Severe Weather In Canada

Summer Severe Weather

Geoff Coulson Warning Preparedness Meteorologist Environment Canada Sept 11 2009 ICLR Friday Forum

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Contents
• • • • Ontario Storm Prediction Centre Forecasting Technology Watch/Warning Program A closer look at August 20th tornado outbreak

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Ontario Storm Prediction Centre Toronto

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Radar data…

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Weather Technology

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Satellite Data…

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Computer Models…

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Forecast Area of Responsibility

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Scale of a Summer Storm

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One storm covering part of a county

Scale of a Winter Storm

Snow

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Heavy Snow Freezing Rain X Rain Showers

One storm covering thousands of square kilometres

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Severe Weather Lead Times
• Summer Severe Weather (severe thunderstorms,
Weather Watch means there is the potential for severe weather --- Be Alert Weather Warning means that severe weather will soon occur or is occurring --- Take Action
Ron Gravelle

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Severe Thunderstorms – A Breed Apart
• 5% of Ontario thunderstorms are categorized as severe each year… • Severe thunderstorm has one or more of the following characteristics
– Wind gusts of 90 km/h or more – Hail of 2 cm diameter or larger (size of a nickel or larger) – Flooding rains – Tornado(s)
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By the Numbers

• On average around 120 summer severe events in Ontario each season (late April to early October)
– – – – 70 due damaging winds 20 heavy rain/flooding 20 hail 11 tornadoes
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Fujita Wind Damage Scale
• F0 – winds up to 115 km/h – Shingle, siding damage • F1 – winds 120 to 170 km/h – Numerous shingles, partial roof removal • F2 – winds 180 to 240 km/h – Roof removed from well-built home • F3 – winds 250 to 320 km/h – Roof and some exterior walls removed • F4 – winds 330 to 410 km/h – 2 storey brick house left with only a few walls remaining • F5 – winds 420 to 510 km/h – Brick house destroyed to foundation
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Tornado Characteristics
• Duration
• 5 minutes to 120 minutes

• Speed of Motion
• 30-70 km/h

• Path