August 09, 2023

Wind-Driven Wildfires on Maui

Large fires are now burning on Maui, Hawaii with severe damage to the historic town of Lahaina on Maui's west side.

Downtown Lahaina burning.   Picture courtesy of Alan Dickar

Satellite imagery shows two major fires... one near Lahaina and the other in the high country east of Kihei (see images below, the orange and red dots show the fires).


As I will discuss below, these fires are the results of strong winds and bountiful grass, plus human ignition sources.  Wetter and cooler than normal conditions during the past six months played a role.

Wildfires and Hawaii

Believe it or not, Hawaii is one of the most fire-prone states in the U.S. (see map below of some historical fires)

With persistent trade winds out of the east or northeast, the eastern side of the Hawaiian Island is quite wet (with moist upslope flow), while the lee (or Kona) sides are dry (see climatological precipitation map of the Hawaiian islands below).

That is why many people vacation at Kona (Big Island), Lahaina (Maui), or  Poipu Beach (Kauai), where warm, dry weather dominates.


There is sufficient precipitation on the lee side of the islands for substantial grasslands to develop, with grasslands increasing during the past several decades as agriculture has declined on Hawaii (e.g., the sugar cane industry is essentially gone).  

To illustrate, here is an image taken by Google near Lahaina.  Lots of grass.

An inferno ready to happen.


You can also view the large grassy areas on Maui on this satellite image (grassy areas are brownish in color)


Such grasses are highly flammable, even a day after rain, with fire growth greatly encouraged by strong winds. Much of the grasses on Maui are non-native, invasive species that burn easily.

And Hawaii frequently gets strong trade winds.

Why did the Maui fires happen now?

Very strong trade winds developed yesterday, as a large pressure difference (gradient) formed between a strong subtropical high and hurrican Dora to the south.


To show how unusual this pattern is, the figure below shows the sea level pressure at 11 PM PDT last night, and the normalized anomalies from the typical sea level pressure (colors). 

MUCH higher pressure than normal was found just north of Hawaii (red and brown colors), while an area of lower than normal (blue colors) was found south of Hawaii (due to Hurricane Dora). 

The result of this anomalous pressure pattern was greatly enhanced winds that fanned the flames and I suspect helped start fires (by downing powerlines).   A familiar story to those of us in the Northwest.


How strong were the winds?     Below are the maximum gusts on Tuesday provided by a NOAA website--some as high as 62 mph.  Other reports were as high as 80 mph.


Model simulations/forecasts suggested strong wind acceleration on the lee slopes of the substantial terrain of Maui and downstream of gaps in  its terrain  (the University of Hawaii high-resolution surface sustained wind prediction for 6 PM PDT Tuesday is shown below)

The situation this year on Maui was made even more dangerous on Hawaii because the past half-year was WETTER and COOLER than normal, which enhanced grass growth.   I repeat wetter and cooler.    

I don't have to tell you what some media will be ascribing the Hawaii wildfires to:  climate change.   Demonstrably untrue.

To demonstrate wetter/cooler conditions, here is the departure of precipitation from normal for the past six months (in inches).   Western Maui was wetter than normal.  Much of the big island was crazy wet.  This excessive moisture was the result of several powerful Kona Storms this winter.


Temperatures the past six months?   As shown below, a bit below normal over western Maui.


So we started with a region prone to grassfires (the western side of Maui).   We had enhanced grass growth due to extra precipitation, and then the area was hit with unusually strong winds.

Many of the same ingredients came together to produce the recent large grass fires in eastern Washington.

29 comments:

  1. While wind was a significant factor on the Newell Road fire near Goldendale and the Eagle Bluff fire in the Okanogan, excess precipitation in the months prior to these fires was not. Precipitation in both areas was below normal in 2023 up to the start of these fires. At Goldendale, it was about 50% of normal for the January thru June period, and also the spring months March thru May. It was a little better at Omak, about 80% of normal for these periods, but June and July were very dry in both areas with precip. about 20% of normal.

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    1. The excessive precipitation was during the PREVIOUS year. The bountiful grass overwintered. Check out the USDA FuelCast website...they document the large dead fuel load

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    2. Your article about the Maui fires discussed the weather conditions of the prior 6 months, wet in the months prior to the fire promoting grass growth, then stating that the situation on the Eastern Washington fires was the same. I was just showing that it was not wet during the months prior to our fires. Dead grass overwinters every winter but the very dry conditions prior to the fires do not happen every spring and summer. l maintain that while these fires would have likely occurred even in a "normal" year, the warmth and dryness of the previous 2 or 3 months made them more intense and larger. While these were considered grass fires there was other larger dead and live vegetation involved which were likely much drier than normal due to the previous dry period.

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    3. I would also factor in that we had a early HEAVY snowfall that covered non frozen ground and insulated it all winter from freezing and when spring melt came all that water made its way into the ground. Ground water here has been great and for a period of time ground stayed moist enough without rain to grow the grass.

