It's Hurricane Season -- Again

Hurricane season got an early start this year when Andrea, a subtropical storm, formed off the east coast of Florida and Georgia.

Andrea never attempted a landfall, but she reminded us that many forecasters are calling for an active 2007 Atlantic hurricane season.

In order to help prepare for travel to the Caribbean during hurricane season, Caribbean Travel News spoke with Adam Moyer from TheStormTrack.com. Adam is a Ph.D. candidate in meteorology at Penn State University.

CTN: Andrea showed up early. Do you think this is a sign of a bad upcoming season?

AM: Andrea was a rare May storm this year. However, you cannot extrapolate that for the whole season. For example, Ana formed in April of 2003, and 2003 was a relatively normal year (this is for the more recent "excited" period for North Atlantic tropical cyclones, 1995-current). Also, Andrea formed under different conditions than we normally expect with tropical cyclones. Andrea was a winter, cold-core low that stalled out off the coast of the Carolinas. The sea-surface temperatures were much lower than the typical threshold forecasters use. Through its thunderstorm activity, however, it developed some tropical characteristics, although I don't think it could ever be actually termed fully tropical. That's why it was named a subtropical storm.

CTN: Forecasters are calling for a busy hurricane season in the atlantic, as they did last year. How are these predictions made and can we trust them?

AM: One of the major reasons forecasters are calling for an active season this year is because the El Nino that persisted throughout the last hurricane season has dissipated. During an El Nino year, when sea-surface temperatures are much warmer than usual off the west coast of South America, there is a tendency for general downward motion over the tropical Atlantic. This works to inhibit thunderstorm development. This year, it appears we may be headed to the opposite of an El Nino, which is called La Nina. La Nina years are often quite active years in the tropical Atlantic. As far as how forecasts are made, I'm not 100% sure. I know Bill Gray's group at Colorado State uses a multiple linear regression to forecast the number of storms and that an El Nino index is included as one of the parameters. I'm really not sure what NHC/NOAA uses for their predictions. However, I think we are in for an active season, simply because we are headed into a La Nina. I think these forecasts are good for getting a general idea as to whether a particular season will be active or not, but I wouldn't put a lot of stock in the exact number they forecast.

CTN: It seems like tropical storms come off Africa, across the atlantic and head straight for the eastern Caribbean islands. Why is this?

AM: The tropical Atlantic is governed in the summertime by disorganized areas of low pressure known as African easterly waves. They are the remnants of large thunderstorm complexes that form over the Sahel region of Africa due to the African monsoon. Once they move out over the open waters of the Atlantic, they can be the seeds for tropical development. African easterly waves are the seeds for 60-80% of the hurricanes we see in the Atlantic in a given year and are definitely the types of storms that affect the weather in the Lesser Antilles in the summer months.

CTN: Everyone knows Weather.com, but can you recommend how travelers can keep an eye on upcoming storms?

AM: The National Hurricane Center's website is the best website to use for tracking possible storms. Not only do they issue the advisories for storms already present, you can read their "Tropical Weather Outlook," which will let you know if there any storms on the horizon. Other good places to go for non-technical (and non-official) discussion are my blog and the tropical page on the Weather Underground.

CTN: Thanks, Adam.

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