No. I think this will take some time.

What's the easiest way to determine cloud height? Both the base and the top.

Get in an airplane and fly up to the base, then the top. Other wise, I know of no accurate way. You could use some type of sextant type angular measuring device, I guess, if you also know the exact distance to the cloud.

I am more interested in what type of clouds they are, and which way they are moving, and what's causing it. Sea Breeze? Cold Front? Building Thunderstorm?

I like to see the big picture (on the Weather Channel) and then allow for the local geographic influences which will affect the surface wind.

Remember, Bethwaite was also a competition glider pilot, so he was very much interested in updrafts/downdrafts, etc. thus his focus on cloud heights.

What I meant was, is this information given in any of the pilot forecasts. I went to the NOAA site and it was all jargon that I didn't understand.

Cloud bases are given, that is called the "ceiling" and could be described as scattered, broken or overcast. The reports are given in shorthand, you need the key to decipher it, or call the 800 number for the airport nearest where you will be sailing.

Start by looking around here:
http://aviationweather.gov/adds/winds/

And I'll try to find the 800 numbers for you to call.

Here's one for Sebring's airport, 863-655-6424

Call this and listen to the automated report. This is the actual weather report for right now, not a forecast for the future, so it's not much use for sailboat racing.

The lower the cloud the worst the weather.

From sitting on the water that may seem often the case but from an aviation perspective that is not entirely correct. Those big cummulo nimbus ( the big vertical clouds with explosive looking tops ) are incrediably destructive due to the amount of air being sucked up ( something to fear if you are a hang glider or parascending plot )but equally at ground level they create fantastic lines of " wind " which you can run along the front of in your boat, thats how they get across the atlantic averaging 30 odd knots.

Now if you start talking about nimbo stratus and the like then you need to start thinking about " dewpoint " which is the key to forecasting height of the cloud and just how much you are going to get hosed down today.

I'm just trying to find a way to predict if an approaching cloud will affect surface wind, especially in light wind conditions.

Look at the water's surface, see what's going on in front of the approaching cloud. The bigger, darker ones usually have built up to the point where they may have a downdraft coming out of the base. Now, is that cloud moving towards you (the outflow will be stronger if it is) or away from you? If it's early in the day, chances are that cloud is being formed buy rising hot air, so it's not going to help you too much, unless it's a huge building thunderstorm, in which case it will be sucking in a lot of air, right up until it "explodes" in a big downburst.

Sturart Walker has an written entire book called "The Sailors Wind". Check it out.

What I'm getting is that a downdraft is associated with rain.

Our normal puffy white cumulus (if I'm understanding this correctly) actually has an updraft immediately in front, which causes a net REDUCTION in wind speed and a header! This is the thermal effect, and the resulting subsidence will create a lift and increased speed along the side of the cloud. This is if and only if, the cloud is low enough to interact with the boundary layer.

If you look at the cumulus and it has a wispy base, that is a sign the cloud is not interacting with the boundary layer.

But, I'm getting a little confused...

The picture I have in my head is my last trip to Wildcat.

very generally speaking, if the cloud is of reasonable size and isn't raining, you will see an increase in windspeed if you are to windward of it, and a decrease if you are to leeward..

If the cloud is raining, it's the opposite because the downdraft caused by the rain will add to the wind to leeward