Stark weather contrasts across the USA

18 02 2015

While the UK continues to see fairly typical winter weather, over the other side of the Atlantic the US is experiencing some stark contrasts.

While some parts in the west are seeing warm and dry conditions, eastern areas are seeing very cold weather.

This week will see a continuation of warmer-than-average conditions in western parts of the USA, with little or no rainfall in the forecast.

Map showing air temperatures across the US, with white (-24C) and blue (below 0C) showing cold air and yellows and oranges showing warm air. From the Met Office's Global Model for 1200HRS GMT on 20 February 2015

Map showing air temperatures across the US, with white (-24C) and blue (below 0C) showing cold air and yellows and oranges showing warm air. From the Met Office’s Global Model for 1200HRS GMT on 20 February 2015

Despite some welcome rainfall at the start of February, California remains in drought, with a large swathe in exceptional drought – which is the highest category that the US Drought Monitor report.

In San Francisco, no rain fell at the downtown observation station or the airport during the whole of January 2015. This is the first January without rainfall since records began in 1850. Normally January is the wettest month of the year, with an average 119mm.

The dry conditions have also resulted in the Sierra Nevada snow pack being at less than 50% of where it should be as we head towards the end of winter.

Meanwhile, the very cold spell of weather is expected to continue across a large part of eastern and northeastern USA, with air originating from the Arctic keeping things icy.

There will be some snow at times, although not as significant as some recent events, though localised heavy ‘lake effect’ snow is likely this week off the Great Lakes.

However, the most noteworthy element will be the extreme cold. Another arctic front will arrive across the East Coast, bringing exceptionally cold conditions.

Places from the Carolinas to the Mid-Atlantic may see some of the coldest weather since the mid-1990s, with numerous record low temperatures expected.

In fact this cold air is expected to reach as far south as Florida, with even the Caribbean expecting well below average temperatures throughout the rest of this week.





Winter storm to hit the U.S.A. and Canada

26 01 2015

While we’re looking at our own wintry weather later this week, a separate weather system is about to bring some very disruptive winter weather on the other side of the Atlantic.

A low pressure system, which is due to bring the severe conditions to the U.S.A., is currently developing over the southeastern United States. It is expected to  deepen very quickly later today. All the ingredients are there: firstly, as it starts to move out over the Atlantic, it taps into the energy provided by warm waters of the Gulf Stream. Secondly, its position relative to the strong jet stream is just right to ensure a rapid development. And thirdly, as it develops, it pulls intensely cold air from Canada into its circulation, which turns much of the rain to snow.

So by Tuesday morning we are expecting an intense depression to be centred off coastal Maine, bringing a combination of hazards. In some areas, especially towards the south and near coasts, heavy rainfall could be an issue but for most places it’s going to be the combination of heavy snow and severe gales which lead to truly atrocious conditions – indeed the word “historic” figures in quite a lot of the American press today.

Blizzards are likely to affect many of the northeastern States from Pennsylvania (Philadelphia) up to Maine and crossing over the border into Canada, with major disruption expected for some communities, including potentially larger cities such as New York and Boston.

As well as posing a major hazard for the road network, impacts on air travel are already starting and are only likely to increase, with knock-on effects for areas quite remote from the weather, including some of the European hubs.

The worst of this particular severe weather should be over by Wednesday but the rest of the week stays very cold in the US, with the risk of renewed snowfall later.





Cold Weather for UK

26 01 2015

Cold weather is again on the way for the UK.  Later this week colder conditions will spread south, bringing a mixture of sunny spells and snow showers from Wednesday onwards.  Temperatures for many will be below normal for the time of year and the wind chill, due to strong winds, will make it feel very cold.

Snow showers are expected to affect parts of the northern half of the UK on Wednesday and Thursday and the Met Office has issued a yellow severe weather warning  for the potential impacts and this will be updated as required this week.  Don’t be surprised to see some snow showers across southern areas too, but these are not currently expected to be heavy enough for the snow to settle.  The northerly winds and cold weather are likely to continue into the weekend.

Is it due to the polar vortex?

There have been reports the cold weather is due to a “displaced polar vortex”.  The large-scale low pressure area in the stratosphere, known as the Polar Vortex, is displaced towards Russia and looks likely to stay that way over the next few days.  However this is not directly responsible for changes in the weather during the coming days. The cold northerly winds we are expecting at the end of the week are not unusual for winter.

What is the jet stream doing?

