UK Weather - Autumn 2023

[Simon Culling]

As we enter meteorological Spring, the weather is taking a big turn for the better. We will see at least a week of warm sunny weather, particularly in England + Wales, and the temperature may approach 30°C in the SE. Indeed we may see our warmest day of the year and it is rather unusual for this to occur in September - the current yearly high is 32.2°C at RAF Coningsby on 25th June and also at Chertsey Abbey Meads on 10th June.

As a large and deep low moves north towards Greenland (containing the remnants of Hurricane Franklin), we are losing the main impetus of the jet stream over the UK and high pressure is now building in from the SW - and it will move over the UK and take up residence over nearby Europe and give us a SE flow to bring the warm, dry + sunny weather for the coming week. This may well persist into and beyond next weekend.

[spwill]

Certainly looking very warm for September.
Looks warm for the start of the Rugby World Cup across the channel in Paris. I'm heading over to Europe this week but not for the rugby.

[Simon Culling]

I hope you enjoy your trip to Europe, spwill. It is going to very warm or hot over most of the continent and quite stormy + wet in Iberia - certainly for the next day or so.

Here in the UK it was warm and sunny on Sunday with a high of 27°C in southern coastal counties - Hampshire, Sussex + Kent. The forecast for the coming week is still warm, or even hot, and sunny with the high for Wednesday through to Friday now expected to be up to 32°C. We may well record our warmest day of the year. GFS has an 850mb temperature in excess of 20°C over SE England on Thursday from tonight's run and has the heat lasting to at least next Monday (11th Sept).

[spwill]

Thanks Simon, enjoy that very warm -hot weather.

[Simon Culling]

We have been enjoying/enduring a late hot spell here in the UK - it rather depends on your perspective. It has been predominantly sunny over much of the country since the weekend, with just a few thundery showers overnight in more western parts - these have all been elevated storms and not given a great deal of rain except to parts of Ireland yesterday. Hot again today (Fri 8th Sept), although there is more medium and high cloud around. These are the UK maximums for the first four days of this week:

Monday 4th September - 30.2°C at Whitechurch (Pembrokeshire)
Tuesday 5th September - 30.8°C at Otterbourne (Hampshire)
Wednesday 6th September - 32.0°C at Kew Gardens
Thursday 7th September - 32.6°C at RHS Wisley (just to the south of London - site of the Royal Horticultural Society)

The hot weather looks like continuing through the weekend with possibly a high of 33-34°C on both days if cloud does not build too much. There is the prospect of a few home grown thunderstorms over the weekend and this may limit the temperatures a bit.

The current record high temperature for September is 35.6°C at Hesley Hall near Bawtry in South Yorkshire on 2nd September 1906. This is the oldest of the monthly UK record maximums. Whilst the predictions for the weekend do not threaten this record, the current run of 5 days with somewhere recording a high of 30°C or more is a record for September and it looks like that run will extend to at least 7 days.

[Simon Culling]

The hot spell lasted through the weekend, but has relented today, Tuesday 12th September. These are the recent maximums which extended the run of days with 30°C or above to 7:

Friday 8th September - 30.9°C at Cavendish (Suffolk)
Saturday 9th September - 33.2°C at Kew Gardens
Sunday 10th September - 32.5°C at Cambridge NIAB
Monday 11th September - 26.9°C at Cavendish

Quite a few thunderstorms developed on Sunday, especially in southern and eastern England with a notable complex of cells developing to the SW of Milton Keynes around 1pm and moving NE to reach The Wash (on the North Sea coast) around 4pm. These cells developed quite a gust front, with a squall recorded to 77mph at the Met Office site at Holbeach on the coast (on The Wash in Lincolnshire). Attached is a graph (courtesy of Blitzortung) of the lightning strikes over the UK between noon and midnight on Sunday. 123K strikes is not bad for mid-September.

