HOT & DRY HEADLINING or WET WEATHER on stage?
In 2017 thousands of heady festival revellers experienced the hottest days in Glastonbury’s history.
Yet coming one week after the summer solstice, and as much as we love it, mud baths are an almost expected part of the line-up. Weird UK weather is an accepted part of the Glasto experience.
After the festival’s much-needed break in the ideal summer of 2018* will weather play the irony card & force festival goers out of the game, or will June 2019 score a hot dry hat trick?
I have delved into historical data and, based on my discoveries, chosen rainfall chances to headline, with support from the wind.
The Run-Up: Things Can Only Get Better…
Long spells of ‘truly’ fine weather have been hard to come by in Southern England in recent weeks, yet it hasn’t been wet either i.e. changeable times; the total rainfall for this region in May 2019 was only about 60% of the 1981-2010 average.
The first half of June may be a wetter story, with the potential to see rainfall totals near or above what’s typically seen across the whole month. Much of this looks to fall on Friday 7th.
Thankfully, numerical predictions suggest this rainy weather pattern will give way to a more settled (drier) third week. Using other forecasting methods, I can see no strong reasons to contradict this.
For Glastonbury, this precipitative transition should allow topmost field soil in Worthy Farm to dry, as the water percolates downward through it (to top up the groundwater).
Festival Weather Insight – on the Slide Again?
Assuming the weather manages to turn drier as anticipated, then the stage will be set for good conditions underfoot provided there isn’t a deterioration in weather conditions in the final week of the month.
Historical years exhibit (Fig. 1) that during the height of summer (though dry is far from guaranteed) rainy weather reduces markedly for the weekend (29th-30th).
Figure 1: Plot showing the percentage of all years on record (no border) and analogue years** only (border) that the daily total rainfall has been at or above 5 mm (aqua blue shading) or 10 mm (light blue shading), for each day 25th June to 1st July.
HOWEVER, when we invite the MetSwift analogue years onto the stage, there’s a higher chance of 5+ mm on all days, and of 10+ mm – ENOUGH TO TURN THE FIELDS INTO QUAGMIRES (look it up) – on all but two days.
Likelihood-wise, this means there’s a good chance more than one day will see enough rain to increase the amount and wetness of muddy conditions at the festival. Sorry guys…
How Might This Rain Fall? … Suspecting Storms & The Magic of The Meteorologist
Weather prediction can reach beyond mathematical modelling when a meteorologist is familiar with the nuanced systems affecting weather impact.
For Glastonbury, I’ve been contemplating the behaviour of major driving forces behind our weather patterns. e.g. tropical thunderstorm organisation and movement.
“Though wind gusts capable of damaging temporary structures (reaching 40 mph +, stages & gazebos) have only been observed in 5-10% of historical years, interpretation suggests 2019 may be one of these.”
I have the impression that the wet weather will most likely be part of a ‘breakdown’ to a spell of warm or hot weather during the preceding week.
Meaning there could be thunderstorms, bringing a risk of torrential downpours, lightning and strong wind gusts.
Though wind gusts capable of damaging temporary structures (reaching 40 mph +, stages & gazebos) have only been observed in 5-10% of historical years, interpretation suggests 2019 may be one of these.
Let’s Keep a Close Eye on This One!
Pack your Macs (cagoules) guys.
Sometimes, the weather takes its historical habits and throws them out the window.
So, I’ll be keeping an eye on the guidance tools as the event draws nearer. Luckily for you, it’s what I do for a living! All you need to do is follow me @peacockreports (and you may as well cross your fingers too. Or is there an ‘anti-rain dance’?).
James Peacock MSc
Head Meteorologist at MetSwift
*A traditional break known as a ‘fallow year’, enacted once every six years allowing land to recover.
** These are historical years (1950-2018) in which Earth’s atmosphere has been found to have behaved most similarly to how it’s expected to in 2019.