Month: October 2023

Thursday was a dry day with limited sunshine but the thermometer did get above the 39-year average again with a maximum of 17.1C (+2.4C). Likewise it has been a mild night with a low of 12.3C being a whole 5C above the average.

Friday began bright with the promise of sunshine, if weak, after 08.15. The anticyclone is still large in area over the continent and keeping the rain bands to the north of our area. The barometric pressure reading at 08.00 was 1024.0mb

The warm weather continued on Wednesday with both the maximum of 17.3C and the minimum of 11.8C well above average with +2.6C and +4.5C respectively. It was the first dry day in October with the UV level now rated as Low.

Thursday began with total cloud cover but with the barometric pressure still high it should be a dry day with hopefully some sunshine later. The centre of the anticyclone is still over France that means the wind will continue from a southwesterly direction.

The maximum of 17.6C on Tuesday was 2.9C above the average although the coolest this month whilst the overnight minimum of 10.8C was 3.5C above the average.

Wednesday revealed a misty and damp start to the day as drizzle and a series of light rain showers passed over the area from 05.30 to 08.00 amounting to 0.4mm. The barometric pressure has been building significantly over the past twenty-four hours with a rise of 10mb to read 1027.6mb at 08.00, the highest for a month, due to an anticyclone centred over France that will dominate our weather for the next few days. The breeze will have backed to southwest or west-southwest today.

The thermometer by day and night registered the peaks above average with 18.4C (+3.7C) and 9.3C (+2.0C) thanks to the flow of warm, moist air from mid-Atlantic. However, a series of showers passed our way in the afternoon with thunder heard at 14.05 and 14.20. The first was from a thunder cell centred over the Devizes area, seen on the lightning radar, the latter was overhead. A more intense but short rainstorm was observed at 16.30. The daily rainfall amounted to 4.3mm.

Tuesday revealed the hang back of cloud from the weather front over the eastern horizon, that initially obscured the sun but just before 07.50 the sun rose above the cloud and shone brightly. An anticyclone is building in the region of the Bay of Biscay that is edging our way so a few drier, warmer and sunnier days are ahead.

The flow of moist, warm air from mid-Atlantic continued on Sunday that saw the thermometer rise to 20.4C, which was 5.7C above the 39-year average. The past night was very mild with a low of 16.1C being 8.8C above the average minimum and 1.5C above the average daytime maximum.

A little moisture was recorded from occasional light drizzle amounting to 0.3mm

Monday dawned dull with low cloud limiting visibility to 400m in total calm conditions, the anemometer having not moved since just after midnight.

September 2023 Review

Records broken again

The start of Meteorological Autumn brought us the summer weather we should have enjoyed earlier in the year. Maximum temperatures by day and night were above average, unlike many days in August.

The threshold for a ‘heatwave’ in Wiltshire, as set out by the Meteorological Office, is for three consecutive days when the maximum temperature exceeds 27C. That criteria was met on the 4th to the 6th with maxima of 28.3C, 28.6C and 30.3C, respectively. Incidentally, the threshold for several counties was raised in 2022 to reflect our changing climate. The East Riding of Yorkshire was raised from 25C to 26C, Lincolnshire was raised from 26C to 27C and the counties of Surrey, Berkshire, Buckinghamshire, Hertfordshire and Cambridgeshire were raised from 27C to 28C.

An anticyclone centred over Scandinavia circulating clockwise, and a depression to the west circulating anticlockwise, ushered in hot air from north Africa that saw the high temperatures sustained from the 3rd to the 9th. The latter day saw the thermometer reach a maximum of 31.0C. This high was a record for September, was the hottest day of the year and the hottest day since 19th July 2022.

This period saw a plume of Saharan Dust, some 1,200 miles in length, arrive over the UK covering surfaces with light dust overnight of the 5th.

There was a short period of dry and warm weather from the 12th to the 16th as the sun, shining strongly for several hours each day lifted the temperature to 22.6C on the 14th and 24.1C on the 15th, being 3C to 5C above the 39-year average.

There was a very wet day on the 17th as many hours of heavy rain meant 49.7mm fell making it the wettest day since 3rd October 2020 (49.9mm)

The remnants of hurricane Lee, having travelled across the Atlantic driven by a strong jet stream travelling at 150mph, arrived on the 19th bringing strong winds gusting to 34mph and twelve hours of precipitation amounting to 29.9mm.

Storm Agnes arrived on the 27th but had little effect over southern England, just a brisk wind gusting to 28mph and a brief rain band mid-afternoon.

The mean maximum temperature for September of 22.07C was a record, the overnight minimum of 17.0C on the 11th was a September record and the mean September temperature of 16.94C was a record.

Not surprisingly, the mean soil temperature at a depth of 5cm, read daily at 08.00, was 15.5C being the warmest since this instrument was installed 10 years ago.

The total rainfall of 104.2mm was the fifth wettest September since my records began in 1984 being 168% of the 39-year average or plus 42.3mm. There were two exceptionally wet days with 49.7mm on the 17th and 29.9mm on the 20th that made 76% of the monthly total.

Fog was observed early morning on two days.

Storm Agnes was the first named storm of the new storm naming season, the ninth naming year, which runs from September to August each year. The Meteorological Office names storms in partnership with Met Eireann in Ireland and KNMI in the Netherlands

Storms are named for the sake of clarity, according to the Meteorological Office, so that the Government and media organisations can clearly inform the public when treacherous weather is on the way.

The Meteorological Office contributions to the list include submissions from the public and names of those involved in responses to severe weather. Met Éireann’s submissions are inspired by famous scientists. Names from KNMI are often of Dutch origin and many were submitted by public visitors to the forecaster throughout the year.

For a storm to be named, it needs to have the potential to cause an amber or red weather warning on the Met Office’s national severe weather warnings service in the UK, or the Irish or Dutch equivalent.

There are three tiers of weather warning: yellow, amber or red. The colour a warning is given depends on a combination of both the effect the weather may have and the likelihood of damage occurring.