The CET for September was 20.4°C (+6.8°C) up to the 11th and the EWR was 6mm up to the 10th, which is 8% of the monthly average of 76mm. The remarkable anomaly of +7°C will fall away over the coming week as more normal temperatures for mid-September prevail.

[Simon Culling]

There has been a general cool down over the UK in the last few days, but the much cooler weather has been restricted to Scotland and the south east is still very warm - today (Sat 16th Sept) it has reached 27-28°C in and around London. In contrast, here in the SW we have had rain off and on all day today in Tiverton and a maximum of just 17°C. The rest of the weekend will be warm + muggy over the southern half of the UK and the conditions are marginal for more thunderstorms tomorrow, some of which could be strong.

As mentioned above, much cooler weather is over Scotland and to emphasise this there was a sharp frost in the far north on the morning of Wednesday 13th September - the temperature fell to -3.5°C at Kinbrace Harchery and this is a new date record low for this date.

Below I have attached a picture of the shelf cloud associated with the strong thunderstorm mentioned in my last post (on the 9th Sept) - the picture was taken at the end of its land track and near to the east coast - in the village of Fosdyke, which is near to The Wash.

https://twitter.com/simon_culling/statu ... 5318997026

[Simon Culling]

Conditions were rather more than 'marginal' on Sunday, with a large area of thunderstorms affecting most of the SE + S half of England during the afternoon and especially the evening. It was a very wet day across the whole country and this was indicated by very high pecipitable water contents in the ascents made during the day. It was particularly wet in Devon, Somerset + Wiltshire during Sunday - these areas caught the early thunderstorms and a number of gauges had around 100mm of rain which resulted in some flash flooding. Here in Tiverton we had around 40mm of rain for Sunday (17th Sept) but thankfully no flooding. We also had a long lightning display in the early hours of Sunday morning with a period of torrential rain making all my gutters overflow!

https://www.bbc.co.uk/news/uk-england-somerset-66840766

Later in the evening on Sunday, another wave of storms moved NE from France and gave a very good lightning display to much of SE England + East Anglia and there was a small tornado on the south coast at Littlehampton (W Sussex) just before midnight.

Since the weekend it has become cooler and we have a low pressure system approaching the UK today (Weds 20th Sept) which contains the remnants of Hurricane Lee and this is giving us a wet and windy autumnal day - the low is just to he west of Scotland at 975mb at noon. The low will be followed by and even cooler NW flow for Thurs/Fri before it warms up a bit at the weekend.

[Richard]

How long did it take for the 40mm of rain to fall Simon

[Simon Culling]

Hello Richard - with regard to the rainfall last Sunday, here in Tiverton it was thankfully spread over the day and hence we avoided the flooding. The more prolonged heavy rain affected other parts of Devon and particularly parts of Somerset. Looking at the trace of a nearby PWS (about 400m to my south), peak rainfall rates in the town were around 50mm/hr, but in the worst affected areas, rates were up to 100mm/hr.

It has turned much cooler in the last few days and become unsettled with rain or showers on most days, and this pattern will continue through the week. A rather deep low is expected to affect the UK on Wednesday, although there is some uncertainty on its likely track. It will contain the remnants of Tropical Storm Ophelia, so there is going to be lots of moisture and rain. There are some tentative signs of very warm or even hot weather returning to southern Europe as we go into October, but it is not clear yet if this will extend north to the UK.

The CET for September was 18.1°C (+4.5°C) up to the 21st and the EWR was 73mm up to the 22nd which is 96% of the monthly average. Unfortunately the much cooler weather expected for the rest of the month will probably mean that September will not end up being warmer than all of the summer months. The average CET for the three summer months was just 16.5°C.

