Let’s get this out of the way: On Wednesday evening, we made a post explaining why we were confident New York City would avoid blockbuster snowfall totals from this weekends storm.
We were wrong.
A last minute, buzzer-beater type north trend resulted in tremendous heavy snow bands moving over New York City on Saturday. All-time snowfall records were broken at Kennedy Airport (30.5″), LaGuardia Airport (27.9″). Central Park reported its second largest snowfall of all time at 26.8″, just .1″ shy of the record set back in February 2006. The impacts on the area were immense – with New York City shut down to all travel from 2:30pm Saturday until 7:00am Sunday.
The atmospheric dynamics at play during the storm system were even more incredible than the snow that fell. Tremendous lift, energy, and moisture surged northward on Saturday as a low pressure system tucked in near the Mid-Atlantic Coast. Bands of heavy snow surged north through New Jersey, with whiteout conditions and snowfall rates of 2″ per hour. These bands of snow quickly made their way toward New York City and Northeast New Jersey on Saturday morning — setting up from southwest to northeast through NJ, NYC, Long Island, and SW CT.
As this occurred, the surface low in the Mid Atlantic states stalled. For several hours, the low pressure system meandered off the coast, as atmospheric dynamics continued to pump moisture and lift for precipitation into a band of prolific snowfall. These bands pulsated and redeveloped, but impacted the same general areas for several hours. Blizzard conditions were widespread with a total whiteout, extreme hourly snowfall accumulation rates, and zero visibility.
What caused the forecast to change?
As detailed in our prior article, much of the forecast during the middle and later part of last week was based on reliable global models and their ensembles showing the bulk of dynamics and moisture missing our area to the south. The general idea was that this guidance was more reliable due to the fast pacific jet and progressive pattern.
This very same guidance had shown a large vortex over Southeast Canada (also known as a 50/50 low) and a ridge on the West Coast collapsing and rolling east. This caused confluence and lower heights over the Northeast United States. This pattern would force the mid level disturbance over the Central US to form a cut-off low over the Mississippi River Valley. With this cutoff low occluding over the Mid Atlantic, the dynamics associated with the storm would decay before reaching our area.
The thought process behind this evolution, shown on almost all global models at one point, was solid and meteorologically sound. But the storm itself had a few tricks up its sleeve.
What exactly happened?
The large vortex over Southeast Canada was incorrectly modeled by global forecast guidance, and moved out quickly. This pattern allowed the mid level disturbance to remain more broad until it approached the Mid Atlantic Coast. Positive vorticity advection (PVA) in the mid levels of the atmosphere was able to streak up the East Coast, bringing intense dynamics directly into our area. Our area’s positioning underneath the right-entrance region of a 120+ knot upper level jet streak enhanced lifting and moisture over much of New Jersey and New York.
High pressure building in from Ontario strengthened the confluence to the north of the area on Saturday — but it also enhanced mid level frontogenesis. This caused very heavy bands of snow with 2 to 3 inch per hour snowfall rates. Further north, over the Hudson Valley and Connecticut, snowfall rates were not as high — with more sinking air from the banding which was sitting over NYC, NE NJ and LI.
Extremely heavy snow, whiteout and blizzard conditions with bands of snow still streaming into NYC, NE NJ, LI: pic.twitter.com/Vv4yPrwpO3
— NY Metro Weather (@nymetrowx) January 23, 2016
As the storm went on, the mid level cut off low began to occlude east of the Delmarva. This allowed the surface low to remain tucked in near the coast, and allowed bands of moderate and heavy snow to continue to pivot over the region into Saturday Night. Finally, the pacific jet stream energy caused the ridge on the west coast to collapse and our storm was pushed east into the Northwest Atlantic.
This exact scenario was depicted quite well by the NAM model and it’s associated SREF ensemble guidance. While some of the model runs were too far north with the storms extent, the NAM and SREF handled the banding quite well for a prolonged period of time, and ended up performing tremendously during this storm, showing the prolific snowfall potential over our area for several days prior to the storm.
In the end, this storm will go down in the record books as one of the greats. Forecast models had the potential for a huge storm pinned down from about 7-8 days in advance, and as we got closer to the storm, high resolution models were able to pin down the bands of record breaking snowfall that our area would experience. The Blizzard of 2016 will certainly be remembered for many years to come.