DATASTREME SUPPLEMENTAL SUMMARY
To complement the Daily Summary for Tuesday, 27 November 2001
SEVERE LOCAL STORM TERMINOLOGY
The following list includes terminology used by the National Weather
Service for those public statements pertaining specifically to severe local
storms. These storms are usually convective and contain severe
weather with large hail (3/4 inch diameter or larger) and/or strong
winds (58 miles per hour or greater) meeting the specific criteria, as well as
tornadoes and flash flooding due to excessive precipitation in thunderstorms. A
description of those statements used to alert the public for flash floods will
accompany Thursday's concept. The other pertinent terms are given:
- Severe thunderstorm watch -- Issued by the Storm Prediction Center
in Norman, OK to alert the public that conditions are favorable for development
of thunderstorms meeting any of the criteria of large hail (3/4 inch diameter
or larger) and/or strong winds (58 miles per hour or greater) in or close to
the watch area. Watches typically are in effect for several hours.
- Severe thunderstorm warning -- Issued by the local National Weather
Service Office to warn the public that a thunderstorm producing 3/4 inch (1.9
centimeters) or larger diameter hail and/or winds equal to 58 miles per hour or
greater is occurring. The warning indicates where the severe thunderstorm has
been located, what communities are to be affected and the primary threats to
public safety that are associated with the storm. Persons in the affected area
should take immediate action.
- Tornado watch -- Issued by the Storm Prediction Center to alert the
public that conditions are favorable for the development of tornadoes in and
close to the watch area, which is delineated in the tornado watch statement.
These watches are issued with information concerning the watch area and the
length of time they are in effect; watches are usually in effect for several
hours.
- Tornado warning -- Issued by the local National Weather Service
Office to warn the public that a tornado has been sighted by storm spotters or
has been indicated by radar. These warnings are issued with information
concerning where the tornado is presently located and what communities are in
the anticipated path of the tornado. The public is expected to heed these
warnings and take appropriate action.
The Storm Prediction Center issues Convective Outlooks and Second
Day Severe Weather Outlooks that are primarily for internal use and outline
the geographic regions where severe weather may develop. However, some of the
information contained in these guidance products are used on television
weathercasts. These Outlooks include levels of risk.
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Prepared by Edward J. Hopkins, Ph.D., email
hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.