Category: Commentary

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.

The two cold fronts passed over our area on Sunday as forecast, just before and after midday, that brought thicker cloud and a cooler air stream on the breeze from the west. The maximum of 15.1C was the coolest day since the 9th but still 1.0C above my long-term average. The cloud meant lower solar energy and the UV level back to the ‘Low’ category, not seen since March, likewise we have not seen a westerly since last month. Variable cloud meant the thermometer did not begin to drop away until after 23.20 due to a bank of cloud, but by 04.52 the thermometer had reached its minimum of 1.5C being 2.2C below average.

First light on Monday revealed the low temperature and a much more moist air stream, a humidity of 95% was the highest at 08.00 all month, which had allowed fog to form that at sunrise limited visibility to 300m. However, just before 07.30 the sun began to break through and by 07.50 it had virtually dispersed, just limited to the north of our area and could be seen in the distance over the Thames Valley.

We are now under low pressure systems to the northwest and southwest of the UK. The small low currently over Iberia will migrate northeastwards over France and is forecast to be over southern England this time tomorrow bringing more cloud and the possibility of light rain, there is some disagreement over this feature between the major forecasters. The barometric pressure had dropped to its lowest all month yesterday due to the departure of the anticyclone and arrival of low pressure systems with a reading of 1003.2mb, but eased upwards to day to read 1006.0mb.

The cooler air and reduced sunshine is slowing up the development of the apple blossom but slowly the trees are beginning to change colour.

The maximum of 21.6C on Saturday was exactly the same as on Friday being a significant 7.1C above my long-term average thanks to the many hours of strong sunshine. The increased cloud cover overnight gave us a mild night that saw the thermometer only dip to 6.5C being 2.8C above average. There were a few drops of rain observed very briefly at 19.55 that only dampened the hard surfaces but was not measurable.

Sunday brought us a brief glimpse of weak sunshine after sunrise but cloud very quickly drifted across from the west just after 07.30. This change is due to the anticyclone having deserted us and the depression, centred just off Iceland, throwing a couple of cold fronts across the country today.

The coming week will see the variable weather patten established with, sadly, much less sunshine, the days will not be quite so warm but conversely, the nights will not be so cold.

The first twelve days of April followed the extended dry period in March with no measurable rain having fallen. There is no forecast rainfall in the next couple of days with the possibility of a light shower on Wednesday morning. The sunshine and warm breezes this month has seen the equivalent rainfall of 37.2mm lost through evaporation from ground sources and plant life.

Friday was the last of the very warm and dry days under the resident high-pressure this month. A maximum of 21.6C was logged at 15.56 being the second highest this month and 7.4C above my long-term average. The day was also notable for the light breeze, there was a peak gust of 9mph but much of the day was calm. There was also a significant change overnight as thin cloud drifted up from the south that minimised loss of warmth into the atmosphere resulting in a minimum of 3.3C at 02.18 being, just 0.4C below average.

The thin and broken cloud was evident after dawn although by 08.00 the weak sun had lifted the temperature to 9.2C making it the second warmest start to a day at that time this month.

The anticyclone that has dominated our weather all month has moved away, far to the east, and we are now coming under the influence of a depression in the eastern Atlantic. This low pressure will bring weather fronts across the country today and is already throwing up more cloud that will thicken as the day progresses. At the moment there is little indication of any precipitation over the weekend.

It is suggested that the name “Pink Moon” was given by Native Americans to represent the colour of the wild ground phlox.

It took a while for the sun to burn back the cloud on Thursday beginning to breakthrough around 10.00 and then strongly after 11.00. The maximum of 15.9C was logged at 16.48 in the strong late afternoon sunshine being 1.8C above my long-term average. Overnight was a repeat of previous evenings with the temperature falling steadily. The thermometer logged freezing air (-0.1C) at 05.23 early Friday and getting back above freezing at 06.48 after the sun got to work. The minimum of -0.4C was recorded at 06.07 being 4.1C below average. Although the cloud limited the morning sunshine the high solar pf 737W/m2 was the second highest all month after the peak of 835W/m2 on the 4th. The peak gust of just 9mph made it the equal calmest day this month.

Thankfully, no cloud drifted across from the east overnight so the sun shone strongly after it had lifted above the horizon raising the temperature to 4.9C by 08.00. It has been a remarkably calm start to the new day with the anemometer stationary for long periods, in fact there was a movement of just 1mph just before 23.00 last night and nothing again until a movement of 2mph at 04.31, 04.32 and 04.33 early this morning then calm again.

The barometric pressure charts show the anticyclone beginning to move eastwards over the next day or two, towards the Mediterranean, with the depression to the west getting closer. The barometric pressure has already dropped a significant 7mb since yesterday. This signals the change to a more unstable weather pattern with the wind on Sunday projected to come from a more westerly direction after the cool easterly quarter that has plagued us all month but offset by the strong sunshine. At the moment the forecast charts don’t show any significant rainfall over the next few days although two weather fronts are likely to cross the country on Sunday.

The apple trees are showing signs of the buds beginning to open so over the next week I will include images of the various stages as the blossom begins to fully open attracting the bees.