Wind direction

You have provided very few specifics with your question. Here is a script to get you started. You can test it by putting it on a cube. It it intended to be put on an arrow in the scene where the head of the arrow points to positive 'z' with a rotation of (0,0,0). It rotates an arrow in a rough wind-like movement. More work is needed if you want a 'realistic' movement. The transform.forward of the object you attach this to should be used as the wind direction however you implement wind. Since I don't know any of the specifics of how or format of the output, I'll leave that to you. Currently it does a Debug.Log() of an angle:

 #pragma strict
 
 var minChangeSpeed = 0.5;
 var maxChangeSpeed = 2.0;
 var maxChange = 45.0;
 var minChangeTime = 1.0;
 var maxChangeTime = 2.5;
 
 private var qTo = Quaternion.identity;
 private var changeSpeed = 0.0;
 
 function Start () {
     Invoke("ChangeWind", 0.0);
 }
 
 function ChangeWind() {
     changeSpeed = Random.Range(minChangeSpeed, maxChangeSpeed);
     qTo = Quaternion.AngleAxis(Random.Range(-maxChange, maxChange), Vector3.up) * transform.rotation;
     Invoke("ChangeWind", Random.Range(minChangeTime, maxChangeTime));
 }
 
 function Update () {
     transform.rotation = Quaternion.Slerp(transform.rotation, qTo, changeSpeed * Time.deltaTime);
     Debug.Log(Mathf.Atan2(transform.forward.z, transform.forward.x)*Mathf.Rad2Deg + 180.0);
 }