Ireland polar vortex weather forecast signals an unusually early change above the Arctic: the polar vortex has weakened and shifted in recent days, and that could raise the chance of colder weather and snow in parts of the UK. Jeff Knight of the Met Office said it would appear to be the earliest on record over 75 years of observations.
Jeff Knight and 75 years
Knight said: “It would appear to be the earliest on record looking back over the 75 years we've been observing…with most experts agreeing this is a very unusual event.” The current earliest major SSW event occurred on 28 November 1969.
The vortex develops every autumn as temperatures fall in the Arctic. Strong westerly winds form in the stratosphere, roughly 10 to 30 miles above Earth's surface, locking the coldest air near the pole.
Arctic winds shift
Atmospheric disturbances can warm the air high up and weaken those winds. A sudden stratospheric warming can then push the westerlies toward easterly winds, changing the jet stream in the following days and weeks.
When that pattern blocks, it can bring a colder northerly or easterly wind carrying Arctic air in. The chance of snow can increase, especially in eastern UK, and similar disruptions in past years have sometimes been followed by colder weather affecting parts of Europe and North America.
Mid-November forecasts
Some forecasts show a reversal of the polar vortex winds by mid-November. If that happens, the event will be known as a major SSW event, but most sudden stratospheric warming events tend to occur from mid-winter, which leaves few historical examples for this early in the season.
That is why the current weakening matters for readers in the UK: it is early, it is rare in the modern record, and it could change winter forecasts over the next days and weeks. If the winds keep weakening and reverse as forecast, the pattern shifts from an unusual disturbance to a named major SSW event.
