Monday, December 3, 2012

Where is the winter?

Ok here is quick post on the change I've been talking about mid month. The timeframe from the 9th to around the 20th of December will see cold arctic air moving south. We will also see more in the way of storminess.

Where is the cold air?

Right now it’s bottled up in Alaska.

  The reason we haven't had any real arctic air in the Northeast is the current orientation of the polar vortex. For those who don't know, in the northern hemisphere, the polar vortex is a large cold core low pressure area located near the North Pole. The polar vortex is analyzed at the 500 millibar level of the atmosphere. The polar vortex can often be located over Canada since the coldest surface air is often found over high latitude icy/land locations. It normally gets stronger during the winter and weaker during the summer.


On this polar chart you can see the PV has been displaced a bit over Siberia. The trough over Eastern Asia and the Bering Sea should help this process along. If they split the PV, we would have a good chance of seeing an arctic outbreak from mid month thru the end of the month. This would collate with the teleconnections I've been talking about.

The NAO, PNA, and the AO.

Over the last week, I've been talking about the PNA and the NAO.  



PNA will be in a positive phase from mid month on.



NAO will be in a negative at the same time.

 The AO


As I said on my weather page the other day; you want a positive PNA and a negative NAO for cold air to infiltrate the Northeast.

The AO will also be in a negative phase. this will give the cold air a chance to dig into the Mid Atlantic and maybe as far south as the Carolinas by mid to late month. With the NAO and AO both negative we should have a Greenland block setup.....this would be good news for snow lovers if the storm track workout.


anomnight_current sst As you can see convection has returned to the mid Pacific tropical zone (around the dateline). Last year, there wasn't a lot of convection in this area. Things will start to change in the Gulf of Alaska . The convection across the dateline extending to the NW will have a part to play on the setup around the Gulf of Alaska.

This ridging is what is going to help displace the vortex near the Gulf of Alaska . This will allow the cold air to move south. These changes will induce stormy weather into the Midwest and East Coast. During this timeframe we should see the lake effect machine also wake up in earnest .  

The convection across the dateline extending to the NW This is what is going to help displace the vortex near the Gulf of Alaska , along with increasing the number of storms move out of the Pacific Northwest. All of this is expected between the Dec 12-17th. which is supporting the change around mid month I've been talking about.  

The 9th and 10th of December.

The Euro showing the 10th of Dec.


 The GFS for the 10th of Dec.


  As you can see the pattern will start to get active around the 9th or 10th.  Right now, We could end up dealing with a severe weather threat in parts of the Tennessee and Ohio river valleys on Dec 9th. This severe threat would move to the east on the 10th. On the GFS you can see the arctic air moving into the Plains….This would end up being a nice snowstorm for the Quad Cities into the northern great lakes. As the cold works it’s way east, so would the snow…

That’s about it, I will have more about this as the time approaches.


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