The jet stream is forecast to move south of the UK from Wednesday onwards. This means we will be on the ‘cold side’ of the jet and cold air from the poles/Arctic will work its way southwards to affect the UK.

Jet Stream forecast map for Saturday showing the track to the south of the UK.

Jet Stream forecast map for Saturday showing the track to the south of the UK.

Is the snowstorm in the USA coming our way?

The snowstorm affecting the east coast of the USA is not coming towards the UK.  It is expected to move away from the States, crossing the Atlantic to the south of the UK to bring heavy rain to Spain and Portugal at the end of the week.

 

 

 





Why are we now seeing colder weather across the UK?

16 01 2015

Over recent weeks, we have spoken about the very strong jet stream across the Atlantic, driving areas of intense low pressure towards the UK. This has bought spells of very wet, windy but relatively mild conditions to the country.

As many of you would have noticed, although the wind and heavy rain has eased, there is now a colder feel to the weather, both by day and night. But what has caused this change in the weather?

Once again the change is down to the jet stream. It has weakened and its track has moved further south, keeping the deep low pressure systems away from our shores. However, now the UK is to the north of the jet stream we are on its cold side, and this has allowed colder weather to feed in across the country.

Current jet stream

Current jet stream across the Atlantic

So what does this mean for us?

As we look ahead into the weekend and next week, the cold weather looks likely to continue. Daytime temperatures will be near or below average and there will be some frosty nights, as temperatures fall below freezing in many areas. We’ll see some sunny spells around and there will also be showers or longer spells of precipitation in places, giving a mixture of rain, hail, sleet or snow, which may settle in some areas.

Because of the threat of wintry weather over the coming days, we encourage everyone to keep up to date with the latest forecasts and national severe weather warnings and to stay weather aware this winter by following the Met Office on Twitter, Facebook, Google+ and YouTube for the latest weather information. You can find information about how to prepare for every aspect of the winter season at Get Ready for Winter.

As we head towards the latter part of the month, we can see some indications that milder weather may return, but there is considerable uncertainty about this so far in advance.





Strongest winds overnight 14 – 15 January 2015

15 01 2015

As expected, a powerful low pressure system affected the UK yesterday evening and overnight bringing gales and heavy rain to many areas.

The low pressure system will continue to affect the UK today, bringing sunny spells and blustery, heavy showers with the chance of thunderstorms and snow over high ground. Severe gales are again expected around western and northwestern coasts, with the strongest winds likely over Northern Ireland and southwest Scotland, extending to northern Scotland later. You can see detail on this on our forecast and warnings pages.

Below are some of the strongest gust speeds recorded at Met Office observing sites between 7pm yesterday and 7am today.

Strongest gusts 7 pm 14 January 2015 – 7 am 15 January 2015
Date / time Site Max Gusts (mph)
15/01/2015 00:00 CAPEL CURIG GWYNEDD 96
15/01/2015 03:00 WIGHT: NEEDLES OLD BATTERY ISLE OF WIGHT 93
15/01/2015 00:00 ABERDARON GWYNEDD 83
14/01/2015 23:00 MUMBLES HEAD WEST GLAMORGAN 81
15/01/2015 02:00 BERRY HEAD DEVON 77
15/01/2015 02:00 AVONMOUTH AVON 76
15/01/2015 03:00 ISLE OF PORTLAND DORSET 75
14/01/2015 23:00 CULDROSE CORNWALL 73
15/01/2015 04:00 TIREE ARGYLL 73
15/01/2015 01:00 LOFTUS CLEVELAND 70
15/01/2015 01:00 PLYMOUTH, MOUNTBATTEN DEVON 70
14/01/2015 23:00 SCILLY: ST MARYS AIRPORT ISLES OF SCILLY 70
15/01/2015 04:00 SOLENT HAMPSHIRE 69
15/01/2015 01:00 LAKE VYRNWY POWYS 69
14/01/2015 23:00 NORTH WYKE DEVON 68
14/01/2015 23:00 SENNYBRIDGE POWYS 68
15/01/2015 06:00 ISLAY: PORT ELLEN ARGYLL 68
15/01/2015 00:00 PEMBREY SANDS DYFED 68
14/01/2015 21:00 DRUMALBIN LANARKSHIRE 67
15/01/2015 07:00 EDINBURGH, BLACKFORD HILL MIDLOTHIAN 67

Below are some of the highest rainfall totals recorded at Met Office observing sites between 7pm yesterday and 7am today.

