Windrush Weather

Both the maximum of 7.5C, logged at 15.29, and the minimum of 4.2C, recorded at 04.15 early Friday, were above average at +0.4C and +2.9C respectively. Sadly,the murky conditions persisted throughout Thursday, there were a couple of very short and brief glimpses of sunshine mid-afternoon. A weather front passed over our area in a northerly direction mid-afternoon that behind it allowed the cloud to thin. A light breeze from the south, with a maximum gust of 10mph in daylight hours but 14mph at 02.47 early Friday, brought a slightly drier air.

The start to Friday revealed a totally cloudy sky but it was much thinner and higher with no fog or mist thanks to the drier air, a humidity of 94% at 08.00 was the second lowest this month at that time.

We are still under the very extensive high pressure, and will do so for a few more days, with a drop of only 5mb since the extreme high on Sunday last. Until this anticyclone eventually moves away, not likely until next week, we will still have much cloud and cooler air although it is being modified from the warmer air being carried up from Iberia.

The fog on Wednesday eased during the morning into misty conditions but began to thicken again after 15.00 and fog was observed forming at 16.00 with visibility shortly dropping to 200m. The lack of any sunshine meant the thermometer did not rise above the 08.00 temperature of 7.7C and began to drop late afternoon falling to a minimum of 0.3C at 00.58 early Thursday producing a sort lived ground frost. Once again there were periods of total calm with a maximum air movement of just 9mph on one occasion.

Thursday after dawn revealed another foggy and murky start to the new day with visibility restricted to around 300m. The temperature had recovered to 4.2C by 08.00. What air movement there is will be from the south today

The high pressure has eased eastwards, now over central Europe, but still extending across the UK. As a result the misty and calm conditions will continue, the barometric pressure having lost just 0.3mb over the past twenty-four hours with a pressure reading of 1034.9M at 08.00.

The Jet Stream is still arching to the north of the UK leaving us on the warmer southern side, which will continue up to Saturday when it becomes fragmented with the pressure falling away and more variable weather likely into next week.

The warmer air won on Tuesday as the ground also became less cold with the thermometer rising to a maximum of 9.4C at 14.27 being the first above average maximum since the 5th at + 2.3C. Cloud began to increase after midday, from a weather front moving south over our area, that also brought the misty conditions in the late afternoon an fog overnight.

The humidity began to rise from a low of 92% after 13.30 and reached 100% at 21.50, holding that value into Wednesday morning.

As a result of the thick cloud overnight, once again providing a duvet to minimise loss of warmth into the atmosphere, the thermometer did not drop below 7.7C logged at 07.58 on Wednesday, which was a significant 6.4C above my long-term average. The precipitation from the mist and very light drizzle amounted to 0.3mm after five consecutive dry days.

There was one very significant change in the weather data on Tuesday as the UV sensor gave a maximum value of 0.7, still very low as we are in January, but the highest value since 30th November.

Wednesday after first light revealed the misty and murky conditions had deepened into a fog limiting visibility to 200m.

The high pressure seems reluctant to move away with little variation in pressure over the past twenty-four hours, down just 0.4mb, with a reading of 1035.2mb at 08.00, and now centred off the coast of Brittany. It is likely to influence our weather until the weekend. This slight relocation, and it is forecast to move east over Germany, will see the calm conditions continue with the wind varying as the day progresses from west-souuthwest to southwest and then south-southwest.

It was a degree warmer on Monday than Sunday although it didn’t feel like it as there was more of a breeze. The thermometer reached a maximum of 5.8C at 12.09 in the morning brightness but cloud then began to arrive that stopped any further sunshine and increase in temperature. The breeze picked up around midday with quite a flurry that produced a gust of 18mph at 12.15, the strongest air movement since Monday 6th. Very little warmth, such as there was, seeped into the atmosphere overnight thanks to the cloud cover with the thermometer only dropping 2C producing a minimum of 3.8C at 07.22 early Tuesday so the first night without a ground frost or air frost.

Tuesday arrived with total cloud cover as a weather front is tracking southwards with the cloud building during the late morning. The temperature had risen a little to 4.3C by 08.00.

The recent high pressure is still maintaining calm conditions with the recent cool air trapped beneath it although the warm air is slowly winning. The barometric pressure dropped just 4mb in the last twenty-four hours with a reading of 1035.6mb at 08.00, still very high.

Last week I logged how the continuing cold was slowly seeping into the ground. The last four days has seen the situation reverse with the ground temperature at a depth of 5cm rising slowly over the last four days with -1.8C, 0.3C, 0.4C and 1.1C today as the cold comes out of the ground but still having an effect on the air temperature. It was only two weeks ago, on the 1st, that the ground temperature at 08.00 and depth of 5cm read 9.4C.

Sunday was the first day when the very cold air began to give way to slightly milder air arriving from the west. As a consequence the temperature rose to a high of 4.8C at 14.45, the highest since the 6th, however, this was still 2.3C below my long-term average. It was a dry day under the influence of the high pressure, centred overhead, but thick cloud meant no UV light triggered the UV sensor. Overnight the thermometer slowly fell away to reach a minimum of 0.9C at 02.44 before rising slightly to reach 1.7C at 08.00 on Monday.

Monday after dawn revealed a sky with much less cloud, which was higher and thinner, that should result in weak sunshine as the day progresses. The wind direction, such as it is, has veered a few degrees from south yesterday into the south-southwest.

I mentioned yesterday that the centre of the high pressure was migrating south to be in a position over Southern England for much of the day. The maximum barometric pressure of 1041.6mb was logged at 20.56 Sunday evening, the highest pressure since 5th February 2023 when a reading of 1048.1mb was recorded. The intense high pressure has brought us the very calm conditions for the past few days as there is little pressure gradient to originate much air movement. The maximum air movement on Sunday was one incidence of just 5mph and 8mph overnight, although for many hours the anemometer was virtually still.

The pool of cool air trapped under the high pressure is slowly giving way to warmer air inching in from the west but it will take a another day before temperatures return to near normal for mid-January.