Category: Commentary

Once again the bulk of the heavy rain was to the west of our area on Friday, with just drizzle observed during the afternoon at 16.50, also the automatic rain gauge was triggered at 03.15 early Saturday that indicted light showers for perhaps 15 minutes. The daily rainfall total was only 0.8mm, which took the monthly total to just 2.9mm against the 41-year average of 57.6m. With just 11 days to go in April I wonder if this month is following the pattern of the very dry month that we experienced in March?

The maximum of 13.3C on Friday, logged at 14.54 due to the cloudy skies with no sunshine, was 0.8C below my long-term average, only the second below average maximum this month. Not surprisingly, it has been a mild night thanks to the thick cloud cover minimising loss of any warmth into the atmosphere with the thermometer hovering around 9.5C for much of the early hours, which in fact was the minimum at 03.40, only rising to 9.6C by 08.00 Saturday.

Saturday dawned dull and grey with very light intermittent and short lived rain around 07.30. As the depression has relocated around the Bay of Biscay the breeze today will come predominantly from the west, a cool direction, possibly strengthening mid-morning, so no heat wave today, especially as there is little chance of sunshine due to the depression lurking close by throwing banks of cloud across the UK. The rain radar at 08.30 indicated a wider rain band heading our way during the morning but if the patten of previous days continues, this will thin and break up as it moves north across our area.

The depression is forecast to hang around for a couple of days, moving across France and eventually probably over the Netherlands by Monday. So the holiday weekend will bring mixed weather, sunshine and showers covers it.

The forecast track of the Jet Stream indicates that later in the week, perhaps from Thursday onwards, a small area of high pressure will develop over the UK, or at at least a ridge of high pressure, that will influence our weather with brighter conditions and slightly higher temperatures.

Thanks to the southerly breeze on Thursday, and also much being lighter than on Wednesday, the temperature rose to a peak of 16.1C being 2.0C above my long-term average. The day was dry with the maximum solar radiation moving into four figures for the first time this year with exactly 1,000W/m2 logged 13.25.

Initially overnight under clear skies the thermometer dropped steadily downwards reaching a minimum 4.2C at 02.23 early Friday but increasing cloud from the depression to the west of the UK saw the thermometer do an about turn and begin to rise reaching 9.4C at 08.00.

Friday gave us a very brief glimpse of brightness after dawn but cloud quickly thickened with spots of rain between 07.30 and 08.00. The rain radar shows an advancing band of fragmented rain heading our way for around midday.

The low pressure system, just off the tip of southwest Ireland, will linger around that area all day throwing cloud and rain northwards. We will once again be on the periphery of heavy, more consistent rain until later in the day and especially Saturday morning when we could have a more substantial fall of rain.

There were many hours of sunshine on Wednesday but a couple of very light showers occurred mid-morning that amounted to 0.3mm but nothing thereafter. The wind was very strong during daylight hours, peaking at 30mph again in the afternoon. The thermometer eventually peaked at 14.4C, logged at 14.41, being just 0.3C above average. As the skies cleared in the evening the thermometer began a steady fall reaching a low of -1.5C at 05.44. Analysing the minute by minute data stream the air frost began at 02.55 and only returned above freezing at 06.58, thus four hours of freezing air. Thankfully, my apple blossom is yet to unfurl, so no damage last night.

After dawn on Thursday the sun began to work lifting the temperature to 4.4C by 08.00, however, it was the coolest start to a day at that time since the 10th (4.1C). The wind will be much lighter today, changing direction from an easterly quadrant first thing to a south-southwest air flow this evening.

We are now under the influence of another major depression, centred in the western approaches, so the unstable weather pattern continues with sunshine and the likelihood of showers occurring. There is the possibility of fair weather clouds, cumulous clouds, occurring again today. As the warmth increases the moist air rises, condensing into white, puffy clouds.

This depression will, as yesterday, move northwards up the western side of the UK, principally later today and on Good Friday, so once again we are likely to be on the periphery of any substantial rainfall.

After a relatively calm and sunny day on Tuesday the thermometer lifted above average again, just, with a maximum of 14.7C being 0.6C above my long-term average. Thicker cloud built up in the afternoon, thanks to the depression that had been lurking over Brittany, throwing up a large area of cloud that produced light rain just after 16.00. Another light rain shower triggered the automatic rain gauge at 00.52 that raised the daily precipitation to just 1.0mm. Considerable rain ran up the east and west coasts during the day and to the west overnight. The low of 4.6C was logged at 05.59 early Wednesday being also above average, just, at +0.9C.

Wednesday after dawn revealed broken cloud scudding fast across the sky. Overnight, the depression had decided to move north and visit the UK, continuing to move north to the west of our region. We have been, and continue to be on the periphery of the depression, however, the wind strength increased markedly during the late evening and overnight as we were close to the centre of the depression. The minimum barometric pressure of 994.1mb was logged, the lowest since 28th January. The first indication of rising wind strength was observed just after 22.00, building to a peak of 33mph at 02.14, but close to that peak for several hours. As the day progresses the cloud is likely to break up and thin as the depression eases away, allowing some variable sunshine with the wind slowly decreasing.

The temperature of 6.7C at 08.30 felt more like 5.0C outside due to considerable wind chill. Wind chill could be called the ‘feels like’ temperature being different to the actual air temperature, which measures air temperature, relative humidity and wind strength at five feet (human height) as well as an understanding of how heat is lost from the human body during cold and windy days.

There is no official definition of wind chill as definitions vary globally, dependent on how it is measured. In the UK, a system called the 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 walking speed of 3mph.

As the depression moves away the barometric pressure is rising rapidly at over 4mb every three hours.

Although the wind was predominantly from the warmer southwest during daylight hours on Monday the variable cloud and limited sunshine restricted the temperature rise to a maximum of 13.5C at 12.56 being the first below average peak this month at -0.6C.

The first spots of rain, only spots on the window, were observed at 19.30 as the main rain band progressed up the western side of the country leaving us on the fringe of a wide rain band. There were a couple of brief showers when the automatic rain gauge was triggered at 23.07 and later at 00.52 early Tuesday producing just 0.8mm of rainfall, the first measurable rainfall since the 27th, which then only produced 0.1mm. Thus we are half way through April with 0.8mm of precipitation against the 41-year average of 57.6mm.

Tuesday revealed a cloudy start to the new day, however, just before 08.00 the sun broke through gap in the cloud with blue sky appearing. The cloud radar shows a heavy bank of cloud to the east, with heavy rainfall, running northwards and another large area of cloud to the west, also moving northwards, with a small triangular gap between the two, which is likely to be short lived but welcome to start the day. The repositioning of the depression will result in the breeze coming from the east today.

The depression to the southwest is currently over Brittany and will head northwards over the UK as the day progresses throwing more cloud across the country, but variable in its content. The centre of the depression is very close with a barometric pressure reading at Marlborough of 995.8mb at 08.00, the lowest pressure since January. The rain is currently falling over eastern parts of the London area and also over Devon and Cornwall with more to come.