A Trip Down Hurricane Lane 2018

Hurricane Lane, Aug. 21, 2018, 10:30 a.m. NOAA animation

The National Oceanic and Atmospheric Administration’s Central Pacific Hurricane Center announced in May that there was an 80% chance of near- or above-normal tropical cyclone activity during the 2018 Central Pacific hurricane season.

NOAA’s prediction was correct.

Hawai‘i’s 2018 hurricane season, officially ending today, Nov. 30, was among the most active—and destructive—in years. Hurricanes and tropical storms this year caused widespread flooding on the Big Island, Maui and Kaua‘i.

The 2018 Pacific hurricane season produced the highest Accumulated Cyclone Energy (ACE) value on record in the Eastern Pacific basin and is the fourth-most active season on record, tied with 1982.

In addition, the season featured the most named storms in the East Pacific proper since 1992, and tied 1994 and 2002 for the most Category 5 hurricanes in a season (which officially began on May 15), with three hurricanes (Lane, Walaka and Willa) reaching that intensity. The Eastern Pacific saw 25 tropical cyclones—a near record-breaker.

The Central Pacific saw six named tropical cyclones over the season, which officially began on June 1.

In early August, Hurricane Hector became one of the few tropical cyclones to cross into the Western Pacific from the Eastern Pacific, and the first hurricane of the season to threaten Hawai‘i. It went on to set a record for the longest-lived hurricane to remain at a Category 3 or above in the NE Pacific, surviving at that intensity for nearly eight days.

A few weeks later, Hurricane Lane formed as a tropical storm in the Eastern Pacific on Aug. 15 and became a hurricane the next day.

On Aug. 21, Hurricane Lane became a Category 5 hurricane, the first since Ioke in 2006, only the second on record within 350 miles of Hawai‘i.

Hurricane Lane obtained Category 5 intensity while also becoming Hawai‘i’s wettest tropical cyclone on record. Lane rapidly weakened as it approached Hawai‘i Island, dropping torrential rains that triggered flooding and landslides. As the hurricane came closer to the state, wind shear began to cut it apart. Lane is the third wettest U.S. tropical cyclone on record, topped only by Hiki in 1950 (52 inches) and Harvey in 2017 (60.58 inches).

Lane brought more than 50 inches of rain to one location on the Big Island; an additional four locations saw more than 40 inches of rain.

Mountain View received 51.53 inches of rain from noon Aug. 22 to 4 a.m. Aug. 26. At Waiakea Uka, located just south of Hilo, rainfall totaled 49.10 inches.

Hilo picked up 36.76 inches of rain in the four-day period from Aug. 22 to 25, making it the wettest four-day period ever observed in Hilo in records dating back to 1949.

Fifteen inches fell on Aug. 24 alone, making it the fifth-wettest calendar day on record. August 2018 is also the wettest August on record in Hilo.

Pāhoa saw 3.36 inches of rain in one hour on the evening of Aug. 24, 1.28 inches of which fell in just 15 minutes.

The heavy rain triggered road flooding on the Big Island, including in Hilo, and mudslides and landslides occurred, blocking numerous roads.

The Bayfront area in Hilo was flooded by overflow from the Alenaio Stream.

In addition to rain, high winds were a factor: Winds of 83 mph with a gust to 107 mph were clocked early on Thursday, Aug. 23.

At the end of August, Hurricane Miriam headed north of Hawai‘i, posing no real threat.

A few days later, in early September, Hurricane Norman dropped heavy rains as it passed north of the the Big Island.

Hurricane Olivia, which entered the Central Pacific on Sept. 8, also impacted Hawai‘i, resulting in slight damage. Tropical Storm Olivia made landfall on Maui and Lāna‘i as a tropical storm.

The only hurricane to form in the Central Pacific over the course of the season was Hurricane Walaka, which remained far away from the main Hawaiian Islands, but overrunning East Island in the Papahanaumokuakea Marine National Monument, wiping it off the map.

What may be in store for next year’s hurricane season?

It is too early for an official prediction from NOAA, which is banking on a 75% chance that an El Niño event—characterized by warming waters in the eastern Pacific Ocean—will develop in the coming months and last through the season, which for meteorologists begins Dec. 1.

If weak El Niño conditions take hold this winter, there is a 55 to 60% chance those conditions will persist into spring 2019.

During an El Niño event, sea surface temperatures become warmer than normal, which can fuel storms, but it’s also known to disrupt easterly trades, resulting in drier weather for Hawai‘i.

However, El Niño tends to increase the number of tropical cyclones in the eastern and central North Pacific regions, creating increased risk of tropical cyclone activity in Hawai‘i during hurricane season…