Rainfall still flirting with southeast

The bulk of the heavier rain is still west of London and flirting with the far southeast again like it did yesterday. The main rainfall band is sprawled across central southern England and towards Lincolnshire, where it’s a thoroughly wet and miserable day with some heavier rain now starting to show its hand (fig 1).

Figure 1

Estimates from the weather radar indicate that Portland was the wettest station from 06 UTC with 20.8 mm, and by the looks of this mornings totals from the SYNOPs I wasn’t far out (fig 2).

Figure 2

I thought that the Met Office had now fixed the ‘spiking’ that they got from the Chenies radar (fig 1), but it looks like the tall trees there are still causing problems. Using the position of each of the six spokes that radiate west from the radar site, you could probably map the position of each of the offending trees. After extensive digging on the Internet I couldn’t locate any of the information regarding the tree’s at Chenies that I used in an article a couple of years ago, but this image from the lane that runs past the site gives you a better picture of the problem courtesy of Google street view (fig 3).

Figure 3 – Courtesy of Google Street View

In the aerial view I can now see why the tree’s are such a problem for the Met Office and how they affect the radar signal when they are in leaf (fig 4), and by means of the same image I can also see why they’ll never be removed. The problem lies in a large ‘stately’ home which lies almost due west of the radar. By the look of it is the original house that RAF Chenies was first built around in the 1930’s, and may have served as the admin offices and quarters for officers, but apart from the radar tower, a large aerial and a few other buildings associated with the 1950’s listening post, the rest of the RAF station has been demolished. The house remains though, and sits in a prime location in an isolated spot in the Chilterns, looking very well maintained and very expensive (fig 4). Interestingly, it’s the only time when I’ve ever used street view that I’ve found that I can’t drag the marker to where I can gain a view of this house. Try it yourself, drop the little man and it will take you back to the gates of the radar site. Be warned each time you do it a little red light will flash at Google HQ and all your personal details will be entered into a report at GCHQ. Maybe I’ve stumbled on Theresa May’s house and I don’t mean Chequers? It’s amazing what you can learn in an article ostensibly about weather radar in my blog.

 

Outlook for the next week – cool, showery and often quite windy

The dumbelling lows that I mentioned yesterday which seemed to be in orbit around the country over the weekend, are still present in the latest forecast charts from the GFS, but this time one of them pairs up with a newly developing low early next week that’s coming out of mid Atlantic, and extends the cyclonic sequence well into the middle of next week (fig 1). All I can say is that the outlook for the next week doesn’t inspire, and can be summed up as: cool, showery and often quite windy. Overall the pattern is very cyclonic in nature, and if these charts are correct we can forget about any more talk of drought, and any spells of drier, sunnier and warmer weather will be in short supply, and limited mainly to the southeast of the country, as they were yesterday.

Figure 1 – Courtesy of OGIMET

May 17 briefing

Just what the Doctor ordered

Not only did the southeast get the warmest day yesterday (which is more that can be said down here in the southwest) they also got a good long spell of moderate rain, which must have come as welcome relief to the farms and gardens that have been crying out for it over the last six weeks or so. For a long time I thought that the rain gauge of the AWS in St James Park must have been faulty or perhaps full of pigeon excrement.

Figure 1

The estimates that I make from radar images were a little high, for example I estimated a 18-06 total for Wattisham of 21.8 mm and in reality they recorded 20.2 mm [06-06]. The coast of Kent seems to have escaped most of yesterday’s rain though.

Figure 2

Wattisham, as well as being the wettest place yesterday with 20.2 mm in the reported SYNOP’s (fig 3), also managed second warmest with 25.2°C (fig 4).

Figure 3

I still suspect that there is some kind of geothermal energy going on in close proximity to the Stevenson screen at Broadness, because yet again they were the warmest station in WMO block #03.

Figure 4

Despite the warmth in the southeast, I reckon the best day yesterday was in the far north or west albeit considerably fresher, Kirkwall reported 12.6 hours of sunshine, and stations in Ireland added more sunshine to their already high totals so far for May (fig 5).

Figure 5

Arctic sea ice stages a late spring fight back

I notice that the latest Arctic sea ice extent for the 14th of May was only the fifth lowest for that particular day of the year, which means it’s staged a late spring fight back from a disappointingly low maximum in early March. Having said that, although it’s higher than last year at the same date, it’s still lower than the record low year of 2012.

Figure 1

I have revised my estimated September minimum up from 3.7 to 3.9 million square kilometres of sea ice. This doesn’t come close to breaking the lowest ever minimum of 3.34 million, which occurred on the 16th of September 2012. If the sea ice pundits are correct though, the pack ice has never been thinner and the Arctic could see an unprecedented collapse in sea ice this summer  – we shall see how right they are in around four months time.

Figure 2 (yellow outlined series is my estimate)

Is our weather getting more stormy (revisited)?

I wrote an article last year in an attempt to answer the question of is our weather getting more stormy here in the British Isles. I did that by using the gale index [GI] from the Objective Lamb Weather [LWT] data from the CRU. This is based on gridded MSLP data produced by the NCEP 20th century reanalysis project by NOAA. I’ve downloaded the entire dataset back to 1871 which includes 6 hourly MSLP data on a 2° x 2° grid for the entire world. I use the same basic algorithm for calculating the GI that the CRU employ, but now I get a much finer feel with the GI, because when you use four observations a day, gales can’t as easily slip between the net than when you’re using just one. Of course the GI is still for just one location, 55° north and 5° west, so it doesn’t cover the entire British Isles, and of course it is a very simple index of pressure gradient, on what is a very coarse grid. Nevertheless I pressed on regardless and here’s the graph that I produced for GI from January 1871 to May 2017.

