Moderate trades will gradually strengthen each day over the next several days with widespread strong trades expected by Thursday and very windy conditions possible on Friday. The main focus for the weather this week will be the tropical cyclone development southeast or south of the Big Island over the next few days. While the potential wind impacts remain uncertain, the threat for flash flooding will increase. A flood watch has been issued from noon Wednesday to 6 PM Saturday for Maui County and the Big Island.
Breezy trade winds will continue into Thursday. Moisture will continue to increase tonight into Wednesday with shower activity increasing across the Big Island Wednesday morning into the afternoon. Shower coverage will spread northwestward through the state late Wednesday into Thursday. Periods of MVFR ceilings and visibility are likely in heavier showers.
AIRMET Sierra is in effect for mountain obscuration and may continue into the morning.
AIRMET Tango is in effect for low level turbulence downwind of island terrain.
Issued at 330 PM HST Tue Sep 22 2026 The gradient between the subtropical high to the northeast a low pressure system (a developing tropical cyclone) to the southeast will cause moderate to fresh trade winds across the Hawaiian coastal waters through Wednesday. A Small Craft Advisory (SCA) is in effect for the typical windy waters of Maui County and the Big Island through Wednesday night. Depending on how the tropical cyclone organizes and approaches the coastal waters from the southeast, gales or tropical storm watches/warnings may also come into play through the second half of the week. Rainfall and thunderstorms will increase as the system nears, particularly across the eastern waters.
Surf along south facing shores will decrease as the current south-southwest swell fades. A moderate southwest swell will build in around Friday into the weekend building surf back up across south and west facing shores.
A small, short period, north northwest swell will fade through Wednesday. Another small northwest swell will fill in this weekend keeping surf slightly elevated along north and west facing shores.
East facing shores will maintain rough, short period wind waves generated from the breezy trade winds. As trades strengthen on Thursday through the weekend, surf will increase and become very rough and choppy, possibly nearing advisory levels.
Flood Watch from Wednesday afternoon through Saturday afternoon for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Big Island Summits-Haleakala Summit-Kahoolawe-Kipahulu-Kohala-Kona-Lanai Leeward-Lanai Mauka- Lanai South-Lanai Windward-Maui Central Valley North-Maui Central Valley South-Maui Leeward West-Maui Windward West- Molokai Leeward South-Molokai North-Molokai Southeast-Molokai West-Molokai Windward-South Haleakala-South Maui/Upcountry- Windward Haleakala.
Small Craft Advisory until 6 AM HST Thursday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
