20 October, 2008

Elizabetha Sets a New World Record

Yesterday, Elizabetha flew from the New Jersey coast to Florida, a distance of 954 miles. To our knowledge, this is a new world record for distance flown by a migrant peregrine in a single day.

Don McCall writes

"This is almost unbelievable. Between yesterday morning's GPS signal at 0500Z and this morning's signal at 0600Z (more about the 1-hour time shift below), Elizabetha has flown an astounding 1535 km (954 mi). Assisted by a strong tailwind, she has covered 2,279 km (1,416 mi) in 49 hours, and is now in Florida about midway between Orlando and Miami. So much for spotting her enroute.

Of course I wondered if there was an error in the data so it's been checked and double-checked. There is a confirming Doppler signal (entirely different technology and different calculations from GPS) at 0703Z that exactly matches her GPS position at 0600Z, so there's no mistake. In an attempt to understand how this distance was achievable, I accessed the current winds analysis chart (used by pilots all over the country) from the National Oceanic and Atmospheric Administration (NOAA) Aviation Center -- a copy is attached. The one that I downloaded was for surface winds at 0800Z but that would give a fair indication of the wind conditions for most of the time that Elizabetha was flying. This wind chart combines current observations around the country with the most sophisticated weather models to predict the current wind speeds and directions at various altitudes (including locations offshore where there are no reporting stations). All the arrows on the chart depict the wind direction at each location, and the number of tufts in the tailfeathers depicts the speed; e.g., 2 large hashes and a small one indicates 25 knots, or about 29 mph (46 kph). Also, a legend at the bottom of the chart shows the range of wind velocities according to map color.

What's obvious from this chart is that Elizabetha has been getting quite a ride on her journey down the eastern seacoast for the past couple of days. A low pressure area just off the coast (with counterclockwise rotation) has generated strong northerly winds (FROM the north) to the west of the low pressure area, and along Elizabetha's route. Assuming that the low pressure area is moving eastward and that Elizabetha was even closer to the center for the past day or two than her current location would indicate, it's reasonable to surmise that she's had tailwinds of at least 15-20 knots (perhaps 25-30 knots) for all or most of the past two days (1 knot = 1 nautical mile per hour = 1.15 miles per hour). So, for a quick reality check, here's a fictitious example: if she's airborne for 15 hours with a normal flying speed of 40 mph, and is boosted by a 20 knot (23 mph) tailwind, she would cover 945 miles. So, it could happen. Also, note that the winds at Elizabetha's flying altitude (800 meters is not unusual) would be somewhat higher than the surface winds shown on the chart. It's also interesting to note that the northerly wind direction down the east coast, then veering to the northeast approaching Florida, closely approximates Elizabetha's known track. We'll never know when or where she made landfall between Maine and Florida, but with those winds she certainly had plenty of time to rest or hunt along the way and still cover the known distance.

Regarding that 1-hour time shift in the GPS reporting times -- the Argos system does this automatically to account for changes in longitude, so that the reporting times stay approximately the same in LOCAL time. On today's updated map, there are GPS fixes for 19 Oct at 2100Z and again at 2200z, indicating that one of these time shifts has occurred. Our overnight signal for Elizabetha is now at 0600Z instead of 0500Z."

Thanks for the detailed report Don. This remarkable flight deserves it. I suspect that this will be a benchmark for some time to come.