Low-Level Jets as "common" or "typical" (NOAA and Wikipedia)
- LLJs seem quite exotic and "rare", when you first learn of them, but they are simply wind maxima low in the atmospheric surface boundary layer ("jet" maximas occur over wing surfaces as well). They follow a general statistical pattern for self similarity across fractal scales. So just as the the entire globe is banded with major Jet Streams, at smaller scales (down to viscosity) Jets occur in proportional distributions. Wikipedia calls them "typical"-
"Low-level jets also are typical of various regions..."
NOAA's NWS Glossary uses "common" as an LLJ adjective-
"Low Level Jet (abbrev. LLJ)- A region of relatively strong winds in the lower part of the atmosphere. Specifically, it often refers to a southerly wind maximum in the boundary layer, common over the Plains states at night during the warm season (spring and summer)."
KiteLab Note- US Plains wind/elevation data brought LLJs to modern scientific fame, KiteLab has directly detected strong LLJs in various other locations (EU and US Pacific NW). Martin Bondestam documented them for kiting in Finland. George Pocock noted them in England, two hundred years ago, as well known to sailors of tall ships.
In season, a strong LLJ forms night-after-night in vast regions, and where terrain is involved, can occur most of the time.