Well, post-mortem may be an erroneous descriptor as the storm is still quite active offshore of our coast and will continue to affect us for days to come, but since the dramatic wind and rain has backed off for now, it’s worth paying the subject a visit.
If you tuned in to the news or kept your eye on social media over the last 24 hours, you know that Winter Storm Saturn did indeed cause quite a bit of storm-surge flooding in certain areas, and considerably less in others; it seemed like the further south you looked, the greater the surge. A few factors were at play in this phenomenon:
The storm ejected a bit south than originally predicted; entry into the Atlantic off the DelMarVa region was modeled, but it appears the center of circulation over open waters wound up being over the Carolinas. That put Delaware Bay and Chesapeake Bay right in that trouble zone (just north of the “eye”) during the height of the storm; water entered the mouths of the bays but had no way out and stacked up. I’ve seen some footage of cars up to their side-view mirrors down in Ocean City, Maryland and at least one floating in a wash-out in North Carolina.
In some localized cases, the strong sustained NE-NNE winds through the height of the storm appear to have pushed water towards the mainland side, relieving flooding pressure on the bay-side of the barrier islands but causing trouble at some low-lying communities situated in/near embayments on the mainland. And while that eventual shift to N-NNW was good for some areas, assisting tidal drainage in North-South oriented bays like Barnegat, it cause trouble for communities on north-facing shorelines within bays like Tuckerton Beach and the north shore of Long Island, pushing water towards them.
Also, once the storm ejected off the coast, it initially took more of an eastward track instead of the anticipated NE path. That resulted in an easing of the surge in the northern half of the state as time went by rather than increased surging from an obliquely-approaching storm; while northern and central NJ did indeed receive quite a bit of swell and surge (including some overwashing of seawalls, breaching of dunes weakened by Sandy, and some minor to moderate street and property flooding), the fetch of the winds (illustrated below) was maximized for southern NJ and the aforementioned DelMarVa region, resulting in feet, rather than inches, of surge in roadways and low-lying communities.
Illustration of the fetch from Winter Storm Saturn. Image credit: Magicseaweed.com
So, the assessment of this storm to date is that it was a bit underwhelming in some areas (particularly if you were anticipating and bracing for the worst or a bit inland and hoping for a snow-event), overwhelming in others (particularly in the coastal areas in the southern half of NJ and DelMarVa), and absolutely fascinating due to it’s complexity. Also, despite improved weather today, Saturn has stalled a bit over the Atlantic thanks to that -NAO I addressed in my post on Monday, making a turn to the NE, and receiving energy and moisture from another system approaching from the west via the Great Lakes, so it will continue to throw precipitation, swell and sideshore winds at our coast through the remainder of the work-week, which means continued storm surge (particularly around high tides) and sustained swell, which means further erosion of our already-battered beaches and dunes. Since it ain’t over, I may post a post-post-mortem down the line, but this should feed your brain a bit for now.