Anemometer failure at Valentia!

Figure 1

It’s quite unusual for a wind group to go missing from a WMO block #03 synop report like it has for the last two hours for Valentia (#03953). Perhaps the met technicians are down there from Dublin, checking it out to make sure it’ll stand up to the pummeling Ophelia will give it on Monday? The rest of the report from the AWS is all there, but minus the wind direction (fig 1). I’m sure it’ll all be up and running for Monday, well at least I hope it is.

I think the plotted observation in the 07 UTC chart, southwest of the Fastnet Rock from EUCDEO is from a ship and not a weather buoy, and which looks like it’s making for port in Ireland before Ophelia makes an entrance.

Hurricane Maria now close to weather buoy 42060

Figure 1

I see that Hurricane Maria is now getting very close to weather buoy 42060 at 12 UTC, it will be interesting to see just how the buoy gets on. Judging by the wind direction at 12 UTC, the hurricane is not far to the E’SE of the buoys position.

Lizard hot spot

Figure 1

It was almost if there were some kind of under sea hot spot just off the Lizard in Cornwall today, that kept producing a continuous stream of thundery showers that tracked northeastward towards west Devon (fig 1). My estimated accumulations from the weather radar put the totals from 0600-1650 UTC in excess of 100 mm just of the Lizard for today (fig 2).

Figure 2

There were certainly some lively winds that came with it across the Lizard, here is the plotted sequence from Culdrose (fig 3).

Figure 3

Since writing this blog I’ve heard on the local news that there has been some serious flash flooding at Coverack on the Lizard, hopefully no one has come to any harm.

 

Tuesday’s low

Figure 1

It seems that the heaviest falls of rain were in the vicinity of the centre of the small low, as it tracked eastward across southern England during Tuesday and Wednesday, in fact you could almost draw a straight line from north Devon to Essex and join up all the wettest places.

Figure 2

New UK 20th Century low pressure extreme

Figure 1

I don’t know if the 937.6 hpa read at Stornoway at 0020 UTC on the 20th of December 1982, was indeed the lowest minimum pressure of the 20th century recorded in the UK, but it was certainly extremely low. This is the midnight chart that I have reassembled from the old SYNOP reports (fig 1).

References

  • Burt S.D, (1982) New UK 20th Century Low Pressure extreme; Weather 38(7) pp. 209-213

June 2017 – sunshine

Jersey just pipped Manston in June as the sunniest place in the British Isles from sunshine figures available in the 06 UTC SYNOP reports (fig 1).

Figure 1

The sunshine network available from the SYNOP reports is a little bit on the holy side (fig 2), I realise that there are many more stations that the Met Office collect daily sunshine data from that don’t report in SYNOP format, but for goodness sake why not? I notice that recently Tibenham has come on-line in Norfolk, I am not sure if it’s a completely new AWS station, or if they’ve promoted a climatological station by giving it a SYNOP number. Of course, there is no obvious reason why the Met Office can’t just provide all the climate stations with a WMO station number and fill in the holes in the SYNOP network across the UK, not only as regards sunshine, but also rainfall, temperature and wind. The SYNOP format is not great for reporting climate data with, but it’s much better than just sitting on the daily data as they’ve been doing for many years.

Figure 2

Remember the sunshine card?

If you remember ever having to change a sunshine card in a Campbell-Stokes recorder as an observer, then I’m sure that you’ll like this new way of visualising hourly sunshine data from stations across the UK that I’ve dreamed up (fig 1).

Figure 1

I don’t have the luxury of being able to receive minute data from the Met Office network, so the next best bet is to access hourly SYNOP data from OGIMET and put it together in some code and plot a gantt chart, which is exactly what I’ve done here (fig 1). It’s unique as far as my knowledge of visualising systems that don’t have network access to a remote AWS. There is a bit of guesswork about how you assign the hourly amount of sunshine to each hour during the day, I’ve made it so that the program defaults to the end of the hour before noon, and to the start of the hour after noon. The gantt chart format allows you to also see the approximate times of sunrise and sunset for each station. I’m pretty chuffed with the end result which only occurred to me whilst sun bathing in the garden this afternoon!

