Turns out all my anemometer code so far is wrong, equations is not my strong suit and I seemed to be always trying to overwork the equation.
// work out wind speeds function
float CalcWindSpeed(int clicks, int seconds)
// Caluculate Wind Speed
// Work out number of clicks per second averaged over time period
float windSpeed = (float)clicks / seconds;
// since we know 1 click over 1 second equals 1.492 mph
// apply the multiplier
windSpeed *= 1.492;
The above is mostly the code I am using now. I have tweaked it since to allow float seconds so I can use the same procedure to work out the gusting speed.
The above code is borrowed from Sparkfuns Weather Station Tutorial.