Message posted by JB737 on May 25, 2007 at 18:06:51 PST:
In the "more info & photos" section of DLR, under "Radio Beacons", there is a "Groom Lake VOR" recording made on 8/7/2005 around 7pm from Tikaboo Peak. It states that the Morse Code identifier is "MCY for Mercury?" and the weather report only says "local" for the location. I listened to the recording, then input the weather parameters into a density altitude calculator, after appropriate conversions of units (some are English, some Metric, etc.) I used the calculator at http://wahiduddin.net/calc/calc_da.htm It shows that the weather report is for a location at approximately 4345 feet elevation. Because the density altitude ("six niner hundred") was presumably rounded to the nearest 100 feet, the accuracy would similarly be only to about 50 feet, even if all the other parameters were absolutely accurate, which of course they probably are not. More precisely, a parametric study using the density altitude calculator shows that if the given density altitude of 6900 was simply a precise rounding to the nearest hundred, a field elevation between 4304 and 4386 would be implied. And if they used truncation rather than rounding, then an elevation up to 4426 would also give 6900 density altitude. But there are other uncertainties, including that the weather station might not be at the same elevation as the runway, plus there is roundoff or truncation on temperature, dewpoint, and altimeter settings...so I'd add another 50 or 100 feet of tolerance, and say it might have been a forecast for any location between 4200 and 4500 feet elevation. The Groom Lake runways, according to Google Earth, are between 4438 and 4482 ft elevation. BINGO! It pretty well rules out Mercury, NV, whose elevation is generally given as 3310ft (e.g., per noaa.gov), while Wikipedia shows Desert Rock Airport serving Mercury as being at 3314 ft. And to make matters even nicer, I couldn't find any other airport in NV much closer than Reno, with an elevation in the right ballpark. Congrats to whoever recorded this weather report. It appears to have been the real deal, an automated weather report for Groom Lake. JB737
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