Thundery wintry showers

To me, it's quite odd that in the archives there haven't been many dry and sunny but cool Aprils, considering that dry and sunny but cool Marches, Mays and Junes have been relatively common. I can certainly think of Aprils that were dry and sunny with average temperatures, warm days and cool nights (1984 and 1990, and allowing for the recent warming of the climate you could add the Aprils of 2010 and 2015), but none that were substantially cooler than average. April seems to have a history of following the warm-dry-sunny relationship that is mainly associated with high summer (July/August). The high summer relationship probably has a lot to do with the dominance of the Azores High and the warm land, cold seas resulting in these slack anticyclonic/northerly types bringing a lot of cloud into eastern areas, although dry sunny cool Augusts were noted in many areas in 1993 and 2007. But I can't think of any explanation why the warm-dry-sunny relationship has reliably held for April. It might just be one of those statistical quirks that has been emphatically countered this year.

https://www.wetterzentrale.de/en/reanalysis.php?map=2&model=avn&var=1&jaar=2021&maand=4&dag=16&uur=0000&h=0&nmaps=24 Hope this works.

I agree about some of the post being melodramatic and I have a strong feeling that if it was warmer but unsettled, we'd be getting a similar amount of complaining about the lack of a sustained settled spell. If we were having a repeat of April 2012 it would be another matter. My part of Lincoln has so far had plenty of sunshine in this anticyclonic spell but today has become the first cloudy day, cumulus clouds (some of which were large enough to produce showers to my east this morning) spreading out into stratocumulus and not much blue sky left. The satellite images indicate that it's still clear and sunny over much of Scotland, NW England and Wales though.

Yes, I think the best we can get now is probably the "GFS analyse" from Wetterzentrale (WZ's archive for the 20th century reanalysis only goes to 2015).

Having defended cold outbreaks in spring earlier, I may as well take the opportunity to demonstrate that I also see the other side of the coin. That GFS 12Z does have a fair amount of cold raw dull weather with rain and drizzle and maybe a little sleet in the longer-term outlook, for East Anglia and the south-east from around T+216 and more widely towards the end of the run. As is often the case with such north-easterly setups, it would be sunny and dry in western Scotland, though. Not too much support for it yet on the ECMWF though and it's a long way off.

Yes, I was wrong about the conditions not being conducive to cumulus spreading out into stratocumulus sheets, judging by the satellite images this has indeed happened over a large part of south-east England in particular. Here in Lincoln it's only partial stratocumulus cover and there's still a fair amount of sunshine, but further south there's somewhat more cloud. It also looks cloudier in the west with some light showers, and heavy ones locally near the south coast, amusingly enough especially around Exeter, where I was located just a week ago.

The University of Reading weather diary is also worth checking out as it gives daily extremes, but so far only up to the end of March as far as I can see: http://www.met.reading.ac.uk/~brugge/diary.html It's possible that these may be updated monthly, in which case at some point in May you should be able to get the April extremes from there. I was surprised by the Met Office's lack of updates though.

The Met Office ones are still working for me: https://www.metoffice.gov.uk/public/weather/observation Edit: no they're not, they were last updated on 11 March 2021, d'oh!

That's very similar to the April 1986 CET (5.8C). It's a very tall order - we're currently running at 5.6C, 1.2C below the 1961-90 average for the first 12 days of April. If that anomaly was maintained in the second half of April we'd end up on 6.7C, which would make it easily the coldest April since 1989, but not up there with April 1986. Also, the model outputs are increasingly agreeing on a warm up around Sunday/Monday - OK, not as warm as many on here would like, but allowing for the GFS's typical underestimations of daytime maximum temperatures there's strong support for daytime highs creeping a little above the seasonal norm, peaking at 13-16C and possibly nudging 18C in the south-east. For comparison 18C is London's long-term average maximum for May, using the more recent averages (for 1961-1990 it was 17C).

That sounds like the typical scenario of cumulus hitting a cap and spreading out into stratocumulus. It can be an issue in anticyclonic spells if the air mass is relatively moist, but I don't see much evidence of it being widely forecast for the coming week - we have a dry polar air mass over the UK where the low relative humidity should help prevent extensive stratocumulus from developing. The most likely source of cold cloudy weather in this setup is if the high pressure drifts north allowing an easterly flow to take hold across a large part of the country. Some recent GFS runs have been showing this, albeit not until into next weekend, but for as long as the UKMO and ECMWF continue to not support this scenario I won't be too concerned.

There was another shower in Lincoln at 8pm last evening, started off sleety and then turned to snow with big flakes coming down. Most of it didn't settle, but there was a bit of lying snow on some surfaces alongside the frost earlier this morning. It's been clear and sunny so far.

