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Post by louross on Mar 7, 2010 17:58:38 GMT -5
The gauge that gives you winds aloft is reporting winds aloft as used by MS. MS gets their winds, and wx, from Jeppesen and bottom line is, that comes from the WA forecasts provided by the government. There are 3 ways that I know of to get the winds aloft: 1) an add-on gauge, 2) making a wind triangle- either with figures on paper or with a flight computer (E6B I think), or 3) most modern a/c give the actual winds thru the FMC- in FS9 that includes the PMDG 744 and the Level D 767. lr.
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Post by Tom Goodrick on Mar 8, 2010 9:34:07 GMT -5
"The gauge that gives you winds aloft is reporting winds aloft as used by MS. MS gets their winds, and wx, from Jeppesen and bottom line is, that comes from the WA forecasts provided by the government. "
Right. That is what my gauge reads and that is what our FS9 aircraft experience in flight. But NOAA's forcasts are based on some measurements at certain locations. But the measurements do not apply to all points in the sky. So, Microsoft applies some numerical interpolation to the data so that we can read particular values at any point in the sky where we happen to be flying. This process can introduce some strange effects but is a reasonable way of doing it.
Today I am going to ride my Learjet 45 around and record some wind data in one weather file downloaded today.
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Post by Tom Goodrick on Mar 14, 2010 15:54:10 GMT -5
I started a study that would take a long time to do -17 cities with wind measurements in FS9 at 10,20,30,40,50k ft. It takes me 30 minutes to get all five measurements over one city as i have to loiter near the city as I climb. I checked Tuscon and found some wind (76 knots at 40k and above) and Salt lake City and found very little (23 kts at 40k ft). I am glad I waited for info from son Scott before proceding. He was busy last week chasing after his daughter at Disney World. To get an idea of the quality of winds aloft data, go here: weather.uwyo.edu/upperair/sounding.htmlThis shows locations on a map at which upper level wind data is measured. The data is collected and displayed by the University of Wyoming under a Govt contract. One thing not shown is the frequency of measuerment: every 12 hours, typically 8 am and 8 pm local time. I jotted down several stations across the country. You can look at the map and move your mouse pointer around to get the precise locations near you. At Huntsville, AL, I am right between several places: LZK, Little Rock to the west, BNA Nashville to the north, BMX near Birmingham to the south and FFC near Atlanta to the east. South of Birmingham there is LIX Slidell to the southwest and TLH Talahassee to the east. North of Nashville ir gets a little spread out. There is ILN Wilmington OH to the northeast and ILX Lincoln IL to the north,northeast. So these are the only places wind at altitude is measured. It should be interesting to get RW and then fly between the three or four places near you while noting the wind speed and direction over various waypoints near your path. I'll check Little Rock to Atlanta and Nashville to Birmingham. The thing to look at is how smoothly the wind data change as you fly. That smoothness reflects the quality of the interpolation scheme. At these stations, wind data is measured using a balloon that caries a data package and radios data back to the station responsible for that balloon. Included in the data area altitude and position data from a GPS device. Speed and direction of motion from the GPS device are considered to represent the wind speed and direction - a reasonable assumption. This data is measured for scientific purposes using scientific units. Altitude is shown in millebars of pressure and translated into meters. You can get feet by dividing meters by .305. The data goes to about 100,000 ft. I don't recommend getting wind data from this source. The only reason I mention it is that it gives us a clue to where we can expect the wind data to be accurate. It will be fairly accurate over these locations and mathematucal guesswork everywhere else. That is not the same as forecast winds aloft. To make a forecast, you must start with the measured data and then apply computer models that take into account other atmosphere data. But we should find good accuracy in FS9 over these location. Everywhere else what we see is a product of Microsoft's interpolation scheme.
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