Weather, weather, everywhere
26 March 2014
Not one corner of the globe is untouched by the weather. This winter, many people felt the impacts of severe gales and storm surges in the UK. Meanwhile, extreme weather around the world put the UK weather into context.
In October, a severe storm, named the 'St Jude's Day storm' by the media, travelled across southern England, eventually reaching northern Europe. Gusts of up to 80 mph are rare in southern England, making the area susceptible to severe weather impacts.
Falling trees disrupted power supplies and transport, with flights diverted from Heathrow and Gatwick airports. Tragically, four people died as a result of falling trees. Our forecasts enabled contingency planners, emergency responders and the general public prepare for and limit the impacts of the storm.
Prime Minister, David Cameron said: "I think the Met Office provided good information and updated it regularly."
November began generally unsettled and wet. There were relatively few dry days, but also few frosts. Mid-November was more settled, but colder with sunshine as high pressure systems dominated. The UK experienced the first widespread frosts and some early-season snowfalls in the north.
Series of storms
From the start of December the UK entered a prolonged period of particularly unsettled weather, with a series of storms coming in off the Atlantic. A major focus of concern was high spring tides and large waves combining to cause coastal flooding. Large waves damaged sea fronts across the UK, including the historic parade in Aberystwyth.
A major winter storm on 5 December brought strong winds and a storm surge, mainly affecting the east coast. To limit impacts, we worked closely with partners, including the Environment Agency. Despite the storm surge flooding about 1,000 properties and being higher than levels experienced in 1953, advanced warnings, coupled with much improved flood defences over the last 60 years, meant that a further million homes were protected.
A succession of low pressure systems brought heavy rain and strong winds for most areas throughout December with frequent gusts of 60 to 70 mph. December was the stormiest in records dating back to 1969 and is one of the windiest months for the UK since January 1993. December was very wet across the UK, with Scotland having the wettest month overall in records dating back to 1910.
Forewarned is forearmed
Following on from last year's successful campaign we again hosted the 'Get Ready for Winter' web pages to help individuals, families and communities prepare for winter.
The pages combined messages from Government, the voluntary sector, local authorities and others. We encouraged people to prepare their properties and vehicles, take responsibility for their own safety, be aware of the latest forecasts and warnings, be prepared to alter plans and look after vulnerable people.
Storms hit transport, flooded hundreds of homes, and cut power to thousands of homes. Sadly, several people died as a result of the severe weather and flooding. Mild, wet winter continued into early January. Parts of England had the wettest January since records began, with the Somerset Levels particularly badly affected by flooding. Late in January, the military was brought in to help alleviate the situation.
Early in February, severe storms destroyed the railway line at Dawlish in Devon. As more areas across southern England suffered from flooding, the first Red Weather Warning of the winter in mid-February warned of heavy rain and strong winds.
Throughout the stormy season - the wettest on record - we directly supported the authorities by providing critical weather warnings and participating in COBRA emergency planning meetings as extreme weather continued to impact the UK.
Why wild weather?
Storms are common in winter because of the big difference in temperature between the cold air in the Arctic and the warm air in the tropics at this time of year. This contrast creates a strong jet stream, a narrow band of fast moving winds high in the atmosphere.
This winter the UK had an exceptional run of winter storms, culminating in serious coastal damage and widespread, persistent flooding. This period of weather has been part of major deviations of the Pacific and North Atlantic jet streams driven, in part, by persistent rainfall over Indonesia and the tropical West Pacific.
The North Atlantic jet stream has also been unusually strong; this can be linked to exceptional wind patterns in the stratosphere with a very intense polar vortex.
The jet stream can guide storms as they come across the Atlantic, bringing storms to the UK. It's possible for the jet stream to increase the strength of storms, but storms can also increase the strength of the jet stream. This 'positive feedback' means storms often cluster together.
As yet, there is no definitive answer on the possible contribution of climate change to the recent storminess, rainfall amounts and the consequent flooding. This is in part due to the highly variable nature of UK weather and climate.
Nevertheless, recent studies have suggested an increase in the intensity of Atlantic storms that take a more southerly track, typical of this winter's extreme weather. There is also an increasing body of evidence that shows that extreme daily rainfall rates are becoming more intense, and that the rate of increase is consistent with what is expected from the fundamental physics of a warming world.
More research is urgently needed to deliver robust detection of changes in storminess and daily/hourly rain rates and this is an area of active research in the Met Office. The attribution of these changes to anthropogenic global warming requires climate models of sufficient resolution to capture storms and their associated rainfall. Such models are now becoming available and should be deployed as soon as possible to provide a solid evidence base for future investments in flood and coastal defences.
Weather often has significant impacts that put lives at risk. From intense heat in Australia and extreme cold over North America to Typhoon Haiyan, we monitor conditions around the world, keeping an eye out for severe weather. Our range of services and advice enable organisations like the Foreign and Commonwealth Office (FCO) and the Department for International Development (DFID) to make informed decisions. We also collaborate with and advise other weather services, for example in Africa (see page 11).
In November, Typhoon Haiyan, one of the most powerful storms ever recorded to hit land, made landfall over the central Philippines, causing catastrophic damage through the Philippine islands of Samar, Leyte and Panay.
As well as strong winds, the storm surge and heavy rain also caused major impacts. Thousands of people were killed and the UN estimates more than 11 million people were affected and some 673,000 displaced. The city of Tacloban was particularly badly hit.
After leaving destruction in its path, the typhoon moved out into the South China Sea, losing some strength before making another landfall in northern parts of Vietnam. Regional warnings for Typhoon Haiyan were produced by the Japanese Meteorological Agency and the Philippine Atmospheric Geophysical and Astronomical Services Administration.
We supply predictions of typhoon tracks from our global forecast model to meteorological centres worldwide, which are used with guidance from other models to produce forecasts. We are currently working closely with the Philippine Government to provide model forecasts and guidance for their region as part of ongoing collaborative work. This has proved beneficial in predictions of the recent tropical storms Lingling and Kajiki which both affected the region struck by Typhoon Haiyan.
Professor Alfredo Mahar Francisco A. Lagmay, who leads Project NOAH (Nationwide Operational Assessment of Hazards) in the Philippines, said Met Office forecasts "...aided greatly in the projections for the typhoon's impact as well as in the storm surge simulations generated by the group to determine vulnerable communities. This led to successful disaster mitigation efforts in various areas which saved numerous lives."
Extreme cold over North America
Weather over North America hit the headlines in January when record breaking cold conditions spread south from the Arctic. In the US, many people linked the extreme cold to a 'polar vortex'. Traditionally, in the UK, this term is normally used to describe the persistent large-scale low pressure situated around 50 km above the poles in the stratosphere.
However, the American use of the phrase 'polar vortex' referring to the extremely cold conditions over North America is different to the definition above, instead referring to features lower in the atmosphere - in the troposphere, where our weather happens.
Usually, in winter, a deep reservoir of cold air becomes established through the lower atmosphere over the Arctic because of the lack of sunlight. This is usually held over high latitudes by the jet stream.
This winter the jet stream weakened and moved southwards over North America in the wake of a low pressure system as it moved east out of the USA and over the Atlantic. This allowed the reservoir of Arctic cold air to move southwards across the US, resulting in extremely low temperatures.
Cold weather in the US didn't mean cold weather in the UK. We get our coldest weather when winds blow from the northeast or east from the continent. In fact, cold weather in the US can strengthen the weakened jet stream and bring the UK milder and wetter weather, much as we have seen.