930mb Low To Impact UK? How Does This Compare To History? Snow Xmas Day?

Written by on December 20, 2013 in Rest of Europe, United Kingdom & Ireland with 0 Comments

We are of course in a very active pattern right now over Western Europe with a storm producing powerhouse jet stream tearing across the Atlantic while high pressure remains in control over eastern Europe. That setup means the wave of lows will continue with the latest pushing through tonight. This pattern as explained in previous posts is turning colder as we near Christmas and snow should become more prevalent into next week with increasingly colder air sweeping in from Greenland on the backside of each passing low.

We continue to watch the models as they come in for the potential of very stormy weather pushing across Ireland and the UK during Monday. The ECMWF in particular has been printing out some rare numbers when it comes to sea level pressure within the centre of a low which will deepen as it tracks from the US to UK. This is just one of three that will influence the UK atmosphere between Monday and Boxing Day but it stands out. Ahead of the early week storm, colder air will push into the UK, increasing snow chances, mainly over Scotland but don’t be surprised to see snow down across parts of England and Wales as well as Ireland.

Here’s the cold air which settled into the UK Sunday in the wake of tonight’s system.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Snow showers are likely, driven in by a cold Greenland based air flow. Highs Sunday should only reach 3-5C, colder in the breeze.

The closely watched low (for Monday) will be the same system that’s pushing off the US coast later Sunday, transported across the Atlantic by an incredibly strong 210-230 mph jet stream and with the high staying put over Europe, this upper atmospheric setup will help really wind this low up on approach to the northwest UK. Thankfully the high over Europe should steer the centre of circulation away from the UK mainland before impact but it appears to get mercifully close and winds are likely to gust well beyond 100 mph over the Northwest corner of Scotland with stormy conditions across a large part of Ireland and the Northern UK.

Check out the jet stream that’s fuelling this low.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Check out the latest ECMWF sea level pressure chart for Monday.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Notice the pressure gradient isn’t too steep. The steeper the pressure gradient, the stronger the winds blow and we’ve got pressure down to 988 through the English Channel which tends to make me think that we’ll have seen far higher pressure within more recent lows, but winds may turn out to be stronger. I could be wrong. In others words this low could be one of the strongest in a generation but far stronger winds will have occurred from ‘weaker’ storms in more recent times.

As I’ve said countless times now, I remain sceptical that pressure will actually drop to 929 or 930mb off the Outer Hebrides Monday with this storm given the rarity of such a deep low so close to the UK. The model could still be overdone but if not, well it will be a very interesting start to next week. Track also remains uncertain as the centre could end of closer, even clipping Scotland or it could track further away, thus impacts would be lesser.


How Does A 930mb Low Compare To History?

As stated above, in order for the atmosphere to generate incredibly deep lows such as the one the models are suggesting Monday at 930mb, you need a super strong jet stream, warm SST’s and often a high further east over Europe and those are ingredients we shall have but how would the upcoming event, if it occurs, compare to history? Essentially we have seen deeper lows in the Atlantic, even since 1990 and beyond that, pressures have been lower even over the UK landmass.

The most recent extreme low was back in January 1993 when a low ‘bombed’ out to the north of Scotland with an estimated central pressure of 914mb. That storm brought very stormy conditions to the UK, generated by a 270 mph jet stream. Incidentally, according to Wikipedia, that storm was only the 3rd in history to see pressure drop below 930mb. A storm which passed south of Greenland back in 1986 saw pressure get close. Yes, this would be in very rare territory in terms of pressure, even out over the Atlantic never mind over the UK.


According to the Netweather.tv forum, the lowest pressure ever recorded in the UK was apparently during a storm which struck back in January 1884 where a pressure reading of 925.6mb was recorded at Ochertyre, near Crieff, Perthshire on the 26th January 1884. Two years later and that all-time UK pressure record was challenged when a storm with a similar track (just north of Scotland) dropped pressure over Northern Ireland down to 927.1mb at Belfast, nearby Lurgan saw pressure down to 928.9mb and 933mb at Penrith, England.


What’s Next? More Storminess And Backside Cold With Some Snow!

An additional TWO systems follow between next Monday and Friday with surges of colder polar-maritime air entraining into the UK in the wake of these lows. Some could see a WHITE CHRISTMAS!

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Here’s a chilly, blustery, showery Boxing Day with highs struggling to get much past 2-5C across the Northern UK but next storm heading towards the UK quickly.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Next front bringing wind, rain and brief push of milder arrives to the UK later Boxing Day.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

More cold air blows in on the backside of this low. Further wintry showers likely.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Cold air visible on the backside via the 850 temps.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Looking towards New Year and it looks to remain quite stormy but I believe the pattern is transitioning with a shift in the large-scale height field. Modelling is now beginning to show building heights further north while they lower further south. The stormy pattern will continue to draw arctic air south but it’s looking colder and colder in the 2-3 week period which could set us up for an interesting January. Worth paying attention to BUILDING HEIGHTS over the North Atlantic and Greenland with hints of a -NAO and AO around January 1.

Here’s the surface chart by Dec 30.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro




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