But on most bodies of water, predicting the clammy gray stuff isn't so easy. For boaters, the marine fog that hides buoys, rocks and other boats is typically advection fog. Dave Feit, Chief of Marine Forecast Branch at the Marine Prediction Center, says there a several problems with predicting fog over the water. First, it is difficult to measure fog density. Unlike airports, which have the means to measure fog, there is no way to measure fog on the water.
Photos taken from satellites simply make fog look like a cloud, which it is.
There is less uniformity, however, where land and water meet, which makes the weather forecaster's job much more difficult. An inlet may be socked in by fog while a few miles away the sun is shining. Maybe it's the difference in tide, a hot thermal wind blowing off of a steamy corn field, or a localized flow of water. Feit, who owns a boat on Chesapeake Bay and has been caught in fog a time or two himself, says it could be quite awhile before numerical models are available that can accurately predict localized marine fog. Unfortunately, in many coastal areas, that's the only type of fog there is.