How do I use winDZaloft quickly on a jump day?

Select a dropzone (or type coordinates in the search box), keep Auto sources unless you need a manual override, tap Get Winds, then read surface and gusts first before checking canopy and exit layers. Use jump run and drift cards as planning aids, and always verify timestamps and alerts.

What does Issued, Valid, and freshness mean?

Issued is when weather data was produced, Valid is when a forecast is intended to represent conditions, and freshness indicates how old the loaded data is. These indicators help users avoid relying on stale weather.

What is jump run and drift in the app?

Jump run is the suggested line of flight based on loaded wind layers, and drift is an estimate of horizontal movement during freefall. They are practical planning aids for spotting and load organization, not guarantees.

How do you calculate parachute wing loading?

Parachute wing loading is commonly calculated as full exit weight divided by canopy size in square feet. Exit weight should include the jumper, rig, clothing, helmet, lead, camera equipment, and other jump gear.

Does wing loading alone tell you whether to downsize?

No. Wing loading is only one part of canopy choice. Downsizing decisions should also consider currency, landing consistency, wind judgment, traffic awareness, instructor input, DZ policy, and manufacturer guidance for the exact canopy model.

How do skydivers calculate drift and wind components?

A simple drift estimate can be made from wind speed multiplied by time, with appropriate unit conversion. Headwind and crosswind components come from resolving wind speed against a planned course using cosine and sine of the angle difference between wind direction and course.

How do you read a winds aloft (FD) report?

Each FD group gives direction, speed, and temperature. In 2438+12 the first two digits are the direction in tens of degrees true (240°), the next two are the speed in knots (38 kt), and +12 is the temperature in Celsius. 9900 means light and variable, under 5 kt. A direction code of 51–86 means the wind is 100 kt or more: subtract 50 from the direction and add 100 to the speed, so 7310 is 230° at 110 kt. Above 24,000 ft the minus sign on the temperature is dropped. Heights are above sea level, so subtract the field elevation to get AGL.

How to Use winDZaloft | Skydiving Weather Guide

How to use the website

1

Select your dropzone or airport. The main selector chooses the location the weather is centered on. You can also type in the search box to filter the list by name, state or province, or country. The GPS button (crosshair icon) will find and select the nearest dropzone to your current location automatically if you allow location access.

Not on the list? Type coordinates. The search box also takes a location anywhere in the world, in any of these formats:

MGRS: 47PNR9953057335 or 47P NR 99530 57335
Decimal latitude, longitude: 14.0851, 99.9220
Degrees, minutes, seconds: 14°05'06"N 99°55'19"E

A 📍 Custom point appears at the top of the list. Pick it to load winds for that spot. Custom points always use Open-Meteo forecast models (Auto, ECMWF, or GFS), with the elevation and local time of the point itself. They don't use airport stations, so there's no METAR, TAF, or NWS data for them. The point stays selected when you refresh, and the page address (?pt=…) can be bookmarked or shared to open the same spot.

2

Choose weather sources only if you need to. The default Auto options are meant to be the easiest starting point. Tap Advanced to reveal controls for aloft source, surface source, cloud source, and station overrides. Use these only when you want to compare another source or force a specific station.

3

Tap Get Winds. The table, planning cards, compass, and weather summary all update together for the selected dropzone. A source row below the table header shows which provider is active for aloft, surface, and cloud data.

4

Read the surface tiles and compass first, then the exit altitudes. The four summary tiles (Surface, Canopy, Exit Otter, Exit Cessna) give you a quick status at the altitudes that matter most. The compass shows surface wind direction at a glance. Then scan the table rows from the bottom up to see how the wind changes through the skydive.

5

Use the Forecast button for a combined hourly table. The Forecast button in the location card opens a multi-hour view so you can see how conditions are expected to change through the day. The Radar button opens an embedded weather radar centered on the DZ. Call Manifest launches a phone call to the DZ manifest line if a number is available.

6

Check the timestamps before trusting the picture. The Issued, Valid, and freshness indicators on the source row tell you how current the data is. Never rely on weather that is several hours old without refreshing.

