Tuesday, October 28, 2014

Tuesday Morning Update: Trend in Tact, Increased Chances at East Coast Storm

Good morning. If you are really interested in how this situation is evolving I recommend you watch my video from last night. Basically as I have been talking about the past several days I am tracking the potential for a big east coast storm this weekend. This is a tricky forecast due to the fact that this whole storm depends on the phasing of the northern and southern branches of the jet stream. I explain in the video how even the slightest deviation of this phase has drastic implications on the forecast.

So what did the models do overnight? In short, the trend for a stronger storm is in tact. The European really went bold and blows up a major storm right over the mid-Atlantic while the GFS is more the the north and east effecting New England more. Lets review a few components to this storm.

All depends on the phasing of the jet streams....we have seen a stronger trend for this. Here is yesterdays European model..

And last nights...

Notice the stronger deeper trend to the disturbances combining. This has big forecast implications as it results in a deeper storm that blows up off the coast. Here is the surface map of the new European..

This results in rain turning into snow showers for the Mid-Atlantic and a snowstorm over the Northeast. 

Things are never as simple as just buying one model however, take a look at its ensemble. What is an ensemble? Basically it takes the main model and tweaks its inputs to test for error. What you get are 52 different solutions. They more they are similar the more accurate a forecast is likely to be. Here is the European ensemble..

Two things to notice. For one, the average of all the members is the circle inside the green. Secondly, every individual member is represented by a low pressure symbol. Quite the spread on the micro level, but on the marco level we can confidently say a storm is coming. 

So where do we go from here...rain,snow,both? Too early to say, it all depends on the track.I will take a first stab at it tonight with a map I will put out, but first let me show you something. 

These are ocean temperature departure from normal. Notice how warm the Atlantic is along the coast. This creates something called a baroclinic zone or basically a boundary between cold air coming in from Canada and warm air over the ocean. Low pressure systems like to form over these zones to balance out the difference. I would not be surprised if that is the track the low takes. The recent trends back this up. A track like this would result in more frozen precipitation for many areas. Yes a more extreme solution but its something we need to consider. 

In Summary:

  • Increased confidence that a storm is coming this weekend
  • Question remains, how early do the jet streams phase, which will dictate how deep and close to the coast the storm is.
  • The ocean temperatures could be the wild card to this forecast
  • My first map will go out tonight on what I think is going to happen.
Stay tuned!


  1. Hey Will. I was just wondering if this is now expected to be all rain for NW NJ and nearby areas, because I just looked at weather.com, and they have me under all rain for Friday night and Saturday, whereas before, I was under a rain/snow mix. I really hope this storm pans out for us, so we can get at least some early season snow. What do you think about this?

  2. That is the million dollar question right now. This is an extremely tough forecast. I should be able to hone in on this over the next 24 hours, but my gut is telling me high elevations north and west see some snow but not much accumulations. Near the coast and most of NJ should stay all rain with maybe a light snow shower or two after the storm passes (it will get very cold). But as I said the next 24 hours will say a lot in terms of how the models trend (nothing would surprise me at this point). I am putting out a preliminary map tonight but I am not gonna lie its not going to be easy to draw.