warm day that saw the thermometer eventually climb to a peak of 24.2C at 15.49 being 1.5C above average. However, thin cloud had drifted across by that time that limited any further rise. For the second successive night the minimum of 8.8C was below average at -3.0C, logged at 05.15, just after sunrise in Marlborough at 04.56.

After a bright start to Friday variable cloud arrived around 07.30 that limited the strength of the sunshine. The warm, dry weather today is the result of a ridge of high pressure from the Azores High.

This will be the last day of high temperatures this week as the recent anticyclone is splitting, as last week, returning from whence it came, with high pressure also building over the Continent. This relocation will allow a low-pressure system near Iceland to encroach over the UK bringing cloud on Saturday with little sunshine. In fact there is the possibility of some light rain, quantities probably limited, sadly, as any precipitation would be very welcome to gardeners for their parched gardens.

High pressure has retreated to the southwest, back to the Azores, and this semi-permanent high pressure that we get near the Azores, known as the Azores High, has been ebbing and flowing from the southwest during the past week, hence this repeating cycle.

The Azores High is a semi-permanent area of high pressure located over the eastern Atlantic Ocean typically near the Azores archipelago. It influences weather patterns across Europe as well as North Africa, and parts of North America.