Definitions
Convective SIGMETs
are issued in the U.S. for any of the following:
- Severe thunderstorm due to:
- Surface winds greater than or equal to 50 knots
- Hail at the surface greater than or equal to 3/4 inches in diameter
- Tornadoes
- Embedded thunderstorms
- Line of thunderstorms
- Thunderstorms greater than or equal to VIP level 4 affecting 40% or more of an area at least 3000 square miles
- Any Convective SIGMET implies severe or greater turbulence, severe icing, and low level wind shear.
A Convective SIGMET may be issued for any convective situation which the forecaster feels is hazardous to all categories of aircraft.
Video Integrator and Processor (VIP )
Video Integrator and Processor, which contours radar reflectivity (in dBZ) into six VIP levels: VIP 1 (Level 1, 18-30 dBZ) - Light precipitation VIP 2 (Level 2, 30-38 dBZ) - Light to moderate rain. VIP 3 (Level 3, 38-44 dBZ) - Moderate to heavy rain. VIP 4 (Level 4, 44-50 dBZ) - Heavy rain VIP 5 (Level 5, 50-57 dBZ) - Very heavy rain; hail possible. VIP 6 (Level 6, >57 dBZ) - Very heavy rain and hail; large hail possible.