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.





Thunderstorms bring intense rainfall to parts of England

28 07 2014

This morning has seen some intense downpours across parts of south east England.

They developed across parts of East Anglia in the early hours of the morning, with further areas of heavy showers across Sussex, Surrey, Kent and the south of London following later.

The showers were very heavy in places with thunderstorms, hail, and torrential rain reported, giving high rainfall totals and localised flooding in some areas.

The high rainfall totals were caused by an area of low pressure and a plume of warm air that moved in from the near continent accompanied by light winds, meaning that the showers were slow moving.

Several spots have seen more than half of their average monthly rainfall for the whole of July in just one hour.

Below you can see some of the highest recorded hourly rainfall totals from Environment Agency rain gauges through the morning of Monday 28th July 2014:

Great Dunmow Essex 43 mm (4am to 5am)
Isfield Sussex 37 mm (8.30am to 9:30am)
Ardingly Sussex 35 mm (8.30am to 9:30am)
Santon Downham Suffolk 33mm (4am to 5am)
Weirwood Sussex 28 mm (9am to 10am)
Northolt London 20mm (7am to 8am)

 

The band of showery rain is now easing, but a yellow warning for rainfall remains in place for the south east of the UK as the risk of seeing some further isolated downpours remains.

In addition, the far south east of England could see further persistent and perhaps locally heavy rain later today and overnight, with parts of Kent and Sussex most at risk. Conditions across all areas should then improve through tomorrow.





Lightning strikes and heavy rain over the weekend

21 07 2014

Parts of the UK saw some very heavy downpours over the weekend, as thunderstorms caused disruption in some regions.

Westonbirt in Gloucestershire saw the most rain with 79mm over the weekend, more than its July full-month average of 59.3mm. Within that total, 34.2mm fell in just an hour Saturday afternoon – with some localised flash flooding as a result.

A rain gauge at Norwich airport saw the highest hourly-rainfall total, with 45.8mm falling between 3pm and 4pm on Sunday – this is close to its full month July average of 50.4mm.

Numerous other spots saw some high rainfall totals, particularly in eastern areas. Below you can see some of the highest recorded hourly and overall rainfall totals from the weekend.

It’s possible that some locations not included in the list saw heavy rain, but thundery downpours can be very localised – sometimes just a few hundred metres across.

This means that they can miss our rain gauge network, but you can explore rainfall totals from our Weather Observations Website (WOW) which has information supplied by observers all over the UK.

As we forecast on Friday, some locations avoided the storms altogether and saw prolonged fine weather over the weekend.

Nick Grahame, chief meteorologist at the Met Office, said: “The ‘Spanish Plume’ event we were forecasting led to some very intense thunderstorms over the weekend, with hourly and overall rainfall totals in line with our expectations.

“As we’d been highlighting in our forecasts, these storms can be very localised and that means some places avoided the storms altogether and saw a good deal of fine weather. It really highlights how events such as this can see some places with fairly severe impacts, while other places – sometimes quite nearby – can see no impacts at all.”

48-Hour Rainfall Totals from 2100HRS on 18 July to 2100HRS on 20 July 2014:

STATION LOCATION COUNTY RAINFALL (mm)
WESTONBIRT GLOUCESTERSHIRE 79
NORWICH AIRPORT NORFOLK 62.2
SHOEBURYNESS, LANDWICK ESSEX 48.6
PERSHORE COLLEGE HEREFORD & WORCESTER 45.6
PERSHORE HEREFORD & WORCESTER 39
ASTWOOD BANK HEREFORD & WORCESTER 35.6
KEELE STAFFORDSHIRE 32.4
ROCHDALE GREATER MANCHESTER 32
NEWPORT (SALOP) SHROPSHIRE 31
NOTTINGHAM, WATNALL NOTTINGHAMSHIRE 29.2

Highest hourly rainfall totals from the weekend:

DATE/TIME STATION LOCATION COUNTY RAINFALL (mm)
20/07/2014 15:00 NORWICH AIRPORT NORFOLK 45.8
19/07/2014 09:00 WESTONBIRT GLOUCESTERSHIRE 34.2
20/07/2014 17:00 MONKS WOOD CAMBRIDGESHIRE 22.8
19/07/2014 16:00 MARKET BOSWORTH LEICESTERSHIRE 15.8
19/07/2014 06:00 LIBANUS POWYS 15

This video shows the storms and lightning strikes as they developed over Spain and France and moved north across the UK.

