June Climate Data

Last year at this time I commented on the unusual high-latitude circulation pattern in June 2025, when a broad but very strong circumpolar circulation extended up into the stratosphere.  Low pressure in the Bering Sea, related to the strong jet stream aloft, produced a wet and windy June for Aleutian and Bering Sea communities last year.

Interestingly, there were some similarities in the flow pattern last month - June 2026 - with a strong polar vortex extending to the stratosphere.  However, this year the vortex was much more compact and intense, residing over the central Arctic Ocean between Alaska and the Pole.  The following figure shows the rank of the June average 500mb height; the mid-atmosphere pressure was the lowest on record for June in the high Arctic, but strong ridges of record high pressure occurred to the south over central Russia, the western Bering Sea, and eastern Arctic Canada.

The coherent vertical structure of the vortex is evident when we look at 100mb height (pressure), above 50,000 feet.

And down at sea level: record low sea-level pressure under the center of the vortex.

A strong polar vortex is a "cold core" feature, so temperatures were unusually low - in fact, record low for the month of June over the sea ice to the north of the Chukchi Sea (based on ERA5 data since 1950):

What relevance did this have for Alaska in June?  With the vortex being very much more compact than last year, the outcome was very different.  In fact, the weather pattern specific to Alaska was in some ways opposite to last June; low pressure was confined to the north, and the Bering Sea saw above-normal MSLP instead of last year's stormy pattern.  As a consequence, it was much drier and sunnier than normal over western Alaska and the Bering region:

Temperatures were also partly inverted from last June, with a relatively cool month in the north and warm in the southwest, approximately opposite of last year:

One major similarity, however, was the extensive lightning; June 2026 ranks as 3rd highest for lightning strikes in the month, and last year saw the most strikes on record for June (data since 2012 - and excluding ALDN-recorded strikes in northwestern Canada).

Comparing Pacific Ocean SSTs between the two years, we see that the zone of unusual warmth extending east from Japan is modestly reduced in size and intensity from last year.  There's also more cool water this year in the Gulf of Alaska; but the overall North Pacific configuration is quite similar and remains indicative of a negative PDO phase.

The big difference, of course, is farther south, and it is an enormous difference: strong El Niño conditions are already established in the equatorial Pacific, and we're well on the way to one of the strongest El Niños on record - and possibly the strongest in more than a century.  More on that important story in another post.