Gust of Wind versus fog / mist effects


Rules Questions


At our recent session we had a bit of a snafu regarding gust of wind and a cloudkill. There was some arguing as to how the various rules interfaced, and I think everyone walked away from the conversation a little miffed with the end result upon which we eventually settled.

My question is thus: how does gust of wind affect fog or mist effects, specifically spell-created effects, such as fog cloud, obscuring mist, and cloudkill?

Some background clutter on things we talked about and considered:

Spoiler:

* My long-time belief in how the spell worked was that wind spells were largely the counter to fog spells. That is, gust of wind shredded and dispersed most fog/mist (I'm going to just say fog from now on) effects in a single round, no questions asked, per the line that reads "A moderate wind (11+ mph) disperses the fog in 4 rounds; a strong wind (21+ mph) disperses the fog in 1 round." And by this I mean that it dispersed (which I define to mean "removed from existence for the purposes of this combat") the entire fog bank.

The primary arguments against this are as follows:

Argument 1: The wind should only affect the area in which it is present. That is, a line of fog would cease to exist, but the fog as a whole would still be there. In the case of cloudkill, this would mean there would be no effect AT ALL because the fog cloud's movement would then roll the fog through an area and erase the erasure of fog.

The primary evidence in support of this argument is the fact that a gust of wind "must" have a sheathe around the wind column that prevents the wind from affecting cloud in any area but its five-foot wide line, since creatures literally adjacent to the line but not in it are completely unaffected by wind, and fluid dynamics states that this could not be the case. Thus, full dispersion of the could would not occur, since the areas around the column are actually unmoving. P.S., I play with three engineers. xD

Argument 2: The wind has zero effect whatsoever, because the fog effect can exist only in the area specified by the spell. The wind effect is incapable of moving the fog effect outside the fog's area, because the spell explicitly defines dimensions for the created fog. As a result, wind blowing inside the fog will move the fog around, but since the fog cannot leave the area, not even a gap will occur within the fog due to the wind.

Any insight people can give me on this would be appreciated. I understand that this has the potential to be a gray area of the rules, so I would value both hard facts and opinions, as long as those opinions are couched upon the basis of some measure of logic, rather than "I would do this because I feel like it." :) My goal here is to make a ruling that is both as fair and as logical as possible, while being consistent and supported by the ruleset to as great a degree as is feasible.

Thanks a bunch. :)

Some related questions that can use answering:

Spoiler:

* Is the fog that is created nonmagical fog, and thus privvy to the natural laws of physics after it is formed, or is it "forced" to stay in its defined area and unable to be acted upon by outside forces?

* How do you define the line "In addition to the effects noted, a gust of wind can do anything that a sudden blast of wind would be expected to do. It can create a stinging spray of sand or dust, fan a large fire, overturn delicate awnings or hangings, heel over a small boat, and blow gases or vapors to the edge of its range."? Do you consider the highlighted "it" to be referring to the gust of wind, meaning that the gust of wind can blow vapors to the edge of the gust of wind's range? Or do you consider the "it" to refer to the vapors, such that the gust of wind can only blow vapors to the edge of the vapors' range (per the restrictions in the above question)?


Argument 2 is definitely wrong, as the fog spells doesn't have a defined area that they are only allowed to exist in or are bounded by. It's not like there are walls around the fog that prevent it from moving outside of. In fact the cloud moves on it's own, and nothing in the spell tells you about a limited area in can exist it.

It simply tell you it creates a cloud of some sort of fog of a certain size, and that it moves 10ft per round away from where the caster cast it.

As for the gust of wind. It creates a line of wind, that moves from the caster out to 60ft away. How exactly that is supposed to interact with with the fog spells isn't explicitly made clear. Gust of wind specifies the winds are 50 mph, which based on the rules of fog cloud would be enough to disperse it in 1 round, but the gust of wind isn't sustained for 1 round.

Considering how niche the spell is, as a GM I've always allowed the use of gust of wind to completely get rid of a fog effect. If you wanted to run things by hard RAW it might only negate the 5ft wide line (the spell actually doesn't specify how wide the line is) of the fog, but honestly that doesn't make a lot of sense and the spell doesn't have a lot of use except to negate fog effects so I just let it happen.


The gust of wind actually is sustained for one round.

Spoiler:

Gust of Wind

School evocation [air]; Level druid 2, sorcerer/wizard 2

Casting Time 1 standard action

Components V, S

Range 60 ft.

Effect line-shaped gust of severe wind emanating out from you to the extreme of the range

Duration 1 round

Also, a line is shown in the magic chapter of the core rulebook as being five feet wide, so the line's width is specified.

As for your purview, and your thoughts that the spells don't have a lot of use otherwise, I think that's reasonable. Thank you. :) I'd love to get lots of opinions so I can weigh them all and have a majority decision from many minds. Anyone else have any ideas? :D


That's what I get for answering questions late at night when I'm not thinking clearly.

I was looking for the size of the line in the spell description, not thinking it should be in the magic chapter under the description of line.

As for the duration of 1 round...well sometimes you just miss things.