7

Night Ops mode. The Night Ops button in the top bar switches the display to a red-light-friendly dark mode that is easier on night-adapted eyes at the DZ after dark.

8

Share a direct link to your dropzone. Once a DZ is loaded, the share link button (chain link icon) copies a URL that opens winDZaloft with that same dropzone pre-selected. You can send it to your team or save it as a bookmark.

What the weather sources mean

winDZaloft pulls from several weather sources, and they aren't all the same kind of data. Some are observations (what the wind is doing right now), some are forecasts, and some are computer models. Here's what each one is and what it's good for.

NOAA / AWC FD Winds Aloft

The classic aviation winds-aloft forecast from NOAA's Aviation Weather Center. It gives wind direction, speed, and temperature at set altitudes for a network of stations. When there's a station reasonably close to your DZ, this is the main source for upper winds and jump planning.

How to decode a raw FD winds aloft report

The raw FD (also called FB) product is a table of coded groups, one row per station and one column per altitude: 3,000, 6,000, 9,000, 12,000, 18,000, 24,000, 30,000, 34,000, and 39,000 ft. Each group packs direction, speed, and temperature into a few digits:

Standard group: 2438+12 means wind from 240° true at 38 kt, temperature +12°C. The first two digits are the direction in tens of degrees, the next two are the speed in knots, and the rest is the temperature in Celsius.
Light and variable: 9900 means the wind is light and variable, under 5 kt.
100 kt or more: the forecaster adds 50 to the direction code, so a direction of 51–86 means subtract 50 from the direction and add 100 to the speed. 7310 is 230° at 110 kt.
No temperature at the lowest level: the 3,000 ft group, and any level within 2,500 ft of the station's elevation, has no temperature. Levels within 1,500 ft of the station's elevation are left blank.
No minus sign up high: above 24,000 ft temperatures are always below zero, so the sign is dropped. 286045 at 30,000 ft is 280° at 60 kt, −45°C.
Heights are above sea level, not above the ground: subtract your field elevation to get AGL. At a DZ that sits at 1,000 ft, the 6,000 ft level is about 5,000 ft above the landing area.
Directions are where the wind comes from, in degrees true. Multiply knots by 1.15 for mph.

winDZaloft decodes all of this for you: it shows the levels as AGL for your dropzone, uses forecast models where no winds-aloft station is close, and turns the winds into a jump run and drift estimate. Open the app and pick your dropzone.

METAR

An airport weather observation, not a forecast. METAR stands for Meteorological Aerodrome Report. It's the best quick look at current surface wind, gusts, visibility, and ceiling. Keep in mind the reporting airport may be a few miles from your landing area, so the wind on your field can be different.

TAF

A Terminal Aerodrome Forecast is a forecast for a specific airport. It's most useful for expected ceilings, visibility, and how the airport's weather should change over the next day. It doesn't cover winds aloft.

NWS Hourly and NWS Alerts

The National Weather Service hourly forecast for the DZ's exact location: surface wind, gusts, temperature, cloud cover, and rain chances. The alerts feed shows any active warnings, watches, or advisories for the area, like thunderstorm or wind warnings.

Forecast models: Auto, HRRR, NAM, GFS, and ECMWF IFS

Models are computer forecasts. They're useful for comparison, for seeing how the day will develop, and for DZs that don't have a winds-aloft station nearby. Treat them as guidance, not exact truth.

Auto: the default in both the aloft and surface menus. It automatically picks the best available forecast model for the dropzone's location, in the US or anywhere else, and returns a full wind profile.
HRRR (High-Resolution Rapid Refresh): NOAA's high-detail short-range model, updated every hour. Usually the best model for today's winds in the US.
NAM (North American Mesoscale): a NOAA model that's useful for comparison and for looking a bit further ahead. Available in the surface menu.
GFS (Global Forecast System): NOAA's global model. It's lower detail, but it works anywhere in the world.
ECMWF IFS (European Centre for Medium-Range Weather Forecasts, Integrated Forecasting System): the European global model, often rated the most accurate global model. It works anywhere in the world and is a good cross-check against GFS, especially outside North America.

