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.





Wet wet wet this winter?

17 11 2014

Every year there’s a huge amount of media speculation about what weather we’ll see during winter, and this year is no different.

After a recent slew of stories claiming we’re in for the coldest winter on record (which weren’t based on information from the Met Office), there are now stories claiming we’re forecasting the wettest winter in 30 years.

That’s not the case and appears to be a misunderstanding of our three-month outlook for contingency planners.

First of all, last winter was the wettest in our digital records dating back to 1910, so if we were to have a wetter winter than that it would be the wettest in over a century – not just for 30 years.

But that’s not what our contingency planners outlook says. As we’ve pointed out here many times in the past, this product isn’t like our short range forecasts – it doesn’t tell you definitively what the weather is going to be and that’s why it’s not really that useful for the public.

What it does do is make an assessment of the likelihood of seeing wetter or drier than average, and milder or colder than average conditions for the whole of the UK for the whole three month period.

Recent outlooks have been signalling increased risk of milder and wetter conditions for the past couple of months, and indeed that’s what we have seen through October and the start of November. So the most likely predicted outcome is what actually happened for these months – but that won’t always be the case.

While the recent three month outlooks also highlighted the risk of more unsettled than average conditions, this does not give specific details or tell us whether any records will be broken.

For detailed weather forecasts, our five-day forecasts and weather outlooks to 30-days give the best and most up-to-date advice.





Top UK wind speeds as Gonzalo’s remnants felt

21 10 2014

TABLE UPDATED AT 11:50AM

Many parts of the UK are seeing strong winds today as the remnants of ex-tropical storm Gonzalo pass over the north of the country.

Below are the top ten strongest gusts of wind we have recorded so far today. We’ll be updating this through the day with the latest information.

Time Station Area Elevation Max gust (MPH)
0600AM WIGHT: NEEDLES OLD BATTERY ISLE OF WIGHT 80 70
0300AM ABERDARON GWYNEDD 95 70
1000AM ST BEES HEAD CUMBRIA 124 69
0400AM MUMBLES HEAD WEST GLAMORGAN 43 67
1000AM ISLAY: PORT ELLEN ARGYLL 17 66
0300AM CAPEL CURIG GWYNEDD 216 66
1000AM EMLEY MOOR WEST YORKS 267 66
0400AM LAKE VYRNWY POWYS 360 63
0600AM SALSBURGH LANARKSHIRE 277 63
0400AM MACHRIHANISH ARGYLL 10 62

The Met Office has issued a severe weather warning for the winds today – you can see the details of this on our warnings pages.

Winds are expected to be strong through much of the day, and people are advised that there may be some traffic and travel disruption.

Rainfall

Ex-Gonzalo also brought a band of heavy rain across the UK earlier this morning, bringing some notable rainfall totals in places.

The table below shows the top ten UK rainfall totals recorded between 1am and 8am this morning.

Station Area Total (mm)
CLUANIE INN NO 3 ROSS & CROMARTY 38.0
CAPEL CURIG NO 3 GWYNEDD 34.4
ACHNAGART ROSS & CROMARTY 30.6
TYNDRUM NO 3 PERTHSHIRE 27.6
KINLOCHEWE ROSS & CROMARTY 25.8
RESALLACH SUTHERLAND 23.4
SHAP CUMBRIA 21.8
LOCH GLASCARNOCH ROSS & CROMARTY 21.8
MORECAMBE NO 2 LANCASHIRE 20.2
LEVENS HALL CUMBRIA 20.0




Windy weather on the way

19 10 2014

As forecast, Hurricane Gonzalo made landfall over Bermuda on Friday with rain and winds of up to 110 mph causing power cuts, flooding, felled trees and damaged buildings.

The storm has continued in its journey since then, and passed the Canadian island of Newfoundland during Sunday morning.

The remnants of this tropical storm are being caught up in the westerly flow across the Atlantic and will be drawn towards the UK, crossing the country on Monday night and early Tuesday.

By the time Gonzalo crosses the Atlantic, however, it will be a very different system to the hurricane that affected Bermuda.

It will undergo what meteorologists call ‘extra-tropical transition’, which means it loses the warm-core typical of a tropical cyclone and becomes a much more standard Atlantic low pressure system – like we regularly see around the UK at this time of year.

As such the low pressure is expected to produce wind strengths and rainfall amounts which are not unusual over the British Isles during the autumn and winter months.

