Yesterdays rainfall totals

Here is a look back at yesterdays rainfall totals [06-06].

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And the ranked tabulated version…

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Rainfall from Matthew

estimated-accumulated-precipitation-for-0000-utc-3-october

Here are the rainfall totals as best I can make them out for the east coast of the United States for the last week. Obviously there are a fair few missing observations from the hurricane affected stations right on the coast. It looks like there was 6 to 12 inches of rain generally, but SYNOP coverage is fairly sparse as you can see. ToDo: fix the legend.

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Rainfall in the last 3 months

estimated-accumulated-precipitation-for-0000-utc-7-july

As most of my English readers will know, we’ve had a pretty long dry spell across southern and southeastern counties for a good part of the summer, and it’s now extending right into early autumn thanks to a large Scandinavian blocking high. A fantastic range in rainfall total accumulations in the map above that I glean from the SYNOP observations I download, from 645.3 mm (25.41″)  in Capel Curig in North Wales to 47 mm (1.85″)  at Shoeburyness in Essex.  I do miss the occasional observations for various reasons, so although these values will be close to the observed they may not be 100% exact. The other thing to note is the recent long period of heavy rain that affected the SW tip of Ireland and is reflected in the 513 mm accumulation at Valentia.

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13 September 2016 – Thunderstorms

Here is my best guess rainfall accumulations for yesterday between 0900 UTC and midnight. I now use 5 minute data and this has increased the accuracy of my estimates.  You can see the south north track of the thunderstorms from when they initially made landfall in Devon and Dorset in the morning before moving up through the west Midlands and curling into northwest England during the evening. The wettest places (09-00) where around the Manchester area with an area of lime green pixels indicating totals of between 32 and 40 mm.

estimated-rainfall-accumulations-0900-0810-utc-on-wed-14-september-2016

Estimated rainfall accumulations 0900-0000 UTC on 13 September 2016

This is a table of 24 hour rainfall totals (06-06) which show even larger totals than those of northwest England occurring at Culdrose and Camborne in the west of Cornwall with over 47 mm at both stations from thunderstorms. Due to Met Office policy, there are currently no SYNOP stations in the Manchester area (population 2.55 million) so you won’t see any totals around the 34.8 mm mark from around there – oh dear, how sad, never mind.

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And finally here are the 40,929 lightning flashes that occurred between 0900 and 2300 UTC yesterday over the British Isles courtesy of Blitzortung.

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The rainfall event of 3rd September 2016

Synops 1500 UTC on Sat, 3 Sep 2016

Synops 1500 UTC on Sat, 3 Sep 2016

A low pressure was deepening and tracking into Western Ireland on this plotted chart for 1500 UTC on the 3rd of September, its associated warm front had crossed all of Wales, and was lying approximately from Llandudno to the Isle of Wight by 1500 UTC.

Estimated Rainfall Accumulations 0600 - 1015 UTC on Sun, 4 September 2016

Estimated Rainfall Accumulations 0600 – 0600 UTC on Sun, 4 September 2016

Above is a map of estimated rainfall totals gleaned from 15 minute weather radar images from the Met Office between 0600 on the 3rd and 0600 UTC on the 4th of September. The wettest places were over South Wales with totals in excess of 50 mm in the 24 hours. For some reason the 21.3 mm estimated total at Carlisle was considerably less than the gauge total of 36.8 mm. Here’s the frame for 0245 UTC on the 4th:

Who knows if more frequent and higher resolution images might have improved that? It’s on a knife-edge here with very high intensities just to the south of Carlisle, and I just wonder if my mapping projection conversion code might be very slightly out particularly when calculating latitudes, I’ll revisit the code, but it’s the kind of code that you don’t ever want to see again.

Daily 24 hour rainfall [06-06] 3 September - Sunday, 4 September 2016 In WMO Block 03 Highest Daily Rainfall [06-06]

Daily 24 hour rainfall [06-06] 3 September – Sunday, 4 September 2016 In WMO Block 03 Highest Daily Rainfall [06-06]

There were reports on social media of flooding at Braunton in North Devon. I estimate that the 24 hour total at Braunton was around 16.6 mm in the 24 hour period, so not a large total, but looking at the (inset) intensity graph a lot of it came in a very short time during the afternoon, and with the ground being baked dry from several months of dry weather there must have been a great deal of runoff that might have contributed to the local flooding.

