No, they wouldn't manipulate the weather by enhancing the severity of a storm. See here:
1. Each State Party to this Convention undertakes not to engage in military or any other hostile use of environmental modification techniques having widespread, long-lasting or severe effects as the means of destruction, damage or injury to any other State Party.
2. Each State Party to this Convention undertakes not to assist, encourage or induce any State, group of States or international organization to engage in activities contrary to the provisions of paragraph 1 of this article.
As used in article 1, the term "environmental modification techniques" refers to any technique for changing - through the deliberate manipulation of natural processes--the dynamics, composition or structure of the Earth, including its biota, lithosphere, hydrosphere and atmosphere, or of outer space.
[link to www.sweetliberty.org
So no, they promised and agreed not to manipulate the weather back in 1976. Which of course begs the question, agreeing not to do it says they must have the capabilities to do it. This was written in 1976, surely they aren't capable of even more ennhanced weather modification through new energy weapons.
So there, we can all rest assured that our leaders would never use something like weather modification as a war weapon