Honolulu weather is entering a high-impact stretch as a large and powerful kona storm moves over Hawaii, with an extended period of flash flooding, damaging winds, and strong thunderstorms expected through at least Saturday.
What Happens When Honolulu Weather enters the first round Tuesday night into Wednesday?
The near-term timeline is shaped by the first of two significant rounds of weather expected in this storm system. The first round is expected late Tuesday night and throughout Wednesday, with the flooding threat increasing as heavier rainfall expands beyond the western islands.
For Oahu, the statewide flood watch is set to begin late Tuesday evening and last through Saturday afternoon. As Tuesday progresses, wind direction is expected to shift to become more southerly, and breezy southeasterly winds are anticipated across the state. Late Tuesday night, heavier rainfall is expected to creep closer to Oahu, while heavy rainfall continues on Kauai through the night. Isolated thunderstorms are possible during this period.
Wind is also part of the early-round concern. Strong southerly (kona) winds are expected to develop, with gusts above 30 miles per hour noted in the forecast for some locations, and locally higher gusts possible in valleys and windward regions. The strongest winds are expected on northern slopes and in windward areas, where the terrain can accelerate downslope gusts.
What If the second round Friday into the weekend becomes the most impactful phase?
The second round, forecast for Friday into the weekend, is currently expected to be the most impactful part of the storm. The forecast calls for flash flooding, damaging south winds, and strong-to-severe thunderstorms, with this later phase expected to drop more rainfall than the first round.
Rainfall totals could be significant in some areas, especially in mountain regions, where above ten inches of rain could be received. The storm environment is also expected to become increasingly unstable by Friday and the weekend, raising the potential for storms that develop to become strong or even severe. The hazards highlighted include damaging wind gusts, intense rainfall, and dangerous lightning.
Winds may intensify as the storm deepens. The forecast notes that as a low-pressure system deepens northwest of the state while high pressure remains to the east, the pressure difference could tighten and produce strong south to southwest kona winds Friday into the weekend. In some locations, especially along north- and east-facing slopes, gusts could be strong enough to knock down trees and power lines.
What Happens When closures and safety steps escalate under flood watch conditions?
The storm is arriving alongside emergency preparations and closures. Hawaii’s governor, Josh Green, issued an emergency proclamation in response to the expected weather in the coming days, aimed at bringing additional resources into affected areas. The state also closed several parks and trails in response to the forecast and urged people to avoid forested and coastal areas, citing dangers that include storm surge, high surf, rising streams, and falling trees.
A flood watch is in effect until Saturday, with timing details varying by island: it is already in effect for Kauai and lasts through Saturday afternoon; for Oahu it begins late Tuesday evening and lasts through Saturday afternoon; for Maui County and Hawaii Island it begins Wednesday morning and lasts through Saturday afternoon. Residents are being urged to prepare by identifying evacuation routes and shelters, and planning for pets and vulnerable family members.
For Honolulu weather specifically, the most immediate takeaway is that impacts may evolve in waves. The first round late Tuesday night into Wednesday brings increasing rain and possible thunderstorms, while the later round Friday into the weekend is forecast to carry the highest risk for flash flooding, stronger winds, and more intense thunderstorms.
