(This article, first published Monday, was updated Tuesday based on updated data which moved the Big Island’s maximum rainfall total to the second highest on record for a tropical cyclone in the United States.)
Hurricane Lane, which collapsed in spectacular fashion as it drew close to Hawaiian Islands, could have been much worse. Had it held together and edged slightly farther north, severe rain, wind and surf would have bombarded Oahu and Maui. Instead, those islands were grazed.
Even so, bands of torrential rain repeatedly slammed into the Big Island’s eastern half over a period of five days. The total amount of rain, measured in feet, soared to historic levels: Over four feet or 52.02 inches were measured on Mountain View, about 15 miles southwest of Hilo.
This preliminary total ranks as the second highest for a tropical storm or hurricane in the United States since records began in 1950, according to the National Weather Service office based in Honolulu. It also marks the greatest rainfall total on record from these storms in the state of Hawaii.
Hurricane Harvey, which engulfed Southeast Texas a year ago with a maximum rainfall of 60.58 inches is the only wetter storm. Hurricane Hiki, which unloaded up to 52.0 inches on Kauai in 1950, ranks third.
Mountain View was not the only recipient of extreme rainfall from Lane. Several other mountain locations on the east side of the Big Island also logged totals over 40 inches.
The Weather Service received an “unverified” report of 58.80 inches of rain, posted by a private station, that it will attempt to validate.
Even locations near sea level were deluged by extreme rainfall amounts. Hilo International Airport reported 36.76 inches of rain between Aug. 22 and 25, its wettest four-day period on record.
“It was almost biblical proportions,” state Sen. Kai Kahele (D), who represents Hilo, told the Associated Press.
The torrent resulted in “significant flash flooding” on the northeast- and east-facing mountain slopes of the island, the Weather Service said. The rains forced multiple evacuations and water rescues, and closed several roads.
While over three feet of rain fell in Hilo, only about an inch came down in Kona, on the island’s west side. The east-facing mountains near the island’s center, which climb to nearly 14,000 feet in elevation, tend to intercept and squeeze out most of the moisture from incoming rainbands. Locations on the downwind (west-facing) side of the mountains sit in a rain shadow and are blocked from getting much rain.
Although the heaviest rain by far, occurred on the Big Island, a few locations on Maui also posted hefty totals, ranging from eight inches to two feet.
Lane has moved safely away from the islands, but long-range forecast models suggest Hawaii will need to keep a close eye on the tropics. It has a been a very busy season for storms in the northeast and north central Pacific Ocean, and long-range models show the potential for more activity.
The latest storm to form in the northeast Pacific Ocean, Tropical Storm Miriam, is not expected to threaten the islands. While it is forecast to strengthen into a hurricane, it should pass well to the north of Hawaii.
That two of the three most extreme rainstorms from hurricanes have occurred in the past two years is consistent with what scientists expect in a warming climate. Studies have shown tropical cyclones are likely to become more larger and more intense while producing heavier rainfall as the planet warms.