Wind Speed Ranges
Foehn – 40 to 60 mi/hr common; up to 90 mi/hr, reported at 20 ft.
Land breeze – 2 to 3 hours after sunset, 3 to 5 mi/hr. at 20 ft.
Sea breeze – 10 to 15 mi/hr. at 20 ft.
Up-valley wind – 10 to 15 mi/hr., early afternoon and evening at 20 ft.
Upslope winds – as high as 4 to 8 milhr. at midflame height
Downslope winds – 3 to 6 mi/hr. at mid flame height
BEAUFORT SCALE FOR ESTIMATING 20-FT WIND SPEED
<3mph: Very light – smoke rises nearly vertically. Leaves of quaking aspen in constant motion; small branches sway; slender branches and twigs oftrces move gently; tall grasses and weeds sway and bend with wind; wind vane barely moves.
4-7mph: Light – trees of pole size in the open sway gently; wind felt distinctly on face; loose scraps of paper move; wind flutters small flag.
8-12mph: Gentle breeze +trees of pole size in the open sway very noticeably; large branches ofpole size trees in the open toss; tops of trees in dense stands sway; wind extends small flag; a few crested waves form on lakes.
13-18mph: Moderate breeze – trees of pole size in the open sway violently; whole trees in dense stands sway noticeable; dust is raised on the road.
19-24mph: Fresh- branchlets are broken [rom trees; inconvenience is felt in walking against wind.
25-31mph: Strong – tree damage increases with occasional breaking of exposed tops and branches; progress impeded when walking against wind; light structural damage to buildings.
32-38mph: Moderate gale – – severe damage to tree tops; very difficult to walk into wind; significant structural damage occurs.
>39mph: Fresh gale – surfaced strong Santa Ana; intense stress on all exposed objects, vegetation, buildings; canopy offers virtually no protection; wind flow is systematic in disturbing everything in its path.
Source: Fire Behavior Field Reference