An Unusual September Storm

Let's *speculate* on this potentially fascinating weather system that is forecast to develop off the East Coast later this week!

The meteorologists are classifying this storm as a nor'easter, not a tropical cyclone. This is, of course, the time of year we keep a sharp eye out for tropical system development. Nor'easters are rare this early in autumn, so this is unusual.

Other than the time of year, another aspect of this storm that seems unusual is the proposed track of its center. In their most classic form, nor'easters form off the Carolinas/mid-Atlantic and move in a northeast-ish direction up the coast. But the models seem to show the system developing several hundred miles offshore, moving north, and then perhaps backing northwestward, towards the East Coast rather than along or away from it. It may even stall out?

On top of that, it might pack tropical storm force winds at the surface.

ECMWF model for Friday, courtesy of Windy.com

Saturday

Sunday

The three images above depict Fri-Sat-Sun runs from the Euro model. The GFS takes a much more easterly track, with the storm eventually backing into Cape Cod.

All this makes me wonder if this might pack some excitement for northeastern birders. There are a few ways in which a storm like this one could impact our land-based birding.

The most obvious way might involve birds that are simply blown towards or over land by the strong sustained winds that circulate counterclockwise around the low. The easterly (AKA onshore) wind ahead of the storm could drift pelagic species closer to land than usual, or in larger numbers than usual. There are actually signs of this already happening before storm formation. We've now had a couple days of strong widespread northeast winds in our region, and at least a small "wreck" of Leach's Storm-Petrels has occurred. One was photographed over land in western MA yesterday, several were seen from land in eastern MA today, and I believe that one or more were reported from the extreme western corner of Long Island Sound, which is really unusual. Neither a low pressure system nor precipitation have been directly involved to this point; these birds have simply been pushed around by prolonged onshore winds. These pre-storm easterlies are setting the table quite nicely. The effect is only likely to increase with the arrival of a nor'easter.

Such a storm could also down overland migrants. When the rain hits, we might see an uptick in shorebirds that are grounded by the weather (i.e. Hudsonian Godwit, American Golden-Plover). A few species of Arctic-breeding seabirds might also be affected on their way to the ocean, such as jaegers and Sabine's Gull. And there could also be a glut of birds pushed down the St. Lawrence River and then over land in New York/New England. Black-legged Kittiwake would be a species to watch for, if that were the case. And whether they come overland or via the ocean, this is prime time for migrating Lesser Black-backed Gulls, so we could see an unusually high number of those.

But what separates tropical cyclones from nor'easters is their ability to entrain birds into its circulation, such as inside the eye of the storm. Might this storm be strong enough to actually entrain pelagic birds, carrying them from open ocean and dropping them wherever the storm either makes landfall or weakens? Seems like quite a longshot, but I think it is worth keeping an open mind. At the very least, it is an interesting thought experiment.

Of course all of this is just fun speculation. The kind of thing optimistic birders love to chat about over a beer or two. None of the above is meant to be any sort of prediction. The most likely scenario is that only the well-known seawatch locations, such as those on Cape Cod, are treated to a modest local seabird event.

Though we often focus on water-loving birds during events like these, landbirds are affected by storms as well. Anything that finds itself offshore will have to deal with quite an obstacle, which could lead to displacement. I'd be extra alert for exhausted warblers and the like, especially along ocean-facing coastlines.

As an aside, the proposed track of this storm kinda recalls that of Hurricane Henri, a legit tropical cyclone, from five years ago. We were all jazzed for that one, only to have it be a total dud bird-wise, to the shock and dismay of many!

But, as they say, chance favors the prepared mind. If this storm actually does affect the northeast US this weekend and you decide to venture out, be safe and keep an open mind.

-Nick