In total the UK are saw 62,277 lightning strikes between 9am on Thursday 17 July and 9am on Monday 21 July 2014





Statistics for winter so far

11 02 2014

As the unsettled UK weather continues this week, the Met Office’s National Climate Information Centre have looked at statistics for this winter so far (from 1 December to 10 February).

These add to previous facts and figures we put out earlier this week, and show a picture of continuing exceptional rainfall across many areas.

Looking at regions around the UK, these provisional figures suggest the region of SE and Central S England has already exceeded its record winter rainfall in the series back to 1910. It is currently at 439.2mm*, less than 2mm above the previous record set in 1915 with 437.1mm of rain.

For the UK as a whole, and also for Wales, both are fairly close to their respective record wettest winter levels in the national series dating back to 1910. Average rainfall for the rest of the month would likely see those records broken.

All countries across the UK have already exceeded their typical average rainfall for the whole winter (according to the 1981-2010 long-term averages). Normally at this stage of the season, you’d expect to have seen only around 80% of that whole season average.

All areas are also on target for a significantly wetter than average winter, with typically around 130-160% of normal rainfall if we get average rainfall for the rest of February.

All countries and areas are also on target for a warmer than average winter.

Current record wettest winters:

Country Year Rainfall Winter 2014 to date*
UK 1995 485.1mm 429.2mm
ENGLAND 1915 392.7mm 328.0mm
WALES 1995 684.1mm 618.7mm
SCOTLAND 1995 649.5mm 558.5mm
NORTHERN IRELAND 1994 489.7mm 360.0mm

 

*These are provisional figures from 1 December 2013 to 10 February 2014 and could change after final quality control checks on data.





UK’s exceptional weather in context

6 02 2014

As the UK’s run of exceptionally wet and stormy weather continues, the Met Office’s National Climate Information Centre has looked at how the last two months compare in the historical records.

Here’s some facts and figures for the weather we’ve seen through December and January:

For the UK

  • For the UK, December was provisionally the equal-fifth wettest December in the national series dating back to 1910 and January was the third wettest January in the same record. When the two months are combined, it is provisionally the wettest December and January in the series.
  • There were more days of rain (any day with more than 1mm of rainfall) for the UK in January than for any other month in a series dating back to 1961, with 23 days.
  • It was the windiest December for the UK in records back to 1969, based on the occurrence of winds in excess 60 kts (69mph).

England and Wales

  • Looking at the England and Wales Precipitation series, which dates back to 1766, it has been the wettest December to January since 1876/1877 and the 2nd wettest overall in the series.

Scotland

  • December was the wettest calendar month on record for Scotland in the series to 1910.
  • For eastern Scotland, December and January combined was provisionally the wettest two month (any-month) period in the same series.

Southern England

  • There have been very few dry days in this area since 12 December and regional statistics suggest that this is one of, if not the most, exceptional periods of winter rainfall in at least 248 years.
  • Despite the rainfall being concentrated in the second half of the month it was the wettest December for south east England since 1959.
  • January was the wettest January for the south England region in the national series dating back to 1910, and the wettest calendar month for the south east region in the same series by a huge margin.
  • The two-month total of 372.2mm for the southeast and central southern England region is the wettest any 2-month period in the series from 1910 .
  • From 12th December to 31st January parts of south England recorded over five months worth of rainfall (based on average January rainfall for the region).

