Correct. You should remove the lambda time altogether, and change the frequency of this timer from once every millisecond to a more appropriate interval, say once every 5 seconds.
Also, your approach of attempting to poll the anemometer every 1ms and hoping to calculate the wind speed from this won’t work. You need to attach an interrupt to the anemometer pin and use that to calculate the windspeed…
Back to the original problem, you should try sending the value of Wind to the serial monitor to visualise your concatenated string.
Pete.