Cyclones

Eastern Promises Update: 28 December 2012

Andrew Farnsworth The Cornell Lab Dec 29, 2012

Well, the Fieldfare you so desired for the holidays certainly may have been beneath whatever vegetation is part of your holiday celebrations, but not if you live in North America. Although a number of Black-headed Gulls and Tufted Ducks are present, along with a suite of Barnacle Geese, presumably little action occurred in what turned out to be a blip of a negative NAO index during December. Clearly, this was not the  easterly blast combined with frigid temperatures in Europe and the UK needed to send a pulse of Eastern goodies to North America. This is clear in the graphic below:

The NAO index was strongly negative during the period of Hurricane Sandy’s passage, and the index for December did not reach this magnitude. Furthermore, the coming 7-, 10-, and 14- day windows are forecast to be unfavorable for any Eastern vagrants moving across the Atlantic to North America.

Forecasters are still mulling the likelihood for a Greenland block later this winter, though it is notoriously difficult to forecast very far in advance with any certainty (of course!). We will keep on eye on our Eastern promises in the New Year! One thing to watch, if you are interested in cycles of climatology and larger scale patterns of circulation Рthe interplay between the Arctic Oscillation and the North Atlantic Oscillation plays a large role in the wind direction and strength across the Atlantic, as well as the incursion of cold air into the United States in winter, among other things. A strong jet stream near the Arctic Circle is indicative of a strong Arctic Oscillation, and likely a weak NAO and low likelihood for a Greenland block to set up shop; however, a weak jet stream near the Arctic Circle allows the high pressure to establish itself in the North Atlantic. It also allows for colder air to press farther south into the US, and presumably could be a cause for substantial facultative movements of wintering species.

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