Monday, December 10, 2012

Winter Will Come

Hi, here it is December 12th and no snow. Today was another abnormally warm day. But the temperatures will cool back closer to normal the rest of the week. I can already hear the comments on this blog saying this winter is just like last year and is hereby canceled. Last year the AO was north all winter, that's about as rare as it gets. Things are starting out warm. But if you read my winter outlook and my Facebook fan page, this warm start to winter 2012-2013 was expected. The first part of December was very warm, 7-10 degrees above normal. But, this will not be the case for much longer and signs are already showing up for more of a cold pattern. We need the low over the Gulf of Alaska (GOA) to be replaced by an Aleutian Low. This will allow a positive PNA pattern with a ridge to the west and trough in the East. With this fix we can get our cold air to come down and visit the Eastern US.

The Teleconnections:

The ENSO is now neutral and should stay there for the remainder of the winter of 2012-2013.

The AO:

The NAO:

The PNA:
There are signs that the low over the GOA is going to breakdown. The current negative Western Pacific Osculation has been going strong for the last few months. it is gone or almost gone. which has been dominant for a couple of months. Because it is gone and forecast to remain gone. This should allow ridging south of Alaska to shift towards the Aleutians, and pump very cold air into Alaska and western Canada. The PNA is super negative at this time. With the negative WPO over, we should see ridging south of Alaska to shift towards the Aleutians, and pump very cold air into Alaska and western Canada.

The EPO is positive right now. The GFS whats to head the EPO back into negative territory. However the EURO is not showing this to any great degree. I think the Euro has a better handle on the EPO, at this time. The Euro is showing a trough for the East and West Coast; this will imply cold air in the east. Based on this I feel the very warm temperatures we've seen in the first part of December are just about history. The air that will be coming in for the 2nd half of the month won't be super cold. But it will be cold enough for snow. It does look like ridging will try to develop northeast of the region. That would favor interior northeast and Northern New England. It looks like the 2nd half of December will be more stormy than the first half; this will be key if we want snow.  

The Euro long range:

The ECMWF (Euro) model long range forecast for the three months of January, February and March is showing that the temps will be near normal for the Northeast. It is also showing that the winter time precipitation will be above normal. Due to licensing issues I can't show the model runs but I can show you this.  
The model is trending toward more in the way of a stormy weather pattern for the Ohio Valley and here in the Northeast for January through March.  One thing that did surprise me was the model is forecasting colder temps for the Great Lakes; if this does verify it would start the lake machine cranking up in a big way, given that the lakes are a few degrees above normal for this time of year.  As always, this is just one of the models and we're looking out three months. But the Euro has a better track record than the other models when it comes to long range forecasting.    
If you what to subscribe to model runs here are a few good sites.  
The models:  
First of all models are not perfect. So a good forecaster only uses them for guidance. If you've been following what I'm saying on blog post and on my Facebook fan page, then you know I said December was not going to be exciting until the second half. The models are showing increased chances for both cold and snowier weather for the Northeast.  
Over the weekend the northern Plains got hammered with a Blizzard. As much as 18 inches of snow fell in parts of Minnesota and Wisconsin. What does this mean for us here in the Northeast, well nothing really. But when the Mid West gets snowstorms in December; the East Coast usually has a good end of December thru February, snowfall wise. why is this? A snowpack in Lower Canada and the Western US allows for the Arctic air to have more staying power. The GFS Ensemble for the 16th of December is showing colder air going into Christmas week.

Christmas week:  After a few snow showers and flurries tomorrow morning. We should see 4 or 5 days of cooler but dry weather. The next storm system will likely move through Saturday night and Sunday with a chance of some rain.
The models overnight have moved towards a solution and are showing two potential significant events. The first one is the low pressure area for December 15th, which looks like it's going to track up through the Northern Plains.  The Second and potentially bigger event would be the first major winter storm the season on or around December 18. With the low pressure area tracking up from Arkansas through Tennessee Eastern Kentucky Eastern Ohio West Virginia and up into the Northeast. The Euro has had it for several runs. The 18 Z GFS is showing activity that could bring snow into the Northeast. I think the Euro is overdoing it a bit, but it's still a possibility.  I feel the Euro will shift toward the GFS. The GFS might come a little more to the west for the 18ht. I do think there is a good chance for a mid-Atlantic/Northeast winter storm early next week.  
The GFS showing the 17th.

gfs_namer_156_1000_500_thickfor the 17th

Winter time precipitation looks to be above average for January, February and March . But remember, This is going to be ENSO neutral, neutral years tend to be see saws as far as temperatures go, with swings between warm outbreaks and cold outbreaks. And since cold air is needed for snow, snow storms would depend on cold air. I can't guarantee which storms will be snowstorms. But if the Euro is right and the next three months in the northeast will be colder and wetter on average. Then I feel it's safe to say snow should end up above average for the winter of 2012-2013. So don't abandon the ship just yet....winter will come.    


Thursday, December 6, 2012

Looking At The Pattern for Mid December.

Many are wondering where is the winter weather, and will this winter be a repeat of 2011-2012. As for where is winter, The real cold air has been locked up across the interior of Alaska and northwest Canada since the middle of November. Parts of Alaska have had  -50 degree temps for over a week, with yesterday being the coldest day yet, –56. As for will this be a repeat of last year? The Short answer is NO. If you’ve read my 2012-2013 winter outlook; you know, I said the first third to half of this winter season would be warmer than average, with the second part of winter coming in colder than average. I still feel this will be the case. Here is a link to the winter outlook. The pattern over the next week or so,will be very unfavorable for sustained periods of cold and snow along the East Coast. But This will change.

