In my numerous web searches to understand wind gradient I came across two websites that are kind of neat and might be of interest to some people who are making their own missions.
They record the weather conditions of every single day of the war.
1. This is a Dutch site that has records of the weather conditions around Flanders: http://www.weerstati...ndex.php?pid=29
2. This is a collection of diaries and official records that mention the weather: http://ww1weatherrep...ikifoundry.com/
I checked and the two sites match up beautifully. For example, on January 1, 1916, two diaries mentioned that there was very heavy wind that day and some rain. The Dutch site lists a south wind that day of 5 on the Beaufort Scale (which is between 8.0 to 10.8 m/s); it also mentions there was rain that day.
I can't quite explain this, but I find this all really cool! It will be very easy to implement this into my missions at certain dates.