It’s interesting to see how the three main NWP models handle tomorrows low and the heavy rain it introduces across the country (fig 1). The Met Office take the main thrust of the rain north into Ireland, whilst the GFS and the ECMWF are in no doubt that the action will be centred much further east over southwest Wales. I think the UKMO model looks out of step with the other models on this one, time will tell.
One of the tricks of the trade as a weather presenter when you want to be as vague as possible about the timing of rainfall events like this, is to leave of the exact time in the graphics, so it’s good to see that Aidan McGivern has picked this one up and is now ready to move on to the next chapter (fig 2).
As well as this cyclonic development on Friday another low threatens to spoil the weather in the southeast of England during Sunday. It’s amazing just how the weather likes to dish out bad weather in as fair a manner as possible isn’t it?
Although tornadoes can occur in any month of the year the ‘tornado season’ is usually thought of as being the months of March through to June, that’s when there’s a greater chance of cooler continental air meeting humid warmer air from the Gulf of Mexico, and hence a much greater chance of thunderstorm development. So far 2018 has been a remarkably quiet year for tornado activity across the United States (fig 1). In fact it could be that April 2018 has one of the lowest tornado counts on record (fig 2).
Here’s a news item from Matt Taylor of the BBC weather team about the slow start to the tornado season in the United States that spurred me into action (fig 2).
It seems that we have been caught in a cycle of cold end to months recently. First there was February, then March and now April. That’s according to the latest run of the GFS model, which indicates that the end of April and beginning of May will be changeable and often cyclonic, with winds in the east or northeast, the anomalous warm start to spring of last week will have retreated to the continent, but even here the warm air will be gradually pushed back further east.
Since moving down to the southwest some fifteen years ago now, I have noticed it’s often the case that in warm sectors (fig 1) although Cornwall and west Devon are plagued by extensive sea fog and low stratus, away from high ground, and in the lee of Dartmoor or Exmoor further east surface visibilities are often remarkably good, such is the case this morning (fig 2).
We might see a week with higher mean maximum temperatures, but I think it’s a distinct possibility that we won’t see a week with higher maximum anomalies or more sunshine than we saw across the southeast of the country. The highest mean maximum anomaly for the week was 8.3°C above the 1981-2010 long-term average at Northolt (fig 1), and the sunniest place was Manston in Kent with 79.3 hours in the seven days (fig 2).
The weather of the last week has provided a welcome fillip to April’s sunshine totals. Sunniest places during the last week in the UK were in the far southeast, with the last four days being sunny from dawn till dusk.
Here are a few graphics to show the extent of this early thundery spell across the country, the severity and extent of which caught both the ECMWF and the UKMO NWP models out yesterday. As far as I can see most of the lightning was from unstable medium level cloud rather than the more traditional cumulonimbus (fig 1). The rainfall from the thunderstorms looks to have been concentrated in a swathe SSW-NNE through Hampshire, where my estimates from weather radar suggest that as much as 32-40 mm fell in the wettest areas (fig 2).
I won’t go on about just how poor or late the warnings were for yesterdays thunderstorms from the Met Office, or just how divorced the NWP graphics used by either themselves or the BBC was from reality, the following screen shots will have to suffice (fig 4).
I was keen to publish the fact that Thursday – the 19th of April – had been the warmest for that day since 1772 in Central England, but because there’s be an ongoing communications or observational problem down at the Met Office, I was delayed till the CET data for Thursday finally arrived this morning.
The 19th also set an extreme maximum record (23.0°C) as well as a new highest mean of 16.4°C, which was 7.95°C above the 1961-1990 long-term average, and a full 1°C higher than the previous high set in 1870.
Extreme records like this don’t happen that often, but in my experience when they do you often get a pair, as was the case with the 18th and 19th of this month. These values are of course provisional but I doubt if they’ll change much.
There may be a chance that the 20th has also set a new extreme to make it three in a row, but because of the data problem I won’t know that till tomorrow at the earliest. Don’t forget you can keep up with the latest daily CET on my Meteograph website.
Central London might have been the warmest place in the UK once again yesterday but is it healthy? The latest forecast of carbon monoxide from the Copernicus site suggest that the air quality here and other European centres is very poor for so early in the year. I only came across the Copernicus website thanks to a tweet, but it does seem to have all the answers when it comes to aerosols, pollution and the quality of the air we breathe.