Dartmoor triggers intense shower

Data courtesy of the Met Office

In the last couple of hours, the high ground of east Dartmoor (possibly around Haytor) seems to have triggered a thundery shower that quickly tracked NNE across the west of the city of Exeter. It looks to have been quite an intense, but short sharp shower. I say thundery, but so far Blitzortung has only detected one flash of lightning from it.

What seems very silly to me, watching the latest forecast on the BBC News channel (which looks like it may have been taped), is how the weather presenters prefer to use NWP model rainfall rather than real-time weather radar images. In a dynamic convective situation like today, you would have thought that’s what they would be most helpful to the public. Likewise the BBC presenters never ever use real-time SFERIC data, or come to that rapid scan 5 minute visible satellite imagery. What’s the point of having all these various ways of observing the weather in real-time, and then not using them?

Certainly use NWP images for forecasting, but masquerading NWP forecast data as real-time observational information is wrong and just plain misleading.

I remember coming home from work on the 16th of August 2004, it must have been just before 4 PM, to watch Michael Fish prattle on in the forecast about how hot it had been recently in Greece. This too was a taped forecast that they used on the same BBC News channel. The news was later interrupted by breaking news about flash flooding that was occurring at that precise moment in Boscastle. It seems to me that little has changed since then in how we present the weather, if this intense shower that I noticed this afternoon had been slow-moving and a little larger, the same thing could have easily happened all over again.

US Tornadoes 1950-2016

I’ve just downloaded the latest updated US tornado data from 1950-2016. First off, this is a big data series, and it’s not easy to navigate and it’s complicated. It’s complicated because for some of the more severe events that run across more than one county, there are multiple entries that share the same common ID. These ID’s are not always stored sequentially in the dataset which makes counting using the EF categories very tricky. Personally, I think this database is in need of a rethink. Maybe by splitting the data into two, with one series of single unique entries for each tornado, and another separate series linked to the first, to store multiple date time and location coordinate data, in much the same way as the HURDAT2 data series does with Hurricanes. Having said that it would be a big task, because there are already over 62,000 entries, but I think it’s long overdue. So with the caveat that the information that I present in the following graphics are done to the best of my programming ability!

This table (fig 1), is a complete list of the occurrence of EF 5 tornadoes from 1950 to the end of 2016, the most recent EF 5 tornado happened over 4 years ago on the 20th of May 2013.

Figure 1 – Data courtesy of SPC/NOAA

This is a map of the start point of each EF 5 event (fig 2), hopefully they should tally with the table above.

Figure 2 – Data courtesy of SPC/NOAA

The annual number of tornadoes has shown some decline in the last decade or so (fig 3), even with the better reporting of tornadic events in recent years, made possible by the rise in the use of mobile devices, and the effectiveness of social media reporting. I don’t have a clue why this is, or what it’s linked to, but I hope it’s not down to the jet stream.

Figure 3 – Data courtesy of SPC/NOAA

Finally, I don’t do much as much as I could with this Tornado application that I’ve written to visualise this data series, because there is so much information regarding tornadoes on the NOAA Storm Prediction website already, and I can’t match the superb graphics that they generate.

In fact – shooting myself in the foot completely – there is now a GIS web application (fig 4) that does much of what I do in a desktop application available on the Midwestern Regional Climate Center [MRCC] website. This is a great resource, and their site is also full of interesting information regarding the destructive power of tornadoes, and the climate of the midwest. Web apps are great, but as a programmer I still prefer the flexibility of writing my own desktop applications, then again I do realise, that you can’t beat the reach of a web application such as this.

Figure  4 – Courtesy of MRCC

More miss than hit from the Met Office

Figure 1 – Courtesy of the Met Office

I might have agreed that the Met Office warnings for Saturday had been warranted, but the yellow warning for Sunday was a little over the top, both in the area of extent and the amount of rain that fell. Here in Devon, we had a very unspectacular 0.4 mm of rain in the 24 hours ending 06 UTC this morning, and that was true for the whole of the southwest and most places in the top half of the yellow warning area (fig 1). True, a lot of the rainfall would have come in sharp bursts because a lot of it was associated with thunderstorms, in fact Blitzortung reports a 183,593 flashes in 24 hours (fig 2), but a good part of Kent which was in the thick of the SFERIC activity, so no more than 2-4 mm of rainfall in the 24 hours in my estimates.

Figure 2 – Courtesy of Blitzortung (28 May 06 UTC to 29 May 06 UTC)

We ended up with a mainly dry day here in Devon, with just a few spots of rain in the mid afternoon, in fact until then the day had been surprisingly bright despite a shield of thick upper cloud.

Figure 3 – 28 May 06 UTC to 29 May 06 UTC rainfall estimates

Figure 4 – 28 May 06 UTC to 29 May 06 UTC reported rainfall

The only mitigating evidence that I can find, is an area of the Sussex coast around Chichester, that may well have received in excess of 40 mm of rain if my weather radar estimates (fig 5), which look a little on the high side for the convective rainfall when comparing them to reality (fig 4). I’ve looked for reports of flash flooding for yesterday, but found none on the Google searches I’ve done. So, looking at the event as a whole, it may have looked very spectacular in the southeast, but as far as can see, it was more miss than hit as far as the yellow warning was concerned.

Figure 5

Yesterday’s thunderstorms

Figure 1

Despite the number of thunderstorms across the country yesterday (fig 2), estimated rainfall totals for yesterday (06-06 UTC) were generally low (fig 1), although there were some more active thunderstorms that tracked NNW across northern England and Scotland that enhanced the totals, one notably over the southern Lakes and another one that clipped Fife.

