Low with no name brings strong winds to west

Figure 1

The low that even the Institute of Meteorology at Berlin couldn’t be bothered to name (fig 2) has been producing a spell of strong to gale force winds across the west and north of the UK and Ireland overnight (fig 1).

Figure 2 – Courtesy of the Free University of Berlin

Most of the lows energy from yesterdays explosive cyclogenesis has been dissipated by agitating the central North Atlantic (fig 3).

Figure 3 – Courtesy of the NWS

I notice that wave heights of 12 metres have been recorded at weather buoy ‘Pap’ (fig 4).

Figure 4

The BBC weather website

Figure 1 – Courtesy of the BBC

I hadn’t noticed the recent changes to the mapping used in the forecasts on the BBC website introduced by MeteoGroup, so I was rather surprised to find just how good a ECMWF viewer it was (fig 1). All they need to do now is add some extra layers such as 300 hPa winds and 1000-850 hPa partial thicknesses, and they’ll have a winner on their hands! The NWP only extends to T+168 but that’s fine, the only thing I can really find fault with is that they still use the same dreadful location labels they do in their TV graphics (fig 2).

Figure 2 – Courtesy of the BBC

Even at full zoom there are some rather curious omissions in the towns and cities that they choose to include in their coverage of the UK. Here are just a few of the holes that I spotted across northern England I would have thought could do with plugging (fig 3). I’m sure they’ll put the reason down to keeping the map decluttered, but that could easily be achieved by giving each location a plotting priority, and removing the solid black rectangle they use to overlay each location name on.

Figure 3 – Courtesy of the BBC

The Pacific Decadal Oscillation

Until last week I knew that the PDO was an acronym for the Pacific Decadal Oscillation but little else. I now know a little more thanks to the Wikipedia and this very informative article from the North Carolina Climate Office of all places (fig 1).

Figure 1 – Courtesy of the North Carolina Climate Office
Two data sets

I had got a little confused when looking for monthly data to graph the series with. I now realise that there are in fact two versions of PDO series one maintained by the people who discovered the relationship in 1997 called the Mantua PDO, and the other maintained by NOAA known as the NCEI PDO and based on the Matua PDO:

The NCEI PDO index is based on NOAA’s extended reconstruction of SSTs. It is constructed by regressing the ERSST anomalies against the Mantua PDO index for their overlap period, to compute a PDO regression map for the North Pacific ERSST anomalies. The ERSST anomalies are then projected onto that map to compute the NCEI index. The NCEI PDO index closely follows the Mantua PDO index

That’s why I decided to write an application to download, parse and plot both the Mantua PDO series which started in 1900, and the NCEI PDO series which started in 1854. This is how the two series have behaved over the last 30 years (fig 2).

Figure 2
The third cycle

As the North Carolina Climate Office says (see above), researchers have found evidence for just two full PDO cycles in the past century. A cold PDO regime prevailed from 1890 to 1924 and from 1947 to 1976, whilst a warm PDO regime dominated from 1925 to 1946 and again from 1977 through to 1998. That suggests to me that in 2018 we are in the cold part of a third cycle at the moment (fig 3).

Figure 3
Latest PDO

This flurry of development on my part was brought about reading a recent post about the PDO to the uk.sci.weather newsgroup from Graham Davis who reported: The Pacific Decadal Oscillation Index has been positive for 50 straight months. This was the longest period that the index has been in either positive or negative territory. However, last month, the index slipped to -0.05. To put this value into some perspective, the highest monthly value of the index on record has been +3.5 and the lowest -3.6. How significant this negative index in March is anyone’s guess at the moment. The Mantua PDO has been oscillating positive negative since 1998, but it has been in positive territory since January 2014.

To complete this quick look at the Pacific Decadal Oscillation I’ve written some JavaScript to plot a chart of the Mantua PDO since 1900 using the Highcharts library and published it to my Meteograph website (fig 4).

Figure 4 – PDO Online Chart

Nowcasting and the problem of forecasting low cloud

All sorts of problems in forecasting the exact position and the extent of low cloud across the country this morning. This is nothing new of course and must be the bane of most NWP models in slack situations like this. Both the UKMO and the ECMWF models (if that’s the one MeteoGroup are currently  using) have a poor grasp of low cloud at 09 UTC as you can see by this mornings visible satellite image, and don’t forget these graphics are probably from the 06 UTC model run so the forecast’s are no more than three hours in the future (fig 1). In the 1980’s the word nowcasting was coined to describe these short-term forecasts, but it looks like low cloud in situations like this are proving difficult to keep track of.

Figure 1 – Met Office forecast – Visible Satellite – BBC forecast

You may have noticed that I’m fixated at the moment in examining and comparing the forecast output from the UKMO and the ECMWF models, by grabbing screen shots of the MeteoGroup forecast on BBC 1, and the Met Office video forecast from their website. Why do I do this? Perhaps it’s out of sheer frustration, knowing that although we indirectly pay for both of these institutions, we see output from either model in any detail except by snatching screen shots. I’m so glad that MeteoGroup did win the BBC contract because it does help in highlighting the differences and shortcomings of both models.

