Flash Flood — Suffolk, New York

2024-08-19 · near Smithtown, Suffolk, New York

Event narrative

The Nissequogue River dam broke due to the flash flooding causing the entire Blydenburgh Pond to empty into the river. The river overflowed its banks, sending water into homes and nearby streets. Two residents were trapped in their homes and had to be rescued.

Wider weather episode

A frontal system over the area on August 18th and into the early morning hours of August 19th allowed for the development of multiple rounds of slow moving heavy thunderstorms which resulted in widespread significant to catastrophic flash flooding for portions of Southeast New York, specifically for the north shore of Long Island. Several rounds of rain moved through during the day on August 18th. By the afternoon, a line of thunderstorms moving in from the west interacted with several mesoscale boundaries and allowed the thunderstorms to intensify and train over Long Island during the overnight hours into early on August 19th. These thunderstorms produced rainfall rates of upwards of 3-5 inches per hour with total rainfall amounts of upwards of 10 inches, much of it falling over a 2-4 hour period. This resulted in numerous water rescues, several dam breaks, several road washouts, and significant damage to numerous buildings across the north shore of Long Island.

View location on OpenStreetMap → (40.8411, -73.2336)

Source: NOAA Storm Events Database, event_id 1213940. Narrative written by the NWS forecast office that issued the report.