22 May 2017 – Mesoscale trough?

Figure 1

I know I shouldn’t have tempted fate going on as I did about how warm it had been today. I wasn’t paying attention to the visible satellite image sequence this afternoon, but finally noticed the increasing cirrus and cumulus bubbling up over northwest Devon (fig 2). From the observations there’s certainly evidence of some kind of trough pushing into western areas of Wales and the southwest at 15 UTC, with a band of thick cirrus strung out along it. The increased humidity must have been enough to cause the convection, and if you look closer you’ll see a wind veer and increase in dewpoint, behind some small falls of pressure over East Wales (fig 1). It could all simply be down to a southward extension to the first of two occlusions that the Met Office are showing in their 06 UTC analysis (fig 3), but it’s certainly put paid to what had been a lovely afternoon here in south Devon till then.

Figure 2

Figure 3 – Courtesy of the Met Office

Probably the warmest day of the year so far in Devon

Plenty of sunshine across the southeast of the country at the moment, and for large parts of Europe. These are the hourly sunshine totals for 12-13 UTC today (fig 1), it’s a shame that Ireland, the Netherlands, Scandinavia and Iberia don’t include this hourly data in their weather reports.

Figure 1

I think I can say without a doubt that today has been the warmest day so far this year, at least in our part of south Devon. It’s not been particularly high, maybe just scraped a 22 or a 23°C this afternoon in the back garden, but it’s enough (fig 2). Personally speaking, this year Spring seems to have been a long time coming.

Figure 2

Certainly the solar radiation has been high (fig 3), and so must the UV, but unfortunately the SYNOP reports don’t include that.

Figure 3

Drought, what drought

Figure 1

Admittedly rainfall accumulations this month are completely topsy turvy, and it’s still been a very dry month in many parts of Scotland, but the meteorological drought that affected many parts of the south did come to an abrupt end this week with some heavy rain, as droughts so often do. I’ve tried to wheedle out plotting totals for stations where I had more than 25% of reports missing, having said that there are still a few oddities, Rhyll being one of them, although the 6.4 mm total there is kind of supported by the 13.6 mm at nearby Hawarden.

I’ve just rejigged the code for this application, and it now uses a combination of priorities to get the most accurate result. If there’s a 24 hour 06-06 total that’s great it will use that, and many of the main UK of stations have a 100% reception rate using that value alone. If there isn’t a 24 hour total, like in Ireland and parts of Europe, I add up the available 12 hour totals (06-18 & 18-06). Finally if there are only 6 hourly totals, as in the United States I add these up. The Americans, as far as I can see, don’t report nil rainfall totals as we used to do at one time, so you have to rely on the indicator in the initial block being correct. The whole area of rainfall reporting in SYNOP from different countries is a complete nightmare to program, and I still have to write code that throws back totals to the previous day, but for now this will have to do. If you have any complaints about any of the totals, please feel free to have a go yourself.

19 May – cold front drops temperatures sharply across Germany

Figure 1

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.

Figure 3

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.

Figure 4

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 5

Figure 6 – Courtesy of Blitzortung

 

Catastrophic climate change

Courtesy of Energy Matters

Interesting blog from Roger Andrews in his Energy Matters blog that you may find of interest. There doesn’t seem away that I can reblog it, so you’ll just have to follow this link. Obviously he may have an axe to grind, but then again these days who doesn’t. I like how he’s listed the main findings of the IPCC, and also his summation.

May 1-15 northern hemisphere temperatures

Figure 1 – Data courtesy of NCEP reanalysis

The extremely high temperature anomalies seem for the moment at least seem to have disappeared from the Arctic. This temperature anomaly chart (fig 1) is for the first 15 days of May 2017, and yes anomalies are still mainly positive in the Arctic, but in a range -2°C to +6°C, rather than in excess of +16°C that they were back in January and February. That might explain why Arctic sea ice has staged a bit of a recovery during late spring. There are a number of anomalous cold areas, one north of the Great lakes in Canada (-4°C) and another one over Scandinavia and northeast Russia (-6°C), the latter causing problems with heavy late spring snowfalls in places. Central North America, Greenland and large parts of central Asia have seen a very warm spring with anomalies typically +4°C above the 1948-2014 long-term average.

