Fire Season Stats

Winter is fast descending on Alaska, and freeze-up is under way for the northern interior.  Snow is lying in northern interior communities from the Kobuk River valley across to the Yukon Flats, and the forecast shows a deepening freeze in the next week that will bring ice formation to lakes and rivers.

Looking back at the 2024 fire season, the AK Fire Service has released statistics for 2024 activity.  Total statewide acreage burned was 667,000 acres, which is just a little higher then the 30-year median of 600,000 acres.  Of course, it's far lower than the hyper-active seasons of the past; here's a figure from the AICC report:

The most significant fire activity was heavily concentrated at the end of June and the very beginning of July - really only about a week.  This is somewhat unusual: it normally takes more than two weeks to accumulate the central 50% of the annual acreage.  The most analogous year in recent decades may be 2000, when statewide acreage jumped from 149,000 on June 29 to 569,000 only 8 days later; and the annual total was 756,000.

The fire preparedness level was elevated (level 3 or higher) for 23 days, and 12 days were spent in the two highest levels:

Alaska is a very big place, of course, and Fairbanks-area residents suffered through more smoke than might be expected with near-normal statewide fire acreage.  There were 9 days with smoke and visibility of 2 miles or less, and that's not much less than the big fire seasons of 2019 and 2015.  Last year was pretty smoky too, despite less than 300,000 acres of Alaska fire; it all depends on lightning and fire locations, and local wind patterns.

September Climate Data

Looking back at September climate anomalies in Alaska, I think the most unusual aspect statewide was the excess cloud cover that was produced by low pressure aloft extending east from Russia.  The abundant cloudiness prevented temperatures from dropping off at night and therefore held frost at bay until the very end of the month in some places.

Here's the estimated percentile of September solar radiation compared to the prior 30 years: below normal nearly everywhere, and among the lowest (cloudiest) in the SE interior, the western North Slope, and the central Aleutians.

Here's the mid-atmosphere pressure anomaly pattern:

Overall temperatures (day and night combined) were not a whole lot different from normal in much of the state, but the North Slope was an exception, with very unusual warmth.  It was the second warmest September on record in Utqiaġvik (formerly Barrow).  In contrast, a lot of unusual coolness persists in the Bering Sea, associated with a very strongly negative PDO phase.

Precipitation was below-normal in parts of northwestern Alaska, a welcome change after an extremely wet summer; but the SE interior was wetter than normal, which also reflects a change from summer.

As for wind, September was much calmer - relative to normal - than summer, and was much less windy than normal in the north and east of Alaska.  This change is closely linked to a major reversal in the Arctic pressure pattern: the Arctic Oscillation was strongly positive in August (Arctic low pressure), but it flipped to significantly negative in September (Arctic high pressure).  This phase reversal appears to be somewhat typical of La Niña.