Why are wWatts higher in the Winter?

During the Winter months your may notice that your wWatts (weather watts) are higher than those you have been seen in the Summer. The main reason for this is Air Density. Colder temperatures bring us higher Air Densities, which means greater air resistance.

air-densityWhat is Air Density?

Air Density is the mass of air in the atmosphere measured in kg/m^3. As the mass of air increases so does the resistance we experience when traveling through it. Here’s an interesting video demonstrating the affects of temperature on Air Density.

Why does this affect wWatts?

We anchor the wWatts metric to an average air density. So as above average Air Densities are experienced when it is cold in the Winter the resistance and therefore Watts required to achieve the same speed.

Low Air Density also explains why PBs are often achieved on warm humid days at the Summer.

New Dashboard View

Premium members can now start using the new Dashboard View. This provides an overview of the weather you have ridden in. There are many charts available including Highest Average Windspeed, Wettest Rides and Hottest and Coldest temperatures.


This is currently a Beta release and therefore we are expecting some troubleshooting. If you would like to provide feedback please contact us.

New chart helps you compare setups

The latest chart to assist you in going faster on your bike is the ‘Delta Compare’ chart. When making pacing changes or alterations to your setup that involve a compromise between power, weight and aerodynamics, it can be useful to view how these changes affect our times in comparison to the original setup.

This is perfect for viewing the advantages and disadvantages between Road and Time Trial bike setups. View the time gains from lighter more powerful positions over a heavier, less powerful but more aerodynamic setup. Can your riding style assist in offsetting the time losses on certain parts of the course?

The new Delta Compare graph shows all this by displaying the time gains and losses.

View where the latest setup or performance change gains and loses time.

This is a Premium member chart, view all benefits of Premium membership here.

Time Trialists: 3. Key Charts

We’ve looked at setting up the forecast and understanding the map. Let’s take a look at some of the key charts for Time Trialists that will help you plan for your upcoming race. Some of these charts require Premium membership, please take a look at all the extra features of Premium including many of these charts here.

Air Penalty Chart


Air Penalty, the accumulative difference between Air and Ground distance

What is it?

Shows the accumulative air distance. When the graph is rising (headwind) air distance is being accumulated faster than ground distance. When it is falling (tailwind) ground distance is accumulating faster than air distance.

How to use it

Where the AP line is rising expect greater air resistance. A steeply rising line informs you of sections where the headwind is at its greatest. In these sections expect ground speed to be slower. Where line falls there is less air resistance and your ground speed is likely to be higher than neutral conditions. Pay attention to how the rises and falls are distributed before a time trial to set expectations of ride experience. In other words how long will I have to grit my teeth into the headwinds.

Rolling Average Speed

Predicted change in Average Speed throughout your Time Trial

What is it?

From the Performance settings you have entered in combination with the rolling weather forecast how will your average speed progress throughout the time trial.

How to use it

When monitoring your average speed during a race you should do so in context of how the entire race is predicted to unfold. On courses where there are fast starts and slow finishes your average speed is likely to be higher than your target average. Where slow starts are expected for example hills or headwinds your average speed will be lower than your eventual average. Being up or down on your predicted rolling average will give you a much better understanding of how you are performing rather than your overall target average speed.

Ground Speed Distribution

Time spent at each speed range.

What is it?

Displays the predicted speeds and time spent at within each speed range.

How to use it

This chart has many uses and is critical for those choosing to ride a fixed gear. Chainline efficiency on geared bikes can be improved by ensuring the cassette and chainring combination has the straightest chainline when at the speed most frequently encountered. Overall average speed can be misleading when making these calculations as often this is affected by large periods below and above this speed. The highest peaks are key speeds to gear for.

Yaw Distribution

Time at each Yaw angle range.

What is it?

The predicted Yaw angles produced by the prevailing wind. A windless day would produce 0 yaw. High crosswinds will increase yaw angles. Increasing a bikes ground speed reduces Yaw angles.

How to use it

This is one for those who have the luxury of equipment selection. Choose the equipment you have available that has been shown to produce the lowest CdA for the most frequently anticipated Yaw angle. For example perhaps the long tail helmet will work better for you on a low yaw day. Where as a stubby tail helmet may be better suited where the yaw angles are higher.


Distribution of forces working against you. Air, Gravity and Rolling Resistances.

What is it?

Combining course weather conditions, elevation profile and your Performance settings this graph depicts the distribution of resistances working against you along the course. Large Red sections show where Gravitational resistance is high in comparison to the other forces. In flat time trials the majority of the graph will be Blue as Air resistance is greater than Gravity and Rolling. Tailwinds will increase the proportion of Gravity and Rolling resistance to the overall resistance that prevents you going faster. A headwind on a hill will increase the air resistance component and reduce the Gravitational proportion of resistance.

How to use it

Look out for large section of Red (gravity) it may be more efficient to relax your position to avoid restricting power output. A Resistance graph predominantly Blue (Air) will favour a TT bike. If a graph is predominantly Red (Gravity) you may find a road bike set up more advantageous.

