Academy › Weather for canopy pilots

Weather for canopy pilots

The wind gradient near the ground, gusts, turbulence and thermals, the sea breeze at coastal drop zones, density altitude, reading the windsock and winds aloft — with an interactive gradient lab, a density-altitude explainer and a quiz.

Practise every drill high and only with your coach and S&TA's agreement. Nothing here is a turn height, a technique to try near the ground, or permission to progress. There is no requirement for any skydiver to swoop.

The wind gradient near the ground

Wind is weaker near the surface than a little higher up. Drag the surface wind, pick the terrain, and watch the canopy's ground speed change as it descends through the profile on final.

higher ↑lower ↓relative height — a generic profile, not altitudeswind speed →ground speed on final →backwardsforwardsairspeed
Wind where the canopy is
21 km/h
surface 14 km/h · up high 21 km/h
Over the ground right now
23 km/h
airspeed − headwind at this height
Change from high to surface
+6 km/h over the ground
the final speeds up as the wind fades
What's happening

Friction with the ground slows the wind, so it is usually weaker near the surface than a little higher up — the wind gradient. The windsock shows only the bottom of that profile. Over rough ground (trees, hangars) the gradient is steeper and bumpier; over water or a beach it is flatter.

Flying into the wind, ground speed is airspeed minus the headwind. As the canopy descends into weaker wind the headwind fades, so the final speeds up over the ground even though the airspeed stays the same. While the wing drops through the change it briefly loses a little airspeed before it settles again — the reason a final through a strong gradient can feel like the wing sinks.

Wind gradient
SkyLara explanation — general meteorology and aerodynamics, not from the sources above
What published guidance says

Conceptual: a textbook power-law profile over a relative height axis. Real gradients vary with the day, the terrain and the hour; this is not a pattern altitude or a landing direction.

Gusts, turbulence and thermals

Gusts and lulls, the rolling air downwind of hangars and trees, and the thermals of a hot afternoon — what each does to the wing.

windrotor downwind of the hangar — many times its heightthermal over tarmacConceptual side view — not to scale
Gusts and lulls

A gust is a short-lived rise in wind speed; a lull is the opposite. A headwind gust briefly adds airspeed (the wing floats or climbs a little); a lull takes airspeed away, and the wing sinks until it re-accelerates. The spread between the steady wind and the gusts — not just the average — is what makes a day feel bumpy on final.

SkyLara explanation — general meteorology and aerodynamics, not from the sources above
Mechanical turbulence and rotor

Wind flowing over hangars, buildings, tree lines and hills breaks into rolling eddies downwind of them. The rolling air can reach many times the obstacle's height downwind and can take pressure and airspeed from the wing.

Turbulence / rotor
Source: Skydivemag — Know your wind limits, part 2 (Pete Allum, Flight-1) ↗
Thermals

On sunny days the ground heats unevenly: tarmac, dark roofs and dry fields warm faster than grass, crops or water. Warm air rises over the hot patches and sinks around them, so the same final can lift the wing one minute and sink it the next — most of all in the early afternoon.

SkyLara explanation — general meteorology and aerodynamics, not from the sources above
What published guidance says

The sea breeze at coastal drop zones

Why the wind at a drop zone by the sea often turns onshore during the day — and what that means at Skytime, Castellón.

sealand — warmersea breeze at the surfacereturn flow higher upConceptual — the real timing depends on the day
What's happening

Land warms and cools faster than the sea. On a sunny day the air over the land heats, rises, and is replaced by cooler air flowing in from the sea: a sea breeze, often setting in late morning and strengthening into the afternoon, roughly at right angles to the coast. At night the pattern can reverse into a weaker land breeze.

At a coastal drop zone this means the surface wind — and with it the landing direction — can change during the day, sometimes within the hour you spend on a load. The winds aloft may keep blowing from a different direction entirely.

SkyLara explanation — general meteorology and aerodynamics, not from the sources above
At Skytime (Castellón)

Skytime's landing area sits by the Mediterranean, so a sea breeze is an everyday feature there. The drop zone's briefing names its patterns by the wind direction; which one applies is decided on the day by the drop zone, not by this page.

Practice pack: Skytime · Drop zone directory

Density altitude — hot and high air

Move the temperature and the field elevation to see how thin air changes true airspeed and descent rate for the same canopy and the same flare.

Density altitude
0 ft
0 ft above the field's elevation
Air density
100% of standard
standard = 15 °C at sea level
True airspeed and descent rate
no change
same flare, same equivalent airspeed
What's happening

Hot or high air is thinner. A wing makes lift from the air it pushes on, so in thin air it has to move faster through the air to make the same lift: everything the canopy does — full flight, the flare, the descent — happens at a higher true airspeed, and therefore faster over the ground, even in the same wind. The flare feels the same in the hands; the ground arrives sooner and the run-out is longer.

Density altitude is a way of saying how thin the air is: the altitude in the standard atmosphere that has the same density. A cool morning and a hot afternoon at the same field can sit thousands of feet apart on that scale.

SkyLara explanation — general meteorology and aerodynamics, not from the sources above
The formula used here

DA = PA + 120 × (temperature − ISA temperature at PA)
ISA temperature = 15 °C − 1.98 °C per thousand feet
true airspeed ∝ 1 / √(air density ratio)

The same rule the Pre-jump planner applies to the day's weather at your drop zone (pressure altitude is taken as the field elevation here; the planner uses the actual pressure).

Pre-jump planner · Winds aloft

The windsock, wind limits and winds aloft

Reading a windsock, why the wind limit is the drop zone's call, and how the winds aloft at opening differ from the surface wind.

Reading the windsock
hanging: light airhalf out: moderatestraight out: strong

The wide end of the sock faces into the wind; the narrow end points where the wind is going — so landing into the wind means landing toward the wide end. The angle gives a rough speed: hanging means light air, straight out means a strong wind. A standard aviation sock stands fully out at roughly 15 knots; drop-zone socks differ, so learn what yours does. Several socks around the landing area that disagree with each other, or one that keeps swinging, are telling you about gusts and turbulence.

SkyLara explanation — general meteorology and aerodynamics, not from the sources above
Wind limits are the drop zone's call

Every drop zone sets wind limits for students and for licensed jumpers, and the staff on the day decide whether the wind is within them. A limit is a maximum, not a recommendation: how the air feels on your canopy, the gust spread and the turbulence around the landing area are a separate conversation with your coach and the S&TA.

Winds aloft vs the surface

The wind at opening altitude is often stronger than at the surface and can blow from a different direction. It decides the spot, how far the canopy drifts before the pattern, and which way a long spot has to be flown; the surface wind decides the landing direction. The two are not the same forecast, and on a sea-breeze day they can even oppose each other.

Your jump page shows the surface wind and the modelled winds aloft at your opening next to the opening itself; the Winds aloft page shows the day's profile for a drop zone. Winds aloft · Analyse your FlySight jumps

Weather quiz

Ten questions on the gradient, turbulence, the sea breeze, density altitude and the windsock — every answer explains itself.

Question 1 of 10 · score 0

Descending through a wind gradient into a headwind, what happens to the canopy's speed over the ground on final?

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Safety notice: This tool is for data review only. It does not replace canopy coaching, DZ rules, traffic awareness, S&TA guidance, or manufacturer guidance. Everything here is information for learning — not advice or a recommendation about any canopy, wing loading, turn or decision. Your decisions are your own. See the Terms of Service.