Whilst there is good confidence that this system will cross the UK on Monday night and Tuesday morning, there is still something to play for in pinning down the exact location of the strongest winds.

The Met Office has issued a weather warning for wind for much of the UK for Tuesday, particularly since the strongest winds look to coincide with rush hour for some locations, leading to possible travel disruption.

You  can see details of what to expect in the warnings page on our website. You can stay up to date with all the latest for the windy weather and what to expect for the rest of the week with our forecasts and warnings.





How will activity in the Atlantic affect UK weather?

15 10 2014

There’s lots of activity going on in the Atlantic at the moment – but how will it affect the UK?

Currently there is a big area of low pressure covering a large part of the Atlantic between North America and the UK.

While it is fairly large in its size, it’s not particularly intense, powerful or unusual.

Forecast chart for 1pm on Wednesday 15 October 2014, showing large area of low pressure in the Atlantic.

Forecast chart for 1pm BST on Wednesday 15 October 2014, showing a large area of low pressure in the Atlantic.

This means that – while it may look impressive on the charts – it’s not going to bring anything out of the ordinary for the UK over the next few days.

It will, however, be generally unsettled across many parts through Friday and the weekend, as the low pressure drives a weather system across the UK.

This will bring strong winds, with gusts of up to 50mph in the most exposed parts of the west, and rain in places. However, some parts will enjoy periods of drier and brighter weather.

Tied up in the general Atlantic circulation is an area of warm air which was originally part of tropical storm Fay.

This will bring very mild air across parts of the country, with daytime temperatures possibly reaching around 20C across southeastern areas by Saturday, well above the October average for the region of 15C.

While it will be very mild, it may not feel particularly warm given the windy and often wet conditions. The unsettled weather is expected to be fairly standard for the middle part of October.

Forecast track of Gonzalo from the US National Hurricane Center.

Over the other side of the Atlantic near Bermuda, Hurricane Gonzalo is currently expected to track north and then east across the ocean over the coming days.

There is large uncertainty about the potential track of this storm, with some models suggesting that the remnants could move across the UK whilst others show them staying away from our shores.

If the ex-tropical storm does move across the country, some parts could see gales and heavy rain, but currently extreme conditions look unlikely.

As ever, we’ll keep a close eye on developments over the next few days and keep everyone up to date if it looks like there is any sign of severe weather heading for the UK.





Arctic sea ice reaches minimum extent for 2014

23 09 2014

Arctic sea ice appears to have reached its minimum for 2014, according to preliminary figures from the National Snow and Ice Data Centre (NSIDC) in the US.

The extent dropped to 5.02 million square kilometres (1.94 million square miles) on 17 September, making it the 6th lowest extent observed since satellite observations became available in 1979.

This year’s minimum is above the 2012 record low extent of 3.41 million square kilometres (1.32 million square miles), but still below the long term (1981-2010) average of 6.22 million square kilometres (2.4 million square miles).

Graph shows Arctic sea ice extent at 17 September 2014 along with daily ice extent for four previous years. Source: National Snow and Ice Data Centre

Graph shows Arctic sea ice extent at 17 September 2014 along with daily ice extent for four previous years. Source: National Snow and Ice Data Center

There is a lot of year to year variability in the Arctic ice extent, as it depends on the Arctic weather.

As the ice cover thins we expect the variability in cover to increase as larger regions of the Arctic become vulnerable to being blown by the wind or melting away completely over the summer.

Overall, the long term trend in ice cover remains downward, as illustrated by the below plot of August ice extents.

Earlier this month in the Laptev Sea, a small portion of the ice edge was within 5 degrees of the North Pole – this is the most northerly position that the ice edge has reached in this region since satellite observations began.

This year the Northern Sea Route has opened to shipping for the seventh year in succession, but the North-West Passage through the Canadian Archipelago remains blocked by ice – emphasising how Arctic summer sea-ice cover depends on the prevailing weather patterns.

The exact date on which the minimum ice extent occurs varies from year to year, depending on the weather conditions along the ice edge. The 1981-2010 average is 15th September, and the latest date so far in the records has been 23rd September.

Graph shows August Arctic sea ice extent for each year since records began as a % difference to the long-term (1981-2010) average for the month. Source: National Snow and Ice Data Center

Graph shows August Arctic sea ice extent for each year since records began as a % difference to the long-term (1981-2010) average for the month. Source: National Snow and Ice Data Center

Future of Arctic sea ice

Based on projections from current climate models, a plausible date for the earliest ice free (defined as extent less than 1 million square kilometres) summer in the Arctic would be 2025-2030.

