A strong upper level disturbance has combined with a slow moving surface trough and abundant moisture, bringing widespread thunderstorms and flooding rainfall. Some areas of Windward Oahu have received nearly 15 inches of rain in the last 24 hours.
On Monday, most of the heaviest showers and thunderstorms will be to the north and northeast, but there's still enough instability for scattered heavy showers and thunderstorms. A Flash Flood Watch remains posted through Monday afternoon and you should be prepared to take quick action if a flash flood warning is issued. A Winter Weather Advisory is also posted for the Big Island summits.
For mariners, scattered strong thunderstorms and locally heavy downpours will reduce visibility, bring locally gusty winds and even produce hail and waterspouts. Also, there are brown water advisories up because of storm runoff and it won't be the best beach weather, but surf on north shores will rise to 6 to 10 feet, with west and east shores rising to 4 to 6 feet Monday.