Relationships Between the Size of Satellite-Observed Cirrus Shields and the Severity of Thunderstorm Complexes

Seventeen thunderstorm complexes, observed by TIROS satellite over the United States, were investigated. The diameter of the conspicuously bright storm cloud shield, composed of integrated thunderstorm anvils, has been found to be a useful index of severity. Seven out of ten complexes with shield diameters greater than 60 n mi were accompanied by severe local storms. Another, but less reliable, index of severity is the presence of cirrus streamers or “blowoffs.” The line structure, commonly observed by radar, is generally masked by the cirrus shield.