Lets see if we can clear up the confusion!

The purpose of this post is to see if we can help clear up some of the confusion that is out there on the internet in regards to what is happening in the world of weather.

To do this the first thing we have to do is look at what pattern we have been in ..

What we derive from those two images is that it has been warm or above normal in the central and Eastern part of the USA and colder along the west. This is indicative of a pattern of a positive NAO..positive AO and a – PNA.

There is no doubt about November being a warm month. However, there is a lot of talk on the internet that because November is warm that this means that this pattern will continue thru the winter ahead of 2011-2012. Is there truth to these statements or are people basically suffering from what we refer to as short term memory when it comes to the weather?

So lets look back some shall we?

Now as you can see this was 2010 and it was also above normal but not as above normal as this year has been..

What about 2009?

Interestingly enough we see that 2009 was perhaps warmer then 2011..

Now lets look at the winters that followed ..

The winter of 2010

The winter of 2011

So as you can see the warm month of November in previous years did not result into a warmer then normal winter over all. In other years back further it has and it has not..The conclusion is that there really is no conclusion on November warmer then normal means warmer then normal for the winter ahead. However..most recently a warmer November has meant a COLDER winter.

So if you were to use the most recent times this has happened I would say that it is pretty apparent that a colder winter is most likely..to occur. 

However..is this warm pattern expected to continue or are things shifting? Well lets take a look at this now as well. We already covered the pattern we have been in..so now lets look at what the models are saying for just ahead..

The above is the 18 Z GFS ensemble means of the 850 mb temperature anomalies as we head into December and as one can tell this is not portraying a warm look. These images would NOT equal a temperature departure map like was shown for November. No..this would show at least the first half of December as below normal across the region.

However…lets look at the ECM ensemble means..

Interestingly enough we can see that the ECM ensemble means are also showing a colder pattern is forthcoming.

These images above would also not equal a warm pattern. So as one can plainly see the guidance is suggesting a “flip” to occur..but when does that “flip” start?

If you been following our Facebook page we have been talking about a step down pattern change..

You can see this occurring already at 48 hrs. out..

This will lead to a more seasonal if not below seasonal day and then moderation for a couple days occur and then we step back down again..

Then we moderate once more, and then we step down again and this time into a more sustained colder period…as the means above from the ECM show.

So the very fact that we are now getting these colder shots in between the moderating times is in itself a pattern change from the consistent above normal pattern that has been in place ALL month prior.

Now..we have covered the most recent pattern and we have covered the step down pattern and have covered the fact that December will not end up looking like the month of November…and we have also covered the fact that a warmer November does NOT indicate a warmer winter overall.. The next thing that we need to cover is the potential that lies in the 6th to 10th of December with the pattern changing..

This was the 18 Z GFS for the time period being discussed now and as you can see the 18 Z GFS has a cold front progressing towards the east and a wave of low pressure developing along the front and brings rain then that rain changing to snow..The air coming behind the front is much colder then the air ahead..

12 Z GFS was similar with this idea but did not really develop a wave on the front…

Now why is this so interesting? Well this is what makes this interesting:

Now what you are looking at is the 12 Z ensemble means members and they can be found at the following link: (click here)

What you essentially notice is that there is 7 out of the 12 members that show the cold front further east and thru the region compared to the operational member in the upper left corner. You also see three of the 12 showing energy or moisture left behind to the south or the southwest …

Now the above is the 18 Z members for 192 hours which can be found by clicking here ..

And interestingly enough you now see there is now seven members that show moisture being left behind compared to the operational in the upper left ..and you also see that the majority of the members have the cold front further east then the operational.

So this gives two potential implications..

1. The colder air is going to be in place faster and before the operational is suggesting and

2. That the development of a wave along this front is becoming more of a possibility…

and perhaps adding another one in here would be perhaps slightly more amplification is being detected now in the guidance.

In other words we have to watch to see if the cold air comes in place BEFORE the wave forms because if it does then we could be talking the potential for a SWFE or a Southwest flow event where warmer air rides over the top of colder air in place at the surface…which would result in a wintery scenario across the region..especially N & W of I-95.

Now the ECM also shows this same general idea with that potential during that same time period and if you look at the ensemble means you will indeed see that the temperatures would be supportive of what is just said above.

You need to be very careful of what you read out there on the internet. People have thrown in the towel for winter based on the month of November.. Pro Mets such as one named Kerry Dean are insisting that there is no pattern change in the making.Instead they say climate should be stepping down..However, what they are not seeing is the pattern that has been in place has been one of much above normal and the pattern that guidance is suggesting and showing is quite the opposite of that pattern that’s been in place.  However as this very lengthy post shows… the thinking a pattern change is not occurring is built on a false foundation.

Perhaps one other area should be addressed and that is the myth that you need a –NAO for the weather to turn cold…

January 1994 is above and that was a severely positive NAO and look at the results..The difference was in the Power of the Negative EPO..The EPO is below:

So when people are trying to determine where the cold air is coming from? Remember the power of the Negative EPO…

Enjoy the weather folks cause it’s the only weather that you got!