Monitoring and forecasting the UK climate and its meteorological changes with analysis
UK Climate Forecasting and Analysis
in association with Weather Analysis organisation UK
Climate Change UK Weather Atlantic Storms Reports & Analysis Jet Stream Flooding Air Quality
The strongest jet streams are the polar jets at 9–12 km and the higher altitude and somewhat weaker subtropical jets at 10–16 km. The Northern Hemisphere and the Southern Hemisphere each have a polar jet and a subtropical jet. The northern hemisphere polar jet flows over the middle to northern latitudes of North America Europe and Asia and their intervening oceans while the southern hemisphere polar jet mostly circles Antarctica all year round. The southern hemisphere mid-latitude jet is a relatively narrow band of strong winds stretching from the Earth's surface to the top of the troposphere at about 12 km increasing steadily in strength with height. Polar jet streams are typically located near the 250 HPa pressure level or 23,000 to 39,000 ft above sea level while the weaker subtropical jet streams are much higher, between 33,000 and 52,000 ft. Jet streams wander laterally dramatically and have large changes in their altitude. The jet streams form near breaks in the tropopause at the transitions between the Polar Ferrel and Hadley circulation cells and whose circulation with the Coriolis force acting on those masses drives the jet streams. (Jet streams are the product of two factors: the atmospheric heating by solar radiation that produces the large-scale Polar, Ferrel, and Hadley circulation cells, and the action of the Coriolis force acting on those moving masses.) The polar jets at lower altitude and often intruding into mid-latitudes strongly affect weather and aviation. The polar jet is most commonly found between latitudes 30° and 60° while the subtropical jet streams are located close to latitude 30°. With the temperature contrast of these air masses greatest in the winter time the high altitude stream of air is stronger at this time of the year reaching 300 miles per hour but have been measured at over 400 miles an hour in south-west Scotland.
Jet Streams are important because they control our weather. In our latitude the jet stream is generally found at around 35,000 feet and is called the Polar Front Jet Stream. The polar front jet stream as its name implies separates the cold polar air to the north and the warm sub-tropical air to the south.
The northern polar jet stream, a band of high-altitude winds that circles the Arctic and influences the climate of the northern hemisphere, is forecast to start noticeably shifting in the 2060’s if greenhouse emissions remain high, leading to dramatic changes in temperature and rainfall, especially in Europe. “This would have drastic consequences for society,” says Matthew Osman at the University of Arizona. “But the ultimate trajectory of the jet stream is still largely under our control.”
A new study finds that the jet stream could shift outside the bounds of its historic range within just a few decades — by the year 2060 or so under a strong warming scenario. The findings were published in the journal Proceedings of the National Academy of Sciences.
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Daily Jet Stream Forecast in 3 hour periods by NetWeather.tv with weather charts and data
