Tuesday, August 15, 2023

July Climate Data

August is rapidly advancing, but for the sake of posterity, here's a look back at July.  The high-latitude circulation pattern was dramatically different from earlier in the summer, and Alaska was primarily influenced by a strong ridge to the east and northeast rather than a persistent trough over the Bering Sea.

The big ridge over Arctic Canada produced some extraordinary warmth, including by far the warmest calendar month on record at Inuvik.  Utqiaġvik also had its warmest month on record, narrowly beating July 2019, and on the other side of the pole it was the warmest month ever measured at Barentsburg on Svalbard.  The maps below show monthly mean departures from normal in absolute terms (top) and in standard deviations (bottom).

The monthly ERA5 and NOAA/NCEI data sets both show the very unusual (locally record) warmth across eastern Alaska and the North Slope.  The ERA5 reanalysis indicates that it was significantly cooler than normal for the southwestern mainland and northwest Gulf coast, but this isn't supported by the NCEI data.  Checking in on data from Bethel and Anchorage, the month was in fact cool enough to fall into the lower third of the 30-year climate distribution at both locations, so ERA5 seems preferable.

The state as a whole eked out another month of above-normal precipitation overall, but not by much, and there were big contrasts between wet in the southwest/west/northwest versus dry in the central interior and Southeast Alaska.  The dry conditions in the interior set the stage for the late-season uptick in fire activity; Rick Thoman notes that Delta Junction had its driest June-July period on record, and evidently this trend is still persisting.

As for wind in July, the high-latitude blocking produced a much more stagnant pattern than in June, with relatively light winds across the North Slope and northern interior, but it was windier than normal in the southwest.  And sunshine was yet again lacking for the southwestern mainland and south-central Alaska: it's been a miserable time for sun-seekers down there this summer.

And in a comment for later elaboration: El Niño continues to develop in the tropical Pacific.  The SST pattern looks very El Niño-like already, but the atmospheric component of the phenomenon is having a difficult time getting its act together.  It will be interesting to see if this dichotomy continues.

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