All of us collectively have endured some very tough times so far this winter season. We have seen some major warmth, really across the entire United States, and a general lack of snow everywhere except for Southwestern Canada. And the whole board is wondering, where is winter? Where is my snow? Well, I think I have an answer, and it may be coming quicker than you think.Before I go any further into specific dates or storms, I wanted to take a look at my winter forecast from October. In my winter forecast I stated a few storm dates : EC Storm Dates: 12-4, 12-27, 1-13, 1-25. The first two have verified to the actual day, and I am becoming confident that the 13th will not verify as a snowstorm, but more so as a pattern changing storm, with the 25th being a completely different story which will be discussed later in the thread. But what will cause the 13th to be such an important date? Lets talk a little bit about this storm, and how it will change the pattern.A few weeks ago I made a post regarding the fact that the East Coast snow fans needed to be patient, and wait until right about now to see the real signs of a pattern change. Well, here they are. Taking a look at the latest ensemble forecasts, we can see that there is strong agreement for a pattern change amount guidance. Firstly, lets take a look at the EPO. Over the past few weeks, ensembles have been extremely consistent in showing the EPO taking a major drop, and lately have been consistent in a period of strongly negative readings, and then a rise towards positive. What does this mean? We all know that the EPO has a major effect on our weather. But after experience with it last year, and now this year, I can tell you that I am extremely confident in a correlation between a changing EPO and a large storm system. In other words, when the EPO goes from strongly Positive to Negative, or visa versa, there is often some sort of large storm system associated with it, much like the NAO. What we see on the map below, is the EPO dropping to negative around Jan 10-12, with an associated storm system Jan 13th to signal the pattern change. Then, we see the EPO staying in strongly negative departures, with guidance showing a cold, but suppressed pattern across the East during this time period. Then, following this, the EPO begins to rise, and wouldn't you know it, around Jan 22-25 Guidance hints at another major storm system.

Secondly, I wanted to mention this, at least a little bit in this post. The MJO has recently become much stronger, and though it has weakened a bit over the past few days, still looks much healthier when compared with the MJO we have seen so far this winter. We have seen so far this winter that the MJO really does control much of the Pacific pattern, and it will be interesting to watch how this progresses over the next few days. Hopefully, this little nap its taking right now doesn't last too long.

Beyond this, we can take a look at the PNA Ensemble Forecasts. Personally, I don't use the PNA to forecast individual storms but more so for overall patterns, unlike the EPO/NAO. We can see the PNA in a very strong negative state, but then shooting up to positive right around the time period of the storm Larry mentioned in his pinned thread.

Now that we know that we have a few indexes that support our storm system, we can begin to look at some of the more detailed features of the system itself, and what exactly each of these detailed features are contributing to changing the Eastern US Pattern to more of a wintry one. I will use todays 12z GFS as guidance for this. The GFS has really been all over the place with every single aspect of this pattern change. It is important not to watch every single individual run of it for what its worth at this time, but it is much more important to watch the trends, and attempt to figure out exactly what the guidance is trying to say. Watching the 00z GFS last night, it became pretty apparent to me that the key feature in this pattern change is the shortwave, and what it does as it heads into the Southwest United States. The 00z GFS last night, showed the shortwave in the Southwest hanging back, and becoming basically its own entity at 500mb. This allowed for a slower, but stronger progression of the arctic front at the surface. The 12z GFS is much different, and keeps the shortwave embedded in Northern Stream energy. Then it does something completely weird and develops a Baja type low situation. Thirdly, a few days ago the GFS had a completely different solution, never really hanging back the energy over the southwest at all, and just moving things right along Eastward. As we can see, this piece of energy will have a significant effect on exactly what this arctic front does. I think we need to watch the 500mb trends carefully over the next few days to see exactly what the Guidance tries to do with it. All in all, we know one thing- A Low Pressure and associated cold front will head from the Southwest up towards the Ohio Valley, likely bringing down a trough and massive cold air behind it.

Now, dare we venture beyond this? I say yes folks..because it is very intriguing to me. As discussed earlier, one of my winter forecast storm dates was 1-25. I usually don't like to get gung ho, or even make a post on a storm this far out, but I think it needs to be discussed. The graphics above already show you that the signals are there for another "pattern changing" type storm, and this was the aim in my winter forecast as well. But, remember that piece of Southwestern Energy that I discussed earlier? Well, it is an important player in this storm developing as well, as we heard DT rant and rave about today. He is right. In fact, it is imperative that this shortwave hang back if we want to even think about having this storm threat materialize as I hoped it would. The 00z GFS did just this, and a major storm developed. The 12z GFS..thought it doesn't seem to have the storm, has it..but it is just delayed. Remember the Baja Type Low? Well, this Baja Type Low would be a blessing in disguise, because once it interacts with the Polar Jet, we would be in business. The 12z GFS is basically just hanging back the energy. Anyway, I really am going to try and avoid getting into too many details about this storm, but I feel strongly that attention needs to be given to this situation, even this far out.In conclusion, I think January 15th-Feb 1st or so will be a very cold, and possibly very snowy part of the winter for the East Coast. Things are looking up at this point, and we need to continue to keep a close eye on the guidance and what exactly it tries to do with the important, key players on the field over the next few days. Get ready, it will be fun.Well, theres my first crack at a real discussion. Let the flaming begin! I was going to post a picture of a worm but I figured that would ruin it.

John

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