North American Monsoon

Narration: George Huffman


Late in the summer, moisture starts coming up the west coast of Mexico and entering the southwestern U.S. And you transition from a relatively dry early season to something that's more prone to thunderstorms and the attendant flash floods. Relatively small amounts of rain in a desert condition can lead to a flash flood, even if it's a long way away. The ground is not very good at absorbing water and so instead it very quickly runs off and can run down channels for miles, perhaps catching people unaware. Huffman: In a general sort of way, we know that it rains in the summer and doesn't rain the rest of the year. But, the question is: Is it strong or is it weak? These kinds of long-range forecasts are still quite challenging. Even at the shorter scale, the monsoon consists of what are called breaks and then surges. And being able to forecast those breaks and surges a few days or weeks in advance would be a really great thing. There's a certain capability to do that now, but if we understand the precipitation processes better that will give us a better handle on how the heat is released in the dynamical systems that are contributing to the breaks and surges.