HONOLULU (HawaiiNewsNow) – Your First Alert Weather Team has declared FIRST ALERT WEATHER DAYS Tuesday through Saturday as a large and powerful Kona storm moves over the state. Here’s what to expect.
The storm is expected to bring an extended period of flash flooding, damaging winds, and strong thunderstorms through at least Saturday.
Flood watch issued
The National Weather Service has issued a statewide FLOOD WATCH on Tuesday morning.
The flood watch for Kauai will begin on Tuesday morning and last through Saturday afternoon.
The flood watch for Oahu will begin late Tuesday evening and will also last through Saturday afternoon.
The flood watch for Maui County will begin on Wednesday morning. Hawaii Island will likely be added later this week.
Hour-by-hour timeline
Here is the latest breakdown of the data from our First Alert Weather team. We will be monitoring this storm throughout the week so check back for updates.
Expect a multi-day flooding threat throughout this week. Strong, potentially damaging, Kona winds are also expected.(HNN Weather)
Monday, March 9
Evening: Breezy southerly winds will continue across the state. A few showers over eastern and southeastern slopes are possible, but will be relatively light compared to the rainfall expected later this week.
Tuesday, March 10
Morning: The Kona Low is expected to approach the Garden Isle throughout Tuesday, and the flooding threat will increase throughout the day. Scattered showers are possible throughout Tuesday morning. An isolated heavy downpour could develop, but the heaviest rainfall will come later Tuesday evening.
The rest of the state should expect breezy southeasterly winds. The wind direction will shift to be more southerly throughout the day on Tuesday.
Evening: Rainfall on Kauai will increase throughout Tuesday afternoon, potentially becoming torrential late Tuesday night into Wednesday. The flooding threat will become significant late Tuesday night for Kauai. Strong southerly (Kona) Winds will also develop at this time, gusting above 30 miles per hour. Wind gusts could be locally higher in the valleys and in windward regions.
The winds will be the strongest on the northern slopes of each island and in windward regions. The Kona winds will rush up the mountains and gain speed as they rush down the other side.
Night: Heavier rainfall will start to creep closer to Oahu late Tuesday night. Heavy rainfall continues for Kauai throughout the night. Isolated thunderstorms are possible. Strong Kona winds continue.
Wednesday, March 11
Morning: The heaviest rainfall is forecast to reach Oahu on Wednesday morning. Heavy rainfall continues on both Kauai and Oahu, along with continuous strong, southerly winds.
Evening: The impacts of the storm are forecast to reach Maui County throughout Wednesday afternoon and evening. Scattered showers could impact Hawaii Island at this time, but a bulk of the moisture will be focused over Maui County, Oahu, and Kauai.
The flooding threat for Hawaii Island will increase throughout Wednesday, becoming more concerning throughout Thursday and Friday.
Night: Heavy rainfall will continue throughout the night, but become more scattered. The risk for flash flooding will decrease slightly throughout Wednesday night.
Thursday, March 12
Rainfall throughout Thursday will be more scattered, and the flooding threat will decrease slightly though it will still be present.
Widespread instability will still be in the atmosphere. Torrential rainfall and flash flooding are still possible throughout Thursday, but will be more scattered in nature.
The southerly winds will also weaken slightly, but could become strong in regions north of the mountains.
There is also the possibility of winter weather on the Big Island summits. Colder air wrapping into the storm system combined with increasing moisture could allow periods of heavy snowfall on the highest elevations later in the week and into the weekend, potentially leading to significant snow accumulation.
Friday, March 13, through the weekend
Another, potentially more impactful round of rainfall is expected to impact the entire state Friday afternoon through Sunday.
This next round of rainfall is currently forecast to drop more rainfall than the first round as described above. Some regions, especially those in the mountains, could easily receive above ten inches of rainfall.
While embedded thunderstorms are possible midweek, the environment could become increasingly unstable by Friday and the weekend. This means storms that develop may have the potential to become strong or even severe, capable of producing damaging wind gusts, intense rainfall, and dangerous lightning.
Winds will also become an important factor as the storm intensifies. As the low pressure system deepens northwest of the state and high pressure remains to the east, the pressure difference between the two systems could tighten. This setup may produce strong south to southwest kona winds Friday into the weekend.
In some locations, especially along north and east facing slopes, these winds can accelerate downslope and potentially bring gusts strong enough to knock down trees and power lines.
Download the HNN Weather app from the Apple App Store or Google Play for the latest updates from your First Alert Weather Team: chief meteorologist Jennifer Robbins, meteorologist Drew Davis, and weather anchors Guy Hagi, Ben Gutierrez, and Billy V.
Download HNN’s weather app for everything you need to plan your day.(Hawaii News Now)
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