Extreme global weather

5 01 2015

The UK may be experiencing what looks likely to be a milder than average winter but other parts of the globe are struggling against some extreme weather conditions.

Middle East

Heavy snow is expected to affect large parts of Turkey, Georgia, Armenia and SW Russia early this week. As the cold conditions spread east later in the week, strong to gale force winds and heavy snow are expected across more eastern parts of the Mediterranean.

This will lead to the Middle East seeing temperatures 10 or 15C below normal for the time of year. For example, overnight temperatures could fall to -10C in Syria by mid week, with daytime temperatures struggling to rise above freezing.

This is likely to have a significant impact on refugees and the humanitarian aid agencies in Turkey, Jordan, Lebanon, Syria and Iraq, with problems enhanced by the threat of frozen water supplies. Although overnight temperatures of -5 to -10C are expected, these values may well fall much lower if there is snow cover.

North America and Canada

Large areas of the USA and Canada are experiencing very cold conditions, with the threat of heavy snowfall across some parts over the coming days.

The eastward movement of a cold front over the weekend has dragged very cold air down from the arctic. Temperatures across parts of Canada have fallen to -30C, and widely across North America, daytime temperatures have ranged between 0 and -6C, with the bitterly cold conditions enhanced by strong winds.

As well as the low temperatures, some parts have seen heavy snowfall, such as the Pacific Northwest and areas to the east of the Great Lakes.

Further heavy snowfall is expected this week, particularly down-wind of the Great Lakes due to “lake effect” snow. This is caused when cold flows across relatively warm bodies of water such as the Great Lakes. The air rises in strong convective currents which creates clouds and heavy precipitation. In these very cold conditions, the moisture in the clouds will fall as snow.

Lake Superior (top left) and Michigan (centre) can be seen generating 'lake effect' snow. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

Lake Superior (top left) and Michigan (centre) can be seen generating ‘lake effect’ snow. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

The significance of this is highlighted by snowfall projections over the coming days. Lake Ontario, the easternmost of the Great Lakes with a surface area of 18,960 km2, is expected to bring narrow bands of heavy snow to areas east of the lake. These narrow bands could generate 2-3 feet of fresh snow over the next 24-36 hours causing significant disruption.

Whilst the freezing temperatures are expected to last throughout the week, temperatures may recover slightly through the weekend.

Will the US weather affect the UK?

The cold conditions will have the effect of strengthening the jet stream, which will move close to the UK over the coming days. This will bring unsettled conditions through this week, with spells of wet and windy weather, particularly across northwestern parts of the country. However, it will be mild, particularly towards the end of the working week when daytime temperatures could reach around 14C.

There is the potential for the remnants of this cold air to move eastwards across the Atlantic to affect the UK over the weekend. However, the airmass will become heavily modified by the Gulf Stream, and there is little risk of the extreme temperatures over North America affecting the UK.





What’s in store this winter? Responding to the headlines

12 11 2012

It seems that it is the time of year for colourful headlines about an impending big freeze. We had them at this time last year, which prompted our Chief Executive to write an opinion piece in The Times.

Now we have very similar stories again, with the front page of the Daily Express declaring ‘Coldest winter freeze on way’ and warning that temperatures are set to plunge as low as -15C.

There have been other stories elsewhere along similar lines, with some saying that the Met Office is briefing the Government about a cold winter ahead.

So what are the facts behind the headlines?

Some of the stories have taken a cue from parts of our current 30-day forecast. Today’s forecast for 26 November to 10 December reads as follows:

As is usual, there are uncertainties in the forecast for this period, but there are signs that the changeable conditions will continue through the start of this forecast period. There is also a signal for temperatures to be close to or just below the seasonal average. Into December, although there are no strong indications that any particular weather type is going to dominate, on balance colder, drier conditions than at present are favoured, rather than milder, wetter weather, especially across the southern half of the UK.

However, perhaps what the newspapers have failed to pick up on and report to their readers is that there is still a great deal of uncertainty about exactly what weather we will see – as there often is when looking at timescales of over five days ahead.

The science does not exist to make detailed forecasts for temperature and snowfall for the end of this month, let alone for December or even the winter as a whole.

With regards to us ‘briefing the Government on a cold winter’, this is related to our three monthly outlook for contingency planners.

This is a complex product designed to help contingency planners making long-term strategic decisions based on risk exposure. However, it’s not useful for most other people as it doesn’t give one forecast for what’s ahead – rather it outlines potential scenarios and their associated probabilities.

It’s worth noting that while contingency planners use our three month outlook to inform long-term decisions, they make their operational decisions on our five day forecasts and warnings.

These will always provide the best possible guidance on any periods of cold weather, frost or the likelihood of snow, giving detailed local information across the UK.

Ultimately, we’re heading into winter and we expect winter to be colder than the rest of the year – but it’s too early to say exactly what temperatures we can expect or where and when we might see snow.








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