During international transitions, some things stay the same – while retaining inherent unpredictability.
Such as Wimbledon.
1st-15th July, top-tier tennis players from far and wide will converge on London’s famous Wimbledon courts to take part in one of the oldest and most world-renowned tournaments in the game.
We’ll look at the likelihood of Middle Sunday play…
At Wimbledon, even a light shower can force delays or stoppages.
This is true despite very quick applications of court covers (or the extendible roof, over Centre Court). It only takes a little dampness to post unjustifiable health risks. In fact, it’s been known for rain to stop play so much that matches become split between two days. This then delays subsequent matches.
During the four rainiest tournaments (1991, 1997, 2004 and 2016), there were so many delays that there was little choice but to stage matches on ‘Middle Sunday’; a traditional break day.
Recent Form: Extremely Inconsistent!
Last year’s exceptionally hot and (mostly) dry tournament was a welcome reminder that despite Britain’s reputation for changeable weather, it’s quite capable of hosting a major summertime sporting event with no more interruption than you’d expect elsewhere in Europe.
Sadly, this year’s soaking wet June has hammered home that it can also be very un-summerlike for weeks on end!
When it comes down to it though, both the cool, rainy June of 2019 and the hot, dry June of 2018 are highly unusual occurrences. The UK just happens to have experienced one of the biggest conceivable contrasts between one June and the next.
‘The UK just happens to have experienced one of the biggest conceivable contrasts between one June and the next.’
I could demonstrate just how amazingly unlikely this was to happen. But then, this article would end up ten times as long, so I’d better not…
Middle Sundays: More Double Faults or A Welcome Break?
Luckily for attendees of Wimbledon 2019, a rainy June doesn’t preclude a rainy July. We only have to look back three years to find an unusually wet June (153% of the usual rainfall in England) followed by a drier than usual July (67%).
‘Let’s delve into the chances of such a switch-up this summer…’
Let’s delve into the chances of such a switch-up this summer, by looking at what past years tell us about the chance of wet weather. Especially those most comparable to this year (the ‘analogues*’).
Specifically, we can look at the cumulative number of days with at least a little bothersome rainfall. Let’s compare all historical years with both the MetSwift ‘analogues’ and those four famous years that saw play on Middle Sunday (Figure 1).
Figure 1: Graph showing the mean number of days with at least 0.5 mm, for all historical years (cyan), the ‘analogue’ years (peach), and the years that saw play on Middle Sunday (red). I’ve grouped the days by the stages of the tournament. The bars are individual for each period, while the lines are cumulative across time.
What Really Happens at Wimbledon?
Even before we focus our view, the climatology (mean of all years) tells us something of interest.
Wimbledon typically becomes a little rainier as it progresses. (The upward curve to the cyan line shows this.) Meanwhile, the number of matches to be played reduces, so the rain has a lessening impact. If it was rainier during the first week instead, play on the Middle Sunday probably wouldn’t be such a rarity.
The scheduling of the tournament looks very wise from this perspective!
Now, what about those Middle Sunday play years (you know what, let’s call them the cheeky years), and how do the MetSwift analogues compare?
Unsurprisingly, the cheeky years were considerably rainier than usual during the opening four days of the tournament. That being when wet weather can be most disruptive.
The analogue years were also wetter than usual during the first half, but during the 3rd round instead. There’s a near-normal frequency of rain beforehand. This suggests 2019 is unlikely to see enough stoppages to force play on Middle Sunday.
For the second half of the tournament, the analogues suggest a near or below average amount of rainy weather. So, a decent likelihood that the rain leaves some of the ‘biggest’ matches alone this year.
Pesky Showers or Autumnal Rain?
So, we know how often it’s likely to rain, but are we talking stoppages of several minutes, or several hours?
Studying the overall weather patterns being suggested by the analogue years (Figure 2), there’s a weak suggestion of low pressure systems close to the west of the UK and areas of high pressure near to the east. This pattern tends to result in hot, dry air battling it out with cool, moist air for supremacy across the nation.
Figure 2: Plot showing the analogue years mean 500 hPa Geopotential Heights compared to the long-term average (1981-2010). As implied by the annotations, lower than usual heights generally correspond to more low pressure systems than usual, and higher heights to more areas of high pressure than usual.
In that situation, rainfall mostly occurs in the form of showers or thunderstorms, rather than longer spells of rain. I’d not be surprised to see some examples of fine, warm or hot weather suddenly giving way to a downpour (inspiring much rolling of eyes and witty remarks on ‘the typical British summer’).
Any Trouble with Toasty Temperatures?
As you’ve probably gathered by now, this pattern means we could see some toasty situations at Wimbledon (regardless of temperaments).
‘As you’ve probably gathered by now, this pattern means we might see some heated situations at Wimbledon 2019… regardless of temperaments.’
In years past, court temperatures have occasionally climbed into the 30s °C (on average, each day has a 3% chance based on historical years). This has been known to cause some health problems for those not used to heat. Rarely have these been tennis players, though, due to their exceptionally high fitness levels.
A possible exception is when temperatures reach the mid-30s, as happened at the start of the 2015 tournament, but this was one of only four years to have reached 33°C or higher.
Overall, it’s the potential for thunderstorms, rather than how much time it might be raining for, that I believe bears watching most closely this year. That’s certainly what I’ll be doing @peacockreports.
James Peacock MSc
Head of Meteorology
* Years which are most comparable to 2019 when considering the overall behaviour of the atmosphere and oceans across the entire globe. Yes, we can do that!