FIRST ALERT: Threat of heavy rain, thunderstorms may bring widespread flooding
The islands will be under the threat of significant rainfall and potentially catastrophic flooding as a strong Kona low develops to the northwest of Kauai. The threat will start Sunday on Hawaii island and Maui County, spreading to Oahu and Kauai County Sunday night and Monday. Weather could remain wet into Tuesday and Wednesday. For now, a flood watch remains posted statewide through Tuesday afternoon.
The cool and drier conditions that brought record low temperatures will change rapidly as winds start to come in from the south to southwest, bringing warmer and more humid air by Monday. The south-southwest winds will become locally strong by Monday. Those winds will also bring bands of deep tropical moisture northward, so expect locally heavy rain and scattered thunderstorms moving in from east to west. There’s the potential for rainfall totals reaching 10 to 15 inches over the next few days for some areas, with some isolated areas getting 20 to 25 inches.
The Kona low will slowly drift northwest and away from the islands through the middle of the week, with a drying trend -- again from east to west -- expected Wednesday and Thursday. High pressure will also develop and push trade winds over the area.
Surf is also active, as a large north-northwest swell will shift more out of a northerly direction. Surf will remain large enough for a high surf warning to continue for most north facing shores, along with a high surf advisory for most west shores. Small surf will increase for east shores from a north swell wrap. South shore surf could rise a bit thanks to locally-generated wind waves, with a small long-period south swell beginning Monday.
Here’s a list of the current severe weather alerts:
Flood Watch: All islands until 6 p.m. Tuesday.
High Surf Warning: North shores of Niihau, Kauai, Oahu, Molokai and Maui, and the north and west shores Hawaii Island until 6 a.m. Monday.
High Surf Advisory: West shores of Niihau, Kauai, Oahu, Molokai and Maui.
Wind Advisory: Haleakala summit until 6 a.m. Monday,
Wind Advisory: Hawaii Island, except the summit areas, from 6 a.m. Sunday until 6 a.m. Monday.
Small Craft Advisory: All Hawaiian coastal waters until 6 p.m. Monday.
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