Updated: Sunday 12th January 2014
Stratosphere Update & Cold Weather:
A very cold stratosphere and its associated very strong polar vortex was what lead to the stormy weather of these past few weeks.
The vortex is currently under attack from waves resulting in its progressive weakening.
2 types of waves of main interest: wave 1 (responsible for displacing the vortex) and wave 2 (responsible for splitting the vortex).
Wave 2 is forecast to peak soon and decrease over next 10 days whereas wave 1 is forecast to increase over next 10 days.
The consequence will be a steady reduction in polar vortex winds, hence a weakening of the vortex.
The vortex is currently over Canada. Displacement by wave 1 could move it to Siberia. This would lead to 2 things:
- build of high pressure at high latitudes in the Atlantic to block the normal W to E progress of milder weather systems
- development of surface low pressure in eastern Europe leading to cold E'ly winds for the UK with snow showers off the North Sea
This is, however, not an exact science and requires an accurate positioning and orientation of high and low pressure systems.
Timescale for potential cold weather: somewhere between the last few days of January and the second week of February.
Updated: Thursday 23rd April 2015
Period: 25/04/2015 - 29/04/2015
Weather event: Rain, wintry precipitations possible. Windy at times.
Colder N'ly flow developing. Maximum temperatures likely into single digits. Snow to return to the hills, wintry precipitation at lower levels not ruled out in the heaviest and more persistent bursts. Some possible as early as Saturday morning. Risk of ice under clear skies. Windy at times.