[Simon Culling]

Storm Agnes passed by yesterday with rather less impact than had been expected by the forecasters. It had deepened very quickly on Tuesday when it was way to the SW of Eire and had already began to fill as it approached the British Isles. Whilst it was a windy day for Eire and UK coasts bordering the Irish Sea, most of us were left wondering what all the fuss and warnings were about. However, it would have been rather different if the depression had arrived 12-24 hours earlier when in its deepest phase as there was plenty of evidence of a sting jet on its SW flank. See this tweet and the interesting discussion in its thread - the water vapour imagery is great:

https://twitter.com/RoostWeather/status ... 8837146892

The picture attached is taken from this tweet - the sting jet is at the tip of the curl of cloud on the left side of the picture. The models suggested top wind speeds (in gusts) in the sting jet as it reached the surface were around 120mph - thankfully that happened over the Atlantic.

Looking forward, the weather looks set to calm down as high pressure becomes the dominant factor for the weather of NW Europe. For us in the UK it looks to be dry and a little warmer than average.

[NZ Thunderstorm Soc]

I see there was a bit of an explosion near Oxford, after a lightning strike.
Probably struck something that had gas in it?

[Simon Culling]

Indeed it did, John. The lightning strike occurred around 7pm yesterday (Monday 2nd October) at a food waste recycling plant in Oxfordshire. The lightning appears to have hit one or more of the digester tanks causing the gas inside (methane) to ignite and explode. This BBC article has plenty more details including a video. Note, it is dark now at 7pm here in the UK.

https://www.bbc.co.uk/news/uk-england-o ... e-66991876

Thunderstorms developed yesterday afternoon along a SW-NE line as per the map below - which gives an idea of the storm distribution. There were more strikes than shown on this map (approx 15,000 strikes for UK + southern North Sea) and some very potent +ve strikes were also recorded. A couple of footballers were also struck (in Hertfordshire) and one was seriously injured.

[Simon Culling]

The weather is warming up for those of us in England + Wales for the coming weekend and into next week - we could easily see a day or two with temperatures up to 25°C in SE England which is not bad for October. In contrast, Scotland and Northern Ireland will be wet at times with a bit of an atmospheric river for Western Scotland where up to 200mm of rainfall could be seen on the mountains. Here in Tiverton we should see three or four days of mostly sunny weather (after overnight mist and fog have cleared) into next week with highs around 22°C. This may well be it for any warmth until next March/April.

The final CET for September was 17.0°C (+3.4°C) and the final EWR was 91mm, which is 120% of the monthly average. The CET figure was the highest for the month of September in the 365 year series - the old record high was 16.9°C, which was set in 2006. The UK figures also show record September warmth - it was the joint warmest September for the UK since this series started in 1884 - again the comparable month was in 2006. The attached Met Office report shows the month was much warmer than average, quite wet, but also sunnier than average over the UK.

https://www.metoffice.gov.uk/about-us/p ... ord-for-uk

[Simon Culling]

Much of England + Wales has enjoyed a nice late warm spell in the last few days, although it did not extend to Scotland or Northern Ireland as they were plagued by cloud and a lot of rain - there has definitely been a north-south divide in the weather in the last week. Here in the south we had a run of five mostly sunny and warm days from last Friday through to Tuesday of this week with very pleasant temperatures - these are the maximums for the four days above 25°C - what we consider a decent 'summer day'.

Saturday 7th October - 25.4°C at Manston (Kent) + London Heathrow
Sunday 8th October - 25.8°C at Kew Gardens + Maison St Louis Observatory (on Jersey)
Monday 9th October - 26.1°C at East Malling (Kent)
Tuesday 10th October - 25.7°C at Writtle (Essex)

The only longer run of such days I can find in October is 7 days in 1921 (4th to 10th inclusive).

The weather is now transitioning quickly to full on Autumn and it has been rather wet since Thursday. As a cold front clears the country tonight and into Saturday we will all be in a NW-N flow with daytime maximums from mid to high single figures in the north to no more than 12-13°C here in the south. Quite a shock to the system but at least we should see plenty of sunshine. First flurries of snow for the Scottish mountains too.