As I said, the cold air is bottled up in Alaska and Canada. Why is this happening? The negative PNA and Positive NAO has high pressure high pressure to our south forcing warm air to move in from the southwest. What is the reason for this. The giant vortex up in Alaska is the reason it's been so warm here in the Northeast. This vortex will start to break down soon. I will once again go to the teleconnections, to show you how all of this should workout.  

The Teleconnections:  

I will be going into four indices, three of them I've talked about quite a few times in the past. However, there is one that I have not...I will talk about that after go into the NAO,AO, and the PNA.

   The NAO:

As you can see on the chart the NAO is currently sitting around neutral. If you follow my post on this blog and fan page, then you know, that when the NAO is positive our weather in the Northeast is generally warmer and drier. This is because of the lack of any real block slowing the storms. Looking ahead especially around the 10th-16th and on, the forecast shows the NAO going strongly negative. When this happens we will see a trough develop and the colder air to our north coming down to visit.

The AO:

In order to get real cold air out of Canada, the NAO needs a helping hand. This is where the AO comes in. When the AO is negative it allows the cold air in Canada to drop south into the United States. Now some of you may be wondering the AO is negative. If you look at the AO forecast chart you will see the AO has been negative since the 20th of November; So why is the cold air still locked up in Canada. To answer that we will have to look at two other indexes. The first I've mentioned before, that one is the PNA. However there is one other that I haven't talked about before, that one is the EPO, both of these are playing a role as well.

The PNA:

The PNA does the same thing for the West Coast, that the NAO does for the East Coast. By this I mean, when it's positive the West Coast is warmer and drier; when it negative the exact opposite is true. If you look at the PNA forecast chart, you will see that it has been weakly negative. So the west has been cold....but the cold can't push farther east. just as the NAO being positive has prevented the negative AO from supplying us with colder air. Looking at the PNA forecast chart again, you can see the PNA looks to stay negative going into mid month. The forecast had been calling for it to be neutral to positive, this is a fly in the ointment. So it will have to be watched to see if it trends back more to the positive side. But, the PNA has a variable effect on the East Coast, I will have more on that in a bit. Looking at the NAO and AO forecast charts you can see they will be in a negative phase. Even with a negative PNA I still think we will see colder air infiltrate the Northeast after mid month. How do I know this? For that we have to look at another teleconnection, the EPO.

The EPO:

12zecmwfensepoeuroEPO Now while the PNA has an impact on northeastern pressure patterns, as I said it is variable. But, the EPO whether directly or indirectly has even more influence over the East Coast and the GOM.

The EPO (Eastern Pacific Oscillation). The EPO is, at its simplest, the alternating pattern of high and low atmospheric pressure, located four to seven miles above the Pacific Ocean. The EPO helps determine the pattern of the jet stream moving from the Pacific across North America. This means it's what controls troughs and ridges around Alaska; when it's negative, a trough will be in place near Alaska. So a positive EPO will produce a ridge in the same place. If you look at the EPO forecast chart, you will see that by mid month the EPO looks to be positive.

OK, why the warm weather?

I'm sure all of this negative / positive teleconnection talk is giving some of you a headache. So I will try to explain it another way. Most of us know that generally in the northern hemisphere weather systems moves from west to east. So in order see what the weather will be like down the road here on the East Coast, one has to look to the west. Since the EPO is influencing the weather in the Pacific Northwest, we must look there first.   

OK since the EPO is negative, we see a trough over Alaska and a ridge off the West Coast. This trough in the west lends support for a ridge in the east. Now since the AO will send the cold where the trough is, which in this case is out west. Add in the positive NAO and ta-dah, we have warm weather in the Northeast.

So it makes sense that when the EPO goes positive along with the negative NAO and AO that's being forecast around mid month, that this all points to colder air moving into the eastern part of the United States. The negative NAO should create a Greenland block which will in-turn force coastal storms to form and move into the northern Mid Atlantic and Northeast. How much staying power the block has will depend on the vortex over the Atlantic. ... But all and all, the way the indices are trending is a very good thing if you're a snow lover.

The GFS showing the 17th of December  .


  A look at the GFS 12Z model run showing the 20th.


And here is the GFS showing the 21st.

If you look at the model runs above, you can see the results of what I was talking about. The EPO is no longer negative. and with the high pressure that's been hanging off the East Coast moving out of the way, cold air is moving into the Northeast. The pattern still looks to become more active than we've seen the last 10 days. The NAO does look to become east based. So if we get any storms this will help steer them our way. As I said in my winter outlook, this winter will be a roller coaster as far as cold and warm air outbreaks. As you can see, the GFS does show a lot of cold air in place just before Christmas. The models also show we have a good chance for a storm around that same timeframe. With the Greenland blocking to the north, the storms after mid month will finally have the cold air to play with.    But the bottom line is, we should have plenty of chances for minor to moderate snow events after the 10th of December.

When I looked at past snowy Decembers, many of them had the same general pattern. We are looking fairly far out for any kind of real forecast. But, I feel our chances are good in seeing more in the way of snow in 10 to 14 days.   

Well that’s it for now, I will have more on all this as we go on…just check back here or follow the sidebar gadget to my Facebook fan page.     


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.