Severe and Unusual Weather ESAS 1115 Spotter Training and Radar Meteorology Part 1 – Introduction to Severe Thunderstorms Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Convective Hazards Wind, Hail, Floods, Lightning, Tornadoes Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Severe Thunderstorms are Severe Many times, the media uses the word “severe” when the storm is something less than the actual meaning of “severe”. Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Severe Thunderstorm Criteria Hail greater than 1” in diameter Winds greater than 50 kts (58 mph) Tornadoes Lightning and heavy rainfall, although posing a great threat to life, are not criteria used to determe whether or not a storm is severe Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Lightning Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Lightning ~25 million CG lightning strikes per year in the US making it the second deadliest aspect of thunderstorms Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Lightning Safety Lightning Stats Lightning Safety Video Lightning Safety Tips Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Flash Floods – Turn Around Don’t Drown Water is an incompressible fluid 1000 kg/m3 Results in buoyancy – 2 feet of water can move an SUV Kills more people than lightning – approximately 100 annually in the US, 50% associated with drowning in vehicles From 1988-1997, average annual cost is $3.7 billion Flash flooding vs. river flooding Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Flash Flood Threat Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Flash Floods – Turn Around - Don’t Drown Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Hail – Big Chunks o’ Ice Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Tarrant County, TX May 5, 1995 10,000 people at Mayfest Baseball hail – 10 miles wide 50 miles long 14 people killed by flooding and collapsed roofs $2 billion (estimated) Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather We Know First Hand Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Damaging Winds Strong outflow from a thunderstorm enhanced by evaporative cooling and downward momentum transfer Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Downbursts A strong and potentially destructive thunderstorm downdraft Microbursts are less than 2.5 miles in diameter Macrobursts are greater than 2.5 miles Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Rain Foot and Dust Foot Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Dust Foot Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Microbursts Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Aviation Hazards Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Danger on Takeoff and Landing On the glide path, too much lift is generated with headwind gain With the loss of a headwind, lift is limited Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Beaufort Scale Winds based on visual observations Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather First Microburst Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Microburst within a Macroburst Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Microbursts Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Microburst Evolution Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Tornado and Hail Climatology There are more than 1000 tornadoes in the US per year. Hail results in over $1 billion of damage annually. Harold Brooks - NSSL Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

61 Years of Tornado Tracks Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Tornado Frequency All Tornadoes Significant Tornadoes Deadly Tornadoes Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Tornado Threats Violently rotating column of air in contact with the ground and pendant from a cumulonimbus cloud (thunderstorm) Tornadoes are ranked on the Enhanced Fujita damage scale: from EF0-EF5 Appearance is deceiving with small tornadoes sometimes having high destruction potential and large tornadoes having low potential Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather EF0, EF1 – Weak Tornadoes Approximately 70% of tornadoes are in this category Well-built houses offer adequate safety for these tornadoes Cars and mobile homes are still very vulnerable to these tornadoes Wind speeds: 65 – 110 mph Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

EF2, EF3 – Strong Tornadoes Approximately 28% of all tornadoes are considered strong Well-built houses will be severely damaged but still can provide adequate life-protection Wind speeds: 111 – 165 mph Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

EF4, EF5 – Violent Tornadoes Only 2% of all tornadoes are violent Will completely level a well-built house The last EF-5’s to hit the US were May 3, 1999 (Moore, OK,) May 24, 2007 (Greensburg, KS,) and May 25, 2008 (Parkersburg, IA.) Wind speeds: 166 - >200 mph Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Rating a Tornado Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

Wind Damage vs Tornado Damage Microburst Damage is divergent Large or diffuse area No signs of rotation Tornado Damage is convergent Narrow path Rotation about vertical axis Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather

ESAS 1115 Severe and Unusual Weather Swirl Marks Prof. Paul Sirvatka ESAS 1115 Severe and Unusual Weather