NI Weather: Is there another Beast from the East on the way?

For many St Brigid's Day on 1 February is considered the first day of spring.

Snowdrops are appearing and green shoots of early spring are visible in the parks and gardens.

Climatically though February is one of the coldest months of the year and is still considered to be part of the winter season in the meteorological calendar.

So far this winter we have had plenty of rain and no named storms.

But there is still time for things to change and there have been whisperings in the media that another Beast from the East is on the way with freezing conditions and widespread snow.

This picture was taken in Italy when the Beast took hold in February 2018

There has been speculation about a Sudden Stratospheric Warming (SSW) taking place and, according to the UK Met Office, this is happening - but on a minor level.

Back in February 2018, the so-called Beast from the East brought widespread cold weather and snow to much of Europe.

This was as a result of a SSW.

What does SSW mean?

The atmosphere can be divided into layers based on its temperature.

These layers are the troposphere, stratosphere, mesosphere and thermosphere

• The troposphere is the lowest layer, closest to earth - planes fly in this area and weather systems develop within it

• Immediately above the troposphere is the stratosphere - sometimes changes within this layer can filter down into the troposphere and affect our weather systems

• The polar vortex forms as polar temperatures drop when we head into autumn. It lies usually 30 to 50km above the earth's surface

Snowdrops might be on the ground but spring is still a while away

A strong polar vortex usually means strong polar circulation.

This locks the colder air into the Arctic Circle, creating milder conditions for most of the US and Europe.

In contrast, a weak polar vortex creates a weak jet stream pattern.

As a result, it has a harder time containing the cold air, which can now escape from the polar regions into the US and Europe.

So warming currently taking place within the stratosphere is expected to weaken the polar vortex but forecasts suggest it will not totally collapse.

This is important and will need to be monitored.

It can take a week or more for any effects from an SSW to work its way down through the atmosphere and to have any influence on the weather in the UK and Ireland.

This phenomenon doesn't always lead to severe cold weather, but it's not out of the question and is only just getting under way.

Watch this space.