SC at 5000 feet

Figure 1

At first I thought that this was low AC when I first saw it, which shows you what a poor observer of cloud I was in my day, but the LCBR at Exeter airport reckons the base is 5,000 feet, and I’m not going to argue with that. Feel free to tag on some extra supplementary varieties to the description such as undulatus, perlucidus (gaps between), or stratiformis.

Dry spell continues

The dry theme that started in late March continues into the last week of April, especially over central southern parts of England (where some stations are still in a state of partial drought), as this graph of precipitation illustrates from Benson in Oxfordshire since the start of this year (fig 1).

Figure 1

A big part of why it’s been so dry is the anticyclonic weather of the past month, as you can see from the Benson barograph (fig 2).

Figure 2

A state of type is now well under way, with cold air set to flood south across the country in a N or AN, but according to the latest NWP guidance that meridional type looks like it will be a relatively short-lived affair, before things become more mobile from Sunday, putting an end to the dry spell even across southern counties.

Sign of things to come at Baltasound

The cold air has dug back in behind the cold front at Baltasound, turning the rain to snow, as the low pressure whizzes across the Northern Isles.

I wish someone would sort out that anemometer at Torshavn, I’m sure that the wind direction is the exact reciprocal of what it should be, it’s happened before, you just can’t trust those AWS.


Eleven of the best NWP viewers on the Internet

If you, like me, are fascinated by what the weather is going to do in a bit finer detail than you’ll ever get from watching the weather on the BBC, then you might be interested in some of the eleven websites that I’ve listed below. They all provide a quick and easy way of looking at NWP forecast data from various models, usually the American GFS, but not always. There have recently been a rash of new websites providing these kind of viewers, and they are increasingly becoming more sophisticated and professional. I’ve tried to put them into some kind of ranking, let me know if you agree, or maybe you know of a website that I’ve missed out completely.

#11 –

A basic GFS viewer from James McGregor in New Zealand, the graphics and maps used are simple and clear once you find them, as are the controls and available map regions, all set in a web page that offers visualisation such as satellite, weather radar and observational data.

Figure 1

#10 –

The Norwegian Meteorological Institute and the Norwegian Broadcasting Organisation have put this NWP viewer together between them. It’s rather Norwegian centric, rather like the Met Office website is with the UK, and as far as I know it’s their own NWP model that they use. Personally I just like the Meteograms, which in my opinion would be even better if they ran out to T+120 or longer.

Figure 2 – Norwegian Meteorological Institute and the Norwegian Broadcasting Corporation. © 2013 – 2017

Figure 3 – Norwegian Meteorological Institute and the Norwegian Broadcasting Corporation. © 2013 – 2017

#9 –

The Wetterzentrale site has been around for years and was recently was re-sited and the NWP viewer spruced up. I like the basic idea of the graphics that they produce, and the overlay of an MSLP field on top on a colour filled contoured chart of geopotential height seems to be a defacto standard. I also like the ability to access other models from around the world, especially the 20th century reanalysis data that the site provides as well. I think the controls are still a little bit basic and could do with a bit of a makeover.

Figure 4

#8 –

The OGIMET site is an old favourite of mine, and is were I go to download SYNOP data, and even though the guy that runs it has never replied to a single one of my emails over the years, it still displays a comprehensive array of GFS model data for various regions. I like the multi-layered graphics which are clean and simple, the functionality and controls are rather basic though.

Figure 5

#7 –

The weather outlook viewer controls are just a little bit more sophisticated than those on the wetterzentrale site, but the graphics are very similar. The controls make selection a little quicker, with flyover selection of model time steps by means of the mouse, with a good range of NWP data fields to access and display.

Figure 6

#6 –

The netweather site have a similar approach to that of weather outlook, but if anything the user interface is clearer and more organised. Again the NWP graphics are not that dissimilar to those produced by wetterzentrale and superbly clear.

Figure 7

#5 –

This site keeps a special eye on tropical cyclones, but that doesn’t stop them enabling their NWP viewer to be pointed at other regions from a variety of NWP models. The graphics offer multiple layers of NWP types which are sharp and clear, and you can view some quite sophisticated overlays on detailed outline maps.

Figure 8

#4 –

The earth viewer from Cameron Beccario has been around for a long while now, but has exquisite animated graphics. The controls are hidden away so as to get the full effect of the viewer when running in full screen mode. What else can you say other than it’s just beautiful.

Figure 9 – © 2017 Cameron Beccario

#3 –

The windytv viewer goes a little bit further than the earth viewer, and gives you an always visible interface, that’s not obtrusive and very tastefully designed, I bet behind the facade it probably uses the same vector graphics and mapping though. A really swish NWP viewer which I don’t use often enough.

Figure 10

#2 –

The ventusky viewer is from the same stable as the earth and windytv viewers by the looks of it. I quite like it, even with the slightly gaudy colours that they’ve chosen to use on their wind fields.

