It’s official! This morning’s blood-red sun was caused by Saharan dust, so says Simon King the BBC weather presenter.
Matt McGrath, an environment correspondent at the BBC, has written an article that clarifies that any increase in frequency or intensity of tropical cyclones, is not directly linked to increases in the sea temperature in the oceans in which they form. This corrects the misleading, and rather strange 30 second news video that David Shukman made on the 19th of September who said that higher sea temperatures meant more tropical cyclones. Although SST is a key ingredient, there are a lot more factors that have to be just so before a tropical cyclone is formed.
Here’s a chart of the number of hurricanes each year since 1851.
And here’s a chart of the combined ACE score for each year since 1851.
You may wonder why the linear trend is upward in both charts, that’s because of the increased scrutiny that each tropical cyclone has been under since the start of the satellite era (~1960), has meant that we are now in a position to watch each subtle move and deviation that a tropical cyclone now makes which was never possible before. There must have been many lesser tropical cyclones, especially in the 19th century that escaped detection and don’t even appear in the HURDAT2 dataset, which must skew the trend down to the left.
At least this article is more balanced in what is a says about what we do know about tropical cyclone formation, and not just using adding it to the list of what increased CO2 is doing to the planet, as David Shukman seems to think.
- Increased global temperature ✔
- Reduction in sea ice ✔
- Shrinking of glaciers ✔
- Increase in intensity of heavy rainfall events ✔
- Increase in the number and severity of tropical cyclones 🗙
Apologies for the scribblings on the news item like I have, I was just interested in the number of clichés Matt McGrath had used in his article – and why is it that tropical cyclones always seem to ‘barrel’ across the ocean?
I was listening to a 30 second science-bite about hurricanes from David Shukman on the BBC News website yesterday. David was presenting a ‘idiots guide’ to just how hurricanes are formed, and for once the explanation didn’t involve that ‘fast moving ribbon of air high in the atmosphere that the experts call the jet stream’. The basic premise of his explanation was that when a thunderstorm forms over the ocean in the tropics, if derives its energy from the warm seas, and if the temperature of that sea was 26°C or higher, and you added a little bit of rotation, then before you know it you would have yourself a tropical cyclone. Of course this was a thinly disguised bit of propaganda to implant in the viewer’s mind the undisputed fact that: higher sea surface temperatures mean more hurricanes, and of course it must logically follow that’s why they’ve been so many this year.
That got me to thinking about El Niño and La Niña events and how they might influence tropical cyclone development in the eastern Pacific. If you apply the same ‘Shukman’ type logic, the extra warmth of the Pacific during El Niño years, should be apparent in the accumulated cyclone energy. So I have produced a couple of graphs that plot ACE for the eastern Pacific from 1950 for both total ACE and ACE anomalies (fig 2). The pale pink and blue stripes in the lower graph are the ENSO events during that time.
I could do further statistical analysis on the results, but I think I wouldn’t find a strong correlation between SST and the ACE index. Active years do occur in El Niño years that’s true, but they also seem to occur just in La Niña or neutral years. I personally think that the BBC should be explaining that although the warmth of the oceans is a key part in tropical cyclone development, any perceived increase in their number and ferocity is a little more complicated, rather than this glib thirty-second news item with its fancy graphics implies.
I did find an analysis concerning El Niño and intense tropical cyclones in the Journal Nature but was unable to download it without getting a second mortgage on the house. I did find this online debate about the conclusion that the report came up with which might be of interest.
Its been over a year now since MeteoGroup won the bidding process to take over the running of the Weather forecast on BBC radio and television. In August 2016, Nigel Charters, a project director at the BBC promised that these services would ‘hit your screens, from mobile to television, in Spring next year’ (fig 1). Well, Spring has gone, and so has summer, and now we’re in ‘meteorological’ Autumn, but we are still stuck with the same old BBC graphics, and not the state-of-the-art graphics system as promised by MeteoGroup, and as far as I can see we are still using forecast model data supplied by the Met Office.
So what’s gone wrong?
It’s impossible to say with any certainty, because the BBC and MeteoGroup are both keeping schtum about:-
- What the new graphics will look like.
