Satellite signatures of a Nor’easter along the US East Coast
GOES-16 (GOES-East) Mid-level (6.9 µm) Water Vapor images (above) showed 2 important signatures associated with the an intense Nor’easter that moved northeastward along the US East Coast during the 16 December – 17 December 2020 period (surface analyses): (1) the development of a baroclinic leaf signature related to the initial batch of heavy snowfall, and (2) a broad deformation zone that lingered behind and slowly pivoted across the Northeast US, helping to prolong heavy snowfall.1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images displayed the well-defined center of the Nor’easter as it moved eastward off the coast of Long Island, Rhode Island and Massachusetts on 17 December (below).
Other features of interest included the development of clusters of parallel convective billow clouds over parts of Massachusetts, New Hampshire and Maine on 17 December, near the rear edge of the departing Nor’easter — a comparison of NOAA-20 VIIRS Visible (0.64 µm), Near-Infrared (1.61 µm) and Infrared Window (11.45 µm) images (below) provided a detailed view of these billow clouds at 1639 UTC. A time-matched comparison of Visible, Near-Infrared and Infrared Window images from NOAA-20 and GOES-16 (below) demonstrated (1) the advantage of improved spatial resolution for detecting such small-scale features, and (2) the slight northward shift on their apparent location on GOES-16 images, due to parallax. 1-minute GOES-16 Visible, Near-Infrared, Infrared Window and Day Cloud Phase Distinction RGB images (below) showed the development and propagation of these convective billows during the 1600-1800 UTC period. A curious aspect of these billows was the fact that even though they exhibited colder infrared brightness temperatures than the surrounding glaciated clouds, the parallel billow band cloud tops appeared to be composed primarily of supercooled water droplets (brighter white on the Near-Infrared and Day Cloud Phase Distinction RGB images). Additional information and images of this Nor’easter can be found at this blog post and on the Satellite Liaison Blog.Here's a quick recap of the snowfall from this week's nor'easter. An extremely heavy band of snow lead to 40+ inch reports in four different states: PA, NY, VT, and NH. Two potential state records for 24-hour snowfall would require additional verification. https://t.co/1wii3BsFlz pic.twitter.com/RSsxEZloaA
— NWS Weather Prediction Center (@NWSWPC) December 18, 2020