Continuing collapse of Antarctic ice shelves will affect us all
News from the BBC: Aircraft contrails bring warmer nights and conspiracy theories
The annual trend in rainfall indicated by the England Wales Precipitation [EWP] series maintained by the Met Office is upward since 1766 when the series started. I have been studying this data for a few years now and I think the best way of looking at the individual monthly totals is by using a 12 month running mean. This removes a lot of the noise you get from any one dry or wet month or season. After that you can add a linear trend through the results to identify what the real trend over time reveals. The first chart does just that and shows that in the last 250 years the annual rainfall for England Wales has increased by 46.5 mm. We do moan at times about the rain and the occasional floods that we have to endure but looking at the record of the last 250 years, the one thing you can’t say is that we’ve ever gone without! In fact for all the oscillating the trace does it never ever drops below 650 or climbs much above 1250 mm a year.
If we zoom in a little to the last 50 years (see chart below) the wetter trend has increased to 65.2 mm. The dry years of 1975 and 1976 are clearly discernible along with the recent wet years and flooding that occurred in 2000, 2007 and 2012. Conversely the last 50 years have also had some noticeable dry spells, notably in 1976 but more recently in 2011.
At the moment we are in a wet streak as the Americans like to call it, with an accumulated total of 1,128.9 mm in the 12 months to April, this is +23.4% above the 1961-1990 long-term average for 12 months. There is a definite pulse in the annual rainfall totals, its erratic and at times incoherent. I just wonder what the rest of 2016 will bring in the way of rainfall for England Wales?
As Wikipedia points out – Ice Saints is a The Ice Saints is a name given to St. Mamertus (or, in some countries, St. Boniface of Tarsus), St. Pancras, and St. Servatius in Austrian, Belgian, Croatian, Czech, Dutch, French, German, Hungarian, North-Italian, Polish, Slovene and Swiss folklore. They are so named because their feast days fall on the days of May 11, May 12, and May 13 respectively, known as the “black-thorn winter”.
The period from May 12 to May 15 was noted to bring a brief spell of colder weather in many years, including the last nightly frosts of the spring in the Northern Hemisphere under the Julian Calendar. The introduction of the Gregorian Calendar in 1582 involved skipping 10 days in the calendar, so that the equivalent days from the climatic point of view became May 22–25.
Ignoring the spanner in the works that the change of calendar introduces – I decided to rework the code in my Central England Temperature [CET] application just to see if there was any evidence in the CET series to justify this singularity. Below is the list since 1970 (let me know if you want more), and as you can see Ice Saints do happen and more often than you might think, but by now the effort in just writing the extraction and plotting routines had got to me. It’s obvious to me from the scatter graph that you can’t say for certain that this singularity does exist and can be relied on for those specific dates in May, certainly H.H.Lamb didn’t think a lot of it in his book “The English Climate”, even though it does coincide with one of Buchan’s infamous cold spells, but it does coincide nicely with what Lamb calls the “Spring Northerlies” (16 April to 20th May).
The way I investigate it was to look at three five-day periods 6-10 May, 11-15 May and the 16-20 May. I then calculated the anomaly of each of these three pentads, calling them A, B and C, and then compared the difference between A and B and then B and C for each year since 1772.
The most striking Ice Saints of recent years in the CET series was in 2010 and here are the analysis charts for that time. As you can see a northerly outbreak very similar to the one occurring this year (2016) was responsible. This period is after all when the peak frequency of N’ly types in the Lamb Weather Type [LWT] series occur. It certainly put paid to the unusual early warm spell that we had been experiencing up until the 13th, and ruined any real chance of an Ice Saints for 2016.
Probably the most severe examples of Ice Saints since 1772 occurred in 1830 and 1816 as you can see in the scatter plot chart.
The eagle-eyed amongst you may have noticed just a very slight cooling in the daily CET graphs (above) of the 1961-1990 long-term average (the green filled area series) between the 13th and 18th of May.
Sentinel’s first map of sea-surface ‘hills and valleys’ – http://www.bbc.co.uk/news/science-environment-36255957
According to the Royal Netherlands Meteorological Institute [KNMI or Koninklijk Nederlands Meteorologisch Instituut] the top ten storms that have affected the Netherlands in recent years are:
- January 25, 1990
- January 3, 1976
- April 2, 1973
- November 13, 1972
- November 27, 1983
- October 27, 2002
- February 26, 1990
- February 1, 1983
- December 24, 1977
- January 16, 1974
They don’t say how far they go back but I bet they stop before the 31st of January 1953. They do describe how they work out the magnitude of the storms in their list though, and rather gratifyingly they use the same simple method that I came up with! All that they do is add all the mean speeds from a network of their observing stations and take the average over the duration of the storm. The problem that I found with this method is – defining the exact start and end of a storm – i.e. when do you start and stop counting. Anyway I do seem to have SYNOP data for 9 out of the 10 storms (#4 occurred before the start of my SYNOP records) so here are plotted charts for each of them in what should be descending order:
As you can see they all seem to follow a very similar scenario. A low tracks across the central North Sea and on into Denmark or northern Germany, surface winds strengthen to gale force from the south or southwest, before veering to the west or northwest. It’s so different from the British Isles because we are an Island and are far more exposed than the Dutch are to storms from a variety of quarters.
The weather station with the WMO designator 03037 has been in the news a lot this week. The station is situated on Lusa on the Isle of Skye, and I thought that I’d just look in a bit more detail at it. Here’s the big picture of where you can find Lusa.
And here it is in a bit more detail…
The blue circle marks a 30 metre radius from the enclosure so this site could be just far enough way to be classified as class 1, but why the Met Office couldn’t have sited just up the road at the Broadford airstrip beats me, but there is obviously a very good reason why not. It’s probably called Lusa because of a small collection of houses close by, and the fact that it lies close to the little bay of Ob Lusa, which if you Google it will find is where you can find cold water coral (never say this site is just all about boring weather), I guess that Ob is Gaelic for bay.
It’s easy to see why this week in the easterly flow this site has been the warmest in the UK on at least two consecutive days, not only because of its location on the west coast of Scotland, but also because its downwind of the Northwest Highlands and the Kylerhea hills (just a few kilometres to the ESE), of which the largest is Sgùrr na Coinnich (739 metres). Interesting Glen Arroch lies to the southeast of Lusa which probably defines the predominant wind for the station. Anyway here’s the thermograph of hourly temperatures for the last two weeks for Lusa. On the 9th of May the 06-18 maximum was 26.7°C and yesterday (the 10th) it was 25.6°C.
The wind, as you can see from the plotted hourly observations for the last few days, was crucial. At times the E’NE flow did veer a little more to the NE, and brought a reduction in the temperature, but for most of the time the gradient was strong enough to keep the sea breeze at bay and maintain a strong easterly component.
It’s interesting to note that in the cold spell, which occurred less than two weeks ago, there was a good snow cover on a lot of the western isles including Skye. You can see that the automatic weather station was having a bit of deciding on the exact weather type during the 28th of April. I cannot doubt that with these temperatures there was a fair amount of wet snow around on the morning of the 28th of April.
If it could snow on the island of Tiree I’m sure it did the same on a coastal site in Skye. Have a look at the following image and observations from Tiree, it’s not that unusual an occurrence but not that common in recent years.
And finally here are a couple of plotted charts to compare the contrast between the 28th of April and recent days.