The next Hurricane Fran will begin as a puff of harmless clouds in the mountains of Ethiopia. The classic Cape Verde hurricane – so named for the islands off the West African coast where it forms – can follow a track that means trouble for East Coast residents. Many Carolinians are beginning the annual tradition of casting a weary eye on the tropics and hoping for the best. As we approach the month of September, the possibility for large and destructive hurricanes reaches its peak.

A Storm is Born

Many hurricanes originate from thunderstorms that blossom over the Sahel region of Africa and pass into the Atlantic Ocean. By August, the warm waters the thunderstorms encounter will hold vast potential energy. Gentle easterly wind belts guide the developing storm to the west where it may eventually reach the Caribbean islands or Bermuda. We may think of hurricanes as destructive brutes, but they exist at the mercy of seemingly simple things. Developing hurricanes must avoid being sheared apart by fast winds high in the atmosphere or being strangled by the regions of dry and warm weather that we typically enjoy. When a hurricane season winds up being lethargic, such as in 2009, these two factors are often at work.

The Turn North

If a hurricane can make it to the Bahamas, it will begin to interact with fronts (the same ones that dictate our weather) as they sweep offshore. The ballet of hurricanes and fronts occupies meteorologists and their computer simulations. Will the hurricane come ashore, and if so, where? Not unlike a rogue cyclist shooting between pulses of traffic to cross Avent Ferry Road, the hurricane chooses the path of least resistance in its northward trek. If blocked by high pressure areas, a hurricane can become trapped and spend days or weeks carving serpentine paths in the open ocean. When strong and stable high pressure persists over the Atlantic and a front stalls along the Appalachian Mountains, the path of least resistance falls along the East Coast of the United States.

Hurricane Danielle

Hurricane Danielle, currently active, has fluctuated in intensity over the past few days. It is located approximately 2,000 miles southeast of Raleigh and about 600 miles away from the nearest Caribbean islands. Danielle is expected to swing wide right in advance of high pressure over the Eastern United States. Bermuda and Newfoundland may receive a glancing blow, but the possibility of a turn towards the U.S. is not likely. If that high front moves or weakens, the next storms that come along may take different paths.

What to Expect

The seasonal prediction issued this spring by NCSU meteorology professor Lian Xie anticipates higher than normal activity with 14 to 19 tropical storms, 7 to 11 of which would become hurricanes. The paper calculated an 80 percent probability that one of these storms would strike the Southeast coast of the U.S. This prediction is similar to many other prominent seasonal forecasts. The coming weeks and months will reveal how accurate those predictions are. In the mean time, meteorologists and residents up and down the East Coast will scrutinize each and every storm as it journeys across the sea.