Which present weather type uses a minus sign (-) to indicate light intensity?

The present weather type that uses a minus sign (-) to indicate light intensity is snow grains, denoted as SG. In aviation weather reports, certain weather phenomena are classified by using specific codes that represent their intensity. When present weather is described, a minus sign is applied to indicate that the intensity is light.

In this context, snow grains are small, white precipitation particles that are often associated with stable atmospheric conditions and occur in light amounts. By using the minus sign for SG, it clearly indicates that the snow grains are falling lightly.

In contrast, the other choices represent different weather phenomena that do not utilize the minus sign for light intensity or are not associated with snow lightness. Thunderstorms (TS), ice pellets (IC), and graupel (GS) have their own specific indications and typically do not employ the same notation for intensity as snow grains do. Thus, SG’s designation with a minus sign effectively communicates the weather condition's lower intensity, making it the correct answer.