https://www.facebook.com/mario.arque.3/posts/1768913503267162

What sky did Sebastien Kayrouz have for his 503 km flight last
Thursday in Texas? It's what someone asked when they saw the photo celebrating
the flight with a clear sky at dusk. Did he make that flight with blue thermals?

No, thanks to NASA's archive, from its Worldview page, we can go back to that
day and see photos of the three satellites that passed by there at noon one
after another (the Terra, Aqua and Suomi NPP VIRS). They follow a helio
synchronous orbit, so every day they pass at the same time over all points of
the planet with a difference of time between them.

Around one in the afternoon the photo shows tropical storm Cristobal and that
jet planted with streets of clouds, drawing a curious wind divergence as that
wind spread through Texas (part of the wind turns to the Gulf of Mexico) and the
upper half feeds that southern wind jet that took advantage to make this record.

Surface pressure maps for that NOAA day, also available for previous dates on
the Storm Prediction Center page, show how the south wind increased to 15-25
knots in its second half over the day of the flight, while in the takeoff area
and earlier, the wind was weaker and more variable, maximum of 5-10 knots.

Obviously this is not a typical day in Texas what with a tropic
storm over Louisiana. On the good cross country days out of Zapata you want a
high pressure located south of New Orleans and rotating clockwise winds bringing
a south southeast flow by Laredo with cloud streets lined up from Zapata to
Amarillo.

In this case there was a strong south southwest wind to the west of the tropical
storm. That was happening in the area without any clouds as is the case with
south southwest winds there in west Texas as the air is coming from over the dry
areas in Mexico. But the moisture was coming from the east from the tropical
storm and the two air masses met just to the west of his route. Pretty
convenient as he could still fly the cumulus clouds with the south southwest
wind.

https://www.spc.noaa.gov/