But yeah, it still has the problem that you could technically say it only disperse the 5ft of the fog cloud it goes through. But that would honestly just be a terrible waste of the spell slot.


I have always rules Gust of Wind disperses fog spells.

The fog is exposed to a wind >21mph for 1 round. Nothing in RAW states the wind must affect the entire area of the spell.

RAI: I cannot think of any other use for the Gust of Wind spell with jumping through hoops.


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RAW -

Under Cloudkill:

"This spell generates a bank of fog, similar to a fog cloud, except that its vapors are yellowish green and poisonous."

"Unlike a fog cloud, the cloudkill moves away from you at 10 feet per round, rolling along the surface of the ground"

"Because the vapors are heavier than air, they sink to the lowest level of the land, even pouring down den or sinkhole openings. It cannot penetrate liquids, nor can it be cast underwater."

Under Fog Cloud:

"A moderate wind (11+ mph) disperses the fog in 4 rounds; a strong wind (21+ mph) disperses the fog in 1 round."

So nothing under cloudkill makes any exception to the rule regarding wind dispersing the cloud. As it is "similar to a fog cloud" I would say all fog cloud rules apply other than that a cloudkill sinks, and moves 10 ft per round.

Gust of Wind -
Range 60 ft.
Effect line-shaped gust of severe wind emanating out from you to the extreme of the range

"This spell creates a severe blast of air (approximately 50 mph) that originates from you..."

"In addition to the effects noted, a gust of wind can do anything that a sudden blast of wind would be expected to do. It can create a stinging spray of sand or dust, fan a large fire, overturn delicate awnings or hangings, heel over a small boat, and blow gases or vapors to the edge of its range."

So it's pretty clear that "gust of wind" can blow gases or vapors (which would include cloudkill) to the edge of it's range. - 60 ft away.

However, as "a strong wind (21+ mph) disperses the fog in 1 round", the line of 60mph wind blowing through the couldkill, would disperse it. per the RAW.

In regard to argument A -
Description of line.
A line-shaped spell shoots away from you in a line in the direction you designate. It starts from any corner of your square and extends to the limit of its range or until it strikes a barrier that blocks line of effect. A line-shaped spell affects all creatures in squares through which the line passes.
The argument is that the wind - ""must" have a sheathe around the wind column that prevents the wind from affecting cloud in any area but its five-foot wide line, since creatures literally adjacent to the line but not in it are completely unaffected by wind, and fluid dynamics states that this could not be the case.
There is no rule as written that there is a "sheathe". Nor any statement that they are "completely unaffected". Only that the wind affects creatures in the 5 foot square along the line via the way described in the spell effects. The creatures adjacent may indeed feel the wind swirl around them, just not enough to be blown back, etc.
The Gust of wind is 50mph, the cloudkill dispersed in 1 round by a 21mph wind. So the wind blowing through the cloudkill is more than double the speed necessary in order to disperse it. If one does not assume there is a "sheathe", the air around the 50mph area would move and be sucked along with the area of the spells affect, just not at 50 Mph.
P.S., I play with three engineers - I would remind them that this is magic, not science. Magic superceeds science, that is it's purpose.

And argument B is right out. per the RAW above the cloudkill would be affected.


@Snowlilly
You are right; nothing in the spell says that wind must affect the entire area of the spell. Simultaneously, nothing says that the entire area is dispersed if any part of it is exposed to wind. The part you quoted refers to the "fog" being dispersed, not the spell, not the area, and not the effect. That's where the ambiguity comes in. This is, in act, the argument that was used against me, and I do admit it has merit. It's still my belief that the intention was for the whole spell area to be destroyed by wind, but (see arguments).

Kaliel Windstorm wrote:


So nothing under cloudkill makes any exception to the rule regarding wind dispersing the cloud. As it is "similar to a fog cloud" I would say all fog cloud rules apply other than that a cloudkill sinks, and moves 10 ft per round.
[/quote[
Same deal. THe spell (s) don't specifically state that the entire cloud is destroyed by the wind, only that "fog" is. How much fog? Which parts of the cloud?

Quote:
However, as "a strong wind (21+ mph) disperses the fog in 1 round", the line of 60mph wind blowing through the couldkill, would disperse it. per the RAW.

Again, my key query here is, "How much?"

Quote:
There is no rule as written that there is a "sheathe".

Actually, the player that brought this up is right, as far as I can tell. I have only a rudimentary understanding of fluid dynamics compared to him, but there would need to be a protective barrier of some kind around the column of wind preventing those nearby from being affected. Otherwise the velocity profile of the gust of wind would taper off rather than ending suddenly, making the gust more like a cone than a line. It's sort of like when a car on the freeway drives past you at 60 mph when you're standing still. It makes your car shake a bit from the wind of its passage.

However, I think you have a fair point when you say that the spell does not say adjacent creatures are *entirely* unaffected. I suppose it's possible they feel some wind, just not enough to have any game effects. However, without those creatures being substantially affected, it means there isn't enough friction between the gust of wind and the surrounding air/cloud molecules for the entire cloud to be dispersed. It *would* only disperse the area immediately hit by the line.

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