After relatively cool conditions for much of autumn in Alaska as a whole, the last week of October brought a change to unusual warmth. Blame a big ridge extending north from the Gulf of Alaska, allowing warm air to be transported northward into the western part of the state and up to the Arctic. Here are the average 500mb height and 850mb winds for the week ending October 30:
And the resulting 850mb temperature departure from normal:
Warmth in Alaska's far north has been an oft-repeated theme in the past two decades, and this year Utqiaġvik ended up with a top-5 warm October, although it wasn't as extreme as 2016 and 2019. Here's the now (I trust) well-known chart of October temperatures there, showing the profound change in the local climate from loss of October sea ice.
For the state as a whole, October 30th was the warmest day of the month in comparison to normal. The figure below shows the widespread distribution of unusual warmth, with the statewide average climbing into the 95th percentile for the time of year. The standardized anomaly numbers reflect my calculations that account for seasonal skewness, as discussed recently here.
Earlier I suggested clouds as a warming influence. Question: Is advection at 500-850mb the source, of surface warmth, or the clouds that follow and are associated? At 2M temps are influenced by....surface advection, or upper level air advection, or clouds slowing radiational loss of heat?
ReplyDeleteHi Gary, it's a good question, and one I'd like to find a way to explore. And not just clouds but water vapor aloft, which is very active in terms of IR radiation.
DeleteWater vapor aloft....very interesting I'll have to read some about that. Might be a good winter to explore any atypical conditions vs the La Nina years. Lots of wx balloons over the years capturing some info.
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