8:30 Sunday Free Nor’ Easter Summary

While the Premium update has been posted a few hours ago on this storm (you can purchase it here), and it includes additional long-range analysis, model analysis, natural gas market implications, and the like, I want to share some analysis freely as well here to open it up to discussion and get the word out about this potential Nor’ Easter.  In general, the storm threat on the 17th looks like nothing at all, but it is December 20/21 that continues to look very interesting, and that is what this post is going to focus on.  So below I have attached some of the premium post that breaks down the weather models that we generally use:

The CMC weather model still shows this.  A weak storm out to sea with no precipitation for the region.  The predominant reason for this is that at 500mb, again the model has confluence (think of this as additional energy separated from the storm) sitting to the north of the region with the low pressure center from this week’s storm way up there, and that keeps the storm from strengthening or moving to the north.  The GFS shows this, as it is more robust at 500mb with the feature and has the first low pressure center moving through on the 17th move through quicker.  The result is that the storm can become a little more defined.  What happens next on the model is even more interesting, however.  The first image was from next Sunday morning.  By Sunday late night, the model shows this.  The storm greatly slows down and strengthens, as the first low to the north acts as a block, this time not shunting the storm out to sea but allowing it to gain energy by having proper positioning.  I won’t get too technical, but this is sometimes referred to as a “50/50″ low (the positioning of it in latitude and longitude), and it is that 50/50 low that will have a key role in determining our fate with this storm.  Thus, despite the storm on the 17th not really meaning too much in terms of real impacts, it will have a very large role in determining the next storm, as it has to be in the right place to guide our storm on the perfect track for snow to be likely to fall down to the coast.  The ECMWF, however, has that low escape perfectly and be placed in a way so that by Sunday morning the model shows this.  That is a rapidly deepening low pressure center sitting just south of Long Island, giving the coast a rain/snow mix and giving inland areas a very heavy, wet snow.  Here, the low to the north is well and the 500mb chart much more supports a strong storm with a deeper trough that digs in and cuts off to an upper level low fairly late-stage in storm development (unlike what the model showed yesterday that I said was unlikely in my last Premium post), and the result is a strong storm further north than the 12z Saturday ECMWF had shown.  The 500mb analysis I did yesterday is thus reflected in this newer model, giving me more confidence in what it prints out.

However, confidence remains very low with this event.  Just look here.  These are all the scenarios of the GEFS ensembles for the storm Sunday afternoon.  Many ensembles show no storm at all, while a couple show a very weak storm.  Only one other ensemble shows a strong storm besides the operational GFS.  Now, it is important that the ECMWF ensembles back up the ECMWF with a strong snow storm there, and that is why I continue to lean towards this event happening rather being pushed out to sea, but there remains an extremely wide range currently in our weather modeling, which is often the case in winter.  The NAVGEM, shown here, even has precipitation with no defined low pressure center forming at all.  The possibilities are wide-ranging, and what I am going to outline next is just my first take given the pattern and the options on the table.

That’s just where we sit right now, and on the Premium post I delve into my specific thoughts on the most accurate model/most likely scenario, but this storm is still far enough out and models continue to swing around so wildly that it is hard to take faith in any one clear solution.  In general, a snowier trend inland and a snow/rain trend at the coast I feel may be warranted, but be sure to stay tuned to see how this forecast twists and turns.

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