UK Weather - Winter 2019/20

[Simon Culling]

The weather has duly turned more unsettled here in the UK and colder as well with some wintry showers yesterday and today (Tuesday 28th Jan). It became showery yesterday here in Tiverton as the more persistent rain cleared in the afternoon and a number of hail showers rattled the window panes overnight and into this morning - we even had a few snowflakes mixed into the showers as well for good measure.

A few cm's of snow has settled further north and particularly in Scotland, which is nearer the source of the westerly airmass currently over the UK. However, this will be a short lived cold(er) snap as milder air will push back from the SW tomorrow to give us another taste of tropical maritime air this winter and extending into the weekend. Whilst not a record-breaker, January looks like being in the top 20 or so mildest in the CET series dating back to 1659.

[Simon Culling]

The weather has reverted to the mild type in the last couple of days and this pattern will persist through the weekend. It has remained predominantly cloudy and drizzly, but the sun did break through yesterday (briefly) here in the SW of the UK and this pushed the temperature up to 14.4°C at Exeter Airport, which is not bad for the time of year.

There has been much chatter this winter about the Polar Vortex and the possibility of a Sudden Stratospheric Warming event occurring. The polar vortex has been unusually strong and persistent all winter (and hence the +ve NAO all winter so far), but the models do suggest it will elongate into early February with the 'bulge' being centred on Canada. The effect of this will likely be some very cold weather for NE America (and Canada) and a strengthening of the jet stream across the Atlantic, which will continue the wet and mild winter for us in the UK. The models suggest this happening in the next week or so.

Interesting blog post by Bob Henson on this subject and its effect on the current northern hemisphere winter:

https://www.wunderground.com/cat6/Polar ... ll-It-Last

[Simon Culling]

The final CET for January was 6.4°C, which is +2.6°C above average. The final EWR was 83mm which is 91% of the monthly average - this is the first month with a lower than average rainfall total since May 2019. With regards to the CET, this January was the equal 11th warmest in the series dating back to 1659 (i.e. 362 years) - the warmest was January 1916 with a CET of 7.5°C. The Met Office has provided a summary of the month and now has a series of gridded temperatures back to 1884 to compare it to - the month was the sixth warmest January in this series.

https://blog.metoffice.gov.uk/2020/02/0 ... ince-1884/

It has remained mild and changeable here in the last few days, but at least we have had a bit more sunshine to cheer us up. The wind has veered round to WNW today so it feels quite a bit cooler, but the mild weather will return by the end of the week as the jet stream strengthens. Some of the model output for next week is positively stormy with a number of deep depressions heading for the UK and with a trend towards a more southerly jet, there could be considerable snow over higher ground in the north. Some very active weather coming to the UK in the next couple of weeks.

EDIT: Minor corrections made to the final CET + EWR figures for January.

[Simon Culling]

We have the usual ramping for the storm (Ciara) due to arrive this weekend, but I think it will have a significant impact both in terms of the wind strength and the duration of the strong winds - could be up to 24 hours in many places. The storm is currently over the east of the USA at the moment, but when it moves into the Atlantic it will engage a very vigorous jet stream (roughly at 250mph currently) and develop significantly and move rapidly eastwards to be near northern Scotland by midday Sunday at around 950mb. We will start to feel the effects later on Saturday and they will last well into Monday as cold air (to the rear of the system) all the way from Canada has a direct westerly flow across the Atlantic to the UK - there will be a lot of squally wintry showers in this airstream. Thankfully this storm currently looks to be a one-off before milder and calmer conditions follow by mid-week. Some good satellite photos on this link as the feature leaves the US eastern seaboard:

https://twitter.com/CarlowWeather/statu ... 9875031040

[Orion]

^ Hope all's well in your area, Simon.

[Simon Culling]

Most of us are OK, Orion, although those in flooded areas get my sympathy. Storm Ciara gave us a very windy and wet day on Sunday, but the disruption caused was somewhat less than might have been the case on a weekday. Sadly, one person was killed by a falling tree:

https://www.bbc.co.uk/news/uk-51439152

The low pressure fell to 947mb as it crossed northern Scotland but the strongest winds were mostly in more southern + western parts, although two squally cold fronts did produce some big gusts. Highest gusts for Sunday (9th Feb) were:

97mph at Needles Old Battery (on the Isle of Wight and a very exposed site)
93mph at Aberdaron (W Wales)
89mph at Capel Curig (NW Wales) + Portland Bill (Dorset)
86mph at Lake Vyrnwy (NW Wales) + Manchester Ringway Airport (in a squall)
82mph at Aberporth (W Wales)

Many unofficial sites along the south coast reported mean wind speeds >50mph with gusts in the 80-90mph range. It was also very wet in northern England and particularly in Lancashire, Yorkshire + Cumbria with 6-7 inches of rain o/night Saturday into Sunday and some serious flooding in the Calder Valley area. The highest rainfall figure I can find is 178mm for the 24 hour period ending 1800GMT on the 9th (Sunday) at Honister Pass (in Cumbria), but most of that fell o/night.

