With Hurricane Season just around the corner and the new Hurricane Tracking Charts coming out, a few questions started popping up around the newsroom regarding these storms. In a couple cases, I'll admit that I wasn't 100% sure about a couple of the answers myself, and learned a few things in the research process.
These seem to be the most commonly asked questions about hurricanes, but I'm sure there are many more. If you have a question, leave a comment below.
How do hurricanes form?
Hurricanes form over the warm ocean waters near the Equator (but not too close to it). With lots of warm, moist air available, convection occurs, forming clusters of thunderstorms in the area. Next, the Coriolis effect takes over. This effect is due to the rotation of the Earth, and will cause the storms to rotate counter-clockwise in the Northern Hemisphere (or clockwise in the Southern Hemisphere). If there is enough energy available (in the form of warm, moist air) the system will continue to strengthen and with 39 mph winds, will become a Tropical Storm and if winds of 74 mph are reached, a hurricane.
Why can't they form very close to or along the Equator?
The Coriolis effect that causes the rotation of the storms does not exist at the Equator. It increases the higher up in latitude you are. We generally only see hurricanes form between 5-20 degrees North and South. Below 5 degrees, the Coriolis force is not strong enough to cause the rotation of the storms. Above 20 degrees, the water is generally not warm enough.
How warm does the water have to be?
Sea surface temperatures must be at least 80 degrees Fahrenheit for hurricanes to form. The temperature must also be this warm in the first 150 feet or so.
Why don't hurricanes form in the Southern Atlantic Basin?
Well, technically they have. In 2004, a hurricane formed in the South Atlantic then made landfall in Brazil. However, they are extremely rare, this having been the only documented hurricane on record. There are two main reasons why they are so unlikely. First, wind shear is much stronger. Like we see in El Nino years in the Northern Atlantic, strong wind shear will rip a storm apart before it can really get going. Unlike in the Northern part of the ocean, this strong wind shear is present nearly all the time. Secondly, there is generally no Intertropical Convergence Zone (ITCZ) in the Southern Atlantic. This is a large-scale area of showers and thunderstorms that form in a nearly linear pattern over the oceans. The ITCZ can easily be seen in the Pacific (the largest ocean) and can most often be picked out in the Northern Atlantic.
Note the clusters of showers and thunderstorms over the Pacific, but the effect fades in the Atlantic basin.
Why don't we see hurricanes along the West Coast of the United States?
In short, the water is too cold. On the Atlantic side, warm, moist air is transported Northward along the coast, so temperatures are much warmer along the east coast. The California current brings cold water from the North. If you've ever been to the beach on the West coast, you know that it feels nothing like the warm Atlantic water. It's usually cold and windy, whereas Atlantic beaches at the same latitude are much warmer. Even as far south as San Diego, it's too cold to get in the water for long without a wet suit.
When are hurricanes most likely to occur?
Hurricane Season runs from June 1 to November 30, but they have occurred in every month of the year. In the Atlantic, they are most likely in August and September, when ocean waters are warmest.
Which names are used if a hurricane forms outside of Hurricane Season?
The hurricane names start at the beginning of every calendar year. Let's say a hurricane had formed January 1, 2010. It would get the first name on the 2010 list (Alex). If one had formed December 31, it would have gotten a 2009 name.
What happens if they run out of names?
Every year, a list of 21 hurricane names is published. Once a storm becomes a Tropical Storm, it gets a name. It wasn't thought that more than that would be needed, but in 2005 it did happen. When we ran out of names, we began with the Greek alphabet (Alpha, Beta, Gamma, etc.)