SEVERE THUNDERSTORMS Chapter 14 ORDINARY AIR MASS THUNDERSTORM

ORDINARY (“AIR MASS”) THUNDERSTORM LIFE CYCLE

SEVERE THUNDERSTORM • • • 1 inch diameter hail, or 50 knot surface winds,

MESOSCALE CONVECTIVE COMPLEX (MCC) • • summer late night, early morning Midwest heavy rain,

Derecho 1) Concentrated area of convectively induced wind damage/gusts greater than 50 knots (60

Severe Thunderstorm Factors (Eagleman, 209)

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SEVERE THUNDERSTORMS (Chapter 14)

ORDINARY (“AIR MASS”) THUNDERSTORM LIFE CYCLE

SEVERE THUNDERSTORM • • • 1 inch diameter hail, or 50 knot surface winds, or tornadoes

SEVERE THUNDERSTORM

SHELF CLOUD

ROLL CLOUD

SQUALL LINE THUNDERSTORM

SQUALL LINE

MESOSCALE CONVECTIVE COMPLEX (MCC) • • summer late night, early morning Midwest heavy rain, hail, high winds, flooding, tornadoes southerly, low-level jet (1. 5 km above surface) (moisture and wind shear)

Derecho 1) Concentrated area of convectively induced wind damage/gusts greater than 50 knots (60 miles per hour) 2) The area must have a major axis length of 400 kilometers. 3) Wind reports should show a continuous and nonrandom pattern of occurrence. For instance, a swath of storms should consistently produce wind reports as the system moves to the east or southeast. 4) In the storm reported areas, at least three reports, separated by 64 km or more, should include wind gusts greater than 64 knots, or 74 mph. 5) A derecho is typically continuous and can sustain itself for hours. With that said, no more than three hours can elapse between successive wind damage events.

DRYLINE c. P c. T m. T

Severe Thunderstorm Factors (Eagleman, 209)

THUNDERSTORM DAYS PER YEAR

HAIL DAYS PER YEAR