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
|
www.nws.noaa.gov 