You can see more statistics on recent weather and through the historical records on our UK climate pages.

Full month provisional statistics from January 2014:

Mean Temperature Sunshine hours Rainfall  
January
Actual Diff from Avg Actual % of Avg Actual % of Avg
  degC degC hours % mm %
UK 4.8 1.1 44.8 95 183.8 151
England 5.4 1.3 57.3 106 158.2 191
Wales 5.3 1.2 38.0 78 269.0 171
Scotland 3.5 0.9 27.2 76 205.3 116
N Ireland 4.5 0.3 37.3 84 170.7 147




Wind gusts and rainfall totals 4-5th February 2014

5 02 2014

Last night another major Atlantic depression affected the UK, bringing further heavy rain and severe gales.

Here are some of the highest gusts of wind and rainfall totals recorded at Met Office observing stations between 3pm yesterday and 8am today.

Location Area Height (m) Max gust (mph)
SCILLY: ST MARYS AIRPORT ISLES OF SCILLY 31 92
BERRY HEAD DEVON 58 91
CULDROSE CORNWALL 76 76
WIGHT: NEEDLES OLD BATTERY ISLE OF WIGHT 80 71
PLYMOUTH, MOUNTBATTEN DEVON 50 71
ABERPORTH DYFED 133 70
CARDINHAM, BODMIN CORNWALL 200 70
ISLE OF PORTLAND DORSET 52 70
ST BEES HEAD NO 2 CUMBRIA 124 68
CAMBORNE CORNWALL 87 67
CAPEL CURIG NO 3 GWYNEDD 216 66
GUERNSEY: AIRPORT GUERNSEY 101 64
ORLOCK HEAD DOWN 35 64
MILFORD HAVEN DYFED 44 63
POINT OF AYRE ISLE OF MAN 9 62
NORTH WYKE DEVON 177 61
JERSEY: AIRPORT JERSEY 84 61
PEMBREY SANDS DYFED 3 61
DUNKESWELL AERODROME DEVON 252 60
MUMBLES HEAD WEST GLAMORGAN 43 60
Location Area Rainfall (mm)
NORTH WYKE DEVON 33.4
CAMBORNE CORNWALL 25.2
DUNKESWELL AERODROME DEVON 24.6
CARDINHAM, BODMIN CORNWALL 24.4
BANAGHER, CAUGH HILL LONDONDERRY 24.0
KATESBRIDGE DOWN 23.8
HIGH WYCOMBE, HQAIR BUCKINGHAMSHIRE 21.4
LISCOMBE SOMERSET 21.4
EXETER AIRPORT DEVON 21.2
DALWHINNIE INVERNESS-SHIRE 18.6
ALICE HOLT LODGE HAMPSHIRE 18.4
OKEHAMPTON DEVON 17.9
CULDROSE CORNWALL 17.6
BENSON OXFORDSHIRE 17.6
ODIHAM HAMPSHIRE 17.2
BUDE CORNWALL 17.0
CARTERHOUSE ROXBURGHSHIRE 17.0
CHARLWOOD SURREY 17.0
UPPER LAMBOURN BERKSHIRE 16.8
TREDEGAR GWENT 16.6

Further severe gales and heavy rain are expected over the next few days and everyone is advised to stay up to date with the latest Met Office forecasts and National Severe Weather Warnings and be prepared that the weather may change or worsen, leading to disruption of your plans.





Strong winds, big waves and a storm surge

9 10 2013

A relatively deep area of low pressure is tracking past the north of Scotland today and is then expected to head south into the North Sea tomorrow.

This will bring some strong winds to northern Scotland tonight, then to the east coast of England tomorrow – particularly through the afternoon.

These northerly winds are expected to gust up to 50-60mph, which is unlikely to cause any wind damage but could generate some big waves in the North Sea.

Forecast surface pressure chart for Midnight tonight.

Forecast surface pressure chart for Midnight tonight.

