Forecast and Analysis

Regional Migration Forecasts: 25 October – 2 November 2012

Andrew Farnsworth The Cornell Lab Oct 25, 2012

As the fall migration continues past its peak, the big story of the forecast period is the passage of Hurricane Sandy, the havoc it may wreck, and the intense northerly and westerly flows that will spawn large movements before and after its passage. Additionally updates will be posted here as forecasts change for Sandy.

As regular movements of fall migration wind down for this season, many areas that do not have rain will experience scattered light migration. Many portions of the Great Basin and northern Rockies will see precipitation for much of the forecast period, as will areas of the Pacific Northwest, shutting down movements. The last of pulses of later season songbird movements will occur across many portions of the Desert Southwest and Four Corners, particularly as these areas are largely free of precipitation for much of the period. Note, seawatchers should consider the approach of a strong system in the North Pacific toward the end of the period, around 1-2 November, as this may be a vehicle for good onshore pelagic viewing (albeit in potentially foul conditions!).

Great Plains
Strong northerly flow in the wake of a frontal passage end the week and begin the weekend creates favorable conditions for one of the last big pulses of passerines and continuing waterfowl movements. These movements will be moderate to heavy across much of the region. As high pressure builds into the region, winds become less favorable and primarily scattered and light movements prevail by Sunday. Early week sees this pattern continue until Wednesday, when slightly more favorable conditions return with light to moderate movements in southern areas. For the remainder of the period, and for much of the region, conditions remain marginal to unfavorable for continued movements, and bird movements that do occur in light winds will be locally scattered and light.

Upper Midwest and Northeast
As low pressure tracks near the Great Lakes, northerly and northwesterly flow prevail from the Ohio River valley west to the Plains. Moderate to heavy movements occur here to end the week and begin the weekend, and these movements spread east as the front pushes toward the Atlantic and then stalls. Farther east, conditions are not favorable for much movement as primarily southerly flow and precipitation spread east. However, far to the east, along the coast, conditions will be marginal for migration, and movements may continue to be moderate or even locally heavy if winds are light and precipitation does not fall. Much of the early week is dominated by the uncertainty of the track of Hurricane Sandy, presently slated to come ashore in New Jersey on Tuesday. Northerly flow to the west of the system may spread from the coastal plain to the Mississippi, facilitating large movements. Heavy rain, easterly and northeasterly flow begin to spread into many coastal areas shutting down all migration until the system passes. Birders should be aware that this tropical system has the potential to bring many far flung pelagic species near shore and inland. First and foremost, birders should exercise extreme caution when birding in tropical systems, particularly in coastal and low-lying areas. Given the forecast strength and the track of this system, expect many common nearshore species to be displaced to coastal and flood plain areas as the storm moves ashore. Entrained birds may appear far inland, and as of now, birders should look closely for storm-driven birds in the Delaware River system, reservoirs and inlands water bodies, and any basins connecting dots between landfall in NJ and dissociation over the eastern Great Lakes. As Sandy passes through the region by Wednesday and Thursday, intense northerly and westerly flow will overspread the region, facilitating major movements to end the week in areas that do not continue to see rain (which may be few!).

Gulf Coast and Southeast
The effects of Sandy are already beginning, shutting down movements in many areas as heavy rain and strong easterly flow moves across coastal portions of the Southeast. Farther west, conditions are mostly marginal, with primarily light movements occurring. One notable exception may be in northern Texas and parts of the southern Mississippi River valley, which may see more moderate to locally heavy movements to begin the weekend. As Sandy passes, strong northerly flow moves across almost the entire region into the early part of the week, spawning moderate to heavy movements of later season passerines in many areas. By Wednesday, high pressure over the Gulf creates mostly unfavorable conditions for such movements to continue, and only areas of the southern Appalachians and coastal Atlantic plain experience continued favorable conditions. The unfavorable conditions intensity to end the forecast period, by which time only scattered light movements may be apparent across the region. One exception may be the coastal Carolinas, where the possibility of strong westerlies will spawn morning flights.