Work continues to improve our understanding of the processes driving the ice decline and how they are represented in climate models. This may lead to revised projections of the date for an ice-free summer in the Arctic.

Impacts on UK weather

Changes in the Arctic ice cover have the potential to influence the weather further afield, by changing atmospheric circulation pattern outside the Arctic.

There is some evidence that low ice cover at the end of the summer can drive easterly winds across Europe, particularly in winter, potentially resulting in anomalously cold conditions.

The relative importance of sea ice conditions and other factors in generating cold conditions in the UK is an active research area for the Met office.





Driest start to September in over 50 years

17 09 2014

The first half of September has been exceptionally dry across much of the UK and temperatures for many areas have also been well above average, according to provisional Met Office statistics.

Figures up to 15th September show there has been 6.7 mm of rain across the UK, which is just 7% of the September average of 96mm. We would normally expect about half of the average monthly rainfall to have fallen by this point in the month.

This makes it the driest first half of September for the UK in available records back to 1960. It’s also the driest start to September for Wales, Scotland and Northern Ireland, but not for England – 1997 and 2003 were drier.

Map showing actual rainfall across the UK from 1-15 September. All parts of the UK have been drier than average.

Map showing actual rainfall across the UK from 1-15 September. All parts of the UK have been drier than average.

Looking at individual countries, Wales has been the driest with less than 1mm of rain up to the 15th. Northern Ireland is just ahead, with 1.2mm of rain. England has seen 4.1mm and Scotland has seen 13.5mm.

The UK mean temperature so far has been 13.9C, which is 1.3C above the full-month average.

Day-time maximums have been particularly high, with an UK average of 18.4C which is 1.9C above the average, while night-time minimums have been closer to average at 9.6C – which is 0.7C above average.

To complete the picture of generally fine weather for the first half of this September, sunshine has also been slightly above normal with 70.8 hours for the UK – about 57% of the full-month average.

These figures have come about after a prolonged spell of settled and fine weather, dominated by high pressure sitting over the UK. This has blocked the usual low pressure systems that move in from the west and bring unsettled conditions to the UK. Instead we have seen very little rain, generally warm conditions, and slightly above average levels of sunshine.

While these figures are interesting, they don’t tell us where the month will end up overall. A few days of wet or cold weather could drastically alter the statistics, so we’ll have to wait for the full-month figures before making any judgements.

Whilst the rest of this week should be dry and warm for many areas, some sharp showers may develop in places, particularly through Thursday and Friday.

Mean Temperature Sunshine hours Rainfall
1-15 September
Actual (°C)
Diff from Avg Actual (hours)
% of Avg* Actual (mm)
% of Avg*
UK 13.9 1.3 70.8 57 6.7 7
England 14.8 1.1 76.5 56 4.1 6
Wales 13.8 1.0 90.8 71 0.6 1
Scotland 12.6 1.7 57.1 54 13.5 10
N Ireland 13.2 0.8 63.2 56 1.2 1

*We would normally expect about 50% of the average by this point in the month.





Volcanic activity in Iceland continues

29 08 2014

The Icelandic Met Office (IMO), who monitor volcanoes in the country, have been reporting increased seismic activity around the Barðarbunga volcano in Iceland since 16 August.

That activity continued with a small fissure eruption being observed some distance from the volcano in the early hours of Friday (29 August). This led to the IMO raising their ‘aviation colour code’ for the Barðarbunga volcano to Red for a few hours.

This has now been lowered back to Orange after further study of the area revealed the eruption is small and activity is decreasing, with no ash emitted. Under the IMO’s codes, Orange means ‘Volcano shows heightened or escalating unrest with increased potential of eruption’.

The volcanic activity has been variable, with the IMO colour code being briefly Red for Barðarbunga on 29 August and also on 23 August before being downgraded back to Orange.

Another nearby volcano, Askja, is currently Yellow on the IMO code, which means ‘Volcano is exhibiting signs of elevated unrest above known background level’.

The IMO will be continually monitoring the region for any further changes – you can see their latest updates on their website.

The Met Office, as one of nine Volcanic Ash Advisory Centres (VAAC) around the world, will continue to keep in close contact with the IMO. The Met Office has responsibility for forecasting the dispersion of ash originating from volcanic eruptions in the North East Atlantic, primarily in Iceland.

