Geoscience Reference
In-Depth Information
Type
Description
Strong winds that cause mobility problems and possible damage to vegetation and
structures.
Wind
Heavy or prolonged rainfall accumulating on a scale sufficient to cause
local/widespread flooding.
Heavy Rainfall
One or more of the following: strong winds causing mobility difficulty, damage to
structures due to wind and hail, heavy rain that may cause local flooding and lightning
Thunderstorm
Presence of tornado(es), damaging hail, heavy rain, strong winds, life and property
exposed to real threat, lightning
Severe Weather
Tornado
Public has real potential to be exposed to tornado(es).
Table 1. Severe Weather Criteria in Canada: Warning Elements
Weather
Centre
Wind
Rain
Hail
Remarks
gusts of
90
km/h
Newfound-
land
No tornado criteria; no tornado warning; may
mention hurricanes in marine warning.
25 mm/h
20 mm
gusts of
90
km/h
25 mm in 1 hr
or 50 mm in 3
hrs
Tornado or tornadic waterspout; no tornado
warning; will issue hurricane prognostic
message and information statements.
Maritimes
15 mm
gusts of
90
km/h
25 mm in 1 hr
or 50 mm in 12
hrs
Tornado, water spout, funnel cloud, windfall;
no tornado warning
Quebec
20 mm
No tornado criteria in severe thunderstorm
warning; tornado watch issued when
confirmed tornadoes threaten to move into
region or issued up to 6 hours in advance
based on analysis or immediately for severe
thunderstorms that indicate potential for
becoming tornadic; tornado warning on
forecast or observation.
gusts of
90
km/h
50 mm/hr for 1
hr; 75 mm for 3
hrs
Ontario
20 mm
90
km/h
50 mm in 1 hr;
75 mm in 3 hr
Tornado or waterspout probable; tornado
warning issued when expected or observed.
Prairie
20 mm
Tornado, waterspout or tornado warning
when observed or expected or waterspout
exists; cold air funnel cloud warning when
cold air funnels expected but not tornadoes.
gust of
90
km/h
Alberta
30 mm/h
20 mm
90
km/h
Tornado, water spout, funnel cloud; tornado
occurrence warning on a confirmed report.
Arctic
25 mm/hr
12 mm
gust to
90
km/h
significant
hail
Potential of tornado; warning is for
thunderstorms; no tornado warning.
Yukon
25 mm in 2 hr
Lightning intensity of 500 strikes in 1 hr over
an area of 1 degree x 1 degree
latitude/longitude; no watches for severe
thunderstorms or tornadoes; no tornado
warnings; thunderstorm warning issued on a
less than severe thunderstorm; will issue
hurricane prognostic messages and
information statements.
gusts of
90
km/h
Pacific
25 mm in 1 hr
15 mm
Table 2. Severe Weather Criteria in Canada: Severe Thunderstorm Criteria
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