The Met Office has issued a warning this possibility as the big waves could combine with a storm surge to overtop sea walls and potentially flood some coastal roads.

A spokeswoman for the Environment Agency said: “Strong winds and large waves could cause minor disruption along the North Sea coast on Thursday from Yorkshire to Essex. Spray and waves may overtop sea walls and people are urged to stay safe and avoid coastal paths and promenades. The high winds and localised flooding on roads could make driving conditions difficult in coastal areas.”

But what is a storm surge?

Essentially this is a very localised rising of sea level – independent of tides – related to the track of an area of low pressure (storm) and its accompanying winds.

The storm causes this surge of water in two ways. Firstly, strong winds push water in their direction of travel, causing water to ‘pile up’ on coasts facing into the wind.

The second element of a storm surge relates to differences in air pressure. Areas of low pressure are always relative, meaning the air surrounding them must be at a higher pressure.

These areas of high pressure push down on the surface of the ocean, forcing water towards areas of lower pressure to create bulges in the sea level. For each 1 hPa drop in pressure, sea levels rise by up to 1 cm.

Bulges move with a low pressure as it tracks across the sea. North Sea areas are particularly prone to storm surges because water flowing south cannot escape through the narrow Dover Strait and the English Channel.

When storm surges combine with higher tides and big waves they can cause localised issues along coasts.





The jet stream and why it’s too early to write-off summer

13 05 2013

There have been one or two stories in the press today saying we’re in for another washout summer, which would rightly inspire collective misery across the country.

However, it’s a far too early to be writing off any chance of a decent summer season – after all, it doesn’t officially start (for us meteorologists) for more than two weeks (on 1 June).

It appears the news stories are borne out of the current position of the jet stream, a band of fast moving westerly winds high up in the atmosphere. But why is this important?

A quick Jet stream explainer

The jet stream tends to guide the generally wet and windy weather systems which come in off the Atlantic. So, if it’s over us or just to the south, we tend to get a lot of wet and windy weather – which is what we expect through winter.

If the jet is to the north of us, it guides that changeable weather to the north to give us more settled conditions – which is what we expect in the summer.

(You can read a bit more about the jet stream, how it impacted our weather last year, and any potential connections to climate change in a blog story we wrote last year).

What’s going on now?

Right now the jet stream is sitting to the south of the country and it is influencing the unsettled weather we are seeing at the moment.

Forecast chart showing position of the jet stream at midday on 13 May 2013

Forecast chart showing position of the jet stream at midday on 13 May 2013

It’s fair to say that this is roughly the position it was in for extended periods during the exceptionally wet weather that we saw last year, particularly in June.

Crucially, however, the jet stream does move around quite a bit and it can change its track significantly in just a few days. So the current position of the jet stream does not mean that it’s stuck in that position.

Looking ahead

Much like our weather, it’s a huge challenge to predict the exact track of the jet stream more than five or six days ahead, so there’s still a great deal to play for in the outlook for our summer.

In short, it’s far too early to write-off summer 2013 based on the current position of the jet stream.

To get the best information on what to expect you can see the latest detailed forecasts out to 5-days on our website, as well as a general view of what we expect out to 30 days.

You can find out more about the jet stream in our YouTube video.





UK snow depths Saturday 26 January 2013

26 01 2013

As forecast, further snow fell across central, northern and eastern parts of the UK yesterday and overnight. The latest snow depth observations as of 0800 this morning for the UK are below. Redesdale Camp in Northumbria has the highest snow depth so far this year with 33 cm recorded.

