Winter officially begins in a couple of days and it may be off to quite a start this year, if things pan out the way they seem to be trending. Within 24 hours, a storm that appeared destined for the fish in the Atlantic Ocean, now has its sights set on the entire eastern seaboard.
There's alot more weather maps I can go through, but I'll leave you with what the potential snow amounts could be. Below is an output form BUFKIT, a tool which produces graphical outputs on many weather parameters. It is outputting 1.9 inches of snow. Now before you start wondering why I'm making a big stink over 1.9 inches... this is liquid equivalent. On average, 1 inch of liquid equates to 10 inches of snow. However, because this could be a dry, powdery snowfall, the ratios could be even higher. So, bottom line here is that we could be measuring snow in feet, not inches.
This will be my first detailed weather model analysis and discussion of the storm. At this time, a good portion of the 00z model data has come in. The real eye opener came this afternoon with the 18Z NAM. It has a major shift of the storm track closer to the coast line. It hopped on board with the EURO (one of the more respected models). The GFS is basically the only model that has not jumped on the bandwagon at this poing. Being that it is currently the outlier, we'll use the 00z as the model of analysis.
Let's set the stage and look at the surface features in play. I have circled the key features in red. A strong, Canadian high pressure system is in control of the northeast. This is one of the coldest airmasses of the season. Unlike many storms that come up from the south, this one will not be able to drag a lot of warm air up with it, so it almost a guarantee that we are going to be dealing with snow only. An area of low pressure has already developed over the Gulf of Mexico. This is the storm we are watching.
Now, let's take a look at the latest run of the NAM. We'll start by looking at the initialized analysis at 500 mb. This gives us a flavor of the overall weather pattern and potential evolution and track of storms. One of the key things Meteorologists look at in determinng the potential of a major east coast snowstorm is a term called the "North Atlantic Oscillation" (NAO), which is the difference of normalized sea level pressure anomaly between Iceland and the subtropical eastern North Atlantic. It has 2 major phases: Positive and Negative. For big snowstorms along the east coast, we look for negative values. Negative values of NAO are associated with unusually high geopotential height values at 500 mb across the north atlantic. This is sometimes known as a "Greenland Block". This anomalous condition forces deep troughs of low pressure to form along the east coast, which can generate big storms. Because there is a blocking upstream, these troughs tend to negatively tilt and even cutoff. This leads to intense and slow moving storm systems that can produce very heavy precipitation. The image below is a great representation of a negative NAO situation, which is leading to this potential nor'easter. Anomalously high geopotential hight values of 570 DM are over Greenland and is producing a blocking situation. This is forcing the polar vortex south eastward to southern Canada. A strong, confluent flow is over the northeast.. a sign of high pressure over the region and typically a forerunner of east coast snow storms.
Now, let's jump ahead to the height of the storm and see how the 500 mb pattern evolves. As you'll see, what has not changed is the Greenland Block. But now, the trough that developed across the central and eastern United States amplified tremendously and a cutoff system is over the Atlantic. Boxed in red is an area of tremendous upper level divergence, which will aid in deepening the surface low pressure along the coast. Though not shown on this map, water temperatures are still rather warm, so the storm will feed on a tremendous temperature gradient and could likely cause a coastal front to form. These can generate a tremendous amount of snowfall.
Now, let's jump ahead to the height of the storm and see how the 500 mb pattern evolves. As you'll see, what has not changed is the Greenland Block. But now, the trough that developed across the central and eastern United States amplified tremendously and a cutoff system is over the Atlantic. Boxed in red is an area of tremendous upper level divergence, which will aid in deepening the surface low pressure along the coast. Though not shown on this map, water temperatures are still rather warm, so the storm will feed on a tremendous temperature gradient and could likely cause a coastal front to form. These can generate a tremendous amount of snowfall.
The surface map for this same timeframe tells the story. A very heavy snowfall would be occurring Saturday night with 2-4 inch per hour snowfall rates.
There's alot more weather maps I can go through, but I'll leave you with what the potential snow amounts could be. Below is an output form BUFKIT, a tool which produces graphical outputs on many weather parameters. It is outputting 1.9 inches of snow. Now before you start wondering why I'm making a big stink over 1.9 inches... this is liquid equivalent. On average, 1 inch of liquid equates to 10 inches of snow. However, because this could be a dry, powdery snowfall, the ratios could be even higher. So, bottom line here is that we could be measuring snow in feet, not inches.
Stay tuned for further updates on the storm and predicted snowfall accumulations.
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