Vortex Records

I need to make just one more comment on the Arctic vortex that dropped down to the Bering Strait region nearly a month ago now: after putting together some new charts of upper-air data from Alaska's sounding sites, it is even more clear just how unusual the event was.

Consider the following chart, showing Nome's recent 850mb temperature observations in comparison to the historical range of observations.  The weather system we're talking about arrived early on July 18 with a dramatic 12.5°C temperature drop in 12 hours at 850mb.  Remarkably, the -6.7°C measurement early on July 18 was the lowest 850mb temperature that's been observed at Nome between June 25 (1949) and August 12 (1973); the previous coldest on record for July was -6.1°C on July 27, 2000.

Even more remarkable is that the 500mb height early on the 19th was the lowest on record between June 6 and August 22.  We can say pretty unequivocally that this was the strongest mid-summer trough in the modern climate history of Nome (1946-present).

The subsequent strong vortex event of two weeks later also shows up on the chart above, with 500mb heights very close to record low levels for the time of year.

The sounding observations from Bethel (below) show the cold blast on August 8, with the -4.3°C measurement sitting right at the record lows for mid-late summer.

I'm working on setting up an interface to view these graphics in realtime for all of Alaska's sounding sites.  It should be handy for quick context on major climate anomalies.