Figure 11

#1 –

The wxcharts viewer does just about everything that you could want of a NWP viewer in a web browser, and it must be the equal of many desktop weather visualization systems. It’s hard to believe that the developers have packed so much into the display, in which they’ve also managed to include meteograms as well as maps. You can tell that the team that’s put this together are real enthusiasts. The NWP graphics might be static, and not just quite as impressive as the animated maps from ventusky or windytv viewer, but I still think wxcharts as the edge on them in my opinion.

Figure 12

National Met service offerings in comparison

The DWD in Germany just like to keep it simple, why complicated things with those funny isolines and colour filled contours.

Figure 14 – Meteo France

Sophisticated stuff from the French, in this screenshot from the Meteo France website. I suppose for the general public this viewer is telling them all that they need to know – generally sunny.

Figure 15 – The UK Met Office

The Met Office are still using the same FAX charts that they’ve been using for the last 50 years or more, they analysis chart still has the same PPVA89 file designator that it’s always had, but at least nowadays it’s in colour. The Met Office have collaborated to produce the Visual Cortex graphics engine which they use on ITV and internally these days. They seem to have placed most of their effort into producing weather forecast videos which they use on their website and social media. It’s a shame that Visual Cortex can’t be used to provide NWP graphical output to a web viewer in a similar way to what ventusky have done, how hard can it be.

At least the Americans are now trying to update their viewers, and have recently started to use GIS web services offered by ESRI I notice.

It’s all very sad when you compare the quality and sophistication in the first eleven NWP viewers with those on offer from some of the worlds National Met Services. The difference is quite stark in most cases, it’s as if these organisations don’t even want to compete, after spending countless millions on the fastest supercomputers, and building the most sophisticated ensemble and deterministic NWP models, they just tire at the last hurdle and leave it to others to provide a web interface for the citizens of their respective countries to use, the question that springs to my mind is, why not?

Convective infill

The convective infill that has affected inland parts of southwest England, has spoilt what started off as rather a lovely day. Having said that it appears that a similar thing has happened but on a much larger scale over Ireland this afternoon, as the whole country seems to be under a sheet of CUSC.

North Atlantic hurricanes – reviewing last season and looking forward to 2017

Figure 1 – Hurricane Sandy courtesy of NASA

The 2016 North Atlantic season ended up being slightly above average, with seven of the fifteen tropical storms reaching hurricane status, there were three category 1’s, two category 3’s and a category 4 & 5 hurricanes (fig 3 & 4). It was the highest number of hurricanes in a year since the ten in 2012.

Figure 2 – Raw HURDAT2 data courtesy of the NHC

Some of the tropical cyclones in 2016 were very long-lived. Hurricane Nicole survived over 15 days, and Hurricane Alex, which started life on the 7th of January, and became the first Hurricane to form in January since 1938, travelled almost nine thousand nautical miles in its ten-day life.

Figure 3

The most severe Hurricane of the season was undoubtedly Hurricane Matthew, which flirted with the eastern seaboard of the United state and reached category five status in so doing , the first category five hurricane since 2007.

Figure 4

I always reckon the best way to compare individual years is by the combined ACE of all tropical cyclones (fig 5), and using that as a yardstick 2016 was the most active year since 2010.

Figure 5

2016 Predictions

If you want to look at the NHC Forecast verification report for 2016 be my guest, you can find the PDF of the report here. To me, it tells you very little about the season, or what the verification says about the various forecasts that the NHC made. I love the old fashion verification system which has just two outcomes, right or wrong, hit or miss I’m afraid. Most of the pundits who made a prediction for how 2016 would turn out were generally correct, including me!

  • Accuweather weather 14/8
  • Met Office 14/8
  • NWS ~ 13/6

Those aren’t the odds but the count of North Atlantic tropical cyclone/hurricanes in the 2016 season, which ended up 15/7.

2017 Predictions

I’ve managed to find some early predictions for 2017 courtesy of Wikipedia

  • Tropical Storm Risk 11/4
  • Colorado State University 11/4
  • The Weather Company 12/6
  • North Carolina State University ~13/5

The general consensus from them is that it’s going to be an average season, although the big players haven’t thrown their hats into the ring yet, probably because the season doesn’t officially start till the 1st of June. The season has already started though because we’ve already seen one tropical storm this month already.

Late April cold spells and the Easter Snowstorm of 1908

Figure 1 – Lymington High Street – April 25th 1908 (courtesy of

Easter in 1908 fell late, so the snow that fell over much of southern England must have come as a big surprise on the Easter Sunday on the 19th of April (fig 1). The following week was intensely cold for late April, and there were periods of heavy snow across much of southern England. In an article in the Met Mag of May 1908, Fred J Brodie said this about the snow at Oxford:

The conditions at Oxford are interesting in a special degree on account of the length of the meteorological records at the Radcliffe Observatory which run from 1853. The depth of snow there was 17 inches, and the only instance of a greater amount being recorded at any time of year was on February 13th and 14th, 1888, when 24 inches of undrifted snow was measured.

