A better way to predict extreme weather? 'Traffic jams' that form in jet streams could help reveal when devastating floods, hurricanes and droughts are about to hit

  • The jet stream helps move air around the globe and maintains a stable climate   
  • A phenomenon known as 'blocking' can cause congestion in the channels  
  • When this happens, extreme events such as hurricanes can occur 
  • Researchers will now be able to predict when this will happen and predict when and where events such as droughts or floods will occur 

By JOE PINKSTONE FOR MAILONLINE

Published: | Updated:

The jet stream is a narrow band of wind which keeps air flowing around the globe, but sometimes it gets clogged up in a phenomenon known as 'blocking'. 

When this happens, the jet stream grinds to a halt and a huge volume of air gets stuck and the consequences can be catastrophic.

Hurricane Sandy and the deadly 2003 European heat wave were caused by this unusual event. 

Scientists have known about blocking for decades, but never understood why it happens or how it impacts on the weather.

Now, researchers have discovered that these bottlenecks in the sky form in a similar way to traffic jams, and experts will now be able to predict when and where it will happen. 

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The jet stream (pictured)  is a narrow band of wind which keeps air flowing around the globe, but sometimes it gets clogged up in a phenomenon known as 'blocking'. This narrow channel of air helps to maintain a stable climate as it moves air from west to east

The jet stream (pictured)  is a narrow band of wind which keeps air flowing around the globe, but sometimes it gets clogged up in a phenomenon known as 'blocking'. This narrow channel of air helps to maintain a stable climate as it moves air from west to east

Research coming out of the University of Chicago used mathematical modelling to try and understand the jet stream and how it can be disrupted.  

'Blocking is notoriously difficult to forecast, in large part because there was no compelling theory about when it forms and why,' said study coauthor Noboru Nakamura, a professor in the Department of the Geophysical Sciences. 

Dr Nakamura conducted the research with then-graduate student Clare Huang. 

The study came up with a new set of measurements to help analyse the phenomenon.

The researchers found that the equation for modelling the weather is nearly identical to one devised decades ago by transportation engineers trying to describe traffic jams.

'It turns out the jet stream has a capacity for "weather traffic," just as a highway has a traffic capacity, and when it is exceeded, blocking manifests as congestion,' said Ms Huang. 

When the jet stream goes over capacity, it becomes overloaded and air gets stuck, with catastrophic consequences. Hurricane Sandy (pictured) and the deadly 2003 European heat wave were caused by this unusual occurrence

When the jet stream goes over capacity, it becomes overloaded and air gets stuck, with catastrophic consequences. Hurricane Sandy (pictured) and the deadly 2003 European heat wave were caused by this unusual occurrence

WHAT IS A JET STREAM?

Jet streams are fast flowing, narrow currents of air that carry warm and cold air across the planet, much like the currents of a river.

They cover thousands of miles as they meander near the tropopause layer of our atmosphere.

They are found in the atmosphere's upper levels and are narrow bands of wind that blow west to east.

The strongest jet streams are the polar jets, found 30,000 to 39,000 ft (5.7 to 7.4 miles/ 9 to 12 km) above sea level at the north and south pole.

In the case of the Arctic polar jet this fast moving band of air sits between the cold Arctic air to the north and the warm, tropical air to the south.

When uneven masses of hot and cold meet, the resulting pressure difference causes winds to form.

During winter, the jet stream tends to be at its strongest because of the marked temperature contrast between the warm and cold air.

The bigger the temperature difference between the Arctic and tropical air mass, the stronger the winds of the jet stream become.

Sometimes the flow changes direction and goes north and south.

Jet streams are strongest - in both the southern and northern hemispheres - during winters.

This is because boundaries between cold and hot air are the most pronounced during the winter, according to the National Weather Service (NWS).

The direction the air travels is linked to its momentum as it pushes away from the earth's equator.

'The reason has to do with momentum and how fast a location on or above the earth moves relative to earth's axis,' NWS explains.

The complex interactions of many factors, including low and high pressure systems, seasonal changes and cold and warm air - affect jet streams.

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On the roads, vehicle movement slows when multiple highways converge.

Similarly, the speed of the jet stream is reduced due to topography such as mountains or coasts. 

The result is a theory that not only reproduces blocking, but predicts it, said Dr Nakamura.

He called the cross-disciplinary connection 'one of the most unexpected, but enlightening moments in my research career - truly a gift from God.'

'It's very difficult to forecast anything until you understand why it's happening, so this mechanistic model should be extremely helpful,' Dr Nakamura said. 

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