Ex-tropical storm Rina holds up cold front clearance on Saturday

Figure 1 – Data courtesy of the NHC (approximate GFS positions from the 00 UTC 10 November model run)

I wondered what was holding up the cold front clearance on Saturday across southwestern parts of England (fig 2), but then I noticed on the Berlin Meteorological Institutes website, that the second shallow low the follows behind the low that tracks WNW- ESE across Ireland, Wales and the southeast of England during Saturday morning, was labeled ex-tropical storm Rina (fig 1). The Met Office of course are having none of that because it wouldn’t be correct would it.

Figure 2

Will Rina be the finale of the Atlantic hurricane season?

The last advisory on Rina highlighted what had been yet another rather unusual tropical cyclone in 2017 (fig 3):

Figure 3 – Courtesy of the NHC

Rina lives on in Europe

Interestingly, that rather shallow low which was Rina was when it crosses the UK is forecast to develop into quite a deep low of 991 hPa by 12 UTC on Sunday, as it tracks southeast across the Alps into the northern Adriatic, and quite a significant feature in that part of Europe (fig 4).

Figure 4 – Courtesy of the Met Office

Yellow Warning for rain?

Even more interestingly, so far the Met Office haven’t issued any yellow warnings for heavy rain in southwestern parts during Saturday. I just wondered if the tropical origins of the air might even enhance the rainfall in theses parts.

Overnight fog rather more extensive and earlier than expected

Figure 1

The overnight fog arrived much earlier and was a little more extensive than the Met Office warned of their yellow warning issued yesterday afternoon (fig 1). The warning was for the period starting 02 UTC this morning (fig 2), but there were visibilities of 100 metres or less at Exeter airport from as early as 21 UTC, which must be quite embarrassing for forecasters, when the airport is such a well-known frost hollow and fog trap. In fact by 20 UTC, under an almost full moon you could see the Culm Valley where we live 8 km to the north filled with fog. The main rail line to London and the M5 also run up the Culm valley towards Taunton. Fog did take longer to form further east, but the Met Office had to extend the area at 0720 UTC this morning to cover areas to the west of London. I wonder if the TAF for Exeter airport required amending?

Figure 2 – Courtesy of the Met Office

Dunkeswell in fog at 20 UTC

Dunkeswell have gone into fog at 20 UTC with a temperature of 4.7°C (fig 1). Maybe my adapted Middle Wallop fog TDA had the right idea after all! Certainly the yellow warning for fog that the Met Office issued this afternoon seems to have already gone awry, because the validity time doesn’t start till 02 UTC! Of course technically it may not be true radiation fog, and could well be upslope stratus, but 100 metres visibility is still an F in the Beauforts in my book.

Figure 1

Tonights yellow alert for fog and the adapted Middle Wallop technique

Figure 1 – Courtesy of the Met Office

I was only saying complaining after the last yellow alert for fog that the Met Office issued, that a bit of advanced notice wouldn’t be a bad idea, and lo and behold, at least with this one, they have!


Coincidentally, I’ve recently been working on a Tactical Decision Aid [TDA] for the forecasting of fog. The idea is based on the Adapted Middle Wallop Technique which featured in an article in the September edition of the Weather magazine. I’ve written an application that downloads forecast data from the Met Office DataPoint web service and observational SYNOP data from OGIMET. This means that you can point the TDA at any of around 100 locations around the UK and check if fog is likely in the coming night. I’ve run out of steam with its development in the last couple of weeks, so it’s still very much a beta, all I need is to come up with a burst of enthusiasm to finish it off (fig 2).

Figure 2

As you can see, I still have work to do on the actual calculation of the forecast visibility. In this example for tonight at Yeovilton, I have it that will go into fog by 20 UTC with a temperature of 7°C, which looks way too early to me, so this is still very much work in progress. Let me know what you think of the idea and how useful it might be, I personally feel it’s just got to be better than doing it in a spreadsheet.

Addendum

I have just come across a very interesting website which features a number of TDA online tools, one of them being for forecasting fog that uses the Adapted Middle Wallop technique. Isn’t it amazing what you can find find when you look!

Storm Brian a bit of a no-show

Figure 1

I have to admit it that in the cold light of the synop observations of wind speed for yesterday until 08 UTC this morning, storm Brian was a bit of  a no-show, and the Met Office were correct in distancing themselves from the naming of it. It looked pretty ferocious on Friday, but Brian was already occluding and starting to fill when it arrived in northwest Ireland, as the models correctly said it would be. The yellow warning issued by the UKMO, could have mentioned possible gusts to 80 mph (fig 2), and the state amber issued by Met Éireann was not really necessary, but they are probably still jittery after the intense exposure they got from Ophelia on Monday.

Figure 2

Coastal waters and headlands took a pounding as they always do, but actual gales when 10 minute mean speeds reach 34 knots or more, were confined mainly to the Atlantic coasts of southwest Ireland and southwest England, the eastern coast of the Irish Sea from St Bee’s head south and the Bristol Channel (fig 3).

Figure 3

I’m personally glad to see the back of Brian and move onto Caroline.