Highest rainfall 7pm 14 January to 7am 15 January 2015
Site Rain (mm)
ACHNAGART ROSS & CROMARTY 40.8
TYNDRUM PERTHSHIRE 39.0
TREDEGAR, BRYN BACH PARK GWENT 35.8
KESWICK CUMBRIA 35.0
THREAVE KIRKCUDBRIGHTSHIRE 31.8
LIBANUS POWYS 31.8
SHAP CUMBRIA 31.6
ESKDALEMUIR DUMFRIESSHIRE 28.2
SKYE: LUSA WESTERN ISLES 27.8
USK MONMOUTHSHIRE 27.4
OKEHAMPTON, EAST OKEMENT FARM DEVON 27.1
STRATHALLAN AIRFIELD PERTHSHIRE 25.6
GOUDHURST KENT 25.4
BLENCATHRA CUMBRIA 25.2
TULLOCH BRIDGE INVERNESS-SHIRE 24.2
WHITECHURCH DYFED 24.0
NORTH WYKE DEVON 23.6
CAPEL CURIG GWYNEDD 23.4
MIDDLE WALLOP HAMPSHIRE 23.4
CAMBORNE CORNWALL 23.0

You can share the weather you have experienced through the ‘Weather Impacts’ section of WOW

The stormy weather we have seen over the last couple of weeks is now coming to an end and conditions over the weekend and into next week look calmer but colder with frosts at night and wintry mix of showers.





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.





White Christmas?

26 12 2014

Most people woke up yesterday to a green Christmas rather than a white one.

Snow was recorded at our observation site at Lerwick and some sleet was also recorded at Wick between 11am and 12pm, however for the rest of the UK it remained dry and clear throughout Christmas Day.

To find out what the forecast for your area is for the next five days visit our website: metoffice.gov.uk





Dreaming of a White Christmas?

17 12 2014
Summit of An Socach, the Cairngorms, Scotland.

Summit of An Socach, the Cairngorms, Scotland.

UPDATED FRIDAY 19th DECEMBER

With less than a week to go before Christmas Day, we are going to look at the likelihood of a white Christmas – will we be waking up to a picturesque covering of snow on the big day?

So far, December has seen some large fluctuations in the weather, with spells of wetter, milder conditions interspersed with colder, sunnier conditions with temperatures closer to average.

Through today and tomorrow, we will see plenty of fine weather across the UK, with some crisp winter sunshine. There will be some showers across the north and west of the country, that are likely to be wintry over higher ground.

A return to largely mild weather is expected from Sunday (21st), with cloudy, damp conditions for many parts, and there is the threat of some heavy rain in places.

As we head into Christmas Eve and Christmas Day, there is still a fair amount of uncertainty – which is as you’d expect this far ahead. The strongest signal currently shown in the computer models is for the colder, showery weather to return across Britain, with showers most frequent across the north and east. But will we see any snow?

At this point, the most likely areas that will see some of the white stuff will be across higher ground in the north, with rain at lower levels. Temperatures will be fairly close to average and there will be some frosty nights under clear skies.

It is important to note, however, that there’s still a small chance we could see different weather for Christmas Day. So with just under a week to go until the big day, it looks most likely that the majority of us won’t be seeing a white Christmas. Because of the uncertainty of long range forecasts, however, we recommend staying up-to-date with our website for the latest information on our forecasts and warnings.





Untangling the global drivers of UK winter weather

25 11 2014

As we head towards the start of winter, which starts for meteorologists on 1 December, there’s always a great deal of media and public speculation about what weather we might have in store.

To answer that question, we need to look beyond the UK. The worlds’ weather is interconnected, and there are certain large scale global drivers which we know have influences on UK weather at this time of year – so what are these doing at the moment?

El Niño, which sees unusually warm sea surface temperatures across the tropical Pacific and can increase the risk of cold winter conditions in the UK, has been much discussed after initial signs of development earlier this year.

Its progress has been slow, however, and while there remains a good chance of a weak event by the end of the year it is also possible that El Niño conditions will remain neutral. In any case, this factor is not expected to be strong enough to exert much influence on weather patterns in Europe during the next three months.

The North Atlantic Oscillation (NAO) describes differences in the usual pressure patterns over the North Atlantic – with positive and negative phases.

A positive phase is thought more likely than a negative one on average over the next three months. This is characterised by enhancement of the westerly winds across the Atlantic which, during winter, brings above-average temperatures and rainfall to Western Europe.