- When the new graphics will start.
- Who exactly will provide the ‘multiple sources of meteorological data’ (see (2) in fig 1).
If you take a look at the MeteoGroup website they have remained tight-lipped about the whole subject since the news that they had been awarded the contract (fig 2).
MeteoGroup seem keen to get started with their own graphics system, which I understand is not an in-house solution, but one that they buy in from WeatherscapeXT from MetraWeather in New Zealand, although I am not even 100% certain about that. As far as I know MetraWeather provides the current graphics system that the BBC have been using for the past 10 years or more. If that’s so, I can’t see that the slowness in switching is down to the new graphics system itself, but more likely to do with the sourcing of the model data that it uses, and what exactly the visualisation of that data will look like, in particularly the mapping. I hope that we have seen the end of 3D fly throughs, which pardon the pun, never really took off in my opinion.
Forecast model Data
MeteoGroup promise ‘better weather forecasts and solutions’, which to me is the most interesting feature of this whole debacle. If they are not going to use UKMO data, and as far as I know can’t use the ECMWF model commercially, that would just leave the ubiquitous American GFS model. I suppose it’s not outside the realm of possibility that MeteoGroup could decide to buy in some cut-price model data in a deal with the French or Germans. The strengths of the various models was recently put to the test in the Caribbean, forecasting the tracks of hurricane Harvey and Irma, some models perform much better than others. The GFS is primarily built to serve North America, and unlike the UKMO model is not tweaked for an island in the eastern Atlantic. So what happens in the future if the GFS model fails to deepen a low as markedly as the UKMO model does, and on the strength of which, the Met Office issue Amber alerts for storm force winds?
So has anything actually happened?
Well, I suppose that all the weather presenters are now no longer working for the Met Office but the BBC, and some of the old lags have been replaced by women presenters to balance the male-female ratio. I did write back in April that the takeover was imminent, and I suppose that it has happened. But rather awkwardly both for the BBC and MeteoGroup nothing visually has changed, if anything the Met Office have come out of this rather well even if they did lose the contract, their recent national weather video service that’s produced using their new VisualEyes graphics system, which they push out on their website and over social media is rather good.
The graphic that the BBC Weather team used in their tweet this morning (fig 1), is of yesterday evenings forecast minimum temperatures for rural places at dawn. If you compare these spot values with the actual minimum temperatures [18-06] from the SYNOPs (fig 2), you’ll see that they’re pretty wide of the mark for many places, but especially so across England, as overnight temperatures were held up in many places by a combination of too much wind and too much cloud. As an example, minimum temperatures in the Vale of York were forecast to be around 2°C, but were actually around 9°C, the ever reliable cold spot of Exeter Airport was forecast to have been 4°C but was over 7°C, southern Scotland was forecast to have been 1°C, but Eskdalemuir could only manage a minimum of 7.3°C.
Initially I did think this cloud and rain was down to one of those magical troughs that suddenly appear in the analysis, and which run parallel with the isobars, but surprisingly, and rarely, the British isles were free of any frontal structures on the midnight analysis (fig 3). It’s quite obvious though, that this week the Met Office mesoscale model has never quite got to grips with the showery northerly airstream left behind in the wake of storm Aileen, and has performed very poorly, both in the handling of convection, and the subsequent forecasting of overnight minimum temperatures, due to the cloud, showers and wind associated with these features.
I think the person that handles the tweets for BBC Weather ought to be a little more careful, that the graphics used in any tweet are factual, and not as much as 7°C colder than they were in reality. The weather has a way of catching you out if you don’t continuously monitor it, and overly rely on a model that seems to be having one of its heads this week.
First off I will admit I haven’t fully read the study “Changing climate shifts timing of European floods” by Günter Blöschl and numerous other contributors from across Europe. The study has been picked up on by the BBC in this news article (fig 1), because they obviously see that it’s just another byproduct of AGW, rather than just climate change, and yes I do think there is subtle distinction. As far as I can see, none of the many contributors are employed by the UKMO, which I find unusual.
