Tropical systems are large-scale events, that can bring a lot of rain into Mexico and the desert Southwest (usually late in the monsoon for us). Warm, moist air is lifted into the atmosphere when the sea surface temperatures climb higher in late-Summer.
Usually, tropical cyclones begin with a cluster of disorganized thunderstorms. Once the storms become organized and circulate around an area of low pressure, it can be classified as a tropical cyclone.
Here is the evolution of a tropical cyclone:
Tropical Depression -
a tropical cyclone with maximum sustained winds less than 39mph. These are labeled by number chronologically through each season.
Tropical Storm -
mph maximum sustained winds. This is the stage that a tropical cyclone gets its name. Many times a tropical system will develop quickly enough to become a tropical storm without becoming a depression first.
A tropical storm becomes a hurricane when winds reach
mph or greater. It's then classified into categories 1 through 5, based on wind speed.
Category 1 - 74
Category 2 - 96
(category 3 to 5 hurricanes are classified as "major" hurricanes)
Categroy 4 - 130
mph or greater