Category: Commentary

An arc of cloud drifted across the sky mid-morning on Tuesday until around 14.00 with variable cloud that did slightly limit the rise in temperature until after that time. However, over the past five days the maxima have steadily fallen downwards with 21.8C,18.6C,16.8C,16.2C and 15.8C respectively under the cool northeasterly breeze having travelled over the cold North Sea. The same is true with the overnight minima, that under clear skies, I have logged 4.4C, 2.5C, -0.1C, -1.2C and -1.4C respectively. The cooler air has slowly seeped into the ground with the temperature at a depth of 5cm reflecting that trend with 8.7C, 7.6C, 7.3C, 6.9C and 6.3C respectively. We must realise that the maxima were all well above average for early April whilst, excluding the minimum of 4.4C on the 5th, the remaining minima were all well below average.

Wednesday began again with strong sunshine soon after sunrise with another sunny, dry and warm day ahead.

The anticyclone has continued to slowly build and will continue to dominate our weather until the weekend with a consequent air stream from the northeasterly quarter.

The cloud radar over the past few hours has seen variable cloud drifting in from the cold North Sea and approaching Reading up to 08.00, but hopefully, as the sun gains in strength, this will burn back before it reaches our area.

March was an exceptionally dry month and that trend has continued into April with now twelve consecutive dry day, eight of them in April. The warm weather and drying wind has seen over 3mm of equivalent rainfall lost daily through evaporation from the ground and plant life and now totals 24mm for April.

The image is of blossom in Priory Gardens, Marlborough.

The maximum of 16.2C on Monday, logged at 16.12, made it the second coolest day this month even though we had wall-to-wall sunshine and the wind was much lighter. However, the distinct variation was the wind direction that had backed a few degrees to come from the north east after a cooler night, even so the high was 2.1C above my long-term average.

Looking at the data for the last three days the UV high was almost identical as was the peak solar radiation and evaporation. The output from my 12 solar panels for each day showed a beautiful, smooth normal curve thanks to the unbroken sunshine even if there was very thin high cloud that limited peak solar generation.

There were no clouds overnight to minimise the loss of warmth into the atmosphere, as a result the temperature slowly declined to register a minimum of -1.2C at 06.33 before the sunrise at 06.28. In fact the temperature dropped to freezing (-0.1C) at 04.56 and did not rise above until 07.09, resulting in just over two hours of air frost. It was the coldest night since 16th March being 4.9C below my long-term average.

As mentioned above, the sun got to work immediately after sunrise lifting the temperature to 3.8C by 08.00.

The anticyclone has built a little since yesterday as the depression slowly fills and begins to move away. It repositioned a little over the past twenty-four hours as the centre moved further north, hence the wind from the northeast after seven successive days with a strong easterly. The barometric pressure read 1027.6mb at 08.00 Tuesday, the highest all month.

The image is of a Snake’s Head Fritillary in Stonebridge Meadow, Marlborough, taken an hour after dawn with ice particles still in evidence after the brief frost.

The breeze on Sunday continued from the cool east that again pegged back the rise in temperature to a maximum of 16.8C, however, this was still 2.7C above my long term average. Out of the wind it felt very warm in the sunshine with the UV level once again at the top end of the ‘Moderate’ category thanks to the very thin high cloud that limited the solar strength to a maximum of 670W/m2 at its peak.

The pattern of numerous hours of glorious sunshine under clear skies again produced the expected cool night as the thermometer very slowly and continuously allowed the warmth to dissipate into the atmosphere with the thermometer only dropping to freezing point of -0.1C at 06.31 early Monday. However, this only lasted for 7 minutes as the sun quickly began to reverse the trend so that by 06.38 the thermometer had returned to 0C. The ground frost lasted for several hours but the air frost was lifted after just 7 minutes.

Monday morning was a repeat of the previous days as the sun shone strongly after the sunrise at 06.30, raising the temperature to 5.7C at 08.00. This will give us another day with likely wall-to-wall sunshine, the maximum well above average and likely feeling warmer with a lighter breeze.

The anticyclone has continued to build over the past two days with its centre closer to the UK, currently over the North Sea, as the depression eased westward and began to fill slowly. This has seen the pressure gradient between the two giants fall thus reducing the wind strength, a little yesterday and will be much lighter over the next few days. The high pressure will move very little over the next few days so more of the same with the wind continuing to come from an easterly quarter and not change direction until possibly Saturday. The barometric pressure has risen 7mb since its low on the 3rd to read 1026.0mb at 08.00 today.

Image from Priory Gardens, Marlborough.

Once again on Saturday, although we had many hours of sunshine, the strong north-northeast then easterly breeze pegged back the temperatures a little although a maximum of 18.6C at 15.58 was still 4.5C above my long-term average but down 3C on the very warm day on Friday. A peak gust of 24mph was logged with the UV level still at the top end of Moderate.

With a clear sky overnight it was not surprising to find that the thermometer dropped steadily to reach a minimum of 2.5C at 06.18 producing a widespread ground frost.

The sun began to shine strongly as soon as it rose above the horizon on Sunday lifting the temperature to 5.1C by 08.00. This is likely to be the last day when the wind from the east is strong, from Monday it will be lighter in strength, thankfully.

The dominant high pressure, that has been with us all month, is likely to continue to bring us dry and sunny days for much of the coming week, just a little relocation after midweek. The barometric pressure has risen 3mb since yesterday.

From time to time I read items in the press, from the weather forecasting site WXcharts, predictions of storms or recently last week on two separate days, snowfall of several inches, which I have never seen materialise. I was interested to read yesterday a comment from a Met Office spokeswomen “that many snow forecasts are based on “one-off simulations” indicating possible extreme weather. These, she said, form, “just one part of the wide range of information used to provide a full forecast picture”. “Different simulations produce different pictures of the weather forecast and one-off, single charts, do not provide the broader forecasting picture.

The picture was taken at Kennet Place during Marlborough in Bloom in 2015 when we were awarded Gold.

The maximum of 21.8C on Friday at 15.38 was a significant 7.7C above my long-term average that made it the warmest day since 19th September (22.3C). The variable cloud in the morning slowly thinned and eventually broke up with strong sunshine after midday. The persistent wind from the east, with a peak gust of 26mph, made it feel cooler producing a modest wind chill.

The past night gave us a minimum of 4.4C, just 0.7C above the average as variable cloud that had drifted in from the east stopped it falling further.

Variable cloud was observed on Saturday after sunrise that initially limited the sun’s strength but by 07.00 the cloud was being ‘nibbled back to the east coast’, a non-technical term I heard from a meteorologist on the TV. The cloud had drifted in from the cool North Sea, which has a current temperature of just 8C.

The forecast charts indicate that the high pressure will be with us well into next week with again tomorrow the strong easterly air flow. There is quite a pressure gradient between the anticyclone and depression, hence the strong breeze these past days.

I have mentioned this week that the brisk easterly had produced a wind chill. I have discovered, to my surprise, that there is no official definition of wind chill as definitions vary globally, dependent on how it is measured. In the UK,a system called Joint Action Group for Temperature Indices is used to realistically measure wind chill. This calculates wind chill by measuring how much heat is lost from a person’s bare face at a height of 5 feet (human height) using wind speed, temperature and humidity data. The temperature today of 7.1C at 08.22 felt more like 5.7C outside.