NBM

The National Blend of Models is NOAA's blend of many models into one forecast. In winDZaloft it's mainly used for cloud bases and general forecast context. Picking NWS NBM in the aloft or surface menu takes the winds from the Auto model and the cloud base from NBM.

Cloud source menu

Clouds can come from a different source than your winds. The cloud menu lets you pick:

Auto: uses the best cloud base available for each hour, in this order: NBM, the airport TAF, the current METAR, then the model estimate. Works anywhere.
Global Model Cloud Base: a cloud base estimated from the forecast model's temperature and dew point, shown with a ~ and labeled Model (est.). It's only shown when the model expects enough low cloud to form a ceiling. When there's no estimate, it falls back to the TAF or METAR. Works anywhere.
NBM Cloud Base (NWS blend): the National Blend of Models cloud base for the nearest major airport or the DZ itself. The default in the US.
TAF Cloud Ceiling: the ceiling from the airport's TAF forecast, falling back to the current METAR when the TAF has none
TAF Lowest Cloud: the lowest cloud layer of any coverage in the TAF, even if it isn't a ceiling, with the same METAR fallback

NBM and the two TAF options are US-only, so they're hidden when you pick a dropzone outside the US or a custom point from coordinates. Auto and Global Model Cloud Base work everywhere.

The Cloud Airport selector lets you choose which airport to use for airport-based cloud data.

It's normal for a DZ to use one source for winds aloft and another for surface wind. Every number is labeled with where it came from, so you can compare observations against forecasts instead of assuming they all mean the same thing.

Get familiar with the interface

Here's what the main parts of the app look like. These examples use made-up weather, but the layout and labels are the same as the real thing.

Drop Zone or Airport

Skydive SkyJunk, DZ

Skydive SkyJunk, DZ · Elev 1,413 ft MSL

33.761 N -117.218 W 1,413 ft MSL

Surface Wind

N S E W

240deg at 14 kt G22
Surface

Surface

14G22 kt

Speed · Gust

Canopy (3k)

21 kt

Around opening alt

Exit (Otter 13.5k)

34 kt

Suggested turbine DZ exit

Exit (Cessna 10.5k)

29 kt

Suggested Cessna DZ exit

Winds Aloft Forecast

Aloft: NOAA/AWC (FD) Surface: METAR Cloud: Auto AGL Issued: 14:30Z

Altitude	Speed	Gust	Direction	Temp (degF)	Layer
1,000 ft	12 kt	18 kt	210deg	61	Surface
6,000 ft	24 kt	N/A	233deg	43	Freefall
12,000 ft	36 kt	N/A	246deg	21	Exit

These are example screenshots built from the real app layout, so you'll know where everything is before you look at live data.

Issued, valid, and freshness

Not every weather source updates the same way. That is why the timestamps matter.

Issued

When the forecast or report was produced

Valid

When the forecast is meant to represent conditions

Freshness

A quick visual cue for how old the loaded data is

Next Update

When a newer cycle is expected to appear

NOAA winds aloft are published in scheduled forecast cycles, not minute by minute. Surface observations and hourly forecasts behave differently. The safest habit is to always look at the timestamps before treating the display as current.

How to read the weather on the page

Altitude rows and the AGL/MSL toggle

By default, altitude rows are shown in feet AGL (above ground level), referenced to the selected dropzone's elevation. This means the row labeled 3,000 ft is approximately 3,000 ft above the DZ, which is the number most skydivers think in. You can switch to MSL (above sea level) using the Units menu above the table, or the Altitude selector in the forecast summary bar, if you prefer or need to cross-check against aviation sources that use MSL.

Units menu

The Units button above the table header opens a panel with four display toggles:

Altitude: AGL (above ground level, the default) or MSL (above sea level). AGL is what skydivers typically use. MSL matches what NOAA winds-aloft charts show.
Height: FT (feet, the default) or M (meters). Changes how altitudes are labeled, for jumpers who think in meters.
Speed: KT (knots, the default and standard for aviation weather), MPH (miles per hour), or M/S (meters per second). Choose the unit you think in.
Temp: °F (Fahrenheit, US default) or °C (Celsius). Temperature is shown in the table for altitude layers when the data source provides it.

