DISCUSSION: This day in weather history remembers the Boxing Day Blizzard of 2010. The Boxing Day blizzard was a record breaking storm for many in the Northeast United States, as well as my personal favorite storm. Widespread heavy snowfall fell from the Mid-Atlantic to the Northeast as a coastal low developed across the Gulf of Mexico and tracked along the coastal waters of the eastern United States.
The image above is an analysis of the atmosphere based on the NAM on the 27th of December, 2010, at 00Z. The upper left panel represents the jet stream at 300 mb, with heights in decameters, and wind speed in knots, filled. The upper right panel shows 500 mb heights in decameters, wind barbs in knots, and vorticity (s^-1) filled. The lower left panel plots 850 mb temperatures and wind barbs and the lower right panel plots sea level pressure (mb), 1000-500 mb thicknesses in decameters, and convective precipitation from 00Z to 12Z on the 27th. Let’s break this down. There is a strong jet streak present along the southeast coastal waters, putting the left exit region of the jet across the northern Mid-Atlantic to portions of Southern New England leading to strong vertical motion.
Accompanied with this, as seen in the 500 mb map, a strong, elongated, intense area of vorticity is present from the deep south states stretching along the east coast and into Long Island and Southern New England. This is leading to positive vorticity advection across New Jersey, Pennsylvania, and into all of New England, and therefore, upward vertical motion, matching well with the upward vertical motion based on the jet dynamics. Neutral temperature advection is shown in the lower left-hand panel, as much of the 850 mb wind barbs, while strong, are parallel to the isotherms.
And to wrap this diagram up, the lower right-hand panel shows thickness lines below 540 decameters all across the northern Mid-Atlantic into the Northeast, indicative of all snowfall at this time where precipitation is falling. The NAM analysis has the low pressure off the New Jersey coastal waters, as the model shows convective precipitation developing across Southern New England which is evidence for weak stability, and hence heavy snowfall rates. Weak stability is an ingredient for bombogenesis, which our storm underwent, as the pressure dropped by 32 mb in 24 hours from 00Z on the 26th to 00Z on the 27th.
As we look at the snow totals from this event, heavy snows fell from all of eastern New Jersey, southern New York State, far western Massachusetts, and southern Vermont, with another heavy snow area across eastern Massachusetts. In-between these areas, as represented by the two circles on the figure above, much less snow fell. Why did this occur when all our synoptic scale features pointed to strong upward vertical motion and hence heavy snowfall all across the northern Mid-Atlantic and Southern New England?
When plotting 850 mb frontogenesis (as well as sea level pressure) from the NAM 00Z, forecast hour 03Z, the answer becomes clear. There are two areas of frontogenesis, shaded, that are of interest. One is the large strong band from eastern Long Island to far eastern Southern New England. The other is a narrow band across central New Jersey and into southern portions of New York State. These areas of frontogenesis create a thermally direct circulation in response to the frontogenetic thermally indirect circulation at the surface. This secondary circulation causes warm air to rise along these frontogenetic regions, while the cold air sinks in-between where the frontogenesis is not present, in essence Le Chatelier's principle.
Looking at a radar imagery around the time of this analysis shows a very heavy snow band from eastern New Jersey up through southern New York state, and into southern Vermont. A second heavy snow band set up shop across far southeast Southern New England. These two areas match well with the two areas of frontogenesis plotted, and the “snow holes”, aka sinking air, show up well across central portions of Southern New England and in western NJ and eastern PA. This frontogenesis played a key role in who received over 20 inches of snow, like what fell in my backyard, and a couple of inches a few miles away.
To finish off this discussion, let’s look at the model guidance on the morning of Christmas Eve, 2010. Virtually every single model had this storm well off into the Atlantic with minimal impacts, except for the GFS and its ensembles. This was a difficult forecast because of this discrepancy in the models, not to mention the extreme totals in isolated regions, but the GFS obviously caught on to something before all the other guidance, at least at this time.
That wraps up this discussion of the Boxing Day Blizzard, but if you want to learn more about weather history, be sure to click here for further stories!
©2017 Forecaster Joe DeLizio