introduce concept of wind assisted travel

[IanMayo]

We should introduce some more temporal weather related aspects.

Instead of the weather being a band moving across the region, that increases the risk of cold, let's do the following:

• it's a cyclone passing through, not a linear barrier of wind
• the cyclone is spinning anticlockwise
• when travelling into the wind there is a drop in speed, and general increase in all risks, particularly cold
• when travelling with the wind behind there is an increase in speed and general decrease in all risks, except for a slight increase in cold risk
• with a 90 deg cross wind there is no impact
• between cross-wind and head/tail wind, exponentially build up to the peak risk impact
• so when this entity is considering "risk at(location, time)", it must determine the direction of the wind at that location at that time, and calculate the risk accordingly.