Flood watch issued for Kauai and Oahu as heavy rain threatens western Hawaii

A flood watch has taken effect across Kauai, Niihau and Oahu, with the National Weather Service warning that slow-moving storms could dump intense, repeated downpours over western Hawaii through Thursday afternoon.

The alert follows a developing area of low pressure north of the Hawaiian archipelago, paired with an approaching cold front from the northwest. The system is pulling deep tropical moisture northward across the islands, shifting prevailing trade winds to the southeast and setting the stage for prolonged, heavy showers and isolated thunderstorms.

What forecasters expect

Forecasters warned of potential "training" storms, where convective bands repeatedly track over the exact same terrain. When rain bands stall in that pattern, rainfall rates can quickly overwhelm ground absorption and drainage networks.

"Flood-prone roads and other low-lying areas may close due to elevated runoff and overflowing streams," the National Weather Service said, adding that built-up urban districts face elevated threats of sudden street flooding and property damage from fast-moving runoff.

Forecasters also noted that while the watch currently covers Kauai County and Oahu, staff will assess incoming data to decide whether the advisory needs expanding eastward into Maui County.

Scattered showers are likely to stick around across the western islands through Saturday, according to forecasters. Drier weather and normal trade winds are not due to return until Sunday.

Marine conditions and Florida alerts

The stormy weather comes alongside active surf conditions across the island chain. A near-advisory south swell is beginning to diminish before another arrives at the weekend, while a moderate northwest swell is peaking, with a stronger swell expected early next week.

Severe coastal conditions are also affecting parts of the US mainland this week. Along the Atlantic coast, the National Weather Service extended a separate flood watch for coastal areas of northeast Florida and southeast Georgia through Wednesday evening. A stalled front there has brought northeasterly winds of 15 to 20 mph, gusts up to 35 mph, and tidal surges 1.5 to 2.5 feet above normal ground levels across Duval, Flagler, Nassau, Clay, Putnam, St. Johns and Camden counties.

In Hawaii, emergency officials urged residents and visitors in low-lying and flood-prone districts to monitor updates closely and prepare to seek higher ground immediately if flash flood warnings are triggered.