“I had to grab my glasses for this one because I saw ‘tornado’ and I thought, ‘This must be the wrong alert,’ ” said Alderete in an interview. “I had been hearing the flooding alerts pretty much all night long.”
But Tuesday’s tornado warnings — the first issued in the Aloha State since 2008 — were no mistake. The first came at 1:22 a.m. local time, when strong rotation was detected just southeast of the island of Niihau. A more intense circulation barreled ashore in Kauai, the northwesternmost populated island in the chain, at around 5:55 a.m.
That second rotation was particularly impressive, even complete with a “bounded weak echo region,” or BWER, on radar. That doughnut hole-like formation occurs when an updraft, presumably from a tornadic circulation, is so strong that rain isn’t able to fall within it.
It appeared as the area of spin responsible for prompting the warning passed over the south side of Kauai, at 6 a.m. local time.
When the alert was issued, Alderete’s mind flashed back to Lawrence, Kan., where he spent several years in his youth.
“I did receive an additional [notification] from a local news source. … The advice they gave was to not wait until you see or hear a tornado,” he said. “It’s been windy here all day, and the [ambient] winds could mask any tornado sound.”
Alderete, a microbiologist, promptly woke his wife and son, grabbed their cat and hunkered down on the lowest floor of their home.
The National Weather Service in Honolulu did not receive any reports of tornadoes or damage from Tuesday morning’s storms.
The rotating thunderstorms are thanks to a larger “Kona storm” sauntering in from the west. The moisture-loaded storm has dropped more than 20 inches of rain atop the highest peaks on Kauai, with a widespread five to eight inches of rain elsewhere.
The mountains of Kauai often help focus tropical moisture into extreme downpours that would be mind-boggling by standards known to the rest of the country.
The roar of heavy rain was even audible on the phone with Alderete.
“You wouldn’t think an island could flood,” he joked, “but I was here in 2018.”
More than four feet of rain came down in the town of Hanalei in just 24 hours between April 15 and 16, 2018 — the rainiest day in U.S. history.
Flash flood warnings were issued for Kauai on Tuesday morning in response to the ongoing heavy rain. “Kaumualii Highway are flooded between mile marker 14 and Pakala,” warned the National Weather Service. The South Fork of Wailua River was also observed to be running very high.
Flooding isn’t terribly uncommon in Hawaii, but severe weather is a different story.
The most recent tornado to touch down in Hawaii was on March 23, 2015, when an EF-0 land spout tornado formed in the lee of the mountains on Oahu.
Before that, an EF-0 twister with 70-mph winds hit Oahu, spawned by the same March 9, 2012, supercell thunderstorm that dropped a record-shattering 4.25-inch hailstone near Kailua.
Most of the time, Hawaii’s weather is comparatively tame. Unlike everywhere in the Lower 48, which relies on the Storm Prediction Center to issue severe thunderstorm and tornado watches, Hawaii’s isolated nature and unique climate means its local National Weather Service forecast office handles any watches, too.
Kauai remained under a severe thunderstorm watch Tuesday morning until 9 a.m. local time. The entire island chain was placed beneath a flash flood watch.