Clouds

Cirrus Clouds:
Cirrus clouds or "Mare's tails" are thin wisps of high altitude clouds. When followed by cirrostratus (high gauzy sheets) deteriorating weather may be approaching in 24 to 48 hours.

chute Colloquial term for spinnaker cirrus Detached clouds in the form of white, delicate filaments, or white patches, or narrow bands.

The weather changed rapidly on the bay and the darkening cumulus clouds were making mischief. Luckily I could see the puff coming as I braced myself at the tiller and spilled the main. Whoosh! ...

Scud: A name given by sailors to the lowest clouds, which are mostly observed in squally weather.
Scudding: A term applied to a vessel when carried furiously along by a tempest.

A huge black bank of clouds arose in the northwest presaging the speedy approach of a savage thunder squall.

Everything feels still on the water, but you will see a tower, puffy clouds, gray in color. The clouds grow darker as the storm approaches.

Waterspouts are unpredictable, but a few signs to watch for as one forms are dark spots on the water, sudden shifts and increases in the wind, and funnels coming from overhead clouds.

Squall: The sudden, short-term burst of wind with passing clouds. May be accompanied by rain.
Stanchions: Vertical poles that stand on the outer edge of the deck to hold the lifelines.

Mackerel sky - A sky streaked with fine clouds, something in the manner of the stripes on the back of a mackerel.

1) To run before the wind in heavy weather. See run. 2) The broken clouds often seen during a storm. Scuddy weather is stormy.
scull
scupper ...

It is described as a sudden increase in wind velocity in tropical and sub-tropical waters, and lacks the usual dark, ominous squall clouds. The white squall may be myth, or it may be a microburst.

See also: After, Below, Stern, Sheet, Sailing