The volcanic ash forecasts are used by airlines, the CAA (Civil Aviation Authority) and NATS (National Air Traffic Services) in the UK, as well as aviation organisations around the world, to make decisions on airspace flight management.

Advice will be issued once ash is released into the atmosphere by an eruption and this can be seen on the Met Office’s VAAC pages on our website.

Because the dispersal of any ash would heavily depend on the type and extent of eruption, as well as the prevailing weather and atmospheric conditions at the time, we can’t provide any speculation on where ash may go. If an eruption occurs that releases ash our advice on potential dispersal will be available on our website.

The Met Office will continue to stay in regular contact with the IMO and will keep the CAA fully informed as the UK’s aviation regulator as well as other stakeholders in the UK and abroad.





How will ex-Hurricane Cristobal affect the UK’s weather next week?

27 08 2014

The third tropical storm in the North Atlantic, Cristobal, has been making some headlines about its potential positive impact on us here in the UK – so what’s actually happening?

Cristobal is currently categorised as a hurricane and is currently between Bermuda and northeast Florida in the western Atlantic.

The storm is forecast to move north-east across the Atlantic over the coming days, changing to an ex-hurricane as it moves away from the warmer waters where it formed.

However, unlike ex-Hurricane Bertha which moved straight to the UK and brought strong winds and heavy rain to much of the British Isles, ex-Hurricane Cristobal is set on a very different track.

Instead it is forecast to move towards Iceland, staying well away from the UK as you can see from the forecast pressure chart below.

Forecast pressure chart for 1pm on Sunday 31 August shows ex-Cristobal heading towards Iceland.

Forecast pressure chart for 1pm on Sunday 31 August shows ex-Cristobal heading towards Iceland.

As Cristobal tracks to the north-west of the UK it could bring stronger winds across northwestern parts of Scotland for a time and there will also be some rain moving across the UK on Sunday into Monday.

It will have a longer lasting and more positive impact on our weather, however, as the track of the storm will result in an area of high pressure building further to the south and over the UK.

This high pressure will be maintained through next week as the jet stream moves to the north of the UK, bringing settled conditions across the country.

At this time of the year, high pressure generally brings dry and fine weather with some spells of sunshine, and that’s what we expect to see from around Tuesday next week.

With high pressure, daytime temperatures could reach the low to mid 20’s Celsius in places. This warmth will be especially noticeable following the cool conditions of late.

This spell of warm weather, however, doesn’t fit the definition of an Indian Summer – which you can read about on our website.





Ex Bertha more likely to miss UK

6 08 2014

7 August update: The latest update about the whether ex-Bertha will affect the UK can be found in our news release

 

Tropical Storm Bertha is currently off the north east coast of the US and is likely to become an ‘extra tropical storm’ on Thursday.

It’s then expected to track across the Atlantic – and while there are still a number of possible outcomes, it looks increasingly likely that the UK will miss any serious impacts from ‘ex Bertha’.

The Met Office has been assessing the likelihood of the UK seeing any effects from Bertha by using our own forecast model alongside models from other world-leading forecast centres.

Map shows likely storm track for ex Bertha by midday Sunday.

Map shows likely storm track for ex Bertha by midday Sunday.

At the moment the majority of forecasts from those models suggest ex Bertha will track to the south of the UK as a relatively weak low pressure system.

In fact it’s debatable whether this is even ex Bertha, as the storm declines to such an extent as it comes across the Atlantic that it fragments.

Some of the warm air which it drags across then leads to a new weak low which generates an area of heavy rain. This could move across northern France and possibly clip eastern parts of the UK on Sunday.

A much smaller number of model outcomes suggest ex Bertha will move across the UK as a more distinct feature which could bring some strong winds and heavy rain. Because these outcomes are in a minority, however, they are less likely.

While there remains a good deal of uncertainty about the weather on Sunday, it currently looks as if it will be fairly unsettled with some rain and breezy conditions – but nothing too unusual for the time of year.

It’s worth noting that it’s likely that the south east of England will see some heavy rain on Friday, which is not part of Bertha. You can see more about this on the Met Office’s severe weather warnings page.

We’ll be keeping an eye on the latest outlook for the weather over the next few days and the progress of ex Bertha to keep everyone up to date with the latest information.








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