Category: Commentary

The northeasterly, cool breeze persisted on Thursday that limited the rise in temperature combined, with reduced sunshine. The peak temperature of 14.8C was logged at 16.55 following strong, variable afternoon sunshine being 0.7C above my long-term average. The thermometer began to fall steadily after 20.00, reaching a low of 3.6C at 04.42, just below average for late April.

Friday after dawn revealed fog that had formed in the early hours. Looking at the minute by minute trace of data the humidity began to climb just after 03.00 so I suspect that is when the fog began to form. The visibility at 06.30 was down to 200m but by 07.00 there was visible improvement with the range extended to around 1,000m by 08.00. The temperature had also seen an improvement having climbed to 7.7C by 08.00. The air stream today will be from the south east, a slightly warmer direction than previous days, before backing into the east again tomorrow and then the significant change when it will come from a southwesterly quadrant on Monday.

The ridge of high-pressure will shortly combine with an anticyclone just off the Iberian coast that will bring us the fine weather next week, but that is not before a weather front tries to make progress across the country on Saturday bringing cloud and possibly some light rain.

The forecast rise in warmth and sunshine is still looking positive, with a significant improvement from Sunday with temperatures rising significantly as the week progresses, probably up to Friday.

The sequence of images for the next few days will be of the extensive range of Bluebells in West Woods, near Marlborough

The depression produced much cloud during the morning and early afternoon on Wednesday that limited the rise in temperature to a peak of 13.6C at 17.08, outside it feet very chilly. Variable sun broke through after 14.00 with increasing strength thus the maximum late in the afternoon being just below average. The improvement was due to the centre of the depression easing away and the pressure beginning to rise behind it. The humidity remained high after the overnight rain with minimal evaporation. The UV peak of 4.6 was in the ‘High’ category, logged at 14.05 when the sun first broke through. The overnight cloud again produced a mild night with a low of 7.6C, logged at 00.48, just after midnight, being 3.9C above average.

Thursday revealed another cloudy start to the new day, this time the light northeasterly breeze has dragged in cloud from the cool north sea, although the depression to the west is very close. The barometric pressure has risen significantly over the past twenty-four hours, a reading of 1022.1mb at 08.00 was a rise of 15mb.

The ridge of high pressure built yesterday and overnight that will over the weekday develop into a larger area of high pressure bringing dry and increasingly warm days, especially after the weekend.

The useful rainfall during Tuesday night was very welcome by gardeners. There is a possibility of light rain on Saturday as a weather front edges in but very little indication of any more rain likely during the next week as the anticyclone builds.

Tuesday brought us a very pleasant day with much sunshine that boosted the temperature to reach a maximum of 16.2C at 14.26, being 2.1C above my long-term average, before thin cloud began to drift across ahead of the depression moving towards the UK. There was a noticeable thickening of cloud during the evening and the first spots of rain from the weather-front were observed at 23.15. The steady rain began shortly after 23.30 with heavier bursts at 01.15, 02.45 and 05.00, that eventually amounted to 8.6mm. This was the heaviest daily rainfall since 26th February (10.8mm). The last of the steady rain ceased just after 05.30 with a few reluctant rain drops over the next hour or so from the hang back of cloud. The low of 8.2C, logged at 05.27 early Wednesday was 4.5C above average. The rain overnight was very welcome to gardeners as it had time to be absorbed by the very dry ground rather than during daylight hours when some of it would have quickly evaporated. The monthly precipitation total is now 11.7mm against the 41-year average of 57.6mm.

Wednesday after dawn revealed very low, thick cloud from the hang back of cloud from the depression that is slowly drifting southeastwards across the Channel towards the Continent.

I mentioned a couple of days ago that the forecast track of the Jet Stream indicated it beginning to loop north of the UK that would indicate a warmer period under higher barometric pressure. The latest charts indicate that a ridge will develop on Thursday and subsequently build, that will bring warmer and dry weather for most of next week. It will not be particularly warm on Thursday as the air stream will come from a northerly quadrant but by Friday this will change to come from a more southerly quadrant with subsequent higher temperatures over the next few days.

Two weather fronts dominated Monday with thick cloud until mid-afternoon with light drizzle observed for a couple of hours, starting just before 11.30. However, the precipitation was light and only dampened surfaces eventually measuring 0.2mm. As the clouds thinned and eased eastwards after 14.00 the sun broke through strongly pushing the thermometer to a peak of 16.2C late in the afternoon at 17.20 being 2.1C above average. The clearing skies meant the past night was chilly that saw the temperature drop to a low of 3.9C at 06.06C before the sun got to work lifting the temperature to 7.8C by 08.00.

Tuesday initially arrived with weak sunshine. The moist air and falling temperature overnight caused radiation fog to form in the River Og valley during the early hours, that quickly dispersed as the sun got to work, as a result by 07.00 it had completely cleared. Humidity of 89% was measured at 08.00, the highest for over a week.

A depression is now approaching Ireland that will later today arrive over central Ireland. This low pressure system is projected to cross southern England this evening pushing two weather fronts across the UK with possible substantial rainfall. The current barometric pressure of 1016.7C, logged at 08.00, will drop substantially as the centre of the depression is currently reading 996mb, this will result in the wind picking up during the afternoon ahead of the rain expected just before midnight.

Any measurable rainfall that falls during the night would be very welcome for gardeners so that it can be absorbed into the soil, rather than quickly evaporating if during daytime, as we have had less than 9mm of precipitaion over the last 52 days. This timing would be fine for those currently on holiday!

At 08.50 the radar showed showers breaking out over Devon and Cornwall with a thick bank of cloud leaving Ireland heading for the west country.

Sunday gave us bright sunshine from mid-morning until mid-afternoon that resulted in the temperature rising slowly to a peak of 14.1C at 14.28 being exactly equal to my long-term average, thereafter cloud built up again. The day was dry although a small area of thicker cloud passed to the northwest of Marlborough that gave some raindrops on my windscreen as I approached the north of Swindon at 18.50. The thick cloud overnight produced a mild night with the minimum of 9.5C at 05.43 being a significant 5.5C above my long-term average.

Monday after dawn revealed very dull, gloomy conditions with almost a total calm. We are under the influence of the recent depression, now heading towards the east, that is throwing considerable cloud over the UK. These conditions will only worsen as we approach midday when two weather fronts pass over central England that over the next few hours might produce a little light rain or drizzle, but of no real quantity. The breeze, when it picks up, will be light and veer from the southwest to west towards the afternoon.

The temperature at 08.00 read 10.2C making it the warmest start to a new day, at that time, this month. The barometric pressure of 1007.9mb at 08.00 is almost exactly the same as yesterday.

A new area of low pressure is developing to the northwest that will close in towards Wednesday, with possible useful rainfall for gardeners!

Two days ago the station recorded an alleged peak wind speed of 62mph. Sadly, with all the progress in electronics these glitches seem to appear occasionally. I could interrogate my older station, that was not on line, to delete these gross errors. Although Davis instruments have been advised by a number of people about the situation, they have yet to come up with a solution that would allow such errors to be removed, such is progress!

The forecast Jet Steam track suggests that it will begin to loop to the north of the UK from Thursday allowing a ridge of high pressure to form. This should bring brighter, perhaps sunnier weather, which will mean it should become a little warmer than at the start of the week.