The other thing that it enables you to do is to watch sunshine total as they increase across the UK in real-time through the day (fig 2).

Figure 2

Something not quite right about this cold front

There’s a cold front – or should I say that there should be a cold front straddled across southwest England this morning. But you would be hard pressed to find it on the plotted 10 UTC chart (fig 1).

Figure 1

You might think that the cold front is associated with this batch of rain that’s now cleared through the southwest and is now moving northeast across the Midlands, but that rain can’t be the cold front because it’s just too far on (fig 2).

Figure 2

The cold front according to the T+06 forecast chart (and why do the Met Office not release their latest 6 hour analysis quicker than they do) is only across Cornwall at 12 UTC (fig 3).

Figure 3

So why is it, that if the cold front went through the Scillies at around 06 UTC (fig 4) (with moderate rain and a slight pressure kick), does the dew point there continue to climb, as if a warm front rather than a cold front has passed through?

Figure 4

Answers on a postcard please, or why don’t you just leave a comment. It would be so educational if the Met Office released the Synoptic Review (part II) that the Chief forecaster produces every six hours on the internet for all to read. I always found it fascinating reading as an outstation assistant, and am sure that a lot of people interested in the day-to-day weather across the country would find it fascinating too, I bet the answer is in there.

Overestimating cloud amounts

Since the Met Office have two AWS within 10 miles of home, I always keep a check on them, especially as regards cloud base and cloud amounts, because both Exeter airport and Dunkeswell come equipped with laser cloud base recorders [LCBR]. I have noticed though that as far as I can see they always seem to overestimate cloud amounts, especially of the low variety. Take this morning for instance, there’s no doubt that there was a good deal of low cloud about first thing, but quickly during the early morning here (and we lie around 8 km to the north of the airport), the cloud broke up to between 2 and 4 oktas, and now at 12 UTC, there no more than an okta. I realise that the LCBR can only sample one spot above the station, but from this morning’s reports from both stations you would have concluded that it had been mainly cloudy for much of the time, which as far I can tell it wasn’t (fig 2).

Figure 1

And here’s the visible satellite image for 11 UTC (fig 2):

Figure 2

It could be that there was stubborn bit of SC that just refused to budge, or maybe it was the algorithm that they use is skewed to guess (because that’s was it’s in effect doing) higher amounts than the LCBR is sensing. I did notice that the AWS reported hourly sunshine for the last three hours (0.5, 0.1 & 0.4) so it maybe that the cloud increased just as the AWS did an observation perhaps. Of course it makes not a jot of difference in the big scheme of things, if they were fed back into the models then it might, but I think very little from a surface observation (apart from pressure) are used in producing NWP forecasts.

Until this morning I was just plotting AWS without filling in the station circle with the total amount of cloud, but I figure if many of these AWS in the UK can report multiple layers of cloud, then why not report N the total amount of cloud, so with a little bit of code I now guess at N and plot it (fig 3).

Figure 3

Drought, what drought

Figure 1

Admittedly rainfall accumulations this month are completely topsy turvy, and it’s still been a very dry month in many parts of Scotland, but the meteorological drought that affected many parts of the south did come to an abrupt end this week with some heavy rain, as droughts so often do. I’ve tried to wheedle out plotting totals for stations where I had more than 25% of reports missing, having said that there are still a few oddities, Rhyll being one of them, although the 6.4 mm total there is kind of supported by the 13.6 mm at nearby Hawarden.

I’ve just rejigged the code for this application, and it now uses a combination of priorities to get the most accurate result. If there’s a 24 hour 06-06 total that’s great it will use that, and many of the main UK of stations have a 100% reception rate using that value alone. If there isn’t a 24 hour total, like in Ireland and parts of Europe, I add up the available 12 hour totals (06-18 & 18-06). Finally if there are only 6 hourly totals, as in the United States I add these up. The Americans, as far as I can see, don’t report nil rainfall totals as we used to do at one time, so you have to rely on the indicator in the initial block being correct. The whole area of rainfall reporting in SYNOP from different countries is a complete nightmare to program, and I still have to write code that throws back totals to the previous day, but for now this will have to do. If you have any complaints about any of the totals, please feel free to have a go yourself.