A hurricane is a type of tropical cyclone, the general term for all circulating weather systems over tropical waters counter-clockwise in the Northern Hemisphere). Tropical cyclones are classified as follows:
Tropical Depression: A tropical cyclone with maximum sustained winds of 38 mph (33 knots) or less.
Tropical Storm: A tropical cyclone with maximum sustained winds of 39 to 73 mph (34 to 63 knots).
Hurricane: A tropical cyclone with maximum sustained winds of 74 mph (64 knots) or higher. In the western North Pacific, hurricanes are called typhoons; similar storms in the Indian Ocean and South Pacific Ocean are called cyclones.
Major Hurricane: A tropical cyclone with maximum sustained winds of 111 mph (96 knots) or higher, corresponding to a Category 3, 4 or 5 on the Saffir-Simpson Hurricane Wind Scale.
Hurricane winds blow in a large spiral around a relatively calm center known as the “eye.” The “eye” is generally 20 to 30 miles wide, and the storm may have a diameter of 400 miles across. As a hurricane approaches, the skies will begin to darken and winds will grow in strength. A hurricane can bring torrential rains, high winds, and storm surge as it nears land. A single hurricane can last more than two weeks over open waters and can run a path across the entire length of the eastern seaboard.
More dangerous than the high winds of a hurricane is the storm surge – a dome of ocean water that can be 20 feet high at its peak and 50 to 100 miles wide. The surge can devastate coastal communities as it sweeps ashore. In recent years, the fatalities associated with storm surge have been greatly reduced as a result of better warning and preparedness within coastal communities.
Most deaths due to tropical cyclones are flood-related. Inland flooding is a common occurrence with hurricanes and tropical storms. Torrential rains from decaying hurricanes and tropical storms can produce extensive urban and river flooding. Winds from these storms located offshore can drive ocean water up the mouth of rivers, compounding the severity of inland flooding. Inland streams and rivers can flood and trigger landslides. In addition, hurricanes can spawn tornadoes, which add to the destructiveness of the storm.
The Saffir-Simpson Hurricane Scale is a 1-5 “Category” rating based on the hurricane’s present intensity. The scale provides examples of the type of damage and impacts in the United States associated with winds of the indicated intensity.
Each year, on average, there are.12 named storms with six becoming hurricanes and three of those becoming major hurricanes (Category 3 or greater).
Although hurricane season runs from June through November, August, September, and the first half of October are the months when the storms most frequently occur in New England.
Watches and Warnings
Tropical Storm Watch: An announcement that sustained winds of 39 to 73 mph are possible within the specified area within 48 hours.
Hurricane Watch: An announcement that sustained winds of 74 mph are possible within the specified area within 48 hours.
Because outside preparedness activities become difficult once winds reach tropical storm force, watches are issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.
Action: During a watch, prepare your home and review your plan to evacuate or shelter-in-place in case a Hurricane or Tropical Storm Warning is issued. Listen closely to instructions from local officials
Tropical Storm Warning: An announcement that sustained winds of 39 to 73 mph are expected within the specified area within 36 hours.
Hurricane Warning: An announcement that sustained winds of 74 mph or higher are expected within the specified area within 36 hours. .The warning can remain in effect when dangerously high water or a combination of dangerously high water and waves continue, even though winds may be less than hurricane force.
Because outside preparedness activities become difficult once winds reach tropical storm force, warnings are issued 36 hours in advance of the anticipated onset of tropical-storm-force winds.
Action: During a warning, complete storm preparations and evacuate if directed by local officials.