HONOLULU—The National Weather Service in Honolulu has issued a Flash Flood Watch for the islands of Oahu, Molokai, Maui, and Hawaii Island through 6:00 a.m. on Wednesday, December 13. Potential heavy rains may come from an upper level trough, which will move slowly eastward across the islands tonight, December 12.
Flash floods occur during extended rainfall events or within a few hours after the rainfall, according to the Pacific Disaster Center. Generally, if rainfall is of long enough duration, it will eventually cause flooding along the rivers, creeks, and streams draining the catchment area where the rain is being collected. But if the intensity of the rain—the number of inches of rain falling in a given time frame—is too great for the stream system, including flood plains, to carry the water away, flash flooding occurs.
The words “watch” and “warning” are used for two different levels of flood alerts. A flash flood watch or flood watch means that flooding or flash flood is possible in the area. The basic message of a flood watch is exactly what it sounds like: “Watch closely, conditions suggest a high likelihood of flooding.” When the word “watch” is replaced by the word “warning,” flooding or flash flooding is imminent or already beginning to occur. If you are in a low-lying or flood-prone area, act immediately to ensure the safety of your family. When a warning is issued, it is too late to prepare property to withstand flooding. You may have only seconds to act.