RTTC National Hill Climb Championships Forecast

Storm Austen has already made landfall in the UK. Some damage has already been caused according to Cerys, a Barista in a Newquay coffee house speaking to the BBC, “We’ve got a very bent mop, but other than that we’re all good”. The big question is, will this impact the RTTC National Hill Climb Championships that are taking place up Porlock Toll Road on the 25th of October? For a detailed run down of the course, without an attached weather forecast, check out our course preview here. If you’re more concerned about the weather though, stick around.

Starters are slated to set off every 30s between 9:30am and 2:20pm. The wind speed shown here is in MILES PER HOUR and it’s currently looking like it’ll also be raining all morning. The big question on the lips of many is will the wind be strong enough to curtail the event and what direction is the wind blowing?

For those of you that want the forecast without the waffle, you can see it yourself in the myWindsock platform here.

The strongest headwind ever at an RTTC National Hillclimb Championships?

Time for the big unveil. We’ve waited as long as we can for this forecast but it’s time. It’s going to be a 40mph block headwind all day.

This is the craziest hill climb forecast we’ve ever seen. 43mph headwind forecast in the morning, dropping a little bit throughout the day but will still be a 39mph wind for the late starters. Gusts will be higher. The course is very sheltered for the most part, lined with trees. Trees do have a tendency to come apart during high winds and riders should make sure to select tyres that can tolerate riding over a twig without ripping.

The shading on the map

Zooming in a little on the map above, the eagle eyed readers will have noticed a shading pattern. This demonstrates the wind’s “surface friction”. This course is a mixture between being lined with trees and open hill side. You can easily see which area is which using the key in the image, the dark shaded area is high friction (lots of stuff in the way – in this case, trees) and the lighter area is exposed with low surface friction for the wind. This course demonstrates the difference in a stark fashion.

Headwinds as hills

This headwind is like adding an extra 70m of climbing – it could be worse but the trees help out a lot!

The Wind Adjusted Elevation (WAE) plot also demonstrates the impact of the headwind. You can clearly see where the course opens up and the WAE separates from the topological elevation. The physical impact of this is equivalent to adding around 70m of elevation onto the climb. Riders can minimise this by being as aerodynamic as possible.

How to behave in a 40mph headwind

At the start, normal service goes ahead. You’re almost immediately into the shelter and you can ride how you normally do. Once the road opens up, the wind gets serious and riders will need to enter their time trial mindset.

A stationary object in 40mph wind has an air speed of 40mph and a ground speed of zero. This is important to remember. The resistance you feel on the bike from the air is not due to the ground speed. A rider going 10mph into a direct headwind of 40mph has a wind speed of 50mph, which is the same amount of air resistance as a rider going 50mph on a perfectly still day. When it gets hard, avoid the urge to stand up and double your surface area, the extra watts you gain by standing up will be lost to the wind.

TT bike or road bike?

Harry Macfarlane, of hill climb championships and Instagram fame, made waves by telling everyone that they should go “full aero” with their set up. Let’s imagine a scenario where a rider’s TT set up is 3kg heavier than their hill climb set up and their power drops 10% in the aero bars. Our imaginary rider’s system mass in 77kg and their hill climb power is 390W, this means their aero bar power is 351W. We will use a cda of 0.24 for the hill climb bike and 0.21 for the TT bike.

Hill climb bike:

The starting point – 17:14 with those numbers (slower than both the KOM and the QOM). This is a “normal” hill climb set up using good, but not nuclear, watts.

You can see from the screenshot above that the weather is worth 1:36. Let’s take a look at how the resistive forces break down to see if that gives us a clue as to whether the TT bike will be faster.

Seeing that white line even play a role in a hill climb is rare. Where the white line crosses the red line, it’s a sign that air resistance is the dominant resistive force. Acceleration forces are represented by the green line and rolling resistance by the blue line. These forces change depending on what bike you use (air resistance makes a lower contribution if you’re more aero, for example).

Let’s see how the forces break down with our new set up with a 10% reduction in power, +3kg and minus 0.03 on the cda!

There is a noticeable reduction in the air resistance measured by this simulation when we switch to the heavier, but more aero set up. There will be a trade off here though, as the forces due to gravity will increase. The key to bike selection is minimising the sum of these forces without over-indexing on any particular one.

The big question is, is it faster?

No, not even close. It’s still a hill climb after all. What if power stays the same?
Almost exactly the same. Only 4 seconds slower. Now, this does beg the question – what about a lightweight “aero” hill climb bike with clip on TT bars. Imagine a scenario where a rider might be able to achieve a cda of 0.22 but for a net gain in weight of less than 500g. Then there’s a big question to answer…

Kit selection, of course, is highly individual to your watts, cda and weight. To have the best chance of a good result, play around with your set up on the newly furnished myWindsock platform.

Click on the link for the National Championships forecast.

Will the forecast be wrong?

You may have read this expecting us to make a prediction for the men’s and women’s winning times. We have not done this as there’s obviously a huge amount of uncertainty caused by the forecast. One thing we do know is that nobody is getting remotely close to a course record with a 60kph headwind.

Forecasting the exact timing of a storm can be difficult. It’s possible that the storm will die out earlier than expected and if the forecast is wrong, it’s most likely to be in the direction of conditions being better for later starters. The easiest way to stay up to date on course specific forecasts is with us.

Click here for metre by metre updates of the conditions.