What is the primary use of the Storm Flag?

The Storm Flag is primarily used to indicate stormy weather conditions or impending bad weather. When this flag is flown, it serves as a warning to mariners, indicating that they should be prepared for potential rough weather and take necessary precautions. This is particularly relevant for naval and maritime operations, where being aware of weather conditions is crucial for safety.

In contrast, the other options pertain to different flags or customs. For example, flags flown at night generally relate to different protocols, celebrations often involve festive flags or banners, and solemn occasions typically feature flags that signify mourning or tribute. Thus, the purpose of the Storm Flag is distinctly tied to signaling turbulent weather, making its primary use clear and specific.