Re: weather guidelines
The Winds and Seas are different for every boat and crew. Crew experience makes a big difference. Type of boat also is a major factor.
I have a 21 Foot close bow Runabout and in general I do not launch if the Seas are over 8 feet or if the swell are closer together than 8 seconds. I have had my boat out in 9 foot seas every 6 seconds in the Pacific Qcean. It was Safe enough but not much fun so we came in early with only 3/4 of a limit. Another condition I try to avoid in the Pacific is a confused Sea where the Swells are going one way and the chop a different way. This happeneds when the normal winds change directions and have winds 30 knots or more. I think the most dangerous condition for my boat is a large following sea. While done right this can be a fun smooth ride in. The key is you need to ride the back of the swell but close enough to the top that you can see over the swell. This allows you to see boat coming out or rocks in your path. So if you do not stay on the top where your can see you may meet a boat coming out at the top of the wave. Wave travel about 20 Miles per hour and if you should go over the top you boat will surf down the face of the wave and bury the bow into the back of the next wave then the wave behind push the stern over the bow. This is call pitch pole and is deadly.
If you go too slow the wave behind will over take the stern and could fill the boat with water.
I think Small craft advisory will very from place to place. Out here it issued at 33 knots and up but can also be issued to hazardous seas.
You talked about harder to dock with 20 knot winds. This is always true more wind or cross current and it harder to control your boat and dock. With a single screw and strong winds or cross currents the docking has to be done with more speed to give you more boat control so the margin for error is smaller. Too slow and the wind will have more control than you do.
Another big factor is the water depth and current. Swells when going against the current will shorten up and put them closer together and more dangerous. Also when Swells come into shallow water the bottom of the wave will slow down and cause the wave to get steeper and break just like a wave comming to a beach. Some area will have a shallow water bar that causes very dangerous wave at low tide but at high tide has very little effect.
Out here the wind blows every day so we get lots of pratice with different types of seas. One thing that I think helps is to keep a log of every trip. Note the swell height and Wind and how well your boat handled the condition. It will not take long and you will know what your boat and Crew can handle.
I post a couple of links that may give you some information you can use. The first one is about warning flags. One thing on warning flags, they will post a small craft advisory because of forcast. I have fished many days when the small craft flag was flying and the water was very smooth and no wind. So listen to the Coast Guard weather report give at almost the same time every day. They will anounce on Channel 16 to switch to channel 22 for the marine Forcast.
http://www.weather.gov/os/marine/cwd.htm
The second one is the buoy I use to decide weather to launch or not. It is 12 miles off of Bodega Bay, North of San Francisco about 40 miles.
http://www.ndbc.noaa.gov/station_page.php?station=46013
Bodega Bay Weather today May 22 2008 I would not launch to go out into the Pacific Ocean.
Winds NW 320 degrees true @ 35 knots with Gust to 42.7, Water temperature 48.2 F
Seas 14.8 feet every 11 seconds, chop at 6.9 seconds, Wave Steepness = average.
