Still not convinced

Figure 1 – Courtesy of Met Office

I’m still not convinced by the midnight surface analysis from the Met Office. They have clung to this same ‘configuration’ of fronts (east to west) in all their forecast charts this week:

  1. Warm
  2. Upper cold (in the warm sector)
  3. Cold (returning warm)
  4. Cold (short)
  5. Trough (concave to west of Ireland)
  6. Occlusion
  7. Occlusion (bent back)

By sticking to this analysis they are certainly being consistent, but consistently wrong, because I can see little evidence of the frontal features 2, 4 or 5 in the weather radar at midnight. If they only could publish a synoptic review that explained the various features they have in their analysis and forecast charts and the thinking behind it, we then might be in a better position to understand the rationale behind it, but as far as I am concerned their approach is just far too complicated.

Figure 2 – Courtesy of Met Office

 

It looks like Hurricane Gert will finally breaks the spell

Figure 1

The remains of Hurricane Gert in the coming few days will break the spell that the weather over the UK has been under since the 20th of July. It looks like, for whatever reason, it will halt the zonal westerly flow of the jet stream that’s plagued the country for the last four weeks (fig 2), and bend the upper air pattern to become more meridional (fig 3), and allow the formation of a large blocking anticyclone to form to the west of the British isles. Of course, this all depends on the latest NWP all holding true for the five days or so.

Figure 2 – Courtesy of www.netweather.tv

Figure 3 – Courtesy of www.netweather.tv

There’s still some more unseasonably windy weather to come between now and then, particularly later on Monday, as an extratropical low, spawned by the remains of the tropical air from Gert, deepens and tracks southeastward across Northern Scotland and into the southern North Sea (fig 1). This marks the end of the zonality of the last four weeks, as pressure build strongly behind the low. The last anticyclonic spell across the British Isles was between the 16th and 20th of June. It won’t be a spell of hot weather, because the flow will be northerly at first, it should be dry, and sunny so day time temperatures should be very pleasant, but the nights may be quite cool if not cold.

Looking further ahead, and according to the GFS, the theme seems set to be high pressure across the eastern Atlantic, with a north or northwesterly flow down across the British Isles and much of northwest Europe. Hopefully, this will finally put an end to the mobility of the last month, we shall see!

Tomorrow looks a little complicated

Figure 1 – Courtesy of the Met Office

You could never accuse the Met Office of not being consistent, consistently complicated that is. The chart for midnight tonight (fig 1) is no less complicated than the forecast chart they produced for midnight on Tuesday night this week, or maybe with the aid of NWP they’ve just taken the work of Vilhelm Bjerknes to a whole new level.

Figure 2 – Courtesy of the Met Office

The KISS principle

Figure 1 – Courtesy of the Met Office

According to Wikipedia the acronym KISS means “Keep it simple, stupid” and was a design principle noted by the U.S. Navy in 1960.

The KISS principle states that most systems work best if they are kept simple rather than made complicated; therefore simplicity should be a key goal in design and unnecessary complexity should be avoided. The phrase has been associated with aircraft engineer Kelly Johnson (1910–1990). The term “KISS principle” was in popular use by 1970. Variations on the phrase include “Keep it Simple, Silly”, “keep it short and simple”, “keep it simple and straightforward” and “keep it small and simple”.

I’m usually reminded of the KISS principle when I see a forecast or analysis chart from the Met Office similar to the one above (fig 1), for some reason. You could argue, that a set of forecast charts is a system in its own right, and if it is, then why over complicate it? Met Office charts in the past weren’t always as complicated as they seem to be today, but try as I may, I can’t find any images of fax charts from the past on the internet to illustrate that fact.

2 August 2017 – frontal analysis

Figure 1

The frontal positions look fine on a plotted surface chart for 11 UTC

Figure 2

…but there doesn’t seem much connection with the weather radar (fig 2), or the visible satellite images come to that (fig 3). Much of the heavy rain over central southern England seems to be contained within the warm sector, and there’s little if any precipitation on where I’ve put the occlusion. The satellite image does seem to hint at some kind of wave on the cold front in the SW approaches.

Figure 3

The south coast of Devon and Dorset and the Channel Islands, seem to have taken the lions share of the rain since 06 UTC, with totals of over 24 mm on the hills overlooking the Chesil beach.

 

You don’t often see that on a weather chart

Figure 1 – Courtesy of the Met Office

It might look like they’ve not quite finished drawing the midnight analysis chart, but the Met Office reckon that there was some kind of upper warm sector off the southwest of England (fig 1). The analysis chart is looking more like a nephanalysis than ever, the chief was obviously in quite an artistic mood on the night shift last night, because he also picked out a couple of other squiggly troughs that he’s added to the chart. There’s certainly a lot of upper cloud in that area on the infra-red satellite image for midnight (fig 2), and very likely it’s tied in with the jet stream that’s blowing at over 100 knots from the W’SW at the moment. I can’t see much sign of the feature on the visible imagery today, and certainly little in the way of weather, perhaps it was responsible for the non-appearance of the rather frequent showers that they had forecast for today across the southwest.

Figure 2

Here’s a key to the symbols that the Met Office use in their weather charts below (fig 3).

Figure 3 – Courtesy of the Met Office

Spot the cold front

It’s almost impossible to spot the cold on the 08 UTC weather radar this morning across Ireland (fig 1).

Figure 1

I had a stab at where it was on the plotted SYNOP observations for the same time (fig 2).

Figure 2

I then had a go using the latest visible satellite image, which ends up a little more advanced than I had it using the surface observations (fig 3). The cold front is certainly very weak, and will probably be no more than a few spots of rain when it passes through later this morning.

Figure 3

 

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

Another breezy day across the country

Figure 1

Another breezy day across the country, bright in the south and with an unusual band of cloud in the visible satellite image, its aligned SW-NE and stretches from Cornwall, through Dorset, and into Norfolk. There are some showers associated with it across south Devon, but none elsewhere.

Figure 2

It’s not too different to a similar band that developed on Thursday and stretched from Cornwall NE with a line of heavy showers along it. There’s obviously some kind of geo-thermal hot spot over Cornwall that’s triggered the convection in both events…

Figure 3 – 1445 UTC 8 June 2017

 

Find the cold front

There’s plenty of orographic rainfall evident in the warm sector across the southwest of England and Wales in this morning’s 0815 UTC weather radar image (fig 1), but you would be hard pushed to find a cold front in the Celtic sea between here and SW Ireland on it though. This reminds me of an almost identical situation that occurred earlier this week.

Figure 1

The cold front is well-marked by the cloud in the visible satellite image (fig 2), it’s just not producing any precipitation at the moment.

Figure 2

Figure 3 – Courtesy of the Met Office