Location Area Depth (cm)
Redesdale Camp Northumberland 33
Eskdalemuir Dumfriesshire 30
Albemarle Northumberland 25
Spadeadam Cumbria 25
Aboyne Aberdeenshire 20
Bingley West Yorkshire 20
Little Rissington Gloucestershire 18
Leek, Thorncliffe Staffordshire 16
Nottingham, Watnall Nottinghamshire 12
Leconfield Humberside 11
Strathallan Airfield Perthshire 11
Church Fenton North Yorkshire 11
Wittering Cambridgeshire 10
Sennybridge Powys 10
Andrewsfield Essex 10
Dyce Aberdeenshire 9
Cranwell Lincolnshire 9
Linton On Ouse North Yorkshire 8
Wattisham Suffolk 8
Scampton Lincolnshire 8
Marham Norfolk 7
Shap Cumbria 7
Leeming North Yorkshire 7
Boulmer Northumberland 6
Shawbury Shropshire 5
Waddington Lincolnshire 5
Rostherne Cheshire 4
Bridlington MRSC Humberside 4
Hawarden Airport Clwyd 3
Glasgow, Bishopton Renfrewshire 3
Coningsby Lincolnshire 3
Bedford Bedfordshire 3
Coleshill Warwickshire 3
Liscombe Somerset 2
Dunkeswell Aerodrome Devon 2
Drumalbin Lanarkshire 2
Hereford, Credenhill Hereford & Worcester 2
Prestwick, Gannet Ayrshire 2
Odiham Hampshire 1

As we continue through the weekend all of us will see a change to milder and unsettled conditions, with further rain, heavy at times pushing east across the UK later on Saturday and into Sunday. A yellow warning of heavy rain has been issued for parts of the UK overnight tonight

The change to milder weather will result in a combination of a thaw of lying snow and periods of rain which inevitably increases the risk of flooding in some areas. The Met Office and Environment Agency are monitoring the situation very closely and advise everyone to stay up to date with the latest weather forecasts, severe weather warnings, and flood warnings.

By thinking ahead we can all be better prepared for severe weather. Throughout the winter, the Met Office works with agencies across the UK to help keep the country safe, well and on the move.





Recent rainfall totals

24 12 2012

Rain has continued to cause disruption across parts of the UK, with overnight rain adding to significant totals over the past few days.

The wettest place in the UK (and Scotland) since the heavy rainfall began on 19th December to 6am this morning has been Tyndrum in Perthshire, with 155.0 mm of rain.

Cardinham near Bodmin, Cornwall, is the wettest place in England with 128.8 mm of rain and the wettest place in Wales has been Mumbles Head, West Glamorgan, with 107.0 mm of rain.

Ballypatrick Forest in Antrim has been the wettest place in Northern Ireland, with 89.0 mm of rain.

Some areas have exceeded their full-month December average since the 19th – such as Plymouth, Devon, which has seen 128.8mm of rain compared to a December average of 118.8 mm.

Below is a table of the wettest places in the UK from 0000 HRS on 19th December to 0600 HRS today, 24th December. The final column shows the monthly average for December, clearly showing some places have exceeded their monthly totals:

SITE NAME AREA PRECIP AMOUNT(mm) DEC AVG(mm)
TYNDRUM PERTHSHIRE 155.0 300.9
CARDINHAM CORNWALL 128.8 155.1
PLYMOUTH DEVON 127.4 118.8
LISCOMBE SOMERSET 125.2 171.2
OKEHAMPTON DEVON 115.0 184.2
MUMBLES HEAD WEST GLAMORGAN 107.0 110.3
TREDEGAR GWENT 102.2 169.0
CARDIFF, BUTE PARK SOUTH GLAMORGAN 97.0 125.3
SENNYBRIDGE NO 2 POWYS 96.2 179.5
ST ATHAN SOUTH GLAMORGAN 93.2 122.4
DYCE ABERDEENSHIRE 92.4 76.1
CARTERHOUSE ROXBURGHSHIRE 92.4 132.0
CRAIBSTONE ABERDEENSHIRE 92.0 79.8
BALLYPATRICK FOREST ANTRIM 89.0 133.9

There is more unsettled weather to come this week, so for the latest information keep up to date with our forecasts and warnings.








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