Yesterday – 18 May 2017

Apart from the area of rain that affected the east of the country,  the other interesting thing in this estimated accumulations chart as far I’m concerned here in the southwest, were a band of showers that started life around Falmouth, and ran ENE across south Devon and into Dorset during the day. The trajectory of those showers was diametrically opposed to that of the rainband in the east which was moving due north, later in the evening the remnants of the showers curved to the right and took a course that was more SE’ly. I notice that already today, there’s a large CB and associated heavy shower coming onto the north coast of Cornwall in the NW’ly flow.

11th mildest start to a year since 1772

Figure 1 – Data courtesy of the Met Office

Now that we’re 136 days into the year 2017, I thought that it was about time I looked to see just how this year was shaping up as regards temperatures in Central England. And as you can see from the table (fig 1), this year is already exceptionally mild, with a mean CET so far this year of 7.47°C which is +1.54°C above the 1961-1990 long-term average. This makes it currently the eleventh mildest start to a year since 1772, but as you can see many of the mildest years in the top 12 have also occurred in recent years.

17 May debrief

Figure 1 – From radar images courtesy of the Met Office

Yesterdays estimated rainfall totals from the weather radar [06-06] showed a wide band of 8-24 mm totals, with an inner central core of 24-32 mm, and small areas of lime green pixels indicating areas in excess of 32 mm particularly in Hampshire (fig 1). Southern Lincolnshire seemed to be wettest from the 24 hour totals in the SYNOP reports (fig 2), with Holbeach reporting 36.2 mm, which I didn’t pick up from the rainfall radar which is surprising as it did much better further south, perhaps the Chenies spiking affected the averaging algorithm, either that or it was the flux capacitor.

Figure 2

Yesterday’s rain will certainly have freshened things up in the southeast, and might even have put a stop to all the talk of drought, but if it hasn’t, then the rain from tonight’s low might well do the trick, as it tracks by just to the east (fig 3).

Figure 3 – Courtesy of the Met Office

Driest ten months in 100 years recorded in southern England [updated]

According to the New Scientist the last 10 months were the driest July to April for southern England in records stretching back more than 100 years, or so say the Centre for Ecology and Hydrology, which I must say is the first time that I’ve ever heard of them.

Possible discrepancy in latest July to April total

When I first read this I didn’t quite believe the claim that this arbitrary 10 month period between July 2016 and April 2017 had been the driest since 1910. I could remember the dry spell of 1976, and thought that this current dry spell couldn’t match it. I’ve now added code to my Met Office 1910 climate application, which I assumed used the same Met Office 1910 gridded rainfall data, so that I could graph any user defined period that I chose, and here are the results (fig 2).

Figure 2

As you can see 1976 was the driest July to April period since 1910, as I suspected it was, and there were four other years drier than 2016-17. So I went back to the CEH site and dug out the PDF of this April’s hydrological summary. I would include the relevant table from the summary in this article but I may well end up in prison if I did so because of the copyright clauses in it, suffice it to say they get a total of 446 mm for this period which I calculate 454.7 mm. Even if you look at the rainfall data for the ‘southern’ region, 1976 is still the driest period since 1910 for July-April rainfall and the latest total, 489.4 mm still don’t tally (fig 3).

Figure 3

Likely reason for the discrepancy

From reading the Hydrological summary, I assume that the Met office use the same gridded data set to create bespoke monthly rainfall totals for most of the regional water companies around the country, and one of them is Southern Water. I guess that the ‘southern‘ in the table of the Hydrological summary doesn’t exactly equate to the Met Office’s ‘southeast and central southern England‘ (fig 5) that they produce for their 1910 monthly climate series, in fact looking at the map from the Southern Water website (fig 4) it could be a combined area that includes Southeast Water.

Figure 4 – Courtesy of Southern Water

Figure 5 – Courtesy of the Met Office

So the difference in ‘catchment areas’ so to speak undoubtedly explains the small difference in totals that I found. But creating bespoke areas is confusing, the 1910 series that you can freely download from the Met Office includes 17 regions, some of which overlap and combine sub-regions, which makes it difficult to decide which area the climate data is for.

There is one thing that I have learnt from writing this article, and that is what an interesting website the CEH have, and what an invaluable publication the Hydrological summary is. Now why can’t the Met Office publish something similar in PDF format which they could email out to subscribers that’s full of climate data, perhaps they could call it the Monthly Weather Report?