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Reading the weather on board
You do not need meteorology. You need three observations that together make a picture, and the habit of making them before the decision arrives.
The barometer
It is not the reading that counts but the change. A fall of more than about one hectopascal an hour over several hours announces rising wind. So read it three times a day and put the value in the log, otherwise you have a number instead of a trend.
The cloud
High cirrus thickening into a milky veil is the classic warm front warning: the wind will back or veer, rain follows, visibility drops. Towering cumulus in the afternoon means something else: short, hard gusts from shifting directions.
Estimating Beaufort
From force four white horses are widespread, from force six foam blows in streaks along the wind and spray begins to fly. That estimate matters more than the reading at the masthead, because it still works when the instrument fails.
The forecast
Listen to the shipping forecast for your sea area before letting go, not afterwards. And hold the forecast against your own observation: where the two disagree, that is the most interesting information of the day.
What this has to do with insurance
After weather damage the question is what you knew and when. A log with pressure, wind and the forecast you heard answers that on its own and shows the decision was made on the picture available at the time. It is the cheapest evidence there is on board.