[Simon Culling]

Both Monday + Tuesday have been blustery and showery days here in the UK with snow to the hills adding to the travel problems in the north. Sadly, another person was killed by a falling tree on Monday (in Liverpool) as the strong winds persisted despite the low pressure centres being over Iceland + Scandinavia - behind and to the south of the twin centred low there was a long fetch of strong westerly winds all the way from Canada. Here in Tiverton, we have been peppered with plenty of showers, many containing hail and a little sleet, with the very blustery wind persisting, and it has felt quite cold. We even managed a few rumbles of thunder on Monday morning. This will be a brief cold snap as more fronts and rain are due from Thursday and we already have another named storm (Dennis) for the weekend.

One of the benefits of this strong jet stream has been faster air travel from the USA to the UK, and overnight into Sunday, a British Airways scheduled service broke the record for the fastest subsonic flight between New York and London when it completed the journey in under 5 hours. For comparison, Concorde used to do it in just over 3 hours.

https://www.bbc.co.uk/news/uk-england-l ... bc_weather

The CET for February was 6.4°C (+2.2°C) up to the 11th so we are on course for yet another very mild month. The EWR for February was 41mm up to the 10th, which is 63% of the monthly average of 65mm. That average may well be exceeded by the end of the weekend as 'Dennis' is likely to be more noteworthy for rain (and flooding) rather than wind.

[Simon Culling]

Storm 'Dennis' has been deepening rapidly as it moves across the Atlantic - it is the second very deep depression in this series. It has deepened by over 50mb in the last 24 hours - at 06:00GMT on Friday (14th Feb) it was at 984mb way across the Atlantic and at 06:00GMT this morning it was at 932mb as it curves NE up towards Iceland. Some of the forecast charts suggest it will get as low as 920mb on Sunday morning as it nears Iceland and this will be not too far away from a North Atlantic low pressure record.

Despite being quite a long way from the UK, it will still give us a very windy weekend as it is a very large system. More worryingly, it will allow a train of fronts to get stuck over the UK for a couple of days and create an 'atmospheric river' over this weekend and gives us a lot of rain - which we do not need after a very wet autumn and winter. The whole of the UK will be affected, but especially more western and southern parts and there will be 50mm+ over much of the high ground in these areas and north of 100mm in places. There will likely be quite a bit of flooding as already full rivers struggle to cope with all this water.

Here in Tiverton, it has continued to rain all night and into Saturday morning, but mostly only light rainfall so far. With a SSW wind we are in the rain shadow of Dartmoor, so I an not expecting massive amounts of rain in the town, but the river Exe drains from Exmoor (to our north) through the town and they will see 50mm+ there in the next day or so. On a more positive note, it will draw very warm air northwards from the south Atlantic + Africa and give some very warm (and sunny) weather for our Continental cousins......blame it on Brexit.

[Orion]

^ A traditional "February fill-dike" month then.

[Simon Culling]

Storm Dennis has had quite an impact on the UK, especially with regard to rainfall and flooding, and like its predecessor, its effects lasted nigh on three days. The worst of the rain was in the west and particularly in South Wales where over 150mm fell on Sat/Sun on the hills - hence the ongoing flooding in that region and where the rivers finally flow too.

https://www.bbc.co.uk/news/uk-51519635

Unfortunately at least three people lost their lives over the weekend messing about on or being too near the sea/rivers.

The main low was analysed by NOAA at 920mb at 18:00GMT on Saturday 15th February, although some have called it as low as 919mb. Either way, I think this puts 'Dennis' in third place on the lowest central pressure in the North Atlantic league.

[Simon Culling]

The flooding resulting from the copious rainfall at the weekend continues as the water makes its way from the Welsh mountains and down the rivers to the east - and particularly the rivers Hay + Severn. Some are only just peaking today and some have reported record levels:

https://www.bbc.co.uk/news/uk-51555075

As the article above mentions, more rain is on the way this week and the next, although at the moment, the emphasis on higher totals has shifted north. However, these areas also have saturated soil, so more flooding looks inevitable.

The CET for February was 6.5°C (+2.8°C) up to the 17th and the EWR was 98mm also up to the 17th, which is already 150% of the monthly average. The record figure for the month is 159mm from way back in 1833, but we could challenge this figure this year. With regard to the expression 'February fill-dyke', this month is actually one of the driest months of the year on average, and considerably so compared to October to January - but of course there can be large variations from year to year as we are finding out at the moment!

[Simon Culling]

The wet and windy weather has continued over the UK, but as suggested above, most of the rain has been in the northern half of the UK in the last couple of days. Flooding remains a real problem for the affected areas as the river levels are only falling slowly and with the rain moving further north, so has further flooding. There has been considerable orographic enhancement of the rainfall, but this rain then slowly fills the rivers and floods the lower ground downstream. In the 72 hours to 08:00GMT on Saturday (22nd Feb) morning, 360.2mm has fallen at Honister Pass in Cumbria and 312.6mm at nearby Seathwaite Farm - these compare to just 44.4mm at St Bee's Head on the nearby coast.

Looking further forward, the rain and wind looks set to continue, with a lot more rain to come particularly for more northern parts of the UK. It will also be mild into next week, but it will turn somewhat colder by Tuesday.