Figure 2 – Courtesy of Blitzortung (27 May 06 UTC to 28 May 06 UTC)

Rainfall amounts from bands of thundery rain like this must be almost impossible to predict, and I think the forecast from the Met Office for yesterday was pretty good, and the warnings that they issued (fig 3) look well justified.

Figure 3 – Courtesy of the Met Office

Normal service is now resumed

After two consecutive days with Lossiemouth in the number one position as the hottest place in the country, normal service has now been restored as far as temperature is concerned in that part of the world.

How to cobble a sensational weather article together by the Daily Mirror

It’s hard to believe these days what can masquerade as good reporting in any news article about the weather from the tabloid newspapers. The Daily Mirror reporter Chris Pharo for example is responsible for this story, ostensibly about the current heat wave, in yesterday’s Daily Mirror (fig 1). It says that according to the Met Office, Eastbourne, with an average of 7.5 hours of sunshine each day so far this month (~187.5 hours to the 25th) is the ‘sunniest seaside spot this May‘. I’ve got some news for him, there are many other ‘seaside spots‘ across the UK that were much sunnier than that.

  • Prestwick (221.7)
  • The Isle Of Man (245.8)
  • Anglesey (236.0)
  • Aberdaron (240.1)
  • Aberporth (211.9)

Of course, these ‘seaside spots’ are not on the south coast, but never let the facts get in the way of a good story. I also strongly suspect that the daily sunshine values he is quoting are the 30 year climate averages which he’s accessed from the Met Office website, and not values for May 2017. For example he states that Orkney is ‘5th on the list‘ of sunniest places this month, but according to my list, so far this month Orkney is 47th out of 56 reporting stations. The link to the Met Office in the article, surprisingly isn’t to the Met Office, and I would love to know exactly where he did source his data, because mixing current weather with climate data to create some kind of Frankenstein monster article about the current ‘heat wave’ is misleading.

Figure 2

Northern Ireland sunniest place in UK so far this May

Figure 1

It’s neck and neck at the top of the sunshine table between Aldergrove and Ronaldsway airport on the Isle of Man this month. With just a few days left this May, Aldergrove with a total of 248.4 hours is just in first place. Tiree, who had been sunniest for the first 12 days has now slipped to 5th place. There are some missing values for stations in my list, but it maybe that Liscombe in Somerset might once again be the dullest place in the UK, but that does look a little suspect to me even though I’ve received all 26 sunshine values from their observations.

Figure 2

Medium level thunderstorms

As expected, and almost dead on time we saw some thunderstorms move up across the Channel from the south to affect southern England, particularly Cornwall and Devon. You don’t get that many thunderstorms in this part of the world, they are almost as rare as snow and quite a novelty. From what I could see from hanging out the Velux in our loft, there was plenty of intra-cloud [IC] and cloud to cloud lightning [CC] that must have lasted for almost 30 minutes before the line of activity steadily swept northward. The flashes briefly illuminated the medium level castellanus cloud and some larger embedded CB cloud particularly to the ESE of us towards Honiton. There was a very brief sharp shower of rain which only lasted a minute or two (1.2 mm). I did try to take some shots with my camera, but you know how it is, its pitch black, and you’re trying to turn the motor drive on, and can’t remember which button to press, as you crash into the foot of the bed with your big toe.

Figure 1 – Courtesy of Blitzortung

It’s nice to see that the LCBR at Exeter airport confirmed what I saw in the way of cloud structure at the time of the thunderstorm (fig 2).

Figure 2

Well done to the Met Office for forecasting the event so precisely. I still think a warning for heavy rain and flash flooding was called for, especially in Cornwall, but what the hell. Here are my estimated totals from 21 UTC yesterday (fig 3). I estimated 19.6 mm for that period for Cardinham, Cornwall, which was way over the top because they only reported a 10 mm 18-06 total, but I put that down to the the nature of thunderstorms and the resolution of the images on the Met Office website!

Figure 3

Hottest 26 May in UK since 1880

Figure 1

Yesterday’s maximum of 29.4°C was the hottest 26th of May since 1880 in the UK, that’s according to the table of daily extreme maximum on the TORRO website. It just pipped the previous record of 29.3°C set 137 years ago in the days of Queen Victoria in Norwood, North London in 1880. It might have gone that bit higher either there or at Kinloss if it hadn’t been for the sea breeze along the Moray coast that didn’t relent till 14 UTC. Temperature may reach the same kind of levels today in that part of the world, but only if the sea breeze slackens its grip.

Figure 2

The anomalies for yesterday’s maximum temperatures, according to the long-term daily averages that I’ve computed, were astonishingly high for the month of May for places in the north and northwest of the UK (fig 3). The maximum at Lossiemouth for example was +14.5°C higher than the average daily maximum for the average I’ve calculated for the 26th of May.

Figure 3


Sea breeze finally relents on the Moray coast

I notice that the sea breeze has finally relented on the Moray coast, well at least at Lossiemouth, where the temperature has just leapt up over 7°C in just a single hour to 28.3°C at 14 UTC, and in so doing so became the hottest place in WMO block 03 (fig 1). This is so reminiscent of the May Day back in 1990 when the identical thing happened and set the warmest May Day record for the UK in the process. How the sea breeze has been holding back the land breeze and a southerly gradient of at least 20 or 25 knots till now beats me. It happened yesterday, but the gradient wasn’t just powerful enough to win out.

Figure 1

The remarkable thing that happened in the last hour was that as Lossiemouth lost the sea breeze and the temperature leapt up 7.1°C (fig 2), the sea breeze re-established itself just a few miles to the west at Kinloss, and the temperature fell by 4.4°C.

Figure 2

Figure 3