Dec 312010
 
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The storm track for the last few weeks has been more to the south than I would have expected. Temperatures this morning are far below normal and tonight the temperature for the Pinecone Drop will be significantly below zero. Temperatures across the Southeastern US, much of the Caribbean and most of Europe have been chilly, too. This can be attributed to the the negative phase of the Arctic Oscillation(AO) that has been in place since the middle of November.

Arctic Oscillation - Negative phase on right. Positive Phase on left. Negative phase drives the polar jet stream and storm track farther to the south.

Arctic Oscillation - Negative phase on right. Positive Phase on left. Negative phase drives the polar jet stream and storm track farther to the south.

The key characteristics of the negative phase are high pressure at high latitudes and lower pressure to the south near 45 degrees. This brings warmer than normal conditions to some places like Greenland, and colder temperatures like we have seen in the Eastern US. It is also responsible for the shift of the Western US storm track to the south, into Arizona. The question is: “Will it last?”

As I pointed out in the fall, I thought we would be moving toward a dry and potentially warm winter. December and November both started that way and shifted along the way. Here is the GFS model outlook for the AO.

Arctic Oscillation Outlook - Climate Prediction Center

Arctic Oscillation Outlook - Climate Prediction Center

The Climate Prediction Center has been fairly consistent in their outlook for the Southwest to be warm and dry this winter, even in their 6-14 day outlooks. But, with this outlook for a mostly negative AO, they seem to be changing their tune. Here are their 6-10 and 8-14 day outlooks.

Climate Prediction Center 6-10 day Precipitation Outlook

Climate Prediction Center 6-10 day Precipitation Outlook

Climate Prediction Center 6-10 day Temperature Outlook

Climate Prediction Center 6-10 day Temperature Outlook

Climate Prediction Center 8-14 day Precipitation Outlook

Climate Prediction Center 8-14 day Precipitation Outlook

Climate Prediction Center 8-14 day Temperature Outlook

Climate Prediction Center 8-14 day Temperature Outlook

In this outlook from yesterday afternoon, they are seeing a persistent storm pattern similar to the last couple weeks. What’s odd is that this morning just about every model has significantly altered the outlook to little chance of significant snow for the next couple weeks. This is a big shift. Joe Bastardi, at AccuWeather, seems to believe that this pattern is going to come to an end and we will see a return to conditions like we had in Early December.

Yesterday, I thought we were looking at a persistent storm pattern. Today, I am not so sure. But, I think the next few model runs will tell the tale. With the cooling in the North Atlantic. We could see more of an average overall winter for Flagstaff.

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 Posted by at 8:52 am

  3 Responses to “Arctic Oscillation and the Recent Storm Track”

  1. much as i want to see a trend, i don’t. looking out a ways into the pacific, take a look at the jet: it sure looks like it’s moving back north for the time being. whatever’s supposed to happen tues-wed looks to get cut off from the stream real soon. just based on that fact alone, whatever happens to it, whenever it tracks over the sw us, it’s not likely gonna have a lot of oomph. beyond that, near-long-term, until we get the jet back, i’m going to take sides and put my most of my chips on ‘ain’t seeing a trend,’ at least not for now.

    • I agree that for the next couple weeks it looks like things are shutdown. But, the AO was negative for most of December. We had great weather, while Scotland and England were getting pounded by snow. It looks to me like that might be about to happen again.

  2. […] terribly different from my pondering on December 31, 2010. Looking at the Arctic Oscillation history and outlook, it has been mostly negative since the […]

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