Monday, May 8, 2023

April 2023 vs 2013

First, "breaking" news from Nenana, where the Tanana River went out this afternoon at 4:01pm officially.  May 8 has seen breakup in 8 previous years, but only one (2001) in the last 35 years.  It used to be a very typical date, but it's very much on the late side compared to the normal of recent decades.  Check out Rick Thoman's latest post on the topic, published yesterday:

Second, the NOAA summary data are in for April.  Their verdict: it was the 4th coldest April statewide since 1925, and that's the same ranking as Fairbanks attained from 1930-present.

The order of the years is different otherwise, however: this April was marginally colder than 2013 for Alaska overall, according to NOAA/NCEI, whereas April 2013 was easily the coldest on record in Fairbanks.  Here's the ranking of the two months relative to the last 60 years according to ERA5 reanalysis data:

2013 was significantly colder in the eastern interior and Southeast Alaska, except for the southern panhandle; but 2023 was considerably colder for western Alaska, and especially in the northwest.  The western interior was just a bit colder this year, as evidenced by data from Bettles (11.2°F vs 11.6°F).  The maps above also illustrate that the 2013 anomaly was part of a much larger cold pattern over interior North America, whereas this April's cold was quite localized over Alaska.

The 500mb height maps confirm the different spatial scale of the monthly-mean anomalies in the two years.  Last month saw a localized trough that was perfectly placed to deliver cold to western and interior Alaska, but in 2013 Alaska was on the western edge of a much larger-scale upper-level cold anomaly.

Here are my usual climate rank maps relative to the prior 30 year climate, for April 2023:

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