In the wake of the recent Bering Sea storm, a deep and very strong southerly flow has transported extremely warm air into northern Alaska, leading to exceptional warmth across the North Slope. Remarkably, temperatures rose above freezing everywhere on the North Slope yesterday (or at least everywhere with a thermometer reporting in real-time), and today isn't much cooler. The map below shows the maximum temperatures observed in the 24-hour period ending 5pm AKST yesterday.
Here is yesterday afternoon's 500mb analysis, showing the torrent of warm air flowing northward over the Bering Sea and far western Alaska.
Looking at the climate observing sites with long term histories, Utqiaġvik (Barrow) and Deadhorse both had a high temperature of 36°F yesterday, and Kotzebue hit 38°F for the midnight-to-midnight period. This is the first time in the common period of record (December 1968-present) that all three stations have exceeded 35°F on the same day in winter; this has never before been observed between October 25 and April 13. The chart below attempts to illustrate this in graphical form.
The northeast slope was getting into the 40's. Was this due to Chinooks over the Brooks? If it wasn't Chinooks, what were the dynamics?
ReplyDeleteAnd likewise, why didn't Fairbanks get that high of a temperature?
Yes, I think it's likely there was some downslope contribution in the northeast. However, the basic mechanism across the region was very warm air aloft combined with strong winds (strong pressure gradient) that aided mixing and eliminated the usual inversion.
DeleteFairbanks was much closer to the ridge axis, so winds dropped off, allowing surface temperatures to drop even while warming occurred aloft. Between Friday afternoon and Sunday afternoon the 850mb temperature above Fairbanks rose 23°F while the surface temperature dropped 25°F.