Just a question / nit pick. Wouldn't you want at least some of the main sail up (maybe with a reef or two)? What if the wind / waves / bouncing / etc cause the engine to suck up some dirt and stall?
I've only been hit by sudden storms twice and both times I left my main up and engine on and kept the boat feathered into the wind.
That's fine in a mild squal.
Thunderstorms can also pack microbursts of over 100 MPH and I've expereinced horizontal hail that was reported 1-mile away at over 90 knots. That's enough to shred a "feathered" sail. It was enough to cartwheel a group of beach cats off a near by beach that had no sail up.
The problem with squalls is you don't know, and unlike a stormy day with sustained high winds, there's little point in pretending to sail through it.
It's certainly good to be prepared to get some sail up. It is also smart to have the anchor ready; it's always surprising how many forget that simple tool.
I learned by sailing small boats on the Chesapeake.
* Squals are not surprises; if it's humid and it's summer, expect it.
* We never needed instruments. Weather sense worked fine. Fear the big black things to the west (MKII Eyeball). Don't sail with your eyes on the intruments; sail with them turned off, most of the time. Watch the water under the clouds (high wind whips up spray). Get your head out of the cockpit.
* Down bursts spread when they hit the water; the wind can come from any dirrection and change dirrection and speed VERY quickly. You may not be able to turn and feather fast enough.
* Sailboats can't outrun anything, in part because the wind dies in front of the squal. Storms change quickly. You get what you get.
* The only thing that really helps with lightening is a harbor with a lot of trees and masts.
* Like the Old Man and the Sea, we all need to be destroyed by a storm one time. We learn respect.
I'll sail in thunderstorm weather; I don't like it, I sail early so I can reach shelter early, and I keep my head on a swivle. If they are morning storms, I'll wait.