Storm Éowyn: What is a weather bomb?

The Met Office explains what happens when a 'weather bomb' occurs.

Transcript

00:00So just what is a weather bomb?

00:03Well, actually, first and foremost, it's quite simply an area of low pressure,

00:07but we see those all the time.

00:08So what makes certain low pressure systems that much more special?

00:11Well, to be a weather bomb, it has to be really intensifying,

00:15really deepening, and that deepening process has to happen rapidly,

00:19so much so that we need to see a drop in the central pressure by 24 millibars

00:25in 24 hours for it to qualify as a weather bomb.

00:28Now, Doris is a prime example of such a phenomenon.

00:32At midday on Wednesday, just an area of cloud, really,

00:35the storm just forming well out in the Atlantic.

00:37The central pressure, 1,004 millibars.

00:40But what happened with Doris?

00:42Well, we need to look high up in the atmosphere towards the jet stream,

00:46a powerful jet digging down.

00:47And where we've got this little kink in the jet stream,

00:50well, that became an area where Doris really intensified,

00:53running through the sequence.

00:54Look at the satellite picture now.

00:56Just look at that low pressure system really forming.

00:58And then as the storm approached the UK,

01:00the isobars just popping out of the center

01:03as Doris really continued to intensify, so that by midday on Thursday,

01:07the storm was down to 974 millibars, a drop of 30 millibars in 24 hours.

01:13That's what creates the number of isobars,

01:15and it's those tightly packed isobars that

01:17drive the strong and damaging winds that we've been seeing.