There has been much debate in the last few years about a perceived increase in flooding and links to climate change, but no real conclusions have been drawn in what is a very complicated subject. A lot of money has been spent in the last 10-20 years on flood defences and this has thankfully reduced considerably the number of properties affected.

https://twitter.com/johncurtinEA/status ... 3180937223

[Parisien]

I feel like more money has to be spent on flood defense measures yet.

[Simon Culling]

With regard to flood defences, Parisien, I am not sure it is as simple as throwing endless money at the issue. I can only speak for the UK, but politicians keep on telling us how many billions are being thrown at an array of issues, but they never seem to be resolved as we appear frightened to address the underlying issues and prefer to paper over the cracks. The UK is densely populated and traditionally much of the settlement has been near rivers and flood plains. Indeed, many new houses have been built on flood plains in the last few decades despite contrary (and good) advice. Combine this with poor upland management and a desire to concrete over everything (even gardens!!) and it is not surprising that flooding is still an issue. Much work has been done on flood defences, but this has resulted in both constricting river flow (and hence raising its level) and transferring the flooding downstream. Defence schemes have been concentrated to where the largest number of homes and businesses can be protected and this has been to the detriment of those not located in towns or cities.

There are still two severe flood warnings in place on the River Severn which looks like it will peak at a record level later today in the towns of Ironbridge + Shrewsbury and I can only have great sympathy for those affected.

https://www.bbc.co.uk/news/uk-england-s ... e-51626098

It has turned colder here in the UK as we are now in polar maritime air and this will be the general trend as we head towards March + Spring. Despite being generally colder looking forward, there is still plenty of rain and showers in the forecast and today we have had hail + sleet showers here in Tiverton and it is just 5°C mid-afternoon.

The CET for February was 6.8°C (+3.1°C) up to the 24th and the EWR was 131mm up to the 23rd, which is 201% of the monthly average. With plenty more rain + showers to come, and the extra day to the month, the record EWR for February is definitely under threat.

[Simon Culling]

The wet weather continues and we have another named storm (Jorge - named by the Spanish Met Office) for the weekend. Lots more rain to come with the potential for some very strong winds for Eire and northern England. The colder air has been shunted north today (Fri 28th Feb) as rain and milder air arrives from the SW but there was quite a bit of snow to higher ground in the north on its leading edge. Milder tonight with the rain, but we will be back in the colder Atlantic air by the end of Saturday.

The flooding situation on the River Severn (the longest river in the UK) continues and there was a close shave for Ironbridge when the flood defences buckled under the weight of the water on Wednesday. Thankfully they held, but there has been further flooding in Yorkshire as a result of all the rain moving slowly down the rivers and overtopping the defences.

https://www.bbc.co.uk/news/uk-england-h ... r-51640880

[Simon Culling]

The rain continued to the bitter end of the month with plenty of rain, sleet and hail showers here in Tiverton yesterday, Saturday 29th February, although it was very clear and sunny in-between the showers. This followed another wet night as yet another low pressure system ('Jorge') gave upwards of 50mm of rain to the high ground of Wales and NW England which will just exacerbate the flooding in these areas.

The EWR for February reached 166mm up to the 28th and this has broken the record for the month - which was 159mm set way back in 1833 in a series dating back to 1766. The Met Office have confirmed that this February has also broken the record for the month in its preferred rainfall series which dates back to 1862. They will publish full details shortly.

The attached graph is for the latter series and comes from the Twitter feed of Simon Lee - @SimonLeeWx. There will always be the issue of 28/29 days depending on whether it is a leap year or not, but this graph has the 2020 figure up to the 28th + it is still a record! Note the upward trend in recent decades which conforms with model predictions in a warmer world.

[Simon Culling]

The final CET for February was 6.3°C which is +2.5°C above average - making it the joint 30th warmest February in the 362 year series. The final EWR for February was a whopping 169mm which is 259% of the average - making this the record highest figure for the month in this 254 year series.

The Met Office have produced a summary of February and the winter as a whole and it naturally concentrates on the rainfall. Despite all the rain, it was a surprise to read that for the winter as a whole, England + Northern Ireland had above average sunshine!!

https://www.metoffice.gov.uk/about-us/p ... uary-stats

This article uses the updated gridded series of rainfall which dates back to 1862, and this February was the wettest averaged over the UK in this series.

[Simon Culling]

This tweet from the Met Office gives an idea of how mild the winter has been - it shows a number of their sites that have not recorded an air frost all winter - that is a temperature of <0.0°C in December, January + February.

https://twitter.com/metoffice/status/12 ... 2620538886

I looked up the average number of frosts per winter for these sites for the period 1981-2010 and they are:

Fair Isle - 10.4 days
Weybourne - 17.8 days
Langdon Bay - N/A, but nearby Manston has an average of 20.3 days
Cambourne - 8.0 days
St Mary's (Isles of Scilly) - 1.4 days
Aberdaron - 6.2 days
Ronaldsway (Isle of Man) - 10.6 days

I appreciate that these are all coastal sites, but they would normally expect a few frosty nights each winter. Perhaps this shows more about the marginality of the UK climate than a strict indication of climate change?