Forecast and Analysis

10 April 2013 Migration Alert: Frontal Boundary Approaches Gulf Coast

Andrew Farnsworth The Cornell Lab Apr 10, 2013

As of 1130AM CDT a pair of cold fronts is approaching the Gulf Coast. Most precipitation is presently North and West of the coast, but in the coming hours it will advance to the Gulf of Mexico.


A frontal boundary is approaching the Gulf coast as trans-Gulf migration is coming ashore (see radar imagery below).

Trans-Gulf migrants are already coming ashore, primarily as light to moderate movements, along the Central Texas coast, above the Upper Texas and Southwest Louisiana coasts, and farther to the east in Mississippi and Alabama. In the image below, they appear as the uniformly stippled patterns of light and darker blues. Contrast these patterns with the blocky, colorful patterns representing precipitation at and near the frontal boundary.


Widespread precipitation is moving East as trans-Gulf migration comes ashore. In areas where the wave of migrants meets precipitation, fallouts will occur. Plan your birding accordingly, though be safe first and foremost! Some of the storms in this front are very strong and dangerous.

In areas where birds meet precipitation, fallouts will occur. The fallout hotzone today (10 April) will likely cover portions of East Texas through Central Louisiana, from the coast north to Interstate 20. Note, however, that portions of the Central Texas coast may experience fallout conditions, as well, as a wind shift may precipitate migrant concentrations in coastal habitat.

Although the beginnings of today’s wave of migrants have already overflown the coast by some distance, particularly shorebirds and stronger fliers that likely arrived this morning (and may have concentrated farther inland where they encountered precipitation), many passerine migrants will continue to arrive for the next several hours. As the precipitation reaches the coast, stopover habitat will begin to accumulate birds. However, this is not necessarily only a coastal scenario, as birds overflying the immediate coast and its habitat will encounter precipitation inland and fallout, for example near the Interstate-20 corridor in East Texas and Northern Louisiana. So, even if precipitation does not reach the coast, which is also quite possible as all Gulf Coast birders know from watching frontal approaches (!), birders should still look for concentrations inland (and farther south along the coast as winds shift there).

As this frontal boundary pushes into the Gulf of Mexico, the likelihood of migrants encountering precipitation and unfavorable winds will shift farther east. Birders along the Gulf Coasts of eastern Louisiana through Alabama should watch the front’s progression carefully tomorrow, particularly presuming that conditions for exodus over Yucatan and the Caribbean remain favorable (as forecast, see image below).


As the cold front pushes east into the Gulf, migrants aloft over the Gulf will begin to encounter increasingly unfavorable conditions. Given the wide isobars and relatively slow wind speeds, fallouts may occur late in the again in Texas, though the primary hotzone will be from the Central Louisiana coast east through Alabama.

First and foremost, birders should be safe, as some of the storms in this system are severe and have potentially damaging winds and hail.