Good Monday, everyone. Temperatures out there to start the week continue to run on the toasty side for the middle of October. We could even challenge record highs in some spots. That’s how the week starts. It will end on a vastly different note.
Temperatures Monday and Tuesday will reach 80 to 85 degrees on a gusty southwesterly wind. This is about as warm as you can possibly get for this time of year.
Scattered showers and storms increase late Wednesday as a cold front nears from the northwest. This front arrives Thursday with widespread showers and storms, gusty winds and a big temperature crash:
Rainfall amounts might top 1 inch in parts of the region. Highs by Friday and Saturday look to stay in the 50s. If skies clear out Friday night, we could be talking about some frost forming.
Additional cold fronts might drop in from the northwest later next week.
The Arctic Oscillation has turned severely negative recently and is forecast to remain there for a while:
You can see how it spent much of the summer and early fall deep into positive territory. That is no longer the case, and that severely negative AO might keep going for a while. Hence, one of the reasons I’ve been looking at the potential earlier-than-normal start to winter.
While I’m on the subject, let me share some work from Dr. Judah Cohen. He has become very popular over the years for his forecasting of the Arctic oscillation and the polar vortex. He has some interesting theories about the buildup of October snow cover in Eurasia and how it might affect the winter ahead. Here are some of his latest thoughts:
- The Arctic oscillation is currently strongly negative and is predicted to remain negative over the next two weeks. The AO is predicted to trend positive toward neutral through the end of next week and then reverse and trend further negative.
- The current negative AO is reflective of positive pressure/geopotential height anomalies in the Arctic, especially north of Alaska and on the European side of the Arctic, and negative pressure/geopotential height anomalies across the mid-latitudes of the Northern Hemisphere, especially in the North Pacific sector. The North Atlantic Oscillation is currently also negative but because the positive height anomalies in the North Atlantic side of the Arctic are closer to Scandinavia than Iceland/Greenland, the NAO is predicted to fluctuate around zero over the next two weeks.
- With pressure/geopotential height anomalies predicted to remain positive across much of the Arctic and pressure/geopotential height anomalies predicted to remain negative across the NH mid-latitudes, the AO is likely to remain in negative territory into the foreseeable future.
- With the AO firmly negative for the remainder of the next two weeks, this favors below normal temperatures across large portions of northern Eurasia including Europe and Siberia. However because North America will be dominated by mostly positive pressure/geopotential height anomalies, temperatures will average above normal much of next week in eastern North America. The following week with heights predicted to build once more near Greenland lower heights and temperatures are predicted for eastern North America for week two.
- Eurasian snow cover is above normal but has currently stalled. However both low sea ice and a persistent negative AO are favorable for the resumption of a more accelerated advance of Siberian snow cover. High Eurasian snow cover and low Arctic sea ice in the Barents-Kara seas favor first, a strengthening Siberian high and then a weakened polar vortex in winter.
- The polar vortex both in the stratosphere and the troposphere look to remain relatively weak for the remainder of October, if this trend continues, severe winter weather is likely for widespread portions of northern Eurasia, including Europe and East Asia, and the eastern United States.
Check out the highlighted part above. Very interesting!
Have a great day and take care.