Hawaii Braces for Days of Heavy Rain and Flash Flooding This Week

Tropical Depression Olana will not make a direct landfall on Hawaii, but it will come close enough to send heavy rain and other impacts to the island chain. Here is a look at the latest tropical weather maker to impact the islands over the last few months as a strong El Niño continues to drive the parade of storms.

Hawaii Braces for Latest Tropical Weather Event

The supercharged Pacific hurricane season is showing no signs of slowing down. Olana is the latest feature to form in the Central Pacific. The most recent forecast models from the National Hurricane Center (NHC) show Olana will make a sharp curve back to the west, sparing Hawaii from a direct landfall. However, increasing moisture east of the storm will result in a steady stream of precipitation and the threat of flash flooding for much of the island chain.

Forecasters had been monitoring this batch of rain showers and thunderstorms since last week. The feature was upgraded to a tropical storm status over the weekend before being downgraded to a mere depression on Monday morning. The system will continue to weaken on Tuesday as it loses its wind intensity.

Despite the weakening trajectory of this feature, the moisture associated with it will be enough to significantly disrupt outdoor plans and travel across Hawaii. Several inches of rain are on tap over a period of three days beginning on Tuesday and lasting through Thursday for much of the Aloha State. The forecast is calling for widespread rain of 2 to 8 inches across Oahu, Molokai, and Maui. Locally higher amounts are possible for the higher terrain.

Honolulu, the largest city in the state, will be in the bullseye of the most potent rain bands and resulting flash flooding. While several other areas of the islands have been slammed by tropical weather this season, Honolulu has managed to avoid the worst impacts thus far.

Although most tropical weather systems approach Hawaii from the east, Olana is coming at the islands from the west. The unique flow of moisture from south to north could result in persistent rain for parts of the islands that are typically protected by the rain shadow.

This rare approach harkens back to Hurricane Iwa from November 1982. Iwa is distinguished as the only tropical cyclone on record to impact the Hawaiian Islands during the month of November.

In addition to the rain associated with Olana, forecasters are also warning residents about the chance of another surge of tropical moisture unfolding as the calendar flips from October to November.  A Kona storm could form west of the islands over the weekend, translating to a soggy Halloween and start to the new month. Meteorologists will be closely watching the track of this potential Kona event in the days ahead.

Historic Tropical Weather Season for Hawaii

It has already been a historic tropical weather season for Hawaii. The islands have seen five named storms pass within a few hundred miles of land so far this year. Fausto was first up, coming within 200 miles of the northern shore of the central islands as a tropical storm at the end of July.

A few weeks later, Hurricane Lala skirted by the southern tip of the Big Island on August 16. While Lala did not officially make landfall, the outer edge of the storm's eyewall grazed the coast. Lala continued to strengthen as it moved to the west of the islands, reaching peak winds of 130 mph. Tropical Depression Moke came within 225 miles of the southern tip of the Big Island on September 23.

Lowell came within 40 miles of the island of Niihau on September 8. This storm had reached a monster Category 5 status with 160 mph winds before reaching Hawaii.

Once again, it was the southern flank of the Big Island that saw more impacts on September 26 when Hurricane Nolo churned about 165 miles to the south. Nolo was a long-lasting storm, traveling over 7,000 miles from its starting point near the coast of Mexico all the way to Japan. This storm peaked at a Category 4 storm with 155 mph winds.

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