13 Jul 2015

Waving weather fronts: a forecaster’s headache

I forgive you if you’ve read the title of this blog and think that the weatherman is just making up another excuse for rainy weather, but stay with me!

Whilst waving weather fronts doesn’t sound like a particularly technical term, it’s how us weather folk are describing the weather pattern that is giving us a bit of a headache in the coming days.

So, what is a waving weather front? Well, it’s exactly as described: a weather front that waves around, like a wriggling snake, often with enough randomness to make it difficult to predict its precise location at a specific time.


Waving weather fronts in action

In the weather world, satellite images shouldn’t just be looked at individually, but also run in a sequence as an animation.

This allows for trends and characteristics of cloud patterns to be viewed and are a good indication of what has happened and what is likely to happen in the near future as a result.

If you watch closely in the looping video in the tweet below, you can see that the band of cloud over and to the west of the UK waves around – much like someone flicking a skipping rope, sending a kink running along it.

See, I’m not making it up. Waving weather fronts do exist…

Why are waving weather fronts a pain?

Waving weather fronts are pain for weather computer models because their movements are very slight in the grand scheme of things.

Weather computer models like big things that they can grab hold of, to analyse and extrapolate over time – like big areas of high or low pressure.

However, they tend to struggle with the nuances of a waving weather front, more especially when its interactions with the jet stream, 30,000ft up in the sky, are taken into account.

Big influence on weather

If a dip in the jet stream coincides in with a ripple in the waving weather front at the right time, you can get a decent area of low people_umbrellas_g_wppressure with rain and possibly gales.

Yet if a dip in the jet stream doesn’t coincide at the right time, you just end up with a band of cloud and some drizzle.

These subsequently have huge impacts on temperature because this waving weather front also separates cool, fresh air from hot, humid air.

If it ripples far enough northwards, and forms a decent area of low pressure, hot and humid air is drawn up ahead of it, allowing temperatures to soar into the mid to upper 20s Celsius.

What do I think will happen?

One piece of advice I would offer this week is to not rely too much on the weather forecasts provided by apps and websites.

In this kind of waving weather pattern, the detail will continually change, so you’ll probably end up with a different forecast each time you look.

The same goes with watching us weather folk on the TV. Whilst we’ll strive to get the forecast spot on, inevitably, things may go a bit awry.

In the meantime, if you have any questions about anything you’ve read here, you can contact me on Twitter – @liamdutton

Images: Met Office, EUMETSAT

Tweets by @liamdutton