I love the comment that Fred went onto make a few lines further on…

The practice of comparing, for the purpose of record making, observations made in two different localities is not to
be commended…

He of course is completely right in what he says, but he must be spinning in his grave these days, on the goings on in the early 21st century with extreme temperature records I would have thought, because no one, and that includes myself seems to give a hoot these days about comparing extremes from weather stations without knowing thinking much about their actual location. You can find an article about the events of April 1908 on the Weather Outlook forum, which includes details of snow depths recorded at the time, plus a lot of other information and photographs about the blizzard. The Weather Magazine of December 1981 also had an article about April 1908 in which it linked it to the April of 1981 and said:

The marked similarity of the graphs for 1908 and 1981, especially in the second half of each, is confirmed by a correlation coefficient of 0.93 for the last 15 days of the month. For the full month the correlation coefficient is 0.65. The weather of late April was remarkably similar in these years.

Since 1981, the daily CET series may well have undergone some slight modifications, but there is most definitely a cold spell that occurred during at the second half of each month, the minimum CET in 1908 was a couple of degrees colder than it was in 1981 though, and those on the 24th and 25th still hold the record for lowest minimums on those two days (blue stars). Personally I only see a broad similarity between the two, I’ll have to spend some time and write some code to generate a correlation coefficients between these two months and see what I come up with. If you look closely at the graph of CET (fig 2), you’ll notice that in just over a week, maximum anomalies rose from around -8°C to +8°C. The resultant rapid thawing of lying snow from the week-long cold spell lead to great flooding in places along rivers in the southeast especially the Thames, and the Great Ouse at Buckingham.

Figure 2

Synoptically, the 25th of April in both 1908 and 1981 were slightly similar in that they were both cyclonic in nature.

Figure 3 – Courtesy of NCEP/NOAA reanalysis

But up aloft in the atmosphere the cold air of 1908 was much deeper than it was in 1981 (figs 4 & 5).

It seems cold outbreaks towards the end of April are not at all uncommon, I’ve just picked on probably two of the more extreme events. Next week promises its own cold outbreak (fig 6), but synoptically, if the GFS model is correct, it will be more of a cold northerly rather than cyclonic as it was either in 1908 or 1981.

Figure 6 – Courtesy of OGIMET


Q: Just why has April been so dry & sunny?

Q: Just why has it been so dry and sunny and dry this April?

Figure 1 – Data courtesy of NCEP/NOAA reanalysis

A: Because for the first 18 days of the month there has been a large (+11 hPa) positive MSLP anomaly sat just to the west of Ireland (fig 1). As I reported earlier this month (never thinking that the first half of April would turn out as anticyclonic as it has), 1938 was the most anticyclonic in records that started in 1871 (fig 2). The two April’s are indeed very similar, but the anomaly chart for 1938 was for the entire month, and not just the first 18 days, and were larger and even more pronounced. That’s not to say that the second half of April 2017 won’t continue to be just as anticyclonic as was the first.

Figure 2 – Data courtesy of NCEP/NOAA reanalysis

I’ve just put quite a lot of programming effort into the program that I use to download, parse and visualise reanalysis MSLP data from NOAA, so hopefully I’ve got things right. The LTA that I have used to calculate the anomalies for years 2012 or earlier is for the whole of the 20th Century i.e 1901-2000. For the years after 2012 the LTA is for the 66 year period 1948-2013. This is because the older reanalysis data uses a 2 x 2° grid, whilst the data after 2012 is from the 20th Century reanalysis on a 2.5 x 2.5° grid.

Jersey the sunny Channel Island

Figure 1 – Courtesy of

Jersey have taken over at the top of the sunshine league this April, with almost 9 hours of sunshine each day for the first 20 days of the month. Their total of 178.6 hours so far is I estimate 66.1% of the possible maximum total. It’s not been sunny everywhere across the British Isles, but without detailed climate statistics to produce anomaly values it’s impossible to be precise, but as usual, it seems to have been duller the further west and north that you are so far this month (fig 2).

Figure 2

Recent cloud images

Here are some of my recent cloud images, it’s been a bit quiet as far as my photography goes this year, we seem to have missed out on any good sunsets. Last night was an exception though, not a colourful sunset but rather a broody dark display of SC with embedded mammatus, the base of the SC sheet was at around 5,000 feet according to the LCBR at Exeter airport.

It all ties in with the cloud in the visible satellite image of the same time that’s aligned ENE-WSW across southern England (fig 1). The 18 UTC analysis has a corresponding trough following behind the warm front on the analysis (fig 2), the bottom bit of the warm front is marked frontolysis by the Met Office no doubt because there is no cloud on it west of 1° east. There were some showery outbreaks of rain along the trough yesterday evening, so there must have been some instability associated with it as it moved SSE ‘ward (fig 3).

Figure 1 – Courtesy of the Met Office & EUMETSAT

Figure 2 – Courtesy of the Met Office

Figure 3 – Courtesy of the Met Office