Home / Weather News /

A weatherbomb - Storm Barra's explosive cyclogenesis

12:00
7 December 2021

A weatherbomb
Storm Barra's explosive cyclogenesis

barra windsStrong winds continue to batter Ireland with strengthening winds affecting the UK this afternoon.

Ahead of slamming into Ireland with strong winds and torrential rainfall this morning, Storm Barra underwent something called explosive cyclogenesis. But what is this?

Cyclogenesis happens with an area of low pressure undergoes rapid intensification with explosive cyclogenesis occurring when pressure drops at least 24 millibars within 24 hours.

Storm Barra saw its central pressure drop from 1010 millibars at noon on Monday to 959 millibars at noon today. That’s more than twice the threshold to meet the explosive criteria!

Barra’s explosive cyclogenesis occurred because of an interaction with the jet stream – a ribbon of fast moving air around 5-8 kilometres high in the atmosphere.

As Barra got caught up in the jet stream, the area of low pressure was able to suck in more air making the system spin faster and lowering its pressure rapidly.

The best known cyclogenesis or ‘weatherbomb’ to hit Ireland was the Fastnet Rock storm in August 1979 where the pressure dropped by 40 millibars in 24 hours leaving 15 sailors dead.

More on the topic
Side-by-side weather maps showing UK and Ireland conditions. Left image: radar showing widespread rain bands spiralling across England, Wales, and Ireland with heavier rain near Cardiff and Liverpool; temperatures range from 16°C in Glasgow to 20°C in London and Cork. Right image: wind gust forecast highlighting strongest winds over southwest England and southern Ireland, with gusts up to 45 mph near Plymouth and 40 mph in Cardiff, Dublin, and Birmingham.
Monday 14 July 2025

Lots of wind and rain

Low pressure reaches the UK and Ireland
dennis oswald selfie supercell stormchaser
Wednesday 16 July 2025

Storm chaser's Blog

USA - Alone with the supercell
sunny
Friday 11 July 2025

Safety first

Tips for the current heatwave!
All weather news
This might also interest you
Thursday 3 July 2025

Gusty too

Rainfall passes through the north
Weather map on the left showing heavy rain over the UK and Ireland. Wind map on the right shows strong gusting winds over Ireland, Wales, and England, strongest in the south.
Tuesday 15 July 2025

Breakfast brief

Wet, gusty, with thundery potential
A temperature and weather radar of the UK and Ireland showing hot temperatures with clear, sunny skies.
Friday 11 July 2025

Breakfast brief

A hot and sunny outlook
All articles
Weather & Radar

www.weatherandradar.ie

facebooktwitteryouTubeContact uslinkList
Privacy Policy | Legal info | Accessibility statement