Estimated Rainfall Accumulations 0600 - 1030 UTC on Sun, 4 September 2016

Estimated Rainfall Accumulations 0600 – 0600 UTC on Sun, 4 September 2016

The recent dry spell across southern England

I thought that I would revisit my application that processes rainfall statistics from SYNOP observations and look at the recent dry spell that as affected the south of England for so much of the summer. I’ve just added some extra code to calculate the total number of dry days and the current number of days since any meaningful rain. If you start looking into what constitutes a ‘meteorological’ drought on the internet I’ll warn you it’s very confused! There is a good Wikipedia article on the subject and I’ve decided to use the one in their that specifies 15 days or more with less than 0.2 mm of rainfall in a day. The programs flexible so I can set any threshold so let me know if you have a better definition.

I can’t remember a period when so many fronts have delivered so little rainfall. I know there has been no shortage of fronts, it seems to have been a summer like a lot of others, with continuous switching between tropical maritime and polar maritime air throughout, even if the number of fronts in the Met Office analysis does seems a little bit overdone at times. As you can see from the table below we are fairly close to another drought in a good part of central southern England, I say another, because there was probably another drought in places that occurred during July. The second column from the right shows how many dry days (<0.2mm) there have been in the last month (31 days) which also shows how seriously dry it’s been, with some places such as Odiham having 26 out of 31 dry days. These values are at best an estimate, because as good as OGIMET is there are always missing observations or observations without a rainfall group. This could be easily fixed by the powers that be, and then we wouldn’t be totally reliant on other countries providing the latest daily climate information for the UK, but I won’t go into that (again)!

Number of days since rain - 14 August 2016

Number of days since rain – 14 August 2016

Number of Dry Days

Current drought days count

Number of dry days in last month

Number of dry days in last month

Driest Places Estimated Accumulated Precipitation 00 UTC on 15 July 2016 - 12 UTC on 14 August 2016 WMO Block 03

Driest Places Estimated Accumulated Precipitation 00 UTC on 15 July 2016 – 12 UTC on 14 August 2016 WMO Block 03

Driest July in England and Wales since 1766

The month of July 2016 is turning out to be a very dry month in the south of the country, so I thought that I’d have a look back to see how July as a month looks in the England Wales Precipitation [EWP] series that starts 250 years ago in 1766 and find the driest years. The EWP data is a monthly series and is free to download from the Met Office. According to the Met Office website the regional estimates are derived as follows:

The England and Wales precipitation totals are based on daily weighted totals from a network of stations within each of five England and Wales regions. A full quality control is performed on the 5th of each subsequent month, allowing data from the most recent six months to be updated.

So essentially it’s very similar to how Central England Temperatures are arrived at, but because of it being a far larger area it requires a lot more representative stations. As you can see from the table below, 1825 was the driest July in the last 250 years with just 8.2 mm of rain (13.2% of the long-term average). The driest July in recent years was 1999 with 26.3 mm.

Tabulated England Wales Precipitation - July's 1766 - 2015

Tabulated England Wales Precipitation – July’s 1766 – 2015

It’s interesting to find that there is over 27% less rain in the July of today than there was 250 years ago.

England Wales Precipitation - July's 1766 - 2015

England Wales Precipitation – July’s 1766 – 2015

Here are the final totals for July 2016 that I gleaned from the SYNOP reports:

Driest Places Estimated Accumulated Precipitation 00 UTC on 1 July 2016 - 06 UTC on 1 August 2016 WMO Block 03

Driest Places Estimated Accumulated Precipitation 00 UTC on 1 July 2016 – 06 UTC on 1 August 2016 WMO Block 03

It will be interesting to see what the England Wales precipitation total for July 2016 turns out to be with a range of just 1.4 mm on the Isle of Wight and 255.1 mm in Capel Curig, North Wales!

Estimated Accumulated Precipitation for July 2016

Estimated Accumulated Precipitation for July 2016

This map displays the daily totals from 00-00 and not the 06-06 total in the table because the Irish as of yet don’t report a 24 hour total.

British Isles Rainfall: 13 April – 13 July 2016

I still think that here in mid-Devon it’s been a rather dry spring and summer so far in 2016, although we did get a very wet day here in Bradninch on the 15th of June. Here are the 3 month totals from the SYNOP observations. Ignore the first mention of Exeter at the #1 spot being the driest place, the Met Office renamed the station on June 27th so that’s why it’s bone dry, the old Exeter total is at #7, so adding the two totals (124 mm) does mean that it has been dry during the last three months. The Rx column in the tables gives the percentage of SYNOP observations that I received to calculate the totals, so treat the Dishforth total with caution because I think the AWS may have been removed!

Wettest Places 13 April - 13 July

Wettest Places 13 April – 13 July

Of course Capel Curig is where it usually is at #1, that will probably remain the case until the Met Office publish more of the rainfall data from their climate stations in the Western Highlands of Scotland.