I have highlighted in yellow the areas in the news article that I have misgivings about, the first one is from Matt McGrath
The scientists believe this is due to changes in the North Atlantic Oscillation (NAO), the weather phenomenon that pushes storms across the ocean into Europe.
The North Atlantic Oscillation is simply an index of the pressure difference between the Azores and Iceland, as far as I know this index doesn’t push anything across any ocean, you might say that the Azores high or Icelandic Low are weather phenomena, but surely the difference between the pressure at two points is just a number?
Günter is the quoted as saying:
In southern England, it has been raining more, longer and more intensely than in the past. This has created a rising groundwater table and higher soil moisture than usual and combined with intense rainfall this produces earlier river floods
I refute that, unless the changes that the study is talking about have suddenly started to occur in the last five years. Cue some evocative pictures of rivers in southern England that have dried up in recent years that I’ve found on the Internet (figs 2 & 3). (N.B. to the BBC, two can play at that game!). Yes, I know these images are from 2012, but what about the River Derwent in the Lake District in May 2017 (fig 4). So it’s a well-known fact that river levels and groundwater tables do fluctuate, and can do so very quickly, that’s what they naturally do.
I can’t get any daily rainfall climate data for anywhere in the UK without paying loads of money to the Met Office, so I am stuck with the free 1910 monthly rainfall gridded data that they produce, I wonder if they used this kind of data or if the Met Office felt pity on their research and gave them the ‘real’ rainfall station data that they guard so jealously on our behalf? From that data here are some graphs with a simple linear trend for the southeast and central southern England region for winter, spring and summer (figs 5-7). I can’t see any discernible upward trend in rainfall in any of those three seasons, although I will admit that the 10 year moving average for summer is on the rise, and won’t be any lower after this wet summer.
Günter goes on further to say:
Half the stations recorded floods at least 15 days earlier than previously. A quarter of the stations saw flooding more than 36 days earlier than in 1960.
This one is a hard one to counter, especially without daily rainfall climate data and the dates of all fluvial flooding incidents since 1960, which I simply don’t have. But I don’t see that there is some kind of flood or monsoon season across the UK that starts at any precise date that you can readily identify, and if you can’t identify it, then how can you then go on to say that it’s starting 15 days earlier than it did in 1960? I do know from my interest in CET, that the spring is probably around 15 days earlier and it was in 1960, and that temperature is linked to increased convection and heavier rainfall, but I see little sign of it from the rainfall climate data that I can access.
Finally, here’s the last 12 months rainfall over southeast England (fig 8). It’s been a funny last 12 months as far as rainfall goes, up until mid May there was talk of an impending drought later in the year across southern and eastern areas, but the wet summer has put paid to that. There have definitely been some wet days in the last 12 months across the southeast of England, but they can occur in any month as far as I can see, and the accumulated rainfall is still only 84.7% of the annual average at the end of July 2017. What I really need is now is data from the environment agency, some kind of daily count on the number of alerts that they issue for rivers across the UK, a bit like the NAO, but not a phenomena, just a daily count.
PS I’ve just download the report to read – for a change it’s free to do so – and better still it’s only four pages long.
Quite a cool night in places across the country last night under clearing skies and cool air for August (fig 2). Marked contrast between the coastal stations and the more rural inland stations as you would expect with SST around the coast of 16 or 17°C. Exeter with a min of 5.1°C and Portland 14.1°C is just one example (fig 1).
A cool night was well anticipated by the BBC, but it was a little colder than they thought in the south of Scotland, the west Midlands and Devon. They never can quite anticipate just how cold it can get at Exeter airport, with a grass minimum of just 2°C (fig 3), and the Met Office supercomputer just a couple of miles up the road.
The crafty Met Office
Of course the Met Office and the BBC are very crafty, and since the demise of the magnetic weather charts, they now always quote a spot value for a particular time as the minimum temperature, rather than the true ‘minimum’ temperature for the whole night, which in my opinion is much more useful, and less misleading. It’s my belief that they don’t display a minimum or maximum temperature chart to hinder any verification of their forecasts, and prevent smart Alec’s like me from saying just how far their forecasts were out by.
