For a first post, I thought I would highlight the extraordinary jump from unusually cold spring conditions to unusually warm summer conditions in Fairbanks this year. I imagine the pace of change might have been dizzying even for locals used to extreme weather variations. In a "typical" year (which rarely exists, of course), the average temperature would increase by about 21° F from the "spring" average (which I'm calling April and May) to early-mid summer (June 1 - July 15). This year the temperature increase was over 34° F, and by far the highest in the Weather Bureau/NWS era (1930-present). The chart below shows the annual values, and 2013 really stands out; the previous record increase was 28.5° F in 1986.
The 2013 change is especially unusual in light of 2010-2012, which saw a much more gentle transition from spring to summer. The seasonal temperature increase in 2010 was the smallest in the record, only 14.2° F.
The remarkable change this year was created by the sequence of the coldest April-May period on record in Fairbanks (except for 1911), followed by one of the warmest early summer periods on record. Among the unusual events was the latest first day with mean daily temperature above freezing (April 24), and then less than two months later there were 6 consecutive days with a high temperature of 86°F or above (June 15-20) which has only happened once before in 1918.
So in summary, the swing from one temperature extreme to the other since spring in Fairbanks has no precedent in the modern era. From a meteorological standpoint, the reversal in extremes seems to be related to persistent high-latitude blocking around the northern hemisphere, which has created many persistent and extreme anomalies in different locations. Another factor seems to be the evolution of sea surface temperatures in the North Pacific in recent months, which seem to have favored cold in the spring and warmth in the summer. But that's a subject for another post...
The effects of this year's weather have been felt:ReplyDelete
1. Late spring/warm breakup leading to flooding along rivers.
2. Drying of soils/vegetation followed by forest fires and potentialy poor conditions for tree growth. My white spruce are dropping needles far more than in the last 33 yrs at my location.
3. Insect infestations. Mosquitoes have been very abundant this year. It remains to be seen how many biting flies emerge in August.
4. Not sure about the rate of permafrost melt and frost depth, especially on Alaska's North Slope. Lots of chatter on the potential release of methane and other entrained gasses.
5. Fewer thunderstorms in the Fairbanks area it seems, maybe statewide (???).The Alaska Fire Service strike records should hold that key.
6. Like last Fall, possibly a delayed freeze-up due to warmer temps linked to increases in ocean temps around Alaska. Remains to be seen.
7. Does another cold winter lie ahead? CPC offers an EC so far through the coming 2013-14 outlook.
June was the warmest on record in Barrow, and it appears July is running well above normal too. I expect you're right that warm sea surface temperatures will lead to another late ocean freeze-up and warm conditions throughout the north in early fall.
It will be interesting to soon start looking at signals for winter. The Pacific Decadal Oscillation has been closer to neutral recently, rather than negative as in the past two years.
I see that the ENSO is forecast neutral, with the long outlook maybe favoring El Nino (http://iri.columbia.edu/climate/ENSO/currentinfo/QuickLook.html)Delete
This isn't my field, but I do pay attention when cold and wet prevail.
Rich has discussed the effects of ENSO forcing, and my take is the PDO has a more immediate effect. For fun, we'll keep an eye on the PDO trend (http://jisao.washington.edu/pdo/PDO.latest)
In spring there was an upper level trough parked over mainland Alaska and that transitioned into a stagnant upper level high. I am wondering what the best way to characterize that transition is from an upper level perspective.ReplyDelete