Anticyclone intensifies

The high pressure now centred over the UK has been intensifying over the past twenty-four hours, as a result it has blocked the flow of Arctic Air but left a pool of very cold, static air over the UK. The thermometer on Monday, during 6.7 hours of sunshine, rose to a maximum of 9.7C, however, this was again below average (-4.3C).

The thermometer fell steadily downwards during Monday evening and at 22.39 dropped below freezing (-0.1C), just six minutes later than the previous night. The past night has been the coldest since 11th February win a minimum of -3.9C at 06.20 on Tuesday morning being a significant 8C below average. In fact we have only had one day and night with temperatures above average.

Tuesday saw bright, if muted sunshine for the first hour but a fog bank, which had been lurking to the north of Marlborough from the Thames Valley, rolled in over the Downs so that by 07.15 the visibility had reduced to 200m. The sun disappeared half an hour later so that by 08.00 the temperature was still below freezing with a reading of -0.4C.

The anticyclone has dampened out the wind of previous days and dropped out entirely for many hours overnight thus allowing the frost to intensify. The barometric pressure at 08.00 was 1033.7mb

Hail then snow – it’s supposed to be Spring!

The welcome 6.9 hours of sunshine on Sunday, intermittent in the morning but more sustained in the afternoon, encouraged the thermometer to rise to a maximum of 9.7C, This was up 4C on the very cold Saturday peak but still 5.4C below the 37-year April average.

A brief light shower of small hail (less than 5mm in size) was observed at 13.00.

The thermometer fell steadily during the late afternoon and evening to reach freezing point (-0.1) at 22.33 on Sunday evening. It continued falling until reaching a minimum of -2.6C at 02.52 early Monday morning. At that time the advancing weather front would have started to ease in the initial cloud with humidity starting to increase after 03.10. The radar showed thick cloud and precipitation arriving over this area at 04.10, which by daylight could be seen as a covering of snow but had ceased by 05.30. In the calm conditions there was a level 1cm of snow that began to slowly melt as the thermometer had risen to 2.0C at 08.00. The equivalent liquid from the melted snow amounted to 0.8mm.

Snow again – in April!

Throughout daylight hours on Saturday an area of thick cloud persisted over the area initially producing drizzle that then became light rain for almost twelve hours. It was an exceptionally cold day with the thermometer rising just a couple of degrees from that at dawn to a maximum of only 5.9C, which was a significant 8.4C below the 37-year average and the coldest since 7th March.

It was the first sunless day since 20th March with the UV peak of 1.4, which is at the lower end of “Low”.

During the early evening the temperature dropped to 2.0C and the precipitation turned to wet snow with a daily total of 6.2mm. This was the wettest day since 26th March and brought the monthly total to 6.6mm when the average is 58.5mm.

The cloud eventually thinned overnight and allowed the temperature to drop to -0.6C at 05.05 on Sunday morning that saw very brief bright intervals between occasional breaks in the cloud, which was thinner and higher than on Saturday.

Northeasterly returns

We enjoyed 6 hours of sunshine on Friday with a maximum temperature of 12.5C. This was the warmest day for a week but still 1.8C below the average. In fact we have yet to have a day in April when the thermometer gets above the 37-year average maximum.

A chilly night followed as the wind late afternoon on Friday, (17.00) began to veer into the north so a colder air flow arrived. The temperature dropped away to a minimum of 3.2C being 0.9C below average.

Saturday dawned dull with a large area of thick cloud producing occasional light drizzle but not measurable thus recorded as a trace. Currently at 08.00 the wind is very light and coming from the north-northeast.

A little rain and warmer, for a time!

The wind having backed into the southwest predominantly on Thursday meant a warm day with a maximum of 11.7C. However, this was still 2.6C below the 37-year April average but with much lighter winds and 3 hours of sunken it felt much warmer.

A very light shower fell at 20.15 that amounted to just 0.4mm, the first measurable precipitation since 27th March.

The minimum overnight was also below average with a low of 3.7C at 06.33 on Friday, which was 0.4C below average. In fact there has only been one night this month that was above average, namely 1st with 7.6C (+3.5C).

There was some brightness and limited sunshine on Friday morning through broken cloud. However, with a cold front on our doorstep, cloud will increase as the morning progresses and it will get colder again.