1989 wasn't a particularly thundery summer overall, well short of both 1996 and 2001 in terms of overall thundery activity, but there were scattered notable events, especially the "Halifax storm" on 19 May 1989, and fairly widespread thunderstorms around 13 June, 6-7 July and 23 July. 1996 is a summer that I remember particularly fondly from my childhood, it had some of almost everything, there were anticyclonic spells, heatwaves, thundery breakdowns and cooler changeable spells. Many perceived it as a relatively cool summer because of the way it suffered by comparison with that of the previous year, but for much of England the mean maximum temperature for summer 1996 was rather above the long-term average, partially offset by cool nights, and most areas were drier and sunnier than average as well.

Having lived in Exeter for the past six and a half years, I don't think it's a case of spring northerlies being more anticyclonic, more that they especially tend not to deliver much for the south and especially south-west of the UK. Even the unusually potent one we had on 5/6 April only gave Exeter a snow flurry at 7am on 6 April followed by sleety showers later on. It's probably down to a combination of factors - being sheltered and in the south, and seeing less showers being generated over the Irish Sea and heading down through Wales into the West Country, due to the air masses not being as cold relative to the seas, especially during the daytime. In April we get a greater emphasis on showers being generated from solar heating during the daytime, but these tend to develop mainly in central and eastern parts of the UK due to high pressure being closest to western areas when we get a northerly regime.

I remember being caught out by this in my childhood - in 1999 I noted in my weather diaries, "October was warmer than April", as if it was somehow unusual! I also remember being surprised when I saw snow on 18 April 1995 (which was the first time I observed snow in April after I had started taking weather records), and again when I saw it repeatedly in the second week of April 1998 (despite the fact that I'd also seen snow on 6 May 1997). However, I recall that by the northerly outbreak of 13-15 April 1999 I had accepted that snow in April wasn't that unusual, at least in north-east England (where I was living at the time). Indeed, although April is warmer on average than November and has fewer days with snow lying, the average frequency of sleet/snow falling is a little higher in April than in November in most parts of the UK.

Yes Roger J Smith confirmed that the 1991-2020 CET average for April is going to be either 8.9 or 9.0 depending on the rounding system that the Met Office uses. For comparison, the 1961-90 average was 7.9C, for 1971-2000 it was 8.1C, and for 1981-2010 it was 8.5C, so there's been a big increase in the rate of warming of April recently after a period of relatively sluggish warming in the 1990s and early 2000s.

I really enjoyed today's mixed bag of weather with "April showers", feeling fairly warm in the sunshine in between the showers and out of the breeze, but also some hail, sleet and snow showers, some proper fluffy snow at 8pm tonight (which didn't generally settle, but I did spot a temporary smattering on the grass), and temperatures oscillating between 3C and 8C (down to 1C at 8pm when the snow shower hit). Some impressive cloud formations too. I ended up taking quite a number of photographs of the weather today. The upcoming outlook also appeals to me with plenty of sunshine, temperatures getting up to near normal by day and it should feel warm in the sun and out of the wind - as long as that anticyclone doesn't drift north and allow an easterly flow to establish widely across England, which could lead to cool grey weather. At the same time I appreciate that many gardeners may be concerned after the very warm end of March and this ongoing spell of below-average temperatures, so take care with those plants. I note that this April hasn't really been that cold so far relative to the 1961-90 average, just 0.8C below the 61-90 average for the CET. The fact that many are describing the recent weather with highly negative terms reflects a mix of the shifting climate (April has warmed by 1C so the recent weather is 2C colder than what people have recently been used to in April) as well as the desire for winter to be followed by a sudden flip to a warm spring rather than a slow, erratic transition from winter to summer.

I've been busy moving house for the last few days so haven't been keeping up much with the model outputs, but certainly there's been a big shift over to the high pressure scenario since I last looked. There's still potential for some scattered showers, wintry in central and northern areas, tomorrow with an upper level cold pool and the high pressure proving slow to build, but by Wednesday the high pressure should be strong enough to kill off the showery activity. The positioning of the high and surface winds will be important, for if the high drifts to the north and pulls in an easterly flow, some rather grey and cool weather could establish across the eastern half of England with maxima below 10C and minima holding up well above freezing, as is shown for example on tonight's GFS run: However, the UKMO/ECMWF are positioning the high pressure further south than that, resulting in a southerly flow for the west and an easterly flow only for the far south. The ECMWF operational and ensemble mean tonight support mostly sunny weather with temperatures creeping back up to the seasonal average by day (12-14C) with frost quite widespread by night.

