Insights & News

Weather Prospects: Cowes Week 2019

21st July 2019

“Hurry up and wait…” told by a Sailor & a Meteorologist

For this blog piece, I’ve teamed up with our in-house sailor Shaun Pammenter (MSc) to provide tailored insight on the regional and local wind patterns of the Solent.

Conditions at Cowes look to be slightly different to usual, and might give competitors a wait for the winds to arrive and a trickier racing when it does…

So, what is Cowes Week?

Cowes Week is one of the world’s most iconic sailing events, with nearly 200 years of history.

This year will see over 1,000 boats and 8,500 sailors battle it out on the Solent. From the CEOs to the apprentice on the sail loft floor, Cowes Week attracts competitors from all walks of life: Great racing by day and plenty of refreshments by night!

Cowes Week takes place in late summer to take advantage of the glorious English summer. Minimising time spent wearing foul-weather jackets and Dubarry boots, and the most time sailing in a sunny sea-breeze, basted in sunscreen.

What is the norm, and what can we expect this year?

Historical data tells us that in the Solent at this time of year, the broad-scale winds (referred to as gradient winds in sailing circles) blow most frequently from the southwest and west.

These winds are driven by extensions of high pressure from the Azores across southern UK or northern France, and low pressure systems moving near or across northern UK.

Westerly Wind

This predominant westerly wind is then enhanced and accelerated by the heating of the land and funnelling into the Solent as what sailors call the “South West Sea Breeze” (see Figure 1 for further details).

For example, when the gradient wind is 15 knots, the heating of the land and the squeezing through the western entrance to the Solent can lead to the South West wind accelerating and exceeding 20 knots!

Figure 1: Depiction of the typical daytime behaviour of wind patterns in the Solent for a southwest to west gradient wind.

Figure 1: Depiction of the typical daytime behaviour of wind patterns in the Solent for a southwest to west gradient wind.

 

Atypical Indications

But an event like Cowes Week which is steeped in tradition could be seeing changes, and I’m not speaking about the change of management of the hallowed Pier View Pub. This is a weather blog after all…

I’m talking more about changes in weather often associated with, and often anticipated for Cowes Week.

Analogue years* in our MetSwift database of over 65 years suggest that the westerly wind will likely be less reliable than usual during Cowes Week 2019 (see Figure 2). The proportion of days with gradient winds from other directions looks to be larger than usual, perhaps even with more days being non-westerly than westerly.

Figure 2: an illustration of how the analogue years suggest weather patterns will differ from average during Cowes Week 2019, with a focus on gradient winds.

Figure 2: an illustration of how the analogue years suggest weather patterns will differ from average during Cowes Week 2019, with a focus on gradient winds.

 

What’s up with the wind?

What the analogue years suggest is the pattern isn’t as reliable as it was in the past. There is evidence, in first-hand accounts and observational data, that this loss of reliability to the westerlies has become more frequent this past decade.

We’re seeing changes in the driving weather patterns, in favour of patterns that bring more in the way of winds from the north to south-easterly directions.

What it All Means for Cowes This Year.

We expect more gradient winds from between the north and southeast direction than usual (detailed in Figure 3).

Figure 3: Depiction of the typical daytime behaviour of wind patterns in the Solent for two classifications of gradient winds blowing at 10-15 knots.

Figure 3: Depiction of the typical daytime behaviour of wind patterns in the Solent for two classifications of gradient winds blowing at 10-15 knots.

North to Northeast Gradient Wind

With this gradient wind and sufficient heating of the land, the winds blowing down the Southampton Waterway become light and variable near midday.

Eventually, by the early afternoon, the Sea Breezes establish. The southwest sea breeze first, then the southeast sea breeze with a large no-wind transition zone in the Central Solent.

Though not as strong as with a Westerly gradient, the southwest sea breeze eventually wins out over the southeast sea breeze and moves the no-wind transition area into the Eastern Solent.

East to Southeast Gradient Wind

With this gradient wind, it will likely be a long day on the water before any racing happens.

In this situation, land heating has to overcome the gradient wind. Whereas the sea-to-land sea breeze works with a westerly gradient wind, it works against an easterly gradient. This is because, as the air moves inland, the rotation of the Earth causes it to turn to the right (i.e. become westerly). This is known as the Coriolis Effect.

So early morning could be looking good for sailing, then as the heating of the land mass takes effect, winds will become light and variable, likely too weak to race in.

Eventually, around 14.00, dependant on heating and a few other factors, including the timing of the tidal flow, the southeast sea breeze can develop. Initially in the Eastern entrance to the Solent, then building and advancing right up the Southampton waterway.

In Summary: More Variable Than Most Years

Signs are, for a generally lighter than usual Cowes Week, with more sailing in South Easterly winds

For some of the sailors the long waits will provide more recovery time from the night before. For the more focused sailors on board it will be a pretty frustrating wait.

A final word to competitors – stay hydrated and pack plenty of sunscreen There may be plenty of time for tales of bravery and valour on the high sea… or in the pub.

And don’t use up best sailing stories too early on…because you might be listening to them again in a day or two.

 

James Peacock MSc
Head Meteorologist at MetSwift

 

* 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.

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