Your unit preferences are saved between sessions.

Simple View and Combined View

Two table layout modes are available via the toggle above the winds table:

Simple View: one column of altitude rows with wind direction, speed, and temperature. Fastest to scan, best for a quick jump-day check.
Combined View: expands to show multiple forecast hours side by side so you can see how the wind profile is expected to change through the day.

Direction

Wind direction follows aviation convention, so it tells you where the wind is coming from. A 270° wind means the wind is coming from the west and moving toward the east.

Speed and gust

Wind speed is the steady wind. Gust is the higher peak value when it is available. If gust is not reported or not available from the selected source, the site will show N/A.

Compass rose

The compass card shows surface wind as an arrow pointing the way the wind is blowing to, like a windsock streaming downwind. A north wind (360°) shows an arrow pointing south. The readout underneath gives the direction the wind is coming from in degrees, plus speed and gust.

Summary tiles

Four quick-status tiles appear below the compass:

Surface: sustained wind and gust at ground level.
Canopy (3k): winds at about 3,000 ft AGL, around opening altitude. This is the wind you'll fly in for most of the canopy ride before you set up your pattern.
Exit (Otter 13.5k): winds near the common turbine DZ jump altitude.
Exit (Cessna 10.5k): winds near the common Cessna DZ jump altitude.

The tiles use the same colors as the full table, so you can get the big picture at a glance before reading every row.

Wind speed color guide

Simple vertical guide using the same color meaning as the live weather cells.

Surface wind and gust (mph)

0-10Calm band

11-14Light band

15-17Moderate band

18-23Brisk band

24+Extreme band

Aloft rows (kt)

0-10Calm band

11-20Light band

21-30Moderate band

31-40Brisk band

41+Extreme band

Blue bands are lower wind speeds, yellow is moderate, orange is brisk, and red is the strongest band. These colors are a fast visual cue, not a universal go/no-go rule.

Surface, canopy, freefall, and exit layers

Layer	Why to check it
Surface	Ground wind, gusts, and landing-area awareness
Canopy	Pattern and post-opening wind picture
Freefall	Mid-skydive drift and movement through the working air
Exit	Upper-wind influence near jump run and exit altitude

USPA-aligned weather technical briefing

A quick summary of the weather and spotting basics covered in USPA training. It's a study aid, not a replacement for the SIM, your DZ's procedures, or your instructors.

Core wind math skydivers should know

Unit conversion: 1 kt = 1.6878 ft/s = 0.5144 m/s
Drift distance (feet): drift_ft = wind_kt * 1.6878 * time_sec
Drift distance (nautical miles): drift_nm = wind_kt * time_sec / 3600
Groundspeed vector idea: aircraft or canopy track is the vector sum of airspeed and wind.

Weather interpretation priorities before a load

Confirm data age and validity window (issued/valid/freshness).
Check surface sustained wind, gust spread, and direction trend.
Check canopy and freefall layer changes (speed and directional shear).
Check cloud/visibility/precip and active hazards or alerts.
Compare against DZ wind limits, student limits, and aircraft/operations constraints.

Technical references

The USPA SIM is copyrighted by USPA. This is an original summary written for this site. Always study the current official SIM.

Companion tools

Two standalone calculators, linked from the footer on every page:

Jump Run & Drift calculator — enter a wind speed and direction, your freefall time, and a course to get freefall drift plus headwind and crosswind components. It also works out exit separation between groups from the plane's groundspeed. Handy for spotting practice and load planning.
Wing Loading calculator — enter your body weight, gear weight, and canopy size in square feet to get your wing loading in lb/sq ft and kg/m², with notes on safe downsizing.

Important limitations

winDZaloft helps you read the weather. It doesn't make the go/no-go call for you.

Winds aloft are a forecast, not a live measurement.
The nearest airport can have different wind than your landing area. Terrain, distance, and afternoon heating all make a difference.
Models can be wrong, and so can any calculation based on them. Jump run and drift numbers are estimates.
Your S&TA, instructors, DZ procedures, and the pilot always have the final say.