Criterion | Physical Characteristics |
Size | A: Cloud shield with continuously low IR temperature -32°C must have an area 100,000 km2.
B: Interior cold cloud reqion with temperature of -52°C must have an area 50,000 km2. |
Duration | Size definitions A and B must be met for a period of 6 hours. |
Maximum Extent | Contiguous cold-cloud shield (IR temperature -32°C) reaches maximum size. |
Shape | Eccentricity (minor axis/major axis) 0.7 at time of maximum extent. |