Wettest Places 13 April 2016 - 13 July 2016 WMO Block 03

Wettest Places 13 April 2016 – 13 July 2016 WMO Block 03

Accumulated Precipitation 13 April - 13 July

Accumulated Precipitation 13 April – 13 July

Treat the Orkney total with caution because I think there was a gauge problem with the AWS during this period.

Wettest Places 13 April - 13 July

Wettest Places 13 April – 13 July

June 2016: Rainfall

I thought that because I’d already written about temperature and sunshine across the British Isles yesterday, I should finish it off with a quick look at the rainfall totals in June. So here they are and guess what Capel Curig with 184.8 mm (7.28″) is the wettest place from the list of all the available SYNOPs!

Wettest Places Total Accumulated Precipitation 1 June 2016 - 1 July 2016 WMO Block 03

Wettest Places Total Accumulated Precipitation 1 June 2016 – 1 July 2016 WMO Block 03

I’m still trying to get my head round the 32.1 mm from Herstmonceux on the south coast, I seem to have 98% of the obs but the value looks low. Perhaps the gauge has a spiders nest in it like mine did early last month. The 153.3 mm from Kenly (to the south of London) made them #5 in the list from all the thundery rain they received.

Accumulated Precipitation for 0600 UTC 1 June

Accumulated Precipitation for June 2016

At the other end of the list Kirkwall finished with the lowest total of the month with just 11.3 mm of rain (0.44″). This is another one that’s hard to believe, yes the first 10 day of the month were fairly anticyclonic, but as the westerlies returned mid month, the Northern Isles were again open to all the various lows that tracked across the country.  Is this another spider? Or is it bugs in my program? That is a strong possibility, as you the reader are my testing team, and I’m notoriously bad at testing the applications that I write.  I am heartened to see that Wick only received 45.8 mm (89% received) in June , so hopefully some kind person at the Met Office might let me know how close I got! Who am I kidding, there is very little chance of that happening with just 13 subscribers, but you can live in Hope, well you could if you can afford the house prices.

Driest Places Total Accumulated Precipitation 1 June 2016 - 1 July 2016 WMO Block 03

Driest Places Total Accumulated Precipitation 1 June 2016 – 1 July 2016 WMO Block 03

Accumulated Precipitation for 0600 UTC 1 June

Accumulated Precipitation for June 2016

Wettest place in UK – St James Park!

The wettest place in the whole of the British Isles from all the SYNOP observations of the last week (18-24th of June 2016) seems to have been St James Park in London (66.4 mm) – how often can that happen!

Rainfall 18-24 June 2016

Rainfall 18-24 June 2016

This is a screenshot from my SYNOP precipitation application that I’ve written to process the rainfall data that’s contained within a coded SYNOP observations that I download from OGIMET. I’ve given the whole application an overhaul as it wasn’t processing the available rainfall data very well. Believe me, there are so many different problems in trying to process them across a whole continent! The first problem is that the UK reports rainfall 6 hourly (06-12, 18-00), 12 hourly (06-18, 18-06) and 24 hourly (06-06), whilst a lot of other countries just report 6 hourly (00-06, 06-12, 12-18 & 18-00). In this age of automatic weather station I think a day should mean 0000-0000 and not the climatological day of 0900-0900 (but what do I know?), so I think rainfall stats should reflect this, so that’s why I’ve tried with the UK and Ireland to derive 6 hourly totals by subtracting a 6 hour total from a 12 total where possible,because the other problem is that there is with UK and Ireland rainfall reports is, is that they drop the 6 group when there is no precipitation to report! This to my mind is incredibly illogical thing to do, a report of no rainfall is just as important as a report of rainfall. This means you have to do a load of jiggery-pokery to generate meaningful statistics. I never thought about this at all when I was as an observer, but as a programmer, and someone who spends a lot of time hunting down and processing climate statistics from the internet, you can never have enough data. The same goes for the reporting of temperature extremes, these too should be reported at each main synoptic hour (00, 06, 12 & 18), rather than at just 06 & 18 as they are in this country now. I know that the max and min are reported in the 09 & 18 National Climate Message [NCM] but the Met Office have that under lock and key and again that harks back to the old 09 to 09 way of doing things, something that we should change now that we are well into the 21st century. When I say change, I don’t mean retrospectively adjust all those climate statistics from the past, but you could set a date (the 1st of  January 2000?) from when all climatological days will start and end at midnight, well not literally, but you know what I mean! Hopefully my new look app will be able to cope with rainfall reporting in SYNOPs from any part of the world, I’ll keep you posted!