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In all the coverage of the tragedy produced by West Maui wildfires, a story that has been a bit overlooked is the accuracy of the forecasts produced in advance of the storm by the National Weather Service Honolulu Forecast Office.

The weather that caused the ongoing tragedy on Maui was complex.

Essentially a high amplitude atmospheric wave forced by strong winds interacting with the mountains of northwest Maui produced powerful, dry downslope winds on the lee slopes of West Maui mountains.

NWS forecasters are familiar with this weather pattern, which meteorologists refer to as a “downslope windstorm.”

The downslope windstorm was well predicted by a NOAA high resolution model (Figure 1).

In this case the downslope windstorm produced 60-90 mph gusts that hit a very localized area; winds strong enough to shear off wooden power poles, tear roofs apart, and down power lines.

Already on Aug. 4, four days prior to the event, extended outlooks foresaw the potential of a high wind event with very low humidity.

Early on Aug. 6 an urgent Fire Weather Watch was issued.

On the afternoon of Aug. 7, the day before the event forecasters issued a High Wind Warning.

In the Area Forecast Discussion, the forecaster wrote, “The strongest winds are expected over mountain terrain and downslope into leeward areas.”

In addition, a Red Flag Warning was issued for leeward portions of all the Hawaiian Islands with wind gusts over 60 mph.

A Red Flag Warning indicates that critical fire weather conditions are either occurring now or will shortly.

Under Impacts associated with a Red Flag Warning, the NWS notes, “Any fires that develop will likely spread rapidly.”

The specificity and the timeliness of the NWS advisories and warnings is a major achievement that reflects the difficult training required of NWS forecasters (most in Hawaii have M.S. degrees in Atmospheric Sciences, aka meteorology) and the quality of the products (e.g., satellite and radar imagery) and the numerical forecast guidance available from NOAA in the Honolulu Forecast Office (see image NOAA wind forecast above).

As better satellites are launched and larger computers are employed, forecasts will continue to improve (e.g., Figure 2).

The outcome of ongoing investigations will help to determine how NWS forecasts, advisories, and warnings can best be used to prevent such tragedies in future.