Thursday, June 29, 2023

Almost Zero Fire

The contrast in wildfire activity between Alaska and Canada so far this season is very extreme.  Canada has just surpassed their all-time record for annual fire acreage - in June! - but meanwhile Alaska's fire acreage is at a record low for the date.



The reason?  The upper-level circulation pattern just won't budge.  This month's 500mb height anomaly has been very similar to last month's, with a trough axis near western Alaska and unusually high pressure over central Canada.

The lower-atmosphere temperature pattern has mirrored the upper-level circulation anomaly, with (according to NCEP reanalysis data) below-normal temperatures from the Chukchi Sea to western and southern Alaska, but very unusual warmth in central Canada.

Lightning has been much less widespread than normal across the Alaskan interior, and fire fuels haven't really dried out.

It's fascinating to see the near-complete absence of Alaska fire even as El Niño has emerged and is strengthening.  I made some comments on the ENSO-fire relationship in a couple of posts last month, and I'm sure I'll return to the topic again this summer.  But for now I'll just note how remarkable it is that last season was very active despite an entrenched La Niña, and this year is record inactive (so far) despite an increasingly robust El Niño.  As so often happens with seasonal forecasting, just when you think you've found a strong historical relationship - everything changes.

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