Forecast and Analysis

Special Bering Sea Forecast: 2-6 September 2013

Andrew Farnsworth The Cornell Lab Sep 01, 2013

From time to time Team BirdCast likes to wander a bit farther afield than usual, and this post is no exception. Several of our colleagues finds themselves on St. Paul and St. Lawrence, Alaskan islands in the middle of the Bering Sea. Fall can be an exciting time in such locations, with the potential of a first North American record lurking with the passage of every low pressure system.

The coming week holds some promise for some far-flung Asian migrants, as a low pressure system works its way East across the Bering Sea. As the low passes over the Aleutians and associated islands very early in the morning on Labor Day, a substantially more westerly component of winds will be apparent. This westerly component should facilitate the arrival on Bering Sea islands of any migrants entrained in the system since departing points in Northeastern Asia. Presumably these arrivals will occur within 1-3 days following the system’s passage. Given the circulation around the system’s center and where it is currently forecast to pass, more southerly and westerly islands will be in better position to receive drop-ins during the Tuesday-Wednesday period.

image03However, Wednesday-Friday may hold a slightly more promising picture for the more northerly islands, probably favoring St Paul over St. Lawrence for a migrant drop-in. This seems plausible because of the path that low pressure is forecast to travel after its initial arrival in the Aleutian area. By early morning 4 September the low moves substantially farther North and West into the Bering Sea, bringing a stronger westerly flow to the St Paul area.


Additional imagery from David Nicosia at NWS-Binghamton shows a similar pattern, with the low moving East across the islands and then eventually North toward the mainland. Circulation around the low brings precipitation and poor visibility conditions, but as the system sweeps past and clearing ensues, any birds entrained in the system can see these isolated islands and drop-in to the only nearby stopover habitat. The three colorized panels below show the progression of the low pressure system from early morning Labor Day through early afternoon on 4 September.




Presumably, this system will hold a nice array of Siberian shorebirds and passerines, and Team BirdCast will post links to whatever drop-ins and vagrants our colleagues in the field turn up! We are certainly eager to see what turns up next!