It will be interesting to see if there is a thunderstorm at 3 pm today in Exeter. The cumulus humilis is now sprouting up into cumulus mediocris, which is hardly surprising as the temperature is now 24°C here in mid-Devon, although Exeter airport have still not caught up with areas to the north that were unaffected by the fog and stratus earlier this morning.
The cumulus is visible on the visible satellite image for 1015 UTC (fig 3), as is the cloud that’s producing the showers in western Cornwall. There’s a nice hole is the SC sheet over the central highlands of Scotland, Aonach Mor reported a dewpoint of -13.4°C at 08 UTC in the clear air above the inversion. Plenty of cloud persisting in eastern areas, it should be better tomorrow and they might get some early sunshine before the rain arrives.
I’ve just watched another interesting installment of Weather World on the BBC and noticed from the credits that it was written by Nick Miller. He and Sarah Keith-Lucas hosted the proceedings that were centred at a number of locations in Northern Ireland:
- Belfast International Airport – Aldergrove to you and me, and saw why weather is so important for aviation at airports.
- Ulster Aviation Society Museum – where they looked at the history of ‘weather flights’ across the Atlantic.
- Armagh Observatory – and saw how observations are made today, and at their long running climate recordings, which started on the 27th of December 1794.
I’ve changed some sunshine cards in my time at a number of stations across the UK, some of the locations that the recorder was sited were far from ideal, but the observatory at Armagh as a novel approach to getting around the problems of trees getting in the way, the sunshine recorder sits in a lift like device that raises and lowers the old Campbell-Stokes sunshine recorder what looks like 50 foot into the air (fig 1), I hope after that platform doesn’t affect the wind speeds that they measure from the anemometer up there though. They take their weather observations very seriously at Armagh!
At a 24 hour station you could always change the sunshine card late in the evening, it seems strange to see it being changed at 09 UTC in the morning, there were times that someone forgot to change the card, or on very wet days the card almost disintegrated because it was so wet. Seagulls also liked to attack the cards for some reason, and then there was the perilous job of checking the previous shift’s sunshine card, was that a continuous burn or not, and just when did you start or stop measuring the trace at sunrise and sunset?
I like Sean Kelly the weather observer at Armagh, he’s been doing the job for the last 18 years, and seems to have the right attitude to technology, they’ve tried automatic weather stations in the past, but found that they weren’t reliable enough. That’s what we said in the Met Office for over 30 years, we had a good run for our money but in the end we were replaced by an AWS, try getting a job as a weather observer at the Jobcentre now, Sean might well be one of the last one of us left here in the UK. Nick explained about how observations are taken each morning at 9 o’clock, “this weather ritual that has been happening for over 200 years” he said, except for last Tuesday when it looks like they had a day off (fig 2).
Given the brief from the producer, and the time constraints of the program, Nick Miller did a pretty good job in getting his story across, Sarah Keith-Lucas came across as a really nice person that I’m sure she is. Interestingly they kept it to just the two of them, and wisely in my opinion, didn’t include any input from the ubiquitous Carol Kirkwood. It’s possible that the BBC have decided to use Nick Miller for these kind of programs in favour of John Hammond from now on, and maybe that’s the reason why he decided to take an early shower.
I watched a fascinating documentary on BBC4 the other night about dust storms and what a serious risk they pose to people’s health, especially in the Middle East, dust storms might look dramatic but they must make people’s lives a misery. I liked the matter of fact tone of the documentary, which is in marked contrast to many other ‘scientific’ documentaries that you see from the BBC about weather and climate in recent years, that’s probably because it was a program made for the BBC World service.
Apparently the Sahara is the source of 50% of all dust in the world’s atmosphere, and 25% of dust storms can be attributed to man, but it’s something we can do something about, if countries can only work together. I had heard about the ecological disaster that man had made of the Aral Sea in the early 1960s, but Lake Urmia in Iran was news to me, a terminal salt lake that’s shrunk to less than 40% of its former size is yet another disaster to add to that list, and because the fine particles from the sediments in the dried out lake bed are an ideal source of dust in storms because they can be so easily lifted by the wind.
You can find the program on iPlayer for the next month and I encourage you to watch it.