Posted by: woodcreeper | September 5, 2008 @ 6:01 am

Hanna triggers migration, then causes fallouts in southeast Florida

Judging by the radar, it appears that the north winds of Tropical Storm Hanna triggered migration over central and southern Florida, while the subsequent feeder bands caused birds to “fallout” in the early morning hours. Here’s the radar from 7:00pm last night through 5:00am this morning.

Frames are every 1/2 hour. Click on the thumbnail to view the full-sized animation.
Base Reflectivity image from Key West, FL Base Velocity image from Key West, FL Base Reflectivity image from Miami, FL Base Velocity image from Miami, FL Composite base reflectivity for the Southeastern USA

Migration was slow over north Florida, as is evident from the composite radar loop, but across the rest of the state birds were clearly moving in good numbers. The Tampa/St. Pete radar showed birds moving over the Gulf and working their way south along the Florida coast, while the Melbourne radar indicated a more southerly trajectory over the mainland. Miami, too, showed a moderate level of migration, heading due south towards the Keys. The Key West radar also indicated a moderate push of birds into the Florida Straits, heading for Cuba.

The interesting part of this migration event occurred around midnight, when the northwest sector of tropical storm Hanna made landfall in southeastern Florida. Midnight is generally the peak time for nocturnal migration, and the effect of the large band of storms coming ashore was to abruptly shut down migration over the region. Fallout conditions should be evident across southeast Florida today, from Palm Beach down through coastal Miami, as well as inland locations such as AD Barnes Park in Miami. The telltale sign will be the time at which heavy rain appeared in your area. If you can recall the rain beginning around midnight, then make sure to check your local woodlot before venturing to a far off destination… you may just have a fallout in your backyard!

Fallout conditions are not expected south of the mainland since Florida Bay and the Keys were under clear skies and northerly winds through the morning. The same goes for locations north of Melbourne and west of Lake Okeechobee.

Good Birding,


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  1. Rain shadow over Cape Florida, maybe? I banded nearly the same number and species composition of birds that Liz did yesterday, and they were pretty fat. Clearly not struggling over the ocean in Hanna’s outer rainbands overnight. WEWA & BAWW most abundant; one SWWA. I heard a lot of birds at my house in South Dade as I ran out the door to get up to the banding station, so stuff definently fell out somewhere.

    Maybe tomorrow….one more day of westerly winds in Hanna’s wake before we start getting influenced by Hurricane Ike’s circulation.


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