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    4. yeah overwintered grass where new grass grows from is basically like kindling. Dry because it's not drinking water and because dead of summer. A field of that would go up so fast. Gosh. Prayers for everyone effected. Terrible tragedy.

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  2. Someone should ask the Seattle Times for their learned take on this...wait, I already know.

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  3. Horribly sad what happened to Lahaina, everything is gone.

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    1. I feel horrible for those who live there. Such a beautiful place, and simply wonderful people. We've been several times. I hope they get all the help they need.

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  4. Consistent with the strong high pressure system, the trade wind inversion at Lihue was anomalously low, especially for summer, and it was close to the mountain heights just upstream of the Lahaina fire. Local downslope wind storm?

    Terrible that so many people have lost everything and there were some fatalities.

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  5. Did the current drought conditions in Maui not play a role in this fire at all? While Maui received more rain over the early spring/winter and with total averages are above normal overall it looks like it has been very dry there recently with the US drought monitor listing it as moderate to severe drought for that area as of yesterday.

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    1. It is unlikely drought played any role. It was actually far wetter during the previous year, which led to grass growth. Grasses are 1-10hr fuels that dry within hours in dry conditions and the strong, low-RH, downslope winds would have dried the grasses within hours.even if wet the day before. Finally, the drought monitor is unreliable and subjective...cliff

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  6. I was there a while ago when a fire broke out in the same area. The fire fighters were on it immediately with relays of helicopters dropping buckets of seawater. Put it out in a couple of hours. The fact that the copters were grounded by the wind was probably a major contributor to this tragedy.

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  7. Another factor might have been the Kona Lows this winter that dumped a lot of rain on the normally dry southwest sections of the islands.

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    1. Concerned.... I think you are quite right. Helicopter could not fly in the strong winds and yes the frequent Kona lows this winter dumped a lot of rain over the islands, encouraging grass growth....cliff

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  8. Well that didn't take long.
    https://www.nytimes.com/2023/08/10/climate/hawaii-fires-climate-change.html
    What is striking is the complete lack of nuance and understanding of the wet/dry geography of Hawaii. Instead we get statements like this. "But the devastation is especially striking because of where it happened: In a state defined by its lush vegetation, a far cry from the dry landscape normally associated with fire threats." Just pure willful ignorance. It's sad that this is what passes for science reporting. Thanks for your spot on analysis Cliff, esp the maps.

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  9. I'm surprised that there have been so many fires on the wet East sides of the islands over the years. I have been there, they are mostly rainforest, not grassland, and rainfall totals are in the neighborhood of 100 inches annually. How??

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  10. This explanation of a proximate cause for the Maui wildfire seems right, but the New York Times, for example, did consult with a climatologist in their story today, and that scientist provides a long-term analysis of climate change's partial blame as well. Who are we to believe? Is that climatologist just wrong?

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    1. That climatologists is quite wrong. There is nothing about this event that can be pinned on climate change....easy to disprove.

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    2. Does it matter? Every weather disaster is going to get associated with climate change going forward. Right, wrong or indifferent. This event will get politicized, and the usual suspects on both sides will double down on pushing their agendas. The town's destroyed. People are dead. Those sad facts will all get lost in the bickering.

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    3. Yet you didn't as per usual Cliff. What you did was another rant on the media, using deaths as your pulpit. You're an awful person.

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    4. Funny that you're using deaths as somewhat of a pulpit for a contrary viewpoint, yet the AGW crowd has been using mass human extermination predictions for years at this point. Projection is your friend.

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  11. Cliff,

    Thank you as always for the very relevant information! You've recently spent a lot of time calling out bad science from various news papers/channels/etc. Do you have any news sources that you would recommend which are reliable when it comes to climate science?

    You've mentioned how bad science negatively impacts work against efforts to mitigate global warming, I'd love to know about the people that actually do good journalism when it comes to mitigating climate change. Thank you!

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  12. It's tragic - terribly tragic - and it breaks my heart to see the causes misinterpreted (or 'made use of'). I wonder what actually (literally) sparked the fire(s). The wind alone didn't start them. Lightning? A reckless beach fire? My guess is the actual cause may never be known, but I doubt it was spontaneous combustion. There ARE multiple fires. That's weird.

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  13. Why are so many extreme weather events, heat waves, marine heat waves, fires, and floods happening simultaneously? Zoom out and look at the whole enchilada Cliff!!!!!!

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    1. Dana...you are making a fundamental error: extreme weather is always happening and has always happened at the same time around the world. It is just being publicized and hyped more, particularly with claims that it all do to global warming....cliff

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    2. Dana, if you have to use fantastical statements coupled with multiple exclamation points in order to get your message across, it might appear that you're falling victim to the climate hysteria we're experiencing now.

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  14. Excellent analysis as always Cliff!

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  15. The Wall Street Journal has an article all should read. It is a pay site, sorry.
    Try your rich uncle or the local library.
    Locals knew there was serious fire danger but very little was done.

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  16. Chris Martz posted this a couple days back. The big squeeze: https://twitter.com/ChrisMartzWX/status/1689630672971780096/photo/3

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Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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