Figure 1

That’s a ten-year centred moving average that I’ve plotted and overlaid on annual totals of GI>=30 (fig 1). Over the top of that I’ve placed a 7th degree polynomial best-fit curve. I did that because it comes as an option in the graphing component that I use, and it does seem to fit the moving average quite nicely, I freely admit that I am no statistician and try to remain an agnostic when it comes to the subject of AGW. Perhaps the recent decline in the best-fit curve is due to me plotting the totals for 2017, which as you probably know is not quite complete yet! It does pick out the very stormy winter of 1989/90 very well, as well as the quiet year of 1955 and 2010. When I wrote that first article last year, I concluded by saying:

So the short answer to the question that I posed in my title is, yes, that’s if the gale index in the objective LWT series is anything to go by. Why it’s getting stormier is another question, and one that I am not even going to try to answer!

I am now going to qualify that because in last years article, the graphs and linear trends did indicate a slight rise in the GI since 1871. This extra data, and the much better way in which I now believe I present the data, leads me to conclude that maybe storminess peaked in the 1990’s and is now on the wane, and maybe I should limit the use of linear trends in the graphs I generate! I suppose it does go to illustrate that you can use graphs to say just about anything, sometimes restricting how big a sample you use can throw you a curve ball, either intentionally or not.

The reason that prompted me to change my views on storminess was an article in yesterdays Guardian, “UK faces sharp rise in destructive wind storms due to global warming”, on which I commented (quite a lot actually). As the Guardian article says:

The new work was commissioned by the Association of British Insurers (ABI), which is concerned by the rising impacts of climate change on its customers, and was carried out by the consultancy Air Worldwide and the UK Met Office.

As far as I can see this is not a ‘new work’, and was completed in 2009 but has just come to light on the ABI website. The report found that AGW would increase the risk of storms across certain areas of the country and insurance premiums, as this table and map taken from the report shows (fig 2).  As I said in one of my comments, I don’t believe that the UKMO are falsifying evidence in this report, it’s just that the results of the report do seem to suit the agenda of both the UKMO and the ABI a bit too closely, and I smell a rat. One quick comment that I would like to make about the graphic I’ve included, and that is for the life of me, I can’t see why Northern Ireland is due to see an increase in destructive wind storms when Scotland isn’t in any of the scenario’s.

Figure 2 – Courtesy of the ABI

What prompted me to comment so profusely in the Guardian, was I reckoned that even before I had seen the report, that it would be based on data from climate models, rather than from the observational record, and now that I have scanned the PDF of the report, I find that I was correct. I feel that the simple way that I’ve used to measure storminess from 1871 till now using available observational data from the internet is just as valid, obviously you would have to extrapolate the GI forward in some way, and obviously that way would have to be by some kind of climate model, but don’t forget that we have a wonderful resource in past observational data from which to start and see how the frequency of wind storms has changed in the past.

16 May briefing

24 hour rainfall

As often happens, Capel Curig was the wettest place, with 65.2 mm in the last 24 hours (06-06) from the available rainfall reports (fig 1). I’m glad that I am not on holiday under canvas in Snowdonia this week. I do wish Met Éireann would report 24 hour precipitation totals in their SYNOPs. Not a great deal of rain for many central and eastern areas though, perhaps tomorrow will change all that.

Figure 1

The estimates from 24 hours of 5 minute weather radar images show the wettest areas being the mountains of the Lake District with totals in excess of 100 mm (fig 2).

Figure 2

Overnight Minimums

A very mild night for mid May across many parts, with Kinloss and Hawarden reporting minimums no lower than 15.8°C (fig 3).

Figure 3

Classic dumbbell lows

Some classic dumbbelling going on between these two lows in the latest forecast frames from the GFS model as they orbit around the British Isles during the next week. I would challenge any broadcast meteorologist to find anything good to say about the weather if these charts are accurate.

Courtesy of OGIMET

Wet in the Lake District

Not a great day to be stuck in a caravan in Keswick today, with the rain drumming down on the roof, where I estimate there has been around 15 mm of rainfall between 06 and 18 UTC, but on the surrounding fells totals are already well in excess of 50 mm as they are in other parts of southwest Scotland and northwest Wales.

Figure 1 – Estimated Rainfall Totals

I would love to see just how full the River Derwent at Seathwaite looks this evening, it certainly will be a little fuller than it was earlier this month.

Figure 2 – © North News & Pictures Ltd

A few minutes later…

An even better ‘before and after’ picture of the River Derwent courtesy of Paul Kingston and Twitter.

Figure 3 – Courtesy of Paul Kingston and Twitter

The driest May’s since 1910 regionally

I was saving this article for later in the month because I thought that judging from the first ten days of May it might end up being record dry affair this year, but now, as we are approaching mid-month, and looking at the latest NWP mid-range forecasts, it looks like the second half of May will be rather cool, cyclonic and showery across the country, with any drier and warmer spells mainly confined to the southeast.

No real consensus on one particular dry year for all regions, although May 1991 was the driest in four out of the ten regions, mostly in western and central areas (fig 1).

Figure 1

15 May briefing

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.

Figure 2

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