If your phone suddenly sounded a loud emergency alert Thursday afternoon, you were in the path of a dangerous flash flooding threat in Monmouth County.
The National Weather Service issued a Flash Flood Warning at 2:18 p.m. Thursday, Aug. 27, after thunderstorms dumped between 1.5 and 2.5 inches of rain across parts of the area. Around 3:15 p.m., rainfall totals had climbed to between 2.5 and 3.5 inches in some locations, with flash flooding reported in Keyport and Holmdel.
That’s when the loud message was received on many smartphones. That’s called a Wireless Emergency Alert, or WEA. These alerts are distributed through the federal Integrated Public Alert and Warning System, known as IPAWS.
But not every weather warning triggers a Wireless Emergency Alert.
For severe thunderstorms, the National Weather Service uses three damage-threat categories: base, considerable and destructive. Only a destructive Severe Thunderstorm Warning automatically triggers a WEA. That designation requires winds of at least 80 mph and/or hail at least 2.75 inches in diameter, roughly baseball-sized.
Flash Flood Warnings also use escalating damage-threat categories. Wireless Emergency Alerts are generally triggered when the threat reaches the considerable or catastrophic level.
In other words, the loud alert is generally reserved for weather situations the National Weather Service considers especially dangerous and requiring immediate action.
Wireless Emergency Alerts are also used for threats beyond weather, including AMBER Alerts, certain public safety emergencies and national emergency messages. NOAA Weather Radio, meanwhile, remains a separate system that can broadcast a broader range of National Weather Service watches, warnings and other hazard information.
Thursday’s flooding showed why the higher-level alerts exist: several inches of rain fell in a short period, roads flooded and portions of Route 36 were forced to close.