The CET for October was 15.5°C (+5.0°C) up to the 11th and the EWR was 25mm also up to the 11th, which is 25% of the monthly average of 103mm. The very high positive temperature anomaly will soon be eroded.

[Orion]

Assorted video of flooding in Cork, Ireland, runs 1:39

https://twitter.com/volcaholic1/status/ ... 2774965706

[Simon Culling]

Thanks for posting that link Orion - the UK + Eire are having a very soggy few days at the moment. For stations local to the flooding in the video, in the 48 hours to midnight on Thursday 19th October Cork Airport had 89.5mm. A climate site further east along the coast at Youghal (and closer to the reported flooding) had 98mm over the same period.

The Met Office issued a rare red warning yesterday which is just coming to the end of its valid period (noon on Friday). It was for heavy rain in Eastern Scotland associated with the named storm Babet. This is a slow moving (gradually north over the UK) system that will give 2-3 day totals of 100-200mm over the higher ground of Northern England and Eastern Scotland by the end of today (Friday 20th Oct) with the resulting flooding lasting over the weekend.

https://www.metoffice.gov.uk/about-us/p ... torm-babet

Down here in the SW it has been quite wet in Tiverton as well. We have had around 30mm of rain in the last couple of days along with a few rumbles of thunder yesterday afternoon + evening. It is still rather mild after the short cold snap of last weekend.

[Orion]

A dogwalker in Mugdock, Stirlingshire has shared clips of the forest floor “moving like the sea” as #StormBabet continues to batter Scotland. (22sec)

https://twitter.com/Clyde1News/status/1 ... ing-latest

- to be honest, I wouldn't hang round there filming it

[Simon Culling]

That is a great video, Orion. I have seen a number of others like it in the past (for British Columbia, for example), but not for the UK.

Storm Babet gave a lot of rain over the UK, but particularly in northern England and eastern Scotland with three day totals over 100mm at quite a few recording sites in these areas - some places had 200mm+. See the attached map (from the Met Office) which covers the 90 hours period to 6pm on Saturday 21st October. The resulting flooding is still affecting some parts three days after the rain ended.

There are numerous reports on the BBC, but these two are representative of Scotland and northern England.

https://www.bbc.co.uk/news/uk-scotland-67041995

https://www.bbc.co.uk/news/uk-67186683


The CET for October was 13.1°C (+2.5°C) up to the 22nd and the EWR was 113mm also up to the 22nd - this is 110% of the monthly average.

[Simon Culling]

It has remained very unsettled here in the UK with rain and/or showers every day - at least it is on the mild side which has meant minimal use of the central heating so far this autumn.

We have another named storm (Ciaran) on the way for Weds/Thurs this week and this will deliver a lot more rain as well as strong winds to the south of England. The track of the low is critical as the strongest winds (likely to have gusts to around 90mph) will be on its southern and south western flanks and currently the low centre is expected to track across southern England from the Bristol Channel to the Wash (at around 955mb). If the track is a little further north, the strong winds will affect the most populated parts of the UK rather than just the far south as currently predicted. The worst of the winds (at the moment) are expected to affect NW France and the UK Channel Islands, but we will not know for certain until tomorrow morning when its arrival is imminent. Has the potential to be a significant event and we may see another red warning posted tomorrow if the track of the low is a little further north than expected.

The CET for October was 12.2°C (+1.7°C) up to the 30th and the EWR was 161mm up to the 29th which is 156% of the monthly average. With the rain of the last two days, this October will likely be in the top 10 wettest in the EWP series which goes back to 1766.

[Simon Culling]

Storm Ciaran duly passed eastwards across southern England today (Thurs 2nd November) which meant the worst of the winds were over the English Channel and northern France. The UK Channel Island of Jersey seemed to have been one of the worst affected areas with not only wind gusts to 100mph during the morning, but also a significant tornado and hailstorm hit the island ahead of Ciaran around midnight 1st/2nd November. Initial estimates of the rating for this tornado would be T4/T5 on the TORRO scale, which is roughly equal to EF2 on the enhanced Fujita scale. The attached tweet has a video recorded in the dark, but you can clearly see the tornado and debris being lifted from rooftops - the accompanying sound is quite eerie.

https://twitter.com/simon_culling/statu ... 5088202974

The hail was easily golf ball sized and some look to be up to around 50mm in diameter - hail of this size is very unusual for so late in the year. Both the hail and tornado affected the eastern side of the main town of St Helier.

