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Sometimes check and double check is not sufficient.

Regretfully it now appears certain that the weather station closest the track (Speedworld) last Saturday, 1/21, was giving erroneous barometric data, thus skewing adjusted track times. That weather station, the DaimlerChrysler Arizona Proving Grounds, Wittman, AZ site, shows a very low barometric reading relative to official weather stations in the valley, as I examine it now. It appears to have been registering low readings for as far back as I have checked.

Ironically, the next closest weather station, Circle City, AZ, which I called up to verify the unusally low baro setting which the Chrysler site was showing, showed surprisingly similar numbers. Accordingly, I considered the original numbers from Chrylser Proving Grounds validated.

As it turns out, unbeknownst to me, both stations derive their data from a common site, a site with a calibration error in its barometric pressure calculator. Thus my verification attempt was ineffective at catching the error. That second weather station, Circle City, AZ, can be found here: http://www.wunderground.com/cgi-bin/findweather/getForecast?query=circle+city Browse down to Station's History to view weather data for any given date.

Here is the 1/21/06 weather printout from the common Wittman, AZ weather station, used by both the DaimlerChrysler Arizona Proving Grounds and by Circle City weather station sites (see thumbnail, below).

The resultant erroneously high Density Altitude (DA) generated a larger-than-normal correction factor, causing the corrected numbers to appear better than they really are.

While DA-compensated times remain the only way to achieve anything approaching a common reference for the purpose of comparing times, the need for accurate barometric data, in particular, has been amply demonstrated. A cross-check of values vs. the nearest official station is a must.

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So what are the real corrected numbers for the best pass of the day?

Due to the large variation in baro data between the local weather stations in the area noted when checking just now, and the lack of available historical weather data from the nearest official weather station, Luke Air Force Base, I've recomputed DA simply using the Standard Day altimeter setting of 29.92 to just get the numbers in the ball park. Using 29.92 gives a DA of 1877', with adjusted values of 13.636 @ 103.950, nice, but well off the numbers the erroneous high DA had generated.

Finally, let's not lose sight of the fact that the time slip numbers, 3 passes in a row, were in the outright 13s. Here is the fastest of those three: 13.936 @ 101.663
 

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Works for me! No matter how you slice it moving this much weight in such a short period of time is impressive.
 
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