Another Friday, another tornado-spewing storm system.  I thought we’d outgrown that cycle, but I should have known better:  May is actually the peak tornado month nationwide, with an average May day generating more than five tornadoes.  As many as 20 were reported yesterday in the Plains states, and here in the mid-South we’re bracing for a hit this afternoon. 

This system is forecast to move into the Gulf during Saturday, and the models look great for fallouts– especially in the TX/LA coastal corridor, which should be seeing rain by early tomorrow morning.  Over the course of the day, winds aloft will gradually shift toward the westerly, steering migrants toward MS/AL for possible late fallouts there (with storms expected to peak mid-afternoon).  Trans-Gulf travelers will have nice tailwinds for most of their trip tonight, so the question is whether they’ll arrive soon enough to beat the front.

They sure have been moving over the last couple of days.  Arrivals yesterday were extremely heavy, especially on the Upper Texas Coast, as you can see from the animation below.  At their early-afternoon peak, when reflectivities reached 30 dBZ, the number of birds passing within range of the Houston beam must have easily numbered in the millions.  Riding a stiff tailwind, birds coming ashore in Louisiana can be seen burning past the coast and arriving in north MS by the end of the day.

Last night, with 925 mb winds reaching a gale-force 40 knots over parts of the South, the pace of nocturnal migration was breakneck.  Birds taking off from coastal forests whizzed completely through Mississippi in a matter of a few hours.  Here’s last night’s animation:

The beginning of May is bittersweet, since it represents the turning of the corner for spring migration, which will be slowing to a trickle in a few short weeks.  But for now, it’s still going full-bore.  Even in the noontime heat yesterday, when I finally got around to stepping outside, the woods were dripping with birds (mostly Tennessee, Chestnut-sided, and Yellow Warblers and American Redstarts; a Swainson’s Thrush, a Warbling Vireo, and a flock of Indigo Buntings were also hanging around). 

Conditions in the Yucatan Monday evening were obviously no good for migration.  Overcast skies, 10-15 mph headwinds – no songbird in its right mind would have taken off; and even if it did, headwinds at all altitudes, stretching over the entire Gulf, would have made it change its mind pretty quick.  So you could forget about birding the Gulf Coast yesterday, glorious weather notwithstanding.

Fortunately, Chazz Hesselein didn’t get wind of this forecast, and he showed up on Dauphin Island yesterday afternoon to witness a superb fallout.  Hundreds or even thousands of Scarlet Tanagers foraged tamely in shrubs and on the ground; thrushes of several species allowed point-blank looks; Orchard Orioles and Indigo Buntings were present in large numbers; and as many as four Black-billed Cuckoos (a species of which most of us feel fortunate to see one) were reported across the island.

Given that anyone at all made the flight Monday night, it stands to reason that they’d be too exhausted by Tuesday to worry about snooping birders.  But why would they depart at all?  A headwind is a big deal, especially for smaller birds (a headwind of just 10 mph can cut down a hummingbird’s flight range – the distance its fat reserves will last – by more than half).  There don’t seem to have been many warblers present on Dauphin yesterday, so there may have been a size bias among Yucatan birds willing to depart.  I’m just surprised that there was a flight at all.  Migrants are full of surprises.

Meanwhile, the high over the mid-South has been moving along somewhat more quickly than predicted, and we started to see the back side of it last night – allowing considerable migration on light tailwinds as far east as Jackson.  Here’s the national animation:

This weekend provided an excellent lesson in the futility of spring forecasting.  Although forecasts were right on target in calling for wet, disturbed Gulf Coast weather throughout the weekend, the details weren’t quite as tidy as weather-watching birders might have hoped.  Remember that one-two punch of cold fronts that were shaping up on Friday?  That went awry as soon afterwards as Saturday afternoon, when the first front came to a screeching halt and planted itself across the Deep South.  The second front came barreling into it early Sunday morning, and they joined forces to generate thunderstorms over a huge swath of the Southeast, before finally getting legs and moving out into the Gulf Sunday night.  The national map remains a spidery tangle of fronts, with a fresh one – spawned by a Great Lakes-area low-pressure cell – moving in today and prolonging our unseasonable coolness.

What did all this mean for birding?  Winds aloft never developed the strong easterly bias that had been predicted over the Gulf, so most coastal areas received arrivals, and persistently nasty weather meant fallouts were possible throughout the weekend – although the storms were patchy enough that many birds may have threaded the gaps and continued inland on the south-ish winds ahead of the stalled front.  On Saturday, though TX and LA received the most birds, migrants were visible over the Gulf from every coastal station, from Brownsville all the way around to Key West:

Incoming flights on Sunday were much thinner, although a rather substantial arrival event could perhaps be seen along the MS/AL coast in mid-afternoon.  The drop-off in traffic from Saturday to Sunday intrigues me, because wind conditions in Mexico appear to have been similar for departees; increasing cloud cover may have been the difference, cluing migrants in to distant trouble.  Sunday’s animation:

Finally, arrivals on Monday seem to have been practically nonexistent (although it’s important to remember the possibility of migrants coming in below the radar beam, as they well might under adverse conditions).  Fortunately, though, coastal areas had accumulated enough birds through the weekend to make for good birding.  15+ warbler species were reported from both Grand Isle and Fort Morgan on Monday.  Yellow, Chestnut-sided, Magnolia, and Tennessee warblers seem to have been prominent constituents of this latest wave, as well as the transient spotted thrushes (Swainson’s, Gray-cheeked, and Veery); good numbers of tanagers, orioles, and grosbeaks continue to be reported as well.

Migration is currently on pause, but it will be the briefest of pauses:  by tomorrow night, the southerlies will have re-exerted themselves, and the Yucatan Express will be rolling again.  I highly recommend getting out before then if you can; grounded migrants in good diversity could be present just about anywhere in the Southeast. 

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