'Weather Bombs' and 'Thunder Snow' - anything new?

Snow storm brewing off the coast of Morecambe Credit: CHRIS COATES

The UK's weather has long been a major talking point in general conversation but the way we describe weather events seems to be changing, largely due to social media - how quickly we get our information, where we get our information and how dramatically we can define it.

In just the last few years we have seen or heard new phrases like 'weather bomb' and 'thundersnow' relating to the weather. These may be new to us, but not necessarily new to other parts of the globe.

Here is an explanation of just a few of the recent weather phrases to hit the headlines, how new they are and what they really mean in meteorological terms.

Thunder Snow

This is nothing new and is 'exactly what it says on the tin' - thunder and snow. You just need a dose of unstable, arctic or polar air and snow showers.

It is caused in the same way as summer thunder storms - warm air rapidly rising into colder air, creating cumulonimbus clouds - but the air it falls through is colder and therefore we get snow rather than rain. The friction between the ice pellets, hail and snow within the cloud creates the electricity and gives us the charge, producing the thunder and lightning.

Thundersnow is not rare but it's quite unusual and often one blink and you miss it. This is partly to do with the fact that humidity is lower in winter than in summer, leading to less dramatic and more transient storm clouds - one flash and you might have missed it. Another reason is that, up until recently, the last few decades have been dominated by milder winters, creating little snow.

Forecast Chart 9th December 2014 - the first time we really heard the term 'weather bomb' used widely in the UK Credit: Met Office

Weather Bomb

If we had been using the word 'weather bomb' in the UK last Winter (2013/14) we would have used it almost every week for the entire season. Recent estimates suggest there are between 45 and 65 across the globe each year and that more "bombs" tend to occur in the northern hemisphere.

In meteorological terms it's known as 'explosive cyclogenesis' which basically means a rapidly deepening area of low pressure. In weather reports and forecasts we talk about 'deep lows' all the time. A weather bomb is a 'deep low', likely to bring some very stormy conditions - gale force winds and often heavy spells of rain.

Although not an official term here in the UK the Met Office classes a storm or deep low as 'weather bomb' when pressure drops 24 millibars within 24 hours.

The term is used more commonly in America and New Zealand, where rapid cyclogenesis happens frequently - most commonly over seas near major warm ocean currents, such as the western Pacific Ocean near the Kuroshio Current, or over the north Atlantic Ocean near the Gulf Stream.

Frost and ice this winter but so far tempertaures nothing out of the ordinary for the northwest Credit: Frosty Morning on Burton Marshes MICHAEL MAXWELL

Ice Quake

The official term is "cryoseism" and either term is relatively unknown across the UK - basically because you need it to be very, very cold. Even in the Winter of 2010, which was exceptionally cold across the UK, could not a whisper of an 'ice quake'.

Similar in sound to an earthquake, an ice quake occurs when water in soil or rock freezes. As it freezes it expands and in extreme cold it will do this quickly, putting stress on it's surroundings and creating pressure. The pressure will eventually build until a sudden cracking takes places, creating the 'boom' sound similar to an earthquake.

The phenomenon is more common in climates that experience extreme lows - such as in parts of the States and the Canadian great lakes.

But if you really want to experience an 'ice quake' head to the glaciers of Alaska, Iceland, Greenland or the Antarctic.

Even the cold and wintry winter of 2010 couldn't bring us an 'ice quake' Credit: Met Office


This is a dramatic name, but for a dramatic event - a tornado full of burning hot flames. It's one that we are unlikely to witness over British soil as the "firenado" is more common across warmer parts of America and Australasia where conditions are better suited.

The key ingredients are warm and dry conditions, strong winds and wildfire. High winds at ground level can propel burning hot embers up into the air for miles, often triggered by bush fires.

A vortex of flame in a bush fire is not something that can easily be contained. Firenadoes can be very destructive - enhancing the already dangerous.

Who knows what the next buzzword in weather will be - but we're looking forward to knowing what it's called and where it comes from.