Storm Severity Index

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A measure of the severity of storms. It is calculated from a formula of the type: V3 × A × D, where V is the maximum surface wind speed (knots), A is the greatest area with damaging winds (105 km3), and D is the duration (hours). A system of six classes may be applied, giving (in decreasing order of severity): class I, SSI > 5 000; class II, c.4 000–1 800; class III, c.1 600–700; class IV, c.600–300; class V, c.250–150; class VI, <100.

Subjects: Meteorology and Climatology.

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