Hawaii to face more downpours, aggravated flooding despite Lane's departure

By Kristina Pydynowski, AccuWeather senior meteorologist

August 26, 2018, 1:20:12 PM EDT

Persistent downpours may further aggravate the major flooding across Hawaii even as Lane departs.

While Lane will continue to track away from Hawaii early this week, needed sunshine and dry weather may not follow for the extensive cleanup and recovery efforts.

Tropical moisture will instead remain and fuel continued localized downpours.

Any substantial rain can worsen ongoing flooding and trigger new mudslides, further threatening lives and property. There may be new evacuation orders, or residents forced from their homes may not be able to return as quickly as anticipated.

More roads and bridges can be damaged, cutting off some areas from receiving aid.

"The most numerous downpours that follow Lane are expected to be over the typical windward locations on the Big Island and Maui County," according to AccuWeather Senior Meteorologist Brett Anderson.

The east- and northeast-facing slopes of the Big Island were hit the hardest by Lane's extreme rainfall. Feet of rain led to catastrophic flooding.

Localized downpours will also target the western islands of Oahu and Kauai, mainly in windward areas, early this week. Isolated flash flooding can occur where Lane left the ground oversaturated.

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Even in the absence of new flooding, the downpours can slow clean-up operations and the progression of flood waters receding.

"It will also be more humid by Hawaii standards across the islands early this week, which will put a strain on crews," according to Anderson.

More typical trade wind weather is expected to return for the second half of the week.

Drier air will drop humidity levels to more typical Hawaii standards and cause showers to become very spotty in nature. The showers will continue to focus mostly on windward communities, and rainfall will be much less than what is expected from the downpours earlier in the week.

There is a risk for additional sporadic tree damage to occur as peak gusts could be strong enough to topple trees weakened by Lane and sitting in saturated soil.

In the wake of Lane, Tropical Storm Miriam has formed in the eastern Pacific Ocean. Miriam is expected to track westward and strengthen into a hurricane early this week. An eventual turn to the north is anticipated well before the storm nears Hawaii.

Residents of Hawaii need to remain vigilant for additional threats from tropical storms and hurricanes through autumn, due to a developing El Niño.

"Because El Niño is a plume of warmer-than-average waters over the tropical Pacific Ocean, the warm water can sustain more hurricanes than average over the eastern and central Pacific, cause them to be stronger in nature and allow them to retain strength for a longer period of time as they approach Hawaii," according to AccuWeather Senior Meteorologist Alex Sosnowski.

Regardless of any tropical threat, the developing El Niño should lead to wetter-than-normal weather in Hawaii through September and October, Anderson stated.

Lane’s inundation can put the state at a higher risk for flash flooding and mudslides during this coming wet stretch.

"There should be a turn to drier weather close to winter, as is typical during an El Nino," according to Anderson.