[Simon Culling]

A site investigation has been completed into the Jersey (Channel Islands) tornado which occurred around midnight on 1st/2nd November and revealed a lot of damage on the 8km track across the eastern side of the island. It has been provisionally rated at T6 on the TORRO scale which is roughly equivalent to a low end EF3 on the enhanced Fujita scale. This is the most destructive tornado to have hit the British Isles since the Birmingham tornado of July 2005 and the London (Kensal Green) one in December 2006. A final rating revision (when all the collected data has been considered) may see it considered slightly stronger than both of these and this would then make it the most powerful tornado since the London (Gunnersbury) event on 8th December 1954.

Attached is the TORRO press release concerning this tornado which was circulated today.

[Simon Culling]

This long run of unsettled weather continues here in the UK with another named storm approaching - this one is called Storm Debi and is set to move across the middle of Ireland tomorrow (Monday 13th November) and continue across Northern England into the North Sea. Whilst it is expected to have a central pressure of around 970mb, it is a small and quite tight low pressure that will bring severe gales to the middle section of the British Isles - wind gusts will be in excess of 80mph in the worst hit areas. Down here in the SW, it will be a windy and showery day, but thankfully, nothing out of the ordinary hereabouts.

The Met Office have produced a summary of the weather in October and it was indeed a very wet month - it has been ranked the fourth wettest in the EWP series which dates back to 1766. The provisional England + Wales figure is 177.3mm which compares to the record of 218.1mm recorded in 1903. It was also a rather mild month and not surprisingly, rather dull.

https://blog.metoffice.gov.uk/2023/11/0 ... -scotland/

The final CET for October was 12.1°C (+1.6°C) and as mentioned above, the final EWR was 177.3mm which is 172% of the monthly average.

[Simon Culling]

Still unsettled here in the UK and generally on the mild side, although we had our first sub 10°C daily maximum yesterday (Thurs 16th Nov) as it rained all day and we were on the north side of the front. Up north in Scotland, Altnaharra recorded the lowest UK temperature of the season so far with an overnight low of -7.1°C. In complete contrast, we have had just two ground frosts here in Tiverton so far this autumn.

The weather remains unsettled in the immediate outlook with more rain + showers to come this weekend and into next week. There are some tentative signs of a build of pressure over the Atlantic after midweek and this will likely divert the jet stream and direct the lows further to our north - so we will hopefully see some drier, albeit cooler, conditions.

The CET for November was 8.6°C (+2.2°C) up to the 15th and the EWR was 91mm also up to the 15th, which is 86% of the monthly average of 106mm.

[Simon Culling]

The weather here in the UK is finally showing some signs of settling down and becoming drier. It is still rather mild at the moment, but at least the prolonged and heavier rain has moved on and we now have just a few light showers to contend with. The winds will go round to more of a northerly later this week and it looks like it will turn rather chilly by the weekend with widespread frost at night - but at least it will remain mostly dry apart from a few wintry showers in the north and east. This will give the ground some time to dry out a bit and for the river levels to drop. Down here in the SW of England the reservoir levels are back over 75% capacity and will continue to fill over the next few weeks - we should start next spring/summer with them back up to full.

There was a small earthquake in SW England in the early hours of Sunday morning - in Cornwall to be exact - and this is not a common occurrence in these parts. It was only of magnitude 2.7, but was felt over a large part of the SW tip of the county. Didn't notice it here in Devon even though I was up and about at the time.

https://www.bbc.co.uk/news/articles/c724le759lro