Cherry picking wind speeds

Figure 1 – Courtesy of Twitter & the Met Office

It strikes me as strange that when the Met Office need to justify a named storm or a yellow or amber warning that they’ve issued for strong wind, how they can seemingly pluck observing sites out of thin air, some of which you might never have heard of before, such as:

  • Berry Head, Devon
  • High Bradfield, South Yorkshire
  • Needles Old Battery, Isle of Wight
  • Orlock Head, County Down
  • Salsburgh, North Lanarkshire
  • Avonmouth, Avon
  • Lydd, Kent

But when the winds have been a little stronger than they forecast, as was the case today with storm Brian, they seem to be able to exclude some stations from the graphics they generate (fig 2) as if the offending station didn’t even exist. In fact the winds are higher in western coastal districts of Wales than anywhere in Ireland, the difference is that Met Éireann did issue an amber warning for gusts to 80 mph, and the Met Office didn’t. I would like to use observational data from these sites myself, but I can’t access them, the reason being that they don’t have a WMO number, and don’t report a regular SYNOP observation, more’s the pity.

Figure 2

Overnight gusts from Brian

Figure 1

Met Éireann might have a state amber warning in force for gusts to 80 mph, but the highest gusts overnight (as there were with Ophelia on Monday) have been in the southwest of England and the west of Wales, with gusts to 78 mph at the Sevenstones lightvessel and 71 mph at Mumbles head at 06 UTC this morning, both exceeding the 70 mph in the yellow warning issued by the Met Office yesterday. I doubt if the Met Office will update this warning, and are just hoping that the gradient doesn’t tighten anymore and there won’t be anymore gusts over 70 mph.

Brian is a stereotypical low that you get every so often in Autumn and Winter across the British Isles, but the way the threshold of the yellow and amber warnings are pitched means that we get into this situation with almost every low that comes along. Is it yellow or is it amber, which is complicated further with the storm naming. Perhaps if the thresholds were based on mean speeds as well as gust speeds, then a mean speed of 34 knots at a coastal site could be the yellow threshold, and a mean speed of 34 knots (gale force 8 or 39 mph) at an inland site amber? Well it’s just an idea.

Storm Brian

Figure 1

Storm Brian was named by Met Éireann yesterday, and reading the news item that the Met Office issued, it looks like if it had been left up to them they wouldn’t have even bothered. As well as naming the storm Brian, Met Éireann have also issued a status amber and yellow wind warning for Saturday for gusts of up to 80 mph (fig 1), and notice that in their warning they specifically mention the expected maximum mean wind speed of 40-50 mph, which makes for a textbook warning as far as I’m concerned (fig 2), and which the Met Office refuse to do.

Figure 2 – Courtesy of Met Eireann

Arguably, the gradient on the latest T+36 from the GFS model is just as tight across the southwest of Wales as it is across Ireland (fig 1), but the Met Office are sitting on their yellow warning, but have enlarged the area (fig 3). This time the Met Office have chosen to use the old 45-55 mph but with 60-70 mph gusts around the coast ploy. I would have thought that there would be gusts to at least 80 mph on the Welsh coast on Saturday, as there were gusts to 90 mph there on Monday when they only had an amber warning for gusts of 80 mph in force.

Why take any chances?

Why not just issue an amber warning for gusts to at least 80 mph for coastal areas, and leave the yellow alert for inland areas?

Half the problem, I’m sure, of why they don’t do this is because of their reliance on hand drawing the various warning areas. If this web interface was improved by the use of a GIS system, they could then much more easily highlight an amber area at regional authority level or even postcode level around the coasts. The finished product would be more accurate, professional and directly tied to the individual grid point wind gusts from the NWP model.

Figure 3 – Courtesy of the Met Office

Whether the wind gusts will reach the yellow or amber threshold (which I guess is 80 mph) depends on when the rapid intensification of Brian occurs, if it’s later, or if it goes on slightly longer the winds will be that much stronger. The Met Office are in no doubt that it’s already underway and by the time the low reaches Ireland it will be already well occluded (fig 4).

Figure 4 – Courtesy of the Met Office

I notice that the process is already well under way at 62095 (fig 5).

Figure 5

Late fog warning from Met Office

Figure 1

A late warning of dense fog for parts of England was issued by the Met Office early this morning. As far as I can see the warning wasn’t issued till 0540 AM when most affected stations, at least in eastern England, had been in fog since midnight. I can’t for the life of me see why this warning wasn’t issued much earlier.

Figure 2 – Courtesy of the Met Office

Saturday advisory from the Met Office

The Met Office have issued a yellow ‘advisory’ warning today for storm Dietrich this coming Saturday. These ‘advisories’ seems to be the way they’ve started doing things these days, which I must say is a vast improvement on last year, when they almost seemed to wait until the last-minute to give the general public a clue about what they were thinking. They’ve chosen to use a brand new ploy in this strong wind warning, the 50-70 mph ploy, and lucky us they even managed to mention the wind direction in this one! Now all that we’ve got to get them to do is to include the maximum mean wind speed that they expect, and we’ll have a proper warning, just like those issued at RAF outstations for the last 70 years. I suspect a big part of the problem is that many Chief Forecasters have never spent any time on an RAF outstation, or ever issued a warning come to that.

Figure 1 – Courtesy of the Met Office