While we are grieving over the deadliest blaze in the U.S., the loss of life, destruction of homes and its aftermath on West and Upcountry Maui, it is also time to reflect on the root causes of this Aug. 8 tragedy. Information gathered so far point out some reasons for such destructive firestorms and can be broadly classified into natural causes and human negligence.

With regard to natural causes, the passing of Hurricane Dora to the south of Maui and a very strong high pressure to the north of the islands generated strong pressure gradient forces and powerful winds. This forcing, aided by the mountainous topography of Maui, fuels destructive winds. As the air is forced to descend the mountain slopes, it increases in speeds due to the gravity effect and then rushes through the leeward side, producing powerful “downslope winds” — reportedly up to 70 miles per hour above Lahaina.

Lahaina is particularly vulnerable to the path of such gusty and dry winds. As the air descends, it is compressed and warmed, and becomes dry as it is heated. Summer is the dry season in Hawaii and by Aug. 8, Maui was already abnormally dry. The dried-out vegetation on West Maui provided fuel for ignition. It is suspected that downed power lines caused by destructive downslope winds initially sparked ignition when the humidity was very low and the ground was covered by dry grasses and pasture.

On the human side, it should be noted that irrigated sugar cane fields on West Maui were replaced with grasses that grow very fast. Once dried, they become tinder. Changes in land use inevitably worsen the blaze. Moreover, the sirens should have alerted the public ahead of time, regardless of whether the warning is intended for tsunami, hurricanes, winter storms, flashfloods, landslides or fires.

It is also sad to learn that there was no water in the fire hydrants because of melting pipes, power outages or other issues. The near-hurricane-force winds also reignited the earlier brush fire and prevented water drops from helicopters. It was also suggested that there was a lack of timely action to divert West Maui stream water to fill reservoirs near Lahaina.

Lack of water from both the ground and air made firefighters unable to contain the blaze and saw Lahaina engulfed in flames.

On a longer time scale, a warming climate can provide an adverse background condition. First, global warming favors more hurricanes and stronger storms to enter into the Hawaiian water, causing the likelihood of strong downslope gusts.

Second, a warming climate also increases vegetation dryness as higher temperatures dry out plants and grasses faster.

Third, high temperature and high winds also increase evapotranspiration, resulting in soil water deficiency. Soil moisture, or lack thereof, influences the amount and flammability of vegetation. To describe the soil moisture deficit, the Keetch/Byram drought index (KBDI) is commonly used to assess wildfire potential as part of the U.S. National Fire Danger Rating System. Our previous studies showed that for Maui, the KBDI and total area burned are strongly correlated.

Separately, in a paper that I co-authored, the study found that drought became prevalent and severe since 1970, particularly during the last three decades (1990-2019) on the leeward side of the island of Hawaii, West Maui and Oahu.

The lesson learned from this devastating disaster is that we should have a state-funded fire-weather-climate center housed at the University of Hawaii. That way we can bring together scientists who specialize in local weather, climate, numerical modeling, fire, GIS (geographic information systems), statistics and computer programming to better predict and prevent the next disaster.

Pao-Shin Chu, Ph.D., is a professor/state climatologist at the University of Hawaii-Manoa’s Department of Atmospheric Sciences, School of Ocean & Earth Science & Technology.