Top view of battle fleet gothic ships
On top of this, nearly every Tau ship that holds torpedoes is also a carrier wise Tau commanders frequently send Interceptors along with a mass torpedo volley from multiple ships in order to tie up enemy Interceptors in a dogfight, allowing the massive number of torpedoes to sail past into the target contested only by the defense turrets which simply will not be able to handle that large a number of torpedoes.
They can't be fired on a non-identified ship, but on an Identified one that is large and/or slow every single torpedo of a volley is highly guaranteed to hit if they aren't destroyed by defense turrets or interceptors. Like many factions the Tau of both subfactions have extensive access to torpedoes, however one key difference is that their torpedoes, while each is slightly weaker (90 damage vs 110 of others) and the volleys have a smaller number of them (5 or 6 vs 8 of others), are GUIDED. Used correctly they can be even more dangerous at long range than the Chaos faction. Used incorrectly they can be a bit of a confusing inefficient mess. Instead, they are built to get into (fairly long) range, park themselves in place and incessantly let rip with every gun on the ship. They aren't built to quickly dash around a battlefield in-and-out of combat like the Aeldari, nor kite around at long range like Chaos, nor dash in close to ram and board repeatedly like the Orks. If only a single word could be used to describe the Tau ships it would be "slugfest".