Here's my non-lawyer opinion for you: (This is not advice, just my opinions)
The term "brandishing a firearm" typically implies that one is displaying it in a threatening manner. Although, definitions may vary from state to state and planet to planet. The M&W dictionary includes the term "ostentatious manner" as a second definition for brandish. As in, it would be ostentatious for you to stand on top of a street vent, knowing well that there is air blowing out of it, so that the wind would blow your [dress] and expose your once-concealed gun for all to see.
Here in Virginia, which is a "gold star open carry state" just as New Mexico
is, a concealed handgun being exposed by the wind as you describe; or even moving your body in such a way as to inadvertently expose the handgun; is not considered brandishing. And in Virginia there *are* separate laws against brandishing weapons ( § 18.2-282
and § 18.2-282.1
). Those laws consider brandishing to be "reasonably induc[ing] fear in the mind of another." Another opinion is that just because someone is afraid doesn't mean that you reasonably induced the fear. I could be out walking my dog on a leash and pass someone who is irrationally afraid of all dogs; just because they see my dog they become afraid, run away, and call animal control about a man with a scary dog on the street. I certainly didn't use my dog in a threatening manner, the person wasn't attacked, and I wasn't breaking any laws. Therefore the fear that the person felt was not reasonable and could not be considered brandishing or assault.
New Mexico may not have any laws using the word "brandish," although the assault law would cover brandishing a firearm:
Assault consists of either:
A. an attempt to commit a battery upon the person of another;
B. any unlawful act, threat or menacing conduct which causes another person to reasonably believe that he is in danger of receiving an immediate battery; or
C. the use of insulting language toward another impugning his honor, delicacy or reputation.
Whoever commits assault is guilty of a petty misdemeanor.
If it is in fact lawful in New Mexico to carry a handgun in plain sight, then it is probably acceptable to accidentally expose a concealed handgun. It's probably also lawful to expose a concealed handgun by removing your shirt or jacket, as long as you are not doing so in order to threaten someone.
The only thing that would make it unlawful, as far as I know, is a law specifically stating that an already concealed firearm must remain concealed at all times while in public.
For some examples of the situation in other states: Texas prohibits open carry, but the penal code states that the failure to conceal the handgun must be intentional for it to be an offense:
Sec.46.035.UNLAWFUL CARRYING OF HANDGUN BY LICENSE HOLDER. (a)A license holder commits an offense if the license holder carries a handgun on or about the license holder's person under the authority of Subchapter H, Chapter 411, Government Code, and intentionally fails to conceal the handgun.
See here for complete law.
However, South Carolina's code, which also prohibits open carry, is worded such that even unintentional exposure of a handgun could be criminal:
SECTION 16-23-20. Unlawful carrying of handgun; exceptions.
It is unlawful for anyone to carry about the person any handgun, whether concealed or not, except as follows, unless otherwise specifically prohibited by law:
(b) concealed on or about his person, and he has a valid concealed weapons permit pursuant to the provisions of Article 4, Chapter 31, Title 23;
See here for complete law.
To be more thorough, I will also suggest that you research New Mexico case law. Specifically, those cases dealing with firearms and/or assault.