2005 Explorer Water Noise

Alright i dont think this is any big problem, i have a 2005 Explorer XLS with 19,000 miles on it. When it rains alot and im driving down the road i can hear water like coming from the front of the dash or lower dash. The noise sounds like air blowing water. and when i stop the noise stops and after it quits raining for a while the noise goes away. i dont know what it is, there isnt any water coming inside the cab. Im wondering if there is water building up on the roof in those ridges and when i drive down the road the wind blows over it and makes that noise, or there is a clog in my cowl and the water builds up in there and when the wind blows over it, it makes that sound, thanks!