Pattern Update & Potential Snowstorm As Of 1/19/13

As is always the case we are going to take a look at where we have been and we stand presently.. 

There is really no way to deny the fact that the first 17 days of January have been above normal and this occurred when many were claiming the month of January was going to become colder then normal. 

If you recall we said that in order for the pattern to change it depended on two things:

A. The progression of the MJO and whether or not it would go back into phase 6 or if it would continue to propagate into 7 and perhaps phase 8. 
B. The PNA and whether or not it would go positive being that it has been in a negative state.

Looking at the Current MJO we can see that this is in phase 7..

And the results of Phase 7  in the month of January? 

As far as going forwards...there is only one model that wants to take the MJO back into phase 6 and that would be the Canadian.. which still takes it back into phase 7 there after.

All the rest of the guidance suggests Phase 7 or Phase 8 as the destination ..

Including the ECM ensembles ... but the ensembles then progress the MJO into the COD. 

For those that are wondering this is what phase 8 looks like for the month of January..

So phase 7 and phase 8 both indicated colder weather across the east coast and this is exactly what the guidance is showing to occur with the up coming pattern which is about 72-96 hrs out. 

Lets look at the European Computer guidance to see what this looks like at the 850 mb temperature level..

 The model brings a shot of extremely cold air into the east and Northeast and the midwest. This lines up perfectly well with what the MJO is doing. And as we mentioned the second thing was the PNA had to take a turn to the positive. What that does is brings ridging into the west and troughing into the east. 

And as you can see the PNA presently is neutral negative but it is shown to be sharply rising. However..the one thing to take note is that after this sharp rise we see that it goes back negative once again..
So how long is this colder pattern going to last? This is going to be dependent on two things once again...
1 The Arctic Oscillation. 

As you can see the Arctic Oscillation is slightly negative but expected to take a dive but then majority of the members are showing the AO to rise to the positive side. The second thing to watch is for the PNA to see if it indeed does take a negative turn after the positive spike. If the AO goes positive and the PNA goes back to negative then we could be switching back into a more warmer pattern. 
This could indeed be the reason why the ECM is showing a warming pattern at Day 10 

And the GFS is showing this in the days 11-15 

Both at the same time frame indicating a return to above normal weather across the Northeast (GFS) and a large chunk of the US on the 00z ECM. 

In the meantime , after a one to two day warm up we are going to get colder once again as shown by the ECM above and while in this cold pattern.. we could be looking at the potential for an East Coast snowstorm. Both the 00z GFS and the 00z ECM suggest this could happen next weekend..

And the European shows the following: 

Both models are plenty cold enough to support a snowstorm across the east coast and into the major cities as well. So we have a pattern change on the horizon and a potential snowstorm to keep an eye on across the east. How long does the pattern last with colder weather? This is something we will be keeping an eye on and be updating about in the days ahead. 

Meanwhile if you have become use to the warmer weather ...the air coming in at 72 hrs is going to remind you that we are in the month of January and still have about 6 more weeks of winter to go.