September already seems like a long time ago, but it's worth looking back at how the month stamped an exclamation point on the outstandingly unusual events of summer. Last month I discussed the extraordinary mid-summer reversal in moisture, such that southern and western Alaska went from record or near-record dryness in early summer to record or near-record high rainfall in July and August.
September continued the trend in abundance, with much above-normal precipitation for large areas. In particular, the eastern interior turned very wet, after not being as wet as the west and south in mid-late summer. The two maps below show the September precipitation ranks relative to the prior 30-year history.
Using a longer baseline consisting of the entire NCEI history (1925-present), the following pair of maps highlights the amazing contrast. For the Cook Inlet division, and for the state as a whole, the driest April-June on record was followed by the wettest July-September on record.
Here's an updated version of a figure I showed last month, showing the unprecedented magnitude of the turn-around. In the prior 97 years, July-September precipitation was never more than 3 times that of April-June, but this year it was almost 5 times higher. This year's anomaly is a 7.7 standard deviation departure from the mean of the previous history.
As for September's other aspects, it was a warm month, although not in the top 10 for the state as a whole. According to ERA5, the most significant warm anomalies were found in the Brooks Range and southeast Alaska.
Unusual warmth also extended east across Arctic Canada, where it was very pronounced and significant in the vicinity of Baffin Bay; this was related to a strong "blocking" pattern near Greenland, with high pressure and a negative Arctic Oscillation.
Back in Alaska, ERA5 data indicates that wind anomalies were variable and not especially pronounced for the monthly mean, but of course we can't forget the extreme west coast storm, ex-typhoon Merbok. September sunshine was uncharacteristically lacking for nearly the whole state - a very dreary end to summer indeed. Soil moisture was, of course, far above normal, and I can't help but wonder if that will worsen ice overflow problems this winter.
Speaking of ice, here's a photo from Bettles that should help eliminate dreariness.
Ice has rapidly formed on rivers across northern Alaska this past week. Here is a beautiful view of the Koyukuk River at Bettles taken by our river observers yesterday. Please feel free to share in the comments any photos of river/lake freeze-up you may have... Thanks! #akwx pic.twitter.com/fSVPY3rL1w
— NWS Fairbanks (@NWSFairbanks) October 16, 2022
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