How does the limited flight from the Storm Sorcerer's Tempestuous Magic feature interact with the character's regular movement?

Question

Tempestuous Magic reads:

Sword Coast Adventurer's Guide, pg. 137

Starting at 1st level, you can use a bonus action on your turn to cause whirling gusts of elemental air to briefly surround you, immediately before or after you cast a spell of 1st level or higher. Doing so allows you to fly up to 10 feet without provoking opportunity attacks.

I've read the PHB on the subject, and I'm still not clear how much the character can move based on the wording.

PHB, pg. 190

However you're moving, you deduct the distance of each part of your move from your speed until it is used up or until you are done moving.

Using different speeds is also listed, but this talks about the fly spell which specifically grants a fly speed of 60.

PHB, pg. 243

The target gains a flying speed of 60 feet for the duration.

Assuming that the character has a 30 speed (base), does this mean that:

1. The storm sorcerer gets 10 additional feet of moment, and therefor can move his full distance then cast a spell to move further. (40 total feet, 10 of which is flown).
2. Is still limited by his speed, but can "fly" for 10 feet. (30 total feet, 10 of which can be flown).
3. Something else entirely.

Answer 1

You can move your normal rate during your turn because you always can and this can be broken up before and after the casting of the spell.

This flying movement is additional movement using your bonus action (which implies that you must use your action to cast the spell). It must be taken as a block before or after the spell casting; it can't be split like normal movement.

Essentially, your option 1 with some additional nuances.

Answer 2

Movement granted by an action (or bonus action) is in addition to base movement

This has been clarified by a sourcebook published several months after the question was asked. In Volo's Guide to Monsters, Orcs have the following racial trait (page 120):

Aggressive: As a bonus action, you can move up to your speed toward an enemy of your choice that you can see or hear. You must end this move closer to the enemy than you started.

If the movement granted by the Aggressive trait was part of your move as suggested by other answers, the Aggressive trait would be entirely worthless. Rather than allowing you to sprint towards an enemy, it would take up your bonus action to do nothing but limit where you can move.

It's clear that the Aggressive trait allows you to move further than you otherwise would be allowed to. Because this movement is part of an action (in this case, a bonus action), it is separate from and additional to the movement granted by the move you get on every turn. This trait has nearly identical wording to Tempestuous Magic: "you can move up to your speed" vs "allows you to fly up to 10ft". By extension, the same rules should apply to Tempestuous Magic.

Answer 3

The 10' isn't stated as part of your movement or part of your action. It's part of the bonus action available when casting a 1st level or higher spell. Since it's a separate part of your turn (a Bonus Action), it should not be subtracted from movement, just as the teleport distance in Misty Step isn't subtracted (both are bonus actions and part of the spell/effect but not part of movement). The way it reads, the spell has an added effect which moves you separately from your normal movement. This is a case where the most specific rule takes precedence over the more general movement rules and restrictions.

Answer 4

This 2020 unofficial designer tweet from Jeremey Crawford directly answers this question, stating that "If you're a Storm Sorcery sorcerer and use Tempestuous Magic, the 10 feet of flight doesn't expend any of your normal movement that turn."

Any movement granted that doesn't specifically add to a speed type doesn't count towards expended speed if used. So, if a spell/ability says that you "move X feet", it is separate from movement speed, but if a spell/ability says you "gain a [type] speed of X feet", then it functions in coherence with the rule on page 190 of the PHB.

Answer 5

You Are Limited to Your Fastest Speed Each Round

You were on the right track looking at page 190 of the PH, but you didn't read quite far enough.

Using Different Speeds

Whenever you switch, subtract the distance you've already moved from the new speed. The result determines how much farther you can move. If the result is 0 or less, you can't use the new speed during the current move.

With a speed of 30 feet and the storm sorcerer giving you a fly speed of 10 feet, you can move a total of 30 feet in a round, 10 feet of which can be flight.

Say you fly 10 feet then switch to ground movement, you then "subtract the [10 feet] you've already moved" from your ground speed, giving you 20 feet left to move.