Comments by "" (@jmitterii2) on "Pentagon officially released 'UFO' videos: BUSTED (Part 1)" video.
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Ground speed starts to increase or decrease greatly from winds aloft.
Even just a few thousand feet you can get a nice tailwind, and so do the birds. At near or above ten thousand feet, normal wind speed is about 30 mph. Ranges from as low as 10 mph to as high as 80 mph at 10,000 MSL.
So you can get a nice boost if that's a tailwind... or the opposite if its a headwind.
Right now, Boise wind surface is calm. Elevation about the airport is 2800 ft MSL. SO the below winds aloft at 3,000 is listed coded as 9900 meaning, that's surface winds or below elevation at this location.
At 9,000 ft MSL winds are 19 kts coming from 270 degrees (west), at 12,000 MSL winds are 35 kts at 280 degrees West by west north.
So if you're going east, you'll get a 35 kt boost to your ground speed, and so do birds or anything else in the air.
So these birds could be flying today where winds are calm at the surface, but at 12,000 MSL they would be going their unassisted airspeed of 24 mph to 37 mph plus 35kts (40 mph) = 64 mph to 77 mph at 12,000 MSL if heading direct tailwind of heading 100 east by east south.
It's really cool to see cranes and geese at high altitudes as you fly over them... was flying in Cessna 172 between 9,000 MSL and 13,000 MSL first noticed cranes just below me by about 1,000 ft... was in June and July. Was amazing.
And Hawks ride and circle thermals going well beyond 13,000 MSL sometimes, I'lll be at "high altitude" for a C172 anyways, and a hawk is circling what appears to be another 10,000 ft above.
FT 3000 6000 9000 12000 18000 24000 30000 34000 39000
BOI 9900+04 2709-04 2719-10 2835-22 2850-34 287348 287754 277654
https://www.aviationweather.gov/windtemp/data?level=low&fcst=06®ion=slc&layout=on&date=
https://sora.unm.edu/sites/default/files/journals/wilson/v070n02/p0184-p0187.pdf
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