Monday, March 2, 2015

Monday Morning Weather Discussion: An Eventful Week Ahead

What a week of weather we have in store guys. March could not have come in with more action on tap and today's post will attempt to break it all down for you. Before we begin here where snowfall reports from yesterday's event..

My Map which was made on Saturday morning..

Clearly some flaws in the map above, but some areas worked out well. The forecast was correct for CT,RI, Mass, NY state and Central and South Jersey. The forecast was wrong with accumulations too high for Northern NJ and too low for Long Island. Overall I did a fair not excellent job with this. I give myself a C. You guys be the judge.

Now to the action! Lets dive right into this week. Now that we are within a few days of the action we can start to trust the models a little more. Remember last week when I was pounding the table saying due to the complexity of the jet stream we had to wait to this period to sort this out. 

It all starts with a storm system tomorrow that will cut to our west. The result will be a quick peroid of front end snow changing to ice then plain rain for a little. The changeover will occur because the storm brings in warm air from the south since its track is to our west. Here is the model projection for Tuesday night..

This is right before the changeover to rain. Now lets pause here and illustrate the role this storm will play for our next system on Thurday that could be the significant weather maker. 

As the storm departs to our west, it sweeps in a cold front. This cold front is KEY as it sets up our baroclinic zone or boundary between warm and cold air for our next storm system to ride along I show the cold front below sweeping into the region..

Lets now turn to 18,000ft in the atmosphere and look at what is going on aloft. We are going to be dealing with two disturbances- one in the northern stream and one in the southern stream. We need both of those disturbances to interact in order for this boundary of cold air to set up in the perfect spot for a storm system to effect our area. Let me illustrate..

The gfs is faster with the northern disturbance. Because of this it pushes the baroclinic zone too far south ahead of the southern jet stream disturbance. The end result is a storm that is more to the south.

Here is the illustration:

The end result at the surface..

Notice how the whole storm is more south.

Is the GFS correct? I do not think so and there are three reasons why:

  • European is further west
  • Canadian is further west
  • The GFS ensembles are further west
For example here is the Canadian at 18,000ft at same time as GFS..

The end result..

As you can see a further north solution. The European looks similar. To illustrate my third point check this out..

Those green lines represent all the different ensemble members projection of the northern disturbance vs the operational in white. The ensemble is saying the operational might be too fast. Thus the ensemble is more like the European and Canadian.

So now that I really dove into this what do I think for my first estimate?

That's all I will say for now. This storm could be a strong one if these variables come together correctly. By strong I mean 6+ inches.

Stay tuned!


  1. Yup, I see it -- 06Z NAM implying around 8 inches of snow on Thursday. NAO forecasts show a temporary weakening to low + on 4th-6th, and EPO will still be negative, albeit fading towards 0 or + thereafter. So yes, the concept of a wet southern jet finally phasing into a big S-shaped northern jet off to our southwest, triggering big growing disturbances with strong thermoclines that aren't in any rush to move northwest, is looking more and more feasible. Possibly the last hurrah, as the spring trends are looking stronger for next week. So, something for both snow-lovers and springtime-lovers. Jim G

  2. Opps, make that "no rush to move northEAST" . . . like, towards BOSTON. Sorry, Monday AM blues. Jim G