As we head later into winter, confidence about the heightened likelihood of positive NAO reduces – suggesting chances of drier and colder conditions return closer to normal.

The Quasi-Biennial Oscillation (QBO) sees high level (stratospheric) winds over the equator change from westerly to easterly phases – and it’s currently in the latter of the two.

In winter months this can lead to a greater incidence of high pressure blocking patterns over the northern hemisphere, which would increase the probability of colder and drier weather across Europe. Essentially this is providing an opposite signal to the NAO.

There are other factors to consider too. For example, Arctic sea ice extent is slightly below average but as yet it is not clear whether this might have an impact on weather patterns in the UK.

No single one of these drivers will determine the UK’s winter on its own – instead they all interact together to govern the weather trends we can expect over the coming months.

Disentangling these different influences remains a challenging area of science which the Met Office is improving all the time, but detailed and highly certain UK outlooks are not possible over these timescales.

The Met Office’s long-range outlooks give probabilities based on scenarios of being considerably wetter or drier, colder or milder than usual.

Currently the outlook for December 2014 to February 2015 suggests that milder and wetter than average winter conditions are slightly more likely than other outcomes. However, compared to day-to-day weather forecasts, the probabilities are much more finely balanced – for example, the outlook gives a 1 in 4 chance of the mildest scenario and a 1 in 10 chance of the coldest scenario. These numbers suggest it would be a mistake to interpret the outlook for a very mild outcome as ‘highly likely’; likewise very cold conditions cannot be ruled out.

The outlook gives similar probabilities for precipitation (rain, hail, sleet and snow), with the chances of the wettest scenario being 1 in 4 and the chances of the driest around 1 in 10.

These three month outlooks cover a whole three month period, taking into account both day and night, as well as the whole of the UK. This means that even in the event of, say, an overall mild winter we could still see spells of cold or very cold weather.

With this in mind, what exactly we’ll see for the winter ahead remains uncertain. In terms of strong winds, heavy rainfall, cold snaps or even snow, while longer-range outlooks can give us general tendencies, the details can only be predicted by our day-to-day weather forecasts.

The Met Office’s accuracy over all timescales is world-leading, however, so you can trust that we’ll keep everyone up-to-date with all the latest information on the weather whatever the winter has in store.





US snowfall and will it impact the UK?

20 11 2014

Parts of the US and Canada are seeing particularly cold weather and heavy snowfall at the moment.

Chart showing the position of the jet stream over North America as at 00:01 on 20 November.

Chart showing the position of the jet stream over North America as at 00:01 on 20 November.

A southward buckle in the jet stream has seen cold polar air flow south to north eastern parts of North America.

In the Buffalo region of New York state, temperatures have fallen as low as -15C and 4-5 ft (about 1.5 metres) of snow has fallen – enhanced by what’s known as the ‘lake effect’. Another 2-4 ft (about 1 metre) is expected through today.

The snowfall is set to ease on Friday with much milder conditions through the weekend giving a rapid and significant thaw – which could bring a risk of flooding.

This risk could increase through the start of next week when some very heavy rain is expected across the area.

What is lake effect 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

This is an effect which applies to areas around large lakes like those seen in the northern US – Lake Superior has an area of more than 30,000 sq miles.

When cold air moves across the relatively warm waters of the lake, air rises due to convection which creates clouds and heavy showers. In cold conditions, the moisture in the clouds will fall as heavy snow.

As Buffalo as it the eastern tip of Lake Erie it has been particularly susceptible to this effect during the recent weather.

While we don’t have any lakes big enough for this effect in the UK, we can occasionally see a similar scenario when we get easterly winds in the winter.

Cold air from the continent can be warmed by the relatively warm North Sea as it moves across the water, bringing snow showers to eastern parts of the UK. However, there’s no sign of this in the immediate future for the UK.

Will the US weather affect the UK?

Many people believe that there’s a rule of thumb that weather in the US will arrive in the UK a few days later – but that’s by no means always the case.

In this instance, there’s high confidence that the cold snowy weather will stay on the western side of the Atlantic.

Also, in past winters similar weather situations in the US have strengthened the jet stream and increased the risk of storms across our shores. Again, in this instance, this isn’t expected at the moment.

What we do expect to see is further changeable weather over the coming few days.








Follow

Get every new post delivered to your Inbox.

Join 6,695 other followers

%d bloggers like this: