Warm but unsettled weekend ahead as cold eases grip on UK

10 04 2013

The UK is set to see some warmer temperatures this weekend as the colder than average weather seen so far this April eases its grip.

Temperatures have been steadily climbing since the exceptionally cold weather towards the start of the month, with today through to Friday set to see double-digit figures for many places.

On Saturday temperatures will be generally between 11 and 13 °C, feeling much milder than recent days. However, the weather will be wet, fairly windy and unsettled for many parts – with the best of any drier and brighter weather in the south and east.

Forecast chart for midday Saturday shows low pressure moving in from the Atlantic to bring mild but wet and windy weather for most of the country. High pressure still dominates in the south and east, bringing the best of any drier and brighter weather.

Forecast chart for midday Saturday shows low pressure moving in from the Atlantic to bring mild but wet and windy weather for most of the country. High pressure still dominates in the south and east, bringing the best of any drier and brighter weather.

Warmest day of the year so far

Sunday looks set to be the warmest day of 2013 so far, with temperatures expected to be widely in the mid-teens Celsius. While the weather will be slightly more settled than Saturday, many places will see cloudy and breezy conditions with a risk of some light showers.

Once again the south and east will see the best of the weather, with drier and brighter conditions and temperatures of 15-18 °C – with a possibility that some isolated spots could reach around 20 °C.

Leading in to next week temperatures look set to cool slightly, but remain around average for the time of year.

Jet stream shift brings milder weather

The reason for the shift away from the colder weather is the re-alignment of the jet stream, a band of fast moving westerly winds high up in the atmosphere which tends to guide Atlantic weather systems. It’s these weather systems that bring us the mild and unsettled weather we normally expect at this time of year.

During the prolonged cold conditions the jet stream tracked far to the south of the UK, guiding those mild weather systems towards the Mediterranean. The UK, meanwhile, saw an easterly flow – bringing in cold conditions from the cold winter climes of north-east Europe.

Now the jet stream has started to shift its track, moving north to a position more in line with what we’d expect at this time of year. This means we expect to see milder, but also more unsettled weather coming in from the Atlantic over the coming week or so.





Infographic: what to do when it snows

22 01 2013

With further warnings for snow in the UK our latest infographic covers what to do before, during and after snow fall.

Infographic what to do when it snows

See our website for the latest severe weather warnings. To find out more about when warnings are issued and what they mean see our guide to warnings.





What is freezing fog?

12 12 2012

Fog has affected many areas over the last couple of days, which in some places has been freezing.

Freezing fog forms in the same way as ‘normal’ fog and is typical in winter, aided by clear skies and calm conditions. The cooling of land overnight under clear skies means that any heat radiates back into space cooling the air close to the surface. This reduces the ability of the air to hold moisture, allowing condensation of water vapour into millions of tiny water droplets to occur and fog in to form.

When temperatures are well below freezing, the tiny water droplets suspended in the air are made up of supercooled water droplets – which remain liquid even though the temperature is below freezing.  This occurs because the liquid needs a surface to freeze upon, such as a dust or pollution particles. However if there are not enough of these particles about then the water can stay as a liquid.

winter-fog

However droplets from freezing fog can freeze to surfaces on contact, forming rime. Often confused with frost, rime is a rough white deposit formed of feathery ice crystals. It can often be seen on vertical surfaces exposed to the wind – like lamp posts and pylons – as the supercooled water droplets freeze on contact as they drift past.

With warnings in force for fog people are advised to take extra care when driving in affected areas with journeys taking longer than usual. By being ‘weather aware’ our warnings help you prepare, plan and protect yourself from the impacts of severe weather.

Visit our website for more information on different types of fog.





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.





How do we measure snow?

6 11 2012

Here at the Met Office, we’re already being asked if it’s going to be a White Christmas and there’s always a lot of interest in snow.

It’s too early to give forecasts that far ahead, forecasting snow is – after all – a challenge which requires detailed information. While forecasting snow is one challenge, measuring it when it’s on the ground poses another.

There are several reasons for this. First of all snow is subject to the vagaries of the wind and can be blown into deep drifts, leaving bald patches of earth nearby.

Snow also melts, refreezes, and new snow can fall on top. This makes it difficult to discern how much snow has fallen at different times or on different days.

Another tricky aspect of measuring snow is that it often falls on high ground, away from where the majority of the UK population live – and also away from our observation sites.

Snow often falls on high ground but is less common closer to sea-level.

So what do we do to measure this problematic precipitation? In days gone by a manual observer (ie a human being) would go out with a ruler and measure snow on a flat surface.

But this is time consuming, limits observations (as there were relatively few manual observers) and, apparently, became a tricky operation when snow got particularly deep!

So modern technology has given us automated snow sensors which measure snow depth with a laser signal. A piece of artificial turf is the preferred surface below the laser, as it doesn’t grow and therefore doesn’t complicate readings as grass might.

It’s not all that simple though, as even artificial turf can expand and contract according to temperature, as can the soil below it (which can push the artificial turf up or down). Moles can also cause the same problem! To tackle this, our network is under continual review and calibration to make it as accurate as possible.

These fairly technical pieces of kit can’t be placed everywhere, and until last year there were less than 50 spread out across the UK.

Snow depth sensor

This year we have extended our network with 21 new snow sensors, bringing the total up to 68 – you can see the full network on the map below.

Map showing snow sensor network in 2012

This means we can get snow readings from a wider range of locations, which can help our forecasting and is useful for building records and statistics about UK climate.

It’s worth pointing out that while these additions to our observation network are a valuable step forward, the snow sensor network is still relatively sparse in comparison to our UK land weather observation network, which has 463 stations.

Fortunately this is supplemented by observations supplied to the Weather Observations Website (WOW), where anyone can give an up to date measurement of snow or even upload a picture of how much snow they have.

The very nature of our weather here in the UK means that it’s not possible to give precise information for every location in the country, but our network is being continually improved to provide the most detailed, accurate and up-to-date information available.

You can read more about snow and snow forecasts on our dedicated snow pages.





Bitterly cold mornings continue for some this weekend

12 02 2012

Following a bitterly cold night across eastern England on Friday night, last night was not quite as cold. Friday night saw the lowest temperatures of the winter so far, falling to a biting -15.6C at Holbeach, Lincolnshire. On Saturday night the lowest minimum temperatures were across parts of southern and eastern England. The coldest locations, with values achieved early in the night before cloud amounts increased, were Cavendish: -12.7C Holbeach: -12.4C Cambridge: -12.2C Santon Downham: -11.9C Rothamstead: -11.7C.





Last night’s temperatures: A night of contrast

9 02 2012

Freezing temperatures combined with rain in the north to bring treacherous ice conditions across parts of southern Scotland, northern England and north east Wales last night and this morning as temperatures fell well below freezing across Wales, England and southern Scotland.

However, there was a marked contrast further to the north and west. Milder Atlantic air across northern Scotland and Northern Ireland to the north and west of the rainband straddling the UK resulted in a relatively mild night for mid February.

The coldest place in the UK was Linton on Ouse in North Yorkshire, recording a low of -9.6 °C, whilst at the other end of the scale, Aultbea in Ross and Cromarty, saw temperatures fall no lower than 7.6 °C.

The two tables below show the coldest and mildest spots in the UK last night.

 Coldest places in the UK overnight 8 – 9 February 2012

SITE NAME MIN TEMP (celsius) AREA
LINTON ON OUSE                         -9.6 NORTH YORKSHIRE     
TOPCLIFFE                              -8.6 NORTH YORKSHIRE     
BALA                                   -7.3 GWYNEDD             
PATELEY BRIDGE           -7.0 NORTH YORKSHIRE     
SENNYBRIDGE                    -6.9 POWYS               
WOODFORD                               -6.7 CHESHIRE            
RAVENSWORTH                            -6.7 NORTH YORKSHIRE     
CHURCH FENTON                          -6.7 NORTH YORKSHIRE     
DISHFORTH AIRFIELD                     -6.7 NORTH YORKSHIRE     
OKEHAMPTON     -6.5 DEVON               
LEEMING                                -6.4 NORTH YORKSHIRE     
TREDEGAR       -6.2 GWENT               
BINGLEY                     -6.1 WEST YORKSHIRE      
GOGERDDAN                              -6.1 DYFED               
EMLEY MOOR                  -6.0 WEST YORKSHIRE      
PRESTON MONTFORD                       -6.0 SHROPSHIRE          
BRADFORD                               -5.8 WEST YORKSHIRE      
ROCHDALE                               -5.7 GREATER MANCHESTER  
ALBEMARLE                              -5.5 NORTHUMBERLAND      
REDESDALE CAMP                         -5.4 NORTHUMBERLAND      
PENNERLEY                              -5.4 SHROPSHIRE          
LLYSDINAM                              -5.3 POWYS               
BRAMHAM                                -5.3 WEST YORKSHIRE      
BAINBRIDGE                             -5.1 NORTH YORKSHIRE     
CAPEL CURIG                -5.0 GWYNEDD             

Mildest places in the UK overnight  8 – 9 February 2012

SITE NAME MIN TEMP (celsius) AREA
AULTBEA                     7.6 ROSS & CROMARTY     
SOUTH UIST RANGE                       6.8 WESTERN ISLES       
STORNOWAY AIRPORT                      6.7 WESTERN ISLES       
KINLOCHEWE                             6.6 ROSS & CROMARTY     
TIREE                                  6.3 ARGYLL              
ALTNAHARRA                    6 SUTHERLAND          
BALLYKELLY                             5.8 LONDONDERRY         
SKYE: LUSA                             5.6 WESTERN ISLES       
ACHNAGART                              5.5 ROSS & CROMARTY     
ISLAY: PORT ELLEN                      5.5 ARGYLL              
MAGILLIGAN                   5.5 LONDONDERRY         
BALTASOUND                   5.3 SHETLAND            
FAIR ISLE                              5.3 SHETLAND            
MURLOUGH                               5.3 DOWN                
RESALLACH                              5.2 SUTHERLAND          
MACHRIHANISH                           5.2 ARGYLL              
CASTLEDERG                             5.2 TYRONE              
KILLOWEN                               5.1 DOWN                
BALLYWATTICOCK                         5 DOWN                
ST ANGELO                              4.8 FERMANAGH           
KIRKWALL                               4.8 ORKNEY              
LOCH GLASCARNOCH                       4.7 ROSS & CROMARTY     
WICK AIRPORT                           4.7 CAITHNESS           
HELENS BAY                             4.6 DOWN                
STORMONT CASTLE                        4.6 DOWN                

The battle between the milder Atlantic air and the very cold air in the southeast continues across the UK, bringing the risk of snow across parts of the country later today and into Friday. Whilst there is uncertainty about where the heaviest and most persistent snow will fall, accumulations of up to 10cm are possible in the worst affected regions. As a result Met Office warnings have been issued and there could be some disruption to travel.

The Met Office is working closely with government departments, contingency planners and transport agencies to make sure they have the best advice available to help them prepare for possible weather impacts.





Another cold night across the UK as snow arrives

4 02 2012

It was another bitterly cold night across the UK last night, especially across England. The coldest place in England was South Newington, Oxfordshire where temperatures fell to -12.4 deg C, beating last night as the coldest night of the winter so far. In Wales, Tredegar was the coldest spot at -9.5 deg C whilst in Scotland Altnaharra saw temperatures fall as low as -7.2 deg C.

The list below gives all stations in the UK that saw temperatures fall below -8 deg C.

Station Name Min Temp (deg C)
South Newington       -12.4
Benson                          -11.7
Pershore                       -11.1
Hurn Airport               -11.0
Larkhill                         -10.2
Brize Norton                -10.1
South Farnborough    -10.1
Yeovilton                       -10.1
Boscombe Down         -10.0
Odiham                         -10.0
Westonbirt                    -9.9
Redesdale Camp          -9.6
Hereford/Credenhill   -9.6
Woburn                          -9.6
Tredegar                         -9.5
Lyneham                        -9.4
Aboyne                           -9.3
Middle Wallop              -9.3
Wisley                             -9.2
Alice Holt Lodge           -9.2
Winchcombe                 -9.
Monks Wood                -8.9
Church Lawford           -8.8
Otterbourne                  -8.8
Shawbury                      -8.6
Sennybridge                 -8.6
Shobdon                       -8.6
Exeter Airport             -8.5
Usk No2                        -8.5
Winterbourne              -8.4
Coleshill                        -8.3
Little Rissington          -8.3
Coventry Coundon       -8.3
Leconfield New            -8.2
Coningsby                      -8.2
Wainfleet                        -8.2
Northolt                         -8.2
Wiggonholt                    -8.2
Scampton                       -8.1
Bedford                           -8.1
Bristol/Filton                -8.1
Dunkeswell                    -8.1
Rothamstead No 2       -8.1
Pershore                         -8.1
Braemar No 2                -8.1
Charlwood                     -8.0
Sutton Bonington         -8.0
Winterbourne No 2      -8.0
Santon Downham        -8.0
Today, as an Atlantic front moves in from the west it will come up against this cold air and we’re likely to see a mixture of rain, sleet and snow across the UK.

Many parts will see some snow through the day and overnight into Sunday morning, but about the risk is highest in central and eastern areas where we could see up to 5-10cm of snow.

With this risk of snow and ice over the next few days it is important people stay up to date with our weather forecasts and warnings for the latest information.”








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