GFS maintains wintry theme

Figure 1 – Courtesy of OGIMET

The latest run of the GFS model maintains the cold cyclonic northwesterly theme across the British Isles for the next week or so, with a succession of vigorous lows crossing the north of Scotland en route for the Baltic. As each low tracks across it allows a milder WNW flow of for a short time, before cold air re-establishes itself in a NW or N surge. All this of course comes with a government health message that all this NWP stuff could all be science fiction and can damage your health. I know I’ve said this before but these forecast charts are very reminiscent of November 1973 to me.

Later tonight and into the early hours of Friday could get interesting over southern England, with a low tracking E’NE along the English Channel  (fig 2), which could bring a spell of wet snow to the highest ground (>200 M). Yes I know, ‘high ground’ is not usually synonymous with ‘southern England’, but in this blogging game sometimes you have to clutch at straws to eek out a possible story.

Figure 2 – Courtesy of OGIMET

Earlier this week the GFS did suggest that a deepening low would threaten a more widespread area of snow across the north of England and Wales. That threat has now all but vanished, as that low is now forecast to track further south across northern France without much in the way of deepening (fig 3).

Figure 3 – Courtesy of OGIMET

Addendum

Might have been hasty saying that there was a risk of wet snow on high ground in the south overnight – the Met Office don’t see any likelihood of that happening (fig 4) – that’s what you get I suppose when you let an old observer like me have a go at forecasting!

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Figure 4 – Courtesy of the Met Office

Snowy Saturday revisited

After my blog about the possibility of a snowy Saturday, I was just looking for some extra detail in the GFS model for Saturday morning when I remembered the excellent wxcharts.eu website. The purple in the 06 UTC map indicates a large area of snow falling over northern England and Wales, and the meteogram for Eggleston in County Durham is forecasting 9 cm of snow.

Snowy Saturday…

During tomorrow it’s certainly set to become very windy and wet over large parts of the British Isles, but I have my eye set on developments during Friday and into Saturday, which if they pan out as the GFS suggests, might well bring a spell of snow to central and eastern counties before the deepening low exits into the North Sea during Saturday morning. Gradients around the low tighten considerably, even if a lot of that gradient can be discounted because of cyclonic curvature (fig 1).

Surface UK [T+108] 12 UTC on Sat, 25 November 2017

Figure 1 – Courtesy of OGIMET

The only thing I can get out of the Met Office is this T+120 image (PPVO89.tif) for the same time (fig 2). The Met Office model is much faster with this feature, and the low ends up being much more elongated and +5 hPa shallower than in the GFS.

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Figure 2 – Courtesy of the Met Office

Peter IV and the week ahead

Figure 1

Low Peter IV has brought strong winds across Denmark and snow to parts of southern Sweden overnight (fig 1). It’s the first time that I’ve seen the Berlin Institute of Meteorology have multiple versions of the same vortex (fig 2), whoever sponsored Peter hit the jackpot with that name.

Figure 2 – Courtesy of the BIM & Deutscher Wetterdienst

We seem to be a bit left out of it when it comes to extratropical lows at the moment, with developments taking place just before they get here in mid-Atlantic, or just as they leave to the east of the meridian. This week things look set to change, across the British Isles because it’s looking decidedly mobile and cyclonic in the coming week according to the latest run of the GFS model (fig 3).  It looks like it could also be quite wintry in the north of Scotland if they manages to keep in the cold air, and there’s a touch of northerly in the chart for next Sunday to keep my idea of a weekly cycle in northerlies going!

Figure 3 – Courtesy of OGIMET

Memories of late November 1973

Looking at the latest long-range forecast charts from the GFS for T+192 (fig 1) and T+336 (fig 2) reminds me of the last few days of November 1973, which saw an early cold spell from a similar outbreak of northerly winds (fig 3). I had just left the Met Office (for the first time), and had started working as a trainee bank clerk for the Trustees Savings Bank at a new branch they had just opened in Dronfield, northeast Derbyshire, and can still remember the snow.

Figure 1 – 8 day forecast – courtesy of www.netweather.tv

Figure 2 – 14 day forecast – courtesy of www.netweather.tv

Figure 3

It also extends the run of northerly outbreaks which started on the 29th of October with a period of approximately 7 days, that’s of course if the GFS forecasts come to pass, although the northerlies now seem to have taken a liking to Thursday rather than Sunday!

  • Sunday 29th October [N]
  • Sunday 5th November [N/NW]
  • Sunday 12th November [N]
  • Sunday 19th November [NW] although the main thrust is east of the meridian at T+84
  • Thursday 23rd November [CN] 7 day cycle slipped a bit!
  • Thursday 30th November [N]

Now the acid test – what do the Met Office think of this northerly theme? Well to be perfectly honest not a lot, if you look at their latest extended forecast out to the end of November (fig 4). This outlook is couched with so many vague and bland phrases I can’t see what practical use it has for most people.

Figure 4 – Courtesy of the Met Office

A cycle of northerly Sundays

Figure 1

If you examine the forecast chart for tomorrow and next Sunday, you might be forgiven for thinking there is something of a weekly cycle going on here (fig 1), both days are northerly, in fact next Sunday is a cyclonic northerly worthy of any cold spell in winter worth it’s salt. And if you look back over the last two weeks (fig 2), you’ll notice that both the 29th of October and the 5th of November had northerly tendencies too.

Figure 2 – Courtesy of the Met Office

Of course it’s all just chance, but just out of scientific curiosity, I’ll be keeping a close eye on the weather pattern for next Sunday, just to see if we can manage four successive northerly Sunday’s.

  • 29th October [N]
  • 5th November [N/NW]
  • 12th November [N] (forecast T+24 but odds on)
  • 19th November [CN] (forecast T+192)

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.

Something for the weekend

Figure 1

The latest run of the GFS model (fig 1) has sided with the UKMO model (fig 2) and decided not intensify the low that runs across Central England on Saturday. It still looks a thoroughly wet day though, especially across the west of Wales and the southwest of England though, with a westerly gale along the English Channel, if this latest forecast is correct (fig 1). Sunday looks a windy day with strong northwesterly winds particularly down the east coast of England and Scotland, with wintry showers down to quite low levels in the northeast of Scotland I would fancy.

Figure 2 – Courtesy of the Met Office.

I wonder if the enhanced troughing in the GFS solution will be justified, the Met Office have little troughing on the cold front in their solution.

One to keep a close eye on…

Figure 1 – Courtesy of OGIMET

The latest GFS model run is looking very windy across southern areas early on Saturday. The GFS model has been running a shallow low across northern areas for the last five days or so but never made a lot of it. The latest midnight run though has deepened the feature more than those previous runs, and I should imagine it’s now a candidate to be added to the “one we will be keeping a close eye on” category.

Remember, remember the 5th of November, gunpowder treason and the 528 line

Figure 1 – Courtesy of OGIMET

The cold trough that’s extending southeastward across the British Isles over the weekend might give us another reason to remember, remember the 5th of November in 2017 (fig 1). 1000-500 hPa partial thicknesses are forecast to be less than 528 dm for midnight on the 5th over most of the British Isles, which although not that unusual, will come as a bit of a shock after the very mild Autumn that we have been enjoying until now.