How often are Convective SIGMET bulletins issued?

1. 1Hourly, at 55 minutes past the hour
2. 2Every 6 hours
3. 3Every 3 hours at 15 minutes past the hour
4. 4Once each day at 0000Z

Source: Aeronautical Information Manual (FAA, Basic with Change 3, 9 July 2026), AIM 7-1-6 Inflight Aviation Weather Advisories, page 530