JeanneP is spot on when suggesting that learning the wind is the criteria for understanding what is out there and what you will need to know to handle sudden changes in velocity and direction.
In the areas of Inter Tropical Convergence where storms play the major role in determining the winds, a real appreciation of Thunder storms , Line Squall and Sea Breeze Fronts is necessary.
See a note on the subject :- LINE SQUALLS
What is important here is to realize that these conditions are common at night , just prior to dawn and after sunset, and as one may not be able to see the wind on the sea - therefore what to look for is Lightening, and if
it's product Thunder increases in volume - then reduce sail to a minimum, if necessary start your motor to keep control. Hatches closed, all loose equipment lashed or stored. Non-vital electronics disconnected. Crew alerted. Slow down head into the oncoming storm if there is no time to avoid it.