Dull start to April continues

The very dull start to April 2018 continues, with many stations across the UK and Ireland reporting less than 20 hours of sunshine for the first 13 days of April, the only bright spots are in the western and northern isles of Scotland, with Stornoway the sunniest place with 67.3 hours (fig 1). There was missing data from both Liscombe and Heathrow.

Figure 1

A lot of hot air over next weeks warmth

Figure 1 – Courtesy of the BBC

Yes it’s official, it looks likely that Thursday and Friday of next week may well be on the warm side for April (fig 2). But there’s nothing unusual about warm days in Spring, and someone should tell the media to cool down and not get so excited (fig 1), because after all spring did spring over six weeks ago according to their definition.

Figure 2 – Courtesy of www.wxcharts.eu

The hype you get these days from the NWP soothsayers is getting to almost biblical proportions. In the winter they are the same people who’ll tell you with great delight that the cold snap that hasn’t even started yet, will only last a couple of days. Well two can play at that game, because it saddens me to report that it looks likely that this weeks warmth may also be fleeting!

Met Office make it three in a row

Figure 1 Courtesy of  BBC/ITV/Actual

The Met Office make it three in a row, with an 8-5 win over Meteogroup on today’s maximum temperatures. On the strength of the last three days the ECMWF seem to over-estimate afternoon temperatures, although I still can’t manage to get them to agree on when to report them in either of their forecast graphics. Today I had to use the ITV graphics for the Met Office forecast because the Met Office are so darn quick at deleting any evidence in their early morning forecast. I’m going to have to find a better way that this to verify their forecasts…

Wall to wall sunshine in Scotland

If you’ve ever read a sunshine card from a Campbell–Stokes sunshine recorder then you’ll probably like this image generated by my SYNOP application. It takes the sunshine reported each hour throughout the day and generates a pseudo mega sunshine trace for all 50 odd SYNOP sunshine reporting stations in the UK (fig 1). I’ve even tried to match the colour of the chart to match that of the sunshine card from memory, but I may not have got the shade quite right.

Figure 1

What today’s mega sunshine card shows is that its been overcast and dull across many parts of the country except the north and west of Scotland and the southwest England, in fact in the Northern Isles the sunshine has been from dawn till dusk by the look of the pseudo trace. The low total from Camborne was a bit of a surprise, but that must have been the convective infill that produced the thunderstorm over west Dartmoor, which produced totals of over 32 mm if my weather radar estimates are to be believed (fig 2).

Figure 2

Today’s poor forecasts

It’s difficult to pin these two organisations down when it comes to verifying just how accurate their maximum temperature forecasts are. But the Met Office model is already one up after yesterday, so I thought I’d just see how they did today.

Figure 1 – Courtesy of the BBC and the Met Office

Here are the actual temperatures at 1600 BST today which I mark 76% to the Met Office. The forecast for London was really dreadful from both models, obviously they expected the stratus to clear but it didn’t. I can’t understand why MeteoGroup have labels for both Glasgow and Edinburgh, but only one temperature, and for which city it’s for. If anything MeteoGroup should have had the edge because the actual and forecast temperatures are both for 1600 BST, but that didn’t stop the Met Office taking a two nil lead.

It wasn’t only temperature that caught out both the Met Office and MeteoGroup today, there was also an area of heavy rainfall that extended across Humberside into Yorkshire during the afternoon that escaped both models. I watched the rolling news on the BBC news during the afternoon and I think even worse than the poor forecast was that the presenter never seemed to noticed that it was happening at all, let alone bothering mention it or show a real-time weather radar image. It reminded me of the taped forecast given by Michael Fish as the Boscastle flash floods was in progress in 2004. I can’t see why the Met Office have bothered to update their weather radar network when no one seems to look at it. Here’s the BBC forecast for the east Midland’s from yesterday evening (fig 2).

Figure 2 – Courtesy of the BBC

Forecast temperature verification

I’ve been trying to compare forecast temperatures from the Met Office and MeteoGroup to see which NWP model was the more accurate. Here are their forecasts for yesterday (fig 1).

Figure 1 – Courtesy of the BBC and the Met Office

As you can see they use a more or less common set of major cities across the UK which helps. On Twitter the Met Office seem to prefer labelling the 1400 temperature rather than the 1600 temperature as the BBC do, so a direct comparison is difficult. It might be a little easier if both of them displayed a much more useful maximum temperature [06-18] for the day, but that would never do would it? I noticed that in their video forecast for today, the Met Office had switched to labelling temperatures at 1500, although I can’t seem to figure out where that 11°C label is for in this mornings (fig 2).

Figure 2 – Courtesy of the Met Office

As you know daytime temperatures are notoriously difficult to forecast with variable cloud at anytime of the year, but especially so in spring with breezes of cold seas, and as you can see there were was a large range in forecast temperatures from the two models for yesterday. Here are the actual air temperatures for 1500 BST for comparison purposes (fig 3).

Figure 3 – Courtesy of Me

Despite the timing differences I mentioned above, I make it that as far as yesterday goes, the Met Office forecast temperature was closer to the actual temperature (at 1500 BST) than was the MeteoGroup forecast at 60% of the 14 city sites. Of course I need to put in quite a bit of work over a longer period to see which model is the more accurate.