In @wwattribution.bsky.social report on the LA wildfires this January we show the frequency and intensity of the atmospheric circulation of the event has increased in winter, raising the risk of weather conditions that drive the spread of wildfire. www.worldweatherattribution.org/climate-chan... - ThreadSky

vikkithompson.bsky.social • 25 days ago

In @wwattribution.bsky.social report on the LA wildfires this January we show the frequency and intensity of the atmospheric circulation of the event has increased in winter, raising the risk of weather conditions that drive the spread of wildfire.
https://www.worldweatherattribution.org/climate-change-increased-the-likelihood-of-wildfire-disaster-in-highly-exposed-los-angeles-area/

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charleyinma.bsky.social•25 days ago

👀

mattpattclimate.bsky.social•25 days ago

Hi Vikki, this is super interesting, thanks for sharing! I'm curious how this might be influenced by trends in the large-scale circulation. I have a paper (currently under review) showing the North Pacific jet has shifted northward since around 1980.

mattpattclimate.bsky.social•25 days ago

This likely means more wave-breaking and cut-off lows on the southward flank of the jet as well as a general drying trend in California. We also show that multidecadal jet variability is quite large in this region (e.g. linked to IPO) so we can't easily attribute this to anthropogenic activity.

vikkithompson.bsky.social•25 days ago

Ooh, that looks very useful! We haven't looked for a 'why' yet but this looks like it'll be at least part of the answer. Have you checked it out in models too?

mattpattclimate.bsky.social•25 days ago

We looked quite extensively at models and they struggled to capture the magnitude of the observed jet trend (not sure why though!). I'll email you the current version of the paper.

vikkithompson.bsky.social•25 days ago

The most similar events show a more intense cut-off low, which strengthens the Santa Ana winds. Whether this trend is attributable to climate change needs further research, but other evidence in the report shows climate change has increased extreme fire weather conditions.

anlomedad.bsky.social•25 days ago

Thank your for your AGW attribution on LA fires and this thread!
Was this cut-off low which strengthened Santa Ana this year, connected to/amplified by the Arctic cold tongue East of the Rockies? Maybe it wasn't there yet on Jan 8, but if so, did this tongue maybe give the winds an additional push?

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