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Canwarn |
Updated March 23, 2001
Slight, Moderate
and High Risk Days
SLIGHT
risk implies well organized severe thunderstorms are expected
but in small numbers and or low coverage. Expect a moderate probability of
between 5-29 reports of 1 inch (25mm) or larger hail, and/or 3-5
tornadoes, and/or 5-29 wind events, OR low to moderate probability of this
outlook being upgraded to a moderate or high risk issued later in the
day/evening.
MODERATE risk implies a greater
concentration of severe thunderstorms, and in most situations, a greater
magnitude of severe weather. Many weather offices will include the phrase
"some thunderstorms may be severe". Environment Canada will
include "remember some severe thunderstorms produce tornadoes".
This category includes a high probability of at least 30 reports of 1 inch
(25mm) or larger hail, or over 30 reports that might be associated with a
squall line or 6-19 tornadoes.
HIGH risk is only issued a few times
per year, because of rare circumstances, almost always means a major
severe weather outbreak is expected. Greater coverage of severe weather
with an enhanced likelihood of extreme severe (includes the possibility of
violent F4+ tornadoes or extreme convective wind events over a large
area). A high probability of at least 20 tornadoes with at least two of
them rated F3+, or a derecho (powerful squall-line) causing 50+ widespread
wind damage events with numerous high end straight line wind (130km/h) and
or structural damage reports.
Information courtesy of Storm Prediction Center (SPC) http://www.spc.noaa.gov/
1313 Halley Avenue, Norman, Oklahoma, 73069
Day 1 Convective Outlook
http://www.spc.noaa.gov/products/outlook/day1otlk.html
Day 2 Convective Outlook
http://www.spc.noaa.gov/products/outlook/day2otlk.html
Ron Gravelle VA3TVS
KWARC CANWARN Co-Ordinator
Waterloo Region
VA3TVS@myrac.ca
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