Which weather phenomenon is characterized by a sudden decrease in visibility and abrupt wind shifts?

The phenomenon characterized by a sudden decrease in visibility and abrupt wind shifts is a microburst. Microbursts are intense localized downdrafts that can occur during thunderstorms. As the downdraft reaches the ground, it spreads out horizontally, creating strong winds that can shift direction rapidly. This can result in significant changes in visibility, often caused by blowing dust or precipitation. The rapid and powerful nature of these wind shifts poses particular challenges for helicopter operations, as pilots must be prepared for sudden changes in flight conditions.

In contrast, downbursts are broader and can encompass a larger area, while a squall line refers to a line of severe thunderstorms that can produce various weather phenomena, including microbursts. The jet stream, on the other hand, is a high-altitude, fast-flowing air current and is not associated with the immediate effects seen in microbursts, such as sudden decreases in visibility or rapid wind changes at the surface level.