Yes I did! I lived there with my parents for a couple of years when I had finished my academic studies and was job hunting, then I moved to Exeter. I've also lived in South Tyneside (Cleadon and South Shields), Lancaster, Leeds and Norwich, so have been around a fair bit.

Just relocated from Exeter to Lincoln on Friday, hoping to get more of "my" type of weather over here, and today certainly hasn't disappointed - in the sunny intervals and out of the wind it's felt quite pleasant, but in between there's been showers of hail, sleet and snow, never quite cold enough for the snow to settle but there was lying hail at around noon today. Temperatures of around 8C when the sun got out, falling to 3-4C in showers. Some impressive TCu and Cb cells about with snow and/or hail shafts. Indeed, I've seen more snow falling today in Lincoln than I did in Exeter during the entire winter of 2020/21!

I'd agree more with the suggestion of April 2007. The warming of April in the period 1987-2006 relative to earlier periods was modest compared with the first three months of the year, and the Aprils of the 1940s were on average warmer than those of the 1990s. But since then, we've had two Aprils in 2007 and 2011 that smashed all records. The 1991-2020 average for April is 1.1C higher than the 1961-1990 average. But I don't think it's primarily a case of recent warm Aprils skewing perceptions. It's more that seemingly the majority of people on Netweather flip from "winter mode" to "summer mode" sometime between late February and early April, and then get disappointed when the warmth of summer sets in slowly and erratically during the spring months. It was at least as noticeable around 2005 as it is today. I remember the Aprils of 2005 and 2006 and May 2005 being widely panned on this forum despite the CET being a little above the 1961-1990 and 1971-2000 averages and many areas of the UK being sunnier than average. Damaging frosts are a problem in the spring months, but for instance I recall that in 1990 we had very damaging frosts in early April following a very mild winter and March, and that in 1995 there were damaging frosts around 18-21 April and 12-14 May, but in both cases the negative impacts of these were dwarfed by the negative impacts of heat and/or drought in the summers that followed. Yet lengthy settled spells in spring and summer are usually welcomed by a large majority on this forum. Thus, I reckon that the observation that damaging frosts in spring get more attention in this space than damaging droughts arises mainly because people who are in summer mode by a certain point of the year don't want to see repeated northerlies rather than the relative magnitude of the impacts.

I finally managed to see some snow! A bit feeble, but I stood outside next to my bins and I saw some fluttery snowflakes blowing past in the wind, it then turned back to sleet.

Certainly the average frequency of lying snow there is 3-4 times what it is in Exeter, and they also average roughly twice as many days per year with thunder, so I'm hoping to see rather more of my favourite weather types over there!

A local informs me that it did snow in Exeter at about 7am. I woke up at 7:15 just after it had passed over, so I didn't see it.

I'm moving from Exeter to Lincoln this Friday so wondered if this northerly would give me a rare snowy farewell to Exeter, but overall it's been pretty standard fare for Exeter with a bit of rain, sleet and graupel. The dry air mass is limiting showery activity though, and it's probably a case of the dry air and the wind sucking out some of the precipitation, so less falls near the ground than is suggested by the radar. It might have snowed here if the showers had been heavier. I had to wrap up warm when out and about, but in the sunny intervals and out of the wind it was fairly pleasant for walking in. Edit: someone who lives locally confirms that it did snow in Exeter at around 7am (though it didn't settle). I set my alarm for 7:15am and woke up just after it had passed over, so I didn't see what the shower fell as.

I think it's down to reduced continentality and modification of the Arctic airmass over the comparatively warm seas. I follow the weather of Munich quite closely and their weather looks like it has been similar to Prague with a rain to snow event yesterday and some heavy snow showers today, though in the city the snow has melted during the daytime, sporadically re-accumulating in the heavier showers. The wind probably helped to keep temperatures near freezing in most parts of the UK overnight, I'm moving from Exeter to Lincoln this Friday and note that this northerly in Exeter, despite being unusually potent for April, has only been cold enough to deliver sleet and graupel showers. It clearly takes a pretty exceptional northerly to deliver snow this close to the English Riviera (the December 2010 one managed it, but that was exceptional). Thus, a rather characteristic non-event for my farewell to Exeter. Regarding outdoor hospitality I reckon the short term outlook, although nothing like as favourable as last spring, is better for outdoor activities and therefore hospitality than a wet and windy washout. Pressure looks set to be quite high, so for many, particularly in the west, there will probably be a fair amount of dry and bright if rather chilly weather. Longer term there are signs on the ECMWF 00Z run that it could turn duller, wetter and windier with a southerly tracking jet stream, but that's still a fair way off.