The cold front that brought all the rain to parts of England earlier this week finally managed to penetrate the warm air over central Europe and bring thunderstorms and a sharp drop of temperature with it. The interesting thing about the 15 UTC visible satellite image (fig 1) is just how sharp an edge of the cloud the cold front had, it was either blues skies or frontal cloud, and in the image I can see at least three large embedded CB’s. The demarcation in cloud reminded me of what occurred earlier this week over southeast England. Here’s the Met Office analysis for yesterday at 12 UTC (fig 2), and as you can see there is not just one cold front but two.
Figure 2 – Courtesy of the UKMO
Here’s the plotted chart for 15 UTC yesterday for the area (fig 3) and notice that temperatures at places ahead of the cold front in eastern Germany where as high as 30°C at that time.
Here’s the observation sequence from Regensburg, Bavaria for the last 24 hours, in the space of just a few hours the temperature fell from over 30°C to around 11°C (fig 4) during the late afternoon.
Judging by the 06-18 UTC rainfall totals (fig 5) the convective activity from the CB’s didn’t produce the heaviest rainfall, that occurred further west in the frontal cloud, even though there was a lot of SFERIC activity (fig 6).
Figure 6 – Courtesy of Blitzortung
Western Ireland saw the heaviest rain overnight, more specifically the higher ground of counties Kerry, Mayo and Donegal seeing accumulations of more than 75 mm (fig 1).
Figure 1 – Estimated rainfall totals from Weather Radar Images
Rain is holding the temperatures down in the southeast, but I notice that there’s much warmer air just across the Channel (fig 2) at 09 UTC.
There was a little bit of rain overnight in the southeast but not nearly enough, but the cold front will drag its heels this week though, and could take till Thursday to clear the southeast, and if the GFS model is correct, will produce a wet day on Wednesday across the south (fig 3).
Figure 3 – Courtesy of OGIMET
Chilly down the east coast of England today with a moderate or fresh northeasterly straight of a relatively cold North Sea (fig 2) keeping temperature at around 9 or 10°C (fig 1).
Meanwhile in comparison, the west of Scotland has seen temperatures as high as 20°C in some places this afternoon, on what’s been another generally sunny day in the north, although with a bit of cirrus (fig 3) and a keen breeze at times.
To coin a weather euphemism that I don’t particularly like, but gets rolled out at times like this, west is best today in terms of warmth…
Mind you, even if it does make it to 21°C or 70°F this afternoon in Skye, it will still fall a long way short of the UK record for May Day of 27.4°C, reached on the Moray coast in 1990. The TORRO site has a list of British daily temperature extremes, which is always worth bookmarking for future reference. It’s cooler down in the south under the remnants of yesterday’s filling low, but the colder air aloft has produced some lovely skyscapes this afternoon, with CU and CB, and dense patches of CI spissatus.
The recent cold weather seems to have cancelled out the earlier warmth in the month of April, because temperature anomalies up until the 23rd are quite close to average across most of Europe, although Iberia has been unusually warm. The Arctic has been its exceptional mild self once again, and is probably one of the reasons why this recent ‘Arctic blast’ has been so relatively innocuous.
I have a theory that northerlies don’t last as long as they did in the past, the general life expectancy of one is probably no more than 48 hours tops. The cold from the current ‘Arctic blast’, has already moved south to allow warmer temperatures to come down from of all places the Arctic. It’s not evident until you run a comparison of temperatures differences that are 24 hours apart that you’re ever likely to notice it though (fig 1). I’m not saying that temperatures aren’t several degrees below average for this time of year, but it’s warmer 2 or 3°C warmer than it was at the same time yesterday over much of the north, and conversely it’s up to 7°C colder across many central and southern areas.
It’s not very often that you’ll see Liscombe in Somerset (and not in Devon as I had always thought) as the warmest place in the British Isles, but it happened today with a temperature of 15.0°C at 15 UTC (fig 1), in fact it was a southwest one two with Exeter Airport second in the table (fig 2), but I bet you won’t hear about that on the BBC weather.
You can’t even call Liscombe a village in all honesty, there is a Liscombe Farm, but the AWS is a little way to the east up what looks a very lonely lane on Exmoor at a height of 348 M (fig 3), so it might be getting a little help from the northwesterly wind.
Figure 3 – Liscombe courtesy of Google Maps
It’s proving to be a cold and showery Easter over Northern Scotland this year, and the showers affecting the area on Saturday afternoon look like they are putting snow down to ~3000 feet if this webcam image is anything to go by (fig 1). That’s because the cold air over Scotland is holding the air temperature on Cairngorm at a very cold -2.9°C (13 UTC) at the moment. The heatmap of air temperatures on the summit since the start of March shows that until this last week, it had been relatively mild since around the 24th of March (fig 2). It looks like the high ground might get a bit more snow overnight, but it might be a bit late to extend the skiing season from what I can see from the other webcams in the area.
At the same time it’s been quite a benign Spring as far as gales and storm force winds are concerned on the summit (fig 3).
I noticed that there were a number of places in Eastern England, that were 10°C or colder this afternoon at 15 UTC, than they were just 24 hours earlier on Sunday afternoon.
I thought that I would look back at yesterday’s (9th April 2017) maximum temperatures forecast by the BBC. This is not a moan about the temperature contrast across the south of the country, their most certainly was a good contrast, it’s more to do with the sites that the BBC choose as representative of their region and label in their graphics. The one that infuriates me the most is Plymouth in the southwest. There is a method in their madness though, because the Met Office bonus is dependent on how these extreme temperatures are scored in verification, choosing a coastal site (which is difficult not to do on an Island) can pay dividends, because the extremes, and therefore any potential misses are not as large. I believe that yesterday’s maximum temperature of 20.0°C at Exeter was more representative for the whole of Cornwall, Devon, Somerset and Dorset, than a forecast maximum of 14°C was for Plymouth, and even here the temperature reached 16.8°C. Rather oddly many of the temperatures on the chart don’t reflect the colour filled temperature contours that they are overlaid on, for example, a forecast maximum of just 16°C at Birmingham was always going to be wrong but the background colour is a mid-orange colour.
I think that I would have the full support of the South West Tourist board if the BBC put a little more thought into how they forecast regional temperatures.
Figure 1 – Courtesy of the BBC
I couldn’t help myself and resist scoring the maximum temperatures on the chart, if anything it underlines the fact that the Met Office model seems to have as many problems underestimating maximum temperatures as it does overestimating low cloud at the moment.