Looking To The StratosphereAdded : Sunday at 15:00 Although the outlook for Britain and Ireland is looking fairly normal for the run-up to Christmas, meteorologists attention is turning to the stratosphere as once again there are signs of a sudden stratospheric warming (SSW) event taking place. An SSW event can split the stratospheric Polar Vortex and weaken it to the extent that the stratosphere warms above the Arctic with this warming then feeding down to the troposphere.
The outcome of this can promote high latitude blocking which in turn can mean that cold air, which is often "locked up" over the Arctic, is released to lower latitudes bringing cold weather to these regions, such as what happened across our part of the world in February/March this year.
However, a word of caution before you all go out and buy sledges and prepare for blizzards! SSW events do not guarantee cold, ice, snow, etc. and at the current time there is no guarantee that a SSW will take place in the next few weeks.
However, if we take a look at the Polar Vortex at the moment:
Warm temperatures or high pressure across western Canada and the vortex displaced across towards northern Russia. As we head towards Christmas the GFS ► suggests further warming with pressure rising across Alaska / eastern Russia and the Polar Vortex displaced across towards north-eastern Scandinavia:
We must stress that it is very much a watching brief at the moment. As we said above, an SSW event is not guaranteed, and even if one occurs, it does not guarantee wintry weather for us - after all we're only a very small part of the world.
Another part of the jigsaw is that we're headed towards a solar sunspot activity minimum. Sunspot activity is expected to reach it's lowest levels during the next year or so, and there is some support for the theory that very low solar sunspot can bring an increased risk of cold and wintry weather. The last minimum, during the period of 2009 to 2011 saw some notably cold and snow weather affecting parts of Britain and Ireland.
Interesting times, but no guarantees. If a cold spell does look like developing, rest assured, we'll tell you as soon as we know!
METEOROLOGIST: BARBER |