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Tropical Definitions

Know your hurricane season terminology

Tropical storms and hurricanes are no strangers to Southern New England. Since 1900, 49 systems have impacted Southern New England, of which 25 were hurricanes and 15 were tropical storms. Any tropical storm or hurricane is capable of bringing a combination of high winds and large storm surges, and on occasion, inland flooding along area rivers and streams.

To better prepare yourself for a possible hurricane strike, you should be familiar with the different terms that may be used. This page will briefly define some terms related to tropical storms and hurricanes.

Tropical Depression: A tropical system in which the maximum sustained surface wind is 33 knots (38 mph) or less. Though the wind speeds are significantly less than those in a hurricane, tropical depressions are capable of producing tremendous rainfall amounts. During the week of July 3rd through the 7th in 1994, Tropical Storm Alberto moved inland and weakened to a depression. It then moved into Georgia and produced up to 28 inches of rainfall causing catastrophic river and small stream flooding.

Tropical Storm: A tropical system in which the maximum sustained surface wind ranges from 34 to 63 knots (39 to 73 mph). These systems are also intense rainfall producers, but often cause enough wind and waves to cause some beach erosion and minor boat damage.

Hurricane: A tropical system in which the maximum sustained surface wind is 64 knots (74 mph) or greater. This is the worst and strongest of all tropical systems. New England was the recipient of one of the worst hurricanes ever, when the Great New England Hurricane of 1938 came crashing ashore on September 21st.

Hurricane Watch: An announcement for specific areas that hurricane conditions pose a possible threat to coastal areas within 36 hours. In New England, due to the rapid acceleration of most of our hurricanes, it is a necessity that you take action during the watch.

Hurricane Warning: A warning that hurricane conditions, including sustained winds of 74 mph or greater, associated with a hurricane are expected in a specified coastal area within 24 hours or less. Any preparedness measures must be rushed to completion once the warning is issued. High winds and coastal flooding will develop many hours before the eye of the storm actually comes ashore.

Hurricane Wind Watch: An announcement for inland areas that sustained winds of 74 mph or greater associated with a hurricane are anticipated beyond the coastal areas. The actual occurrence, timing and location are still uncertain.

Hurricane Wind Warning: An announcement for inland areas that sustained winds of 74 mph or greater associated with a hurricane are anticipated beyond the coastal areas in the next 6 to 24 hours.

Tropical Storm Watch: An announcement for specific areas that tropical storm conditions pose a possible threat to coastal areas within 36 hours.

Tropical Storm Warning: A warning that tropical storm conditions, including sustained winds of 39-73 mph, associated with a tropical storm are expected in a specified coastal area within 24 hours or less. Any preparedness measures should be completed as soon as possible.

Tropical Storm Wind Watch: An announcement for inland areas that sustained winds of 39-73 mph or greater associated with a tropical storm are anticipated beyond the coastal areas. The actual occurrence, timing and location are still uncertain.

Tropical Storm Wind Warning: An announcement for inland areas that sustained winds of 39-73 mph or greater associated with a tropical storm are anticipated beyond the coastal areas in the next 6 to 24 hours.

Hurricane Eye: A relatively calm area in the center of the storm. In this area, winds are light and the sky often is only partly covered by clouds. Never go outside in the eye of a storm. This period of relative calm may only last 10 to 20 minutes before hurricane force winds and torrential rains return from the opposite direction.

Storm Surge: An abnormal rise in sea level accompanying a hurricane or other intense storm. The height of the storm surge is the difference between the observed level of the sea surface and the astronomical tide that would have occurred in the absence of the storm. In Southern New England, storm surges of 10 to 20 feet have occurred, totally devastating the coastline.

Saffir-Simpson Hurricane Scale: A scale ranging from 1 to 5 based on the maximum sustained wind speed of the hurricane. This can be used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane. Extreme care should be used if using this scale as a quide to preparation steps when the sustained wind speed brings the storm within 10 mph of the next highest scale category. There is not much difference between a 110 mph (Cat 2) storm and a 111 mph (Cat 3) storm.

Hurricane Local Statement (HLS): A public release prepared by the local National Weather Service office serving the threatened area. This statement will provide specific details on: expected and observed weather conditions, evacuation decisions made by local officials, and other precautions necessary to protect life and property.

For a more complete list, please visit this page at the National Hurricane Center



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