You have probably heard about the Nor’ Easter that is going to bring likely historic snowfall amounts to regions in the Northeast and Blizzard Conditions to areas around Boston Friday into Saturday. So, how in the world is this happening, and what comes together to get us a snowstorm of this magnitude and size?
To start off, here is a recent image of the radar (left image), and the infrared satellite (right image).
As the two systems for Friday’s system continue to get sampled (specific data and observations are fed into models), and forecasters continue to get a better handle on the evolution of this storm system, a northern stream system will combine with a southern stream system to produce a much larger scale system off the east coast. This is known as “phasing”, and is shown in the graphics below.
The image below shows the synoptic (large scale) setup, which is quite complex.
1.) We see our developing low pressure system being influenced by the southern jet stream, and this will be very moisture laden as it gains latitude and travels up the Eastern Seaboard.
2.) Our Northern energy is heading southeast, a weak clipper at the current moment.
3.) As the two systems near, the northern system will transfer energy to the southern system. This is called a “phase”. The Northern stream system will weaken, and the southern stream system will then intensify. This is perhaps the most important step in the synoptic process.
4.) Once the phase completes, the system will intensify very rapidly, and dump potentially record levels of snowfall on the Northeast.
Early Friday Morning (1 AM), the image directly below shows the 850 Millibar vorticity. Simply, vorticity is the amount of counterclockwise spinning motion that is going on in the atmosphere, and the darker colors (yellow, orange, and red) symbolize a very high energy content approximately 5,000 feet up in the atmosphere. Notice the two areas of vorticity. The system in the Ohio Valley will be our Northern stream system, and will be weakening, at it is in the process of transferring its energy to the developing low pressure system in the Southeastern states. This is the beginning of the “phase”.
Exactly 24 hours from that, (1AM Saturday Morning), we see that the storm has completely phased into one; note the single center of energy off of the coast. This indicates the center of the low pressure, and at that time the storm will be rapidly intensifying.
However, there still remains some considerable uncertainty regarding the intensity and phasing of the two systems.
Two Wildcards – What will they come out to be?
There are two wildcards that will be addressed as the event nears closer. One, is the concept of exactly when the phase between the two system starts, and finishes. We break that down for you below.
The timing of the phasing remains uncertain. If an earlier phase occurs, places from New York City South and West into Central NJ could be dealing with quite a heavy snowstorm, which is seen in the 18z 4 km NAM, 18z RGEM and 18z GFS having an earlier phase. Also, given the trend to an earlier phase, Philadelphia and surrounding areas could see moderate snowfall also.
However, a later phase would mean less snow and more rain into these locations. From Central New Jersey to New York City is where there is currently the most forecast uncertainty, since a slight shift in the phasing would result in considerably different snowfall totals for these regions. The areas where there is the most snowfall certainty is into Southern New England where Blizzard Watches are currently in effect for one to two feet of snow. The overall trend with the models has been for a sooner phase, which would benefit New Jersey, New York City, and Philadelphia greatly in terms of higher snow totals.
Snow totals are affected by the phase time, because an earlier phase would mean that while the system is still further south, it can pull colder air into itself, and cool the atmosphere in locations that will receive rain faster into seeing accumulating snowfall.
Another wildcard is where the axis of heaviest snowfall sets up on the western portion of this impressive system, and how south it gets. The western section of precipitation will be snow, as enough cold air is going to be wrapped into all levels of the atmosphere to support that. A good indication to see where this will likely reach into is by seeing what the humidity content is at the 700 Millibar Level (approximately 10,000 feet). The graphic indicates that there will be plenty of moisture available, and the team expects this to be resolved in the evening and overnight model runs tonight.
Stay tuned with GeoEnvironmental Atmosphere, as the team will keep you informed, as tonight’s model runs will be a very telling evening, and look for another from the team overnight, complete with a snowfall forecast. For updates throughout the storm, please like the Facebook page below, and check out our exclusive Snowplow service.