Energy Requirement

Accumulative energy requirements

What is it?

The accumulative energy expenditure throughout the time trial. The line will rise steeper where power out put is at it’s greatest.

How to use it

Beneficial to medium and long distance time trials where energy consumption is required during the event. The frequency and quantity of energy intake can be planned from this chart. You may choose to plan your feed stops/hand ups around the predicted times and locations. Ensure you have taken on sufficient energy with enough time for digestion prior to steep rises in energy requirement.

Time Trialists: 2. The Map

Now that we have the basics set up for an accurate time trial forecast, we covered this in part 1, we are now ready to assess the forecast.

Key weather map features for Cycling Time Trials

  1. Weather overview: Every forecast has a weather overview at the start and along the route where changes to the weather are detected. Within the overview box the following details are displayed: Wind Direction, Wind Speed, Temperature and Air Density.

    Weather Overviews are displayed along the course where weather changes are detected.
    Weather Overviews are displayed along the course where weather changes are detected.
  2. Wind Lines: The colourful Wind Lines illuminate the apparent wind direction along the course. Light blue indicates a tailwind, dark blue and purple crosswind and deep red a headwind. Use the colours to instantly see where the wind will assist or hamper your progress. Tip: You may consider increasing your effort into the red sections to limit your time exposed to the slower conditions.

    Wind Lines show the apparent wind direction.
    Wind Lines show the apparent wind direction.
  3. Crosswind Warnings: When running deep section front wheels knowing where the crosswinds are and how severe the wind speed will be is useful. When warnings are displayed a shallower rim width may be preferable.

    Crosswind warning markers show where the crosswinds are at there strongest.
    Crosswind warning markers show where the crosswinds are at there strongest.
  4. Eye on the Ground: On the day of your time trial the Eye on the Ground shows a recent image from locations near the course.
    Eye on the Ground
    Eye on the Ground

    In our next post we find out how to use key charts to get the best time possible in the conditions.

Time Trialists: 1. Setting up your forecast

Racing a time trial is all about squeezing every bit of your potential out within the distance and time set. Falling short in race preparation is a disservice to the efforts you make in training, lifestyle and during the race itself. In this series of posts I will guide you on how to get the most out of myWindsock.com cycling weather forecasts for your time trial event.

Let’s take a look at how to get set up with the most accurate forecast.

Time trial course loaded
Time trial course loaded

The very first thing to do with any forecast is check the time and date of the forecast. If you have used the Open Events directory or Time Trial Finder this should be correct but it’s worth checking or adjusting for later start times. Click the icon to reveal the available forecasts.

Before we start checking out the numbers we first of all I need to check that the physics engine is using good estimates for my expected performance on the day. Clicking the icon in the top left corner reveals the Performance options tab. From here I can set some loose parameters for the physics engine to use when making predictions and metric calculations.

Adjust the parameters for accurate forecasting
Adjust the parameters for accurate forecasting

If you don’t know what numbers to enter for Watts, Rolling resistance and CdA check out the advice here Performance Options.

In the next article we look at getting the most out of the myWindsock forecast maps and charts.

Experiment with pacing with the new Interval function

The latest feature for Premium Members is the facility to draw intervals on forecasts. This is fantastic for experimenting with pacing strategies. You can experiment with more power on the up hill sections and less on the down hills. Pressing on in the headwind and backing off in the tailwind. Perhaps change your aerodynamic drag on sections where sitting up or standing on the pedals will be required.

Aside from coming up with best power plan for your forthcoming race how about taking your Virtual Partner out on your next interval training session. Simply draw on the intervals, download your Virtual Partner to your GPS device and get out and chase after your VP.

Learn more about creating intervals.

Recent chart update

You may have noticed a change in the appearance of your myWindsock charts. I hope you like the change. The new chart system is far more flexible than the previous version allowing for new and exciting functionality that I will give detail on soon.

With any major change like this I am expecting there to be gremlins to iron out. If you spot something please let me know.

Some features of the new charts you can enjoy right now:

  • Zooming: Drag or use the Zoom buttons to get closer detail to sections of a forecast.
  • Smoothing & Sampling: For speed and clarity you can now change the smoothing of charts
  • New chart ‘Ground Speed Distribution
  • Wind Lines now illuminate the elevation chart for improved context
  • Route reversal, any route can now be reversed
  • New metrics including Total Rainfall

The new chart system allows greater interactivity and with this the possibility for improved forecasting. Stay tuned for the next big update.

Hill Climbers: Using our forecasts

The wind can completely alter a Hill Climb effort adding or subtracting minutes from the climb. This makes judging the effort and choosing a gear if riding fixed challenging.

If you plan to ride fixed and you have estimations of Power, Weight and CdA. Take a look at the Ground Speed chart on hill climbs to assist you in picking the correct gear. The average, min and max speeds will help you judge gear choice.

Here’s a quick infographic on how to set up your chart and use the basic functions of a myWindsock forecast to get the best foresight for your hill climb event.