What are the maximum expected surface wind speeds indicated for severe thunderstorms as per Convective SIGMET?

Severe thunderstorms are associated with significant and potentially hazardous weather phenomena, particularly in terms of wind speeds. The Convective SIGMET specifically highlights that severe thunderstorms can produce surface wind speeds exceeding 50 knots. This threshold is set because wind speeds of this magnitude can lead to damaging effects such as downed trees, power lines, and structural damage.

Wind speeds of 40 knots are considered strong but do not reach the level classified as severe when it comes to thunderstorms. Meanwhile, while wind speeds of 60 knots and above are noted in the context of extreme weather, they fall under specific scenarios such as tornadoes or certain types of extreme thunderstorms but are not the standard maximum indicated for severe thunderstorms in the principal Convective SIGMET criteria. Hence, the correct answer reflects the significant threshold for surface wind speeds in the context of severe thunderstorms as recognized in aviation weather reporting.