How do I use winDZaloft quickly on a jump day?

Select a dropzone, 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 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 or state. The GPS button (crosshair icon) will find and select the nearest dropzone to your current location automatically if you allow location access.

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 can combine several weather sources. Here is the short version of what each one is and what it is mainly used for in the app.

NOAA / AWC FD Winds Aloft

This is the classic aviation winds-aloft forecast text product from the Aviation Weather Center under NOAA. It is mainly used for upper-wind direction, speed, and temperature at altitude.

METAR

This is an airport weather observation, not a forecast. METAR stands for Meteorological Aerodrome Report. In the app it is typically delivered through NOAA aviation weather feeds. It is mainly used for current surface wind, gusts, visibility, ceiling, and basic flight-category context.

NWS Hourly

This is the National Weather Service hourly forecast for a point on the map, provided by NOAA's National Weather Service. It is forecast guidance for surface conditions such as wind, gusts, temperature, cloud cover, and precipitation chances.

NWS Alerts

This is the National Weather Service alert feed for the selected area, provided by NOAA's National Weather Service. It is used to show active warnings, watches, advisories, and other weather headlines that may matter to jump operations.

Open-Meteo Auto

This is the app's fast model-based default for many locations, delivered through Open-Meteo. It is used to provide quick profile-style winds and weather context when a model-backed view is more useful than raw aviation text.

HRRR

The High-Resolution Rapid Refresh model is a short-range forecast model from NOAA's National Centers for Environmental Prediction. It is often useful for near-term wind trends and shorter-range jump-day checks.

RAP

The Rapid Refresh model is a fast-updating short-range forecast model from NOAA's National Centers for Environmental Prediction. It is useful for near-term conditions and is sometimes used when HRRR coverage or behavior is not ideal for a location.

NAM

The North American Mesoscale model is another forecast model from NOAA's National Centers for Environmental Prediction used for broader forecast guidance. It can be useful for comparison, especially when looking beyond the most immediate short-range window.

NBM

The National Blend of Models combines guidance from multiple forecast models and is produced by NOAA. In winDZaloft it is mainly used as a blended weather source for cloud and forecast context rather than a single raw observation source.

TAF

A TAF is an airport forecast written for aviation use. TAF stands for Terminal Aerodrome Forecast. In the app it comes through NOAA aviation weather feeds. It is mainly useful for forecast ceiling, visibility, and general airport weather expectations rather than direct winds-aloft planning.

No single source is perfect. The app labels sources so you can compare observation-based data and model-based guidance instead of assuming every number means the same thing.

Get familiar with the interface

These static examples mirror the key areas you use in the app. They do not update or pull live weather, but the layout and labels match what you will see on jump day.

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

Typical pattern 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 static snapshots using the live UI structure and styles so your eyes can learn the exact layout before briefing actual data.

What the weather sources mean

The site can show information from more than one weather source. That does not mean they are all the same kind of data. Each source answers a different question.

NOAA/AWC winds aloft

This is the classic winds aloft forecast used in aviation. It is best for the upper-wind picture and is the main source for jump planning when nearby station coverage is good.

Surface observations (METAR)

This is current observed weather from an airport station, including wind and gusts when they are reported. It is the best quick look at what the ground wind is doing near the selected dropzone, but it may still be a few miles away from the actual landing area.

NWS hourly forecast and alerts

This helps with near-term weather awareness. It is useful for things like rain chances, cloud cover, expected gusts, and active advisories or warnings near the dropzone.

Model sources such as GFS, HRRR, NAM, and Open-Meteo

These are forecast models. They are useful for comparison, short-range planning, or locations where a nearby winds-aloft station is not ideal. They should be treated as guidance, not as exact truth.

Cloud source menu behavior

Clouds can be sourced independently from the aloft and surface wind sources. The cloud menu enforces the cloud mode directly:

Auto: blended cloud-base strategy using available upstream sources
Strict NBM: NBM airport/DZ grid only
Strict Model: model cloud-base field only
Strict TAF: TAF cloud layers only

The Cloud Airport selector lets you force the airport reference used for airport-based cloud sourcing workflows.

A dropzone can use one source for aloft winds and a different source for surface winds at the same time. That is normal. winDZaloft combines those pieces into one weather picture while still showing clear source labels.

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 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 three 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.
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 the surface wind direction as an arrow pointing toward the origin of the wind. If the arrow points north, the wind is coming from the north. The readout below shows degrees, 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 approximately 3,000 ft AGL, the typical canopy pattern altitude.
Exit (Otter 13.5k): winds near the common turbine DZ jump altitude.
Exit (Cessna 10.5k): winds near the common Cessna DZ jump altitude.

These tiles use the same color bands as the full table and give you the critical snapshot before you read the full wind profile.

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

This section summarizes the kind of technical weather and spotting concepts skydivers are expected to learn in USPA training pathways. It is not a replacement for the official USPA SIM text, DZ SOPs, instructor guidance, or pilot-in-command decisions.

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_hours
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

USPA Skydiver's Information Manual (SIM)
USPA SIM Online (mobile-friendly)
USPA downsizing guidance
Skydive Mag downsizing article
Manufacturer owner's manual and published wing-loading guidance for the exact canopy model
14 CFR Part 105 (Parachute Operations)
NOAA Aviation Weather Center (AWC)
National Weather Service (NWS)

Copyright note: USPA SIM is copyrighted by USPA. This page provides an original summary and training aid only. Always study and apply the current official USPA SIM and your local DZ procedures.

Companion tools

winDZaloft includes two standalone tools accessible from the footer on any page:

Jump Run & Drift calculator — enter your exit altitude, freefall time, and wind layers to estimate horizontal drift, suggested jump run heading, and exit offset. Useful for spot planning, load organization, and jump-course preparation.
Wing Loading calculator — enter your exit weight and canopy size in square feet to see your wing loading. Includes a reference chart and context for understanding what different loading numbers mean at different experience levels. Not a go/no-go tool — just a reference.

Important limitations

winDZaloft is an informational and prediction aid, not a go/no-go recommendation engine.

Forecast winds aloft are not the same as real-time winds at every second.
Airport observations may not exactly match the landing area at the dropzone.
Terrain, distance, and local heating can create real differences from the nearest station.
Model guidance can be useful, but models can also be wrong.
Jump run and drift outputs are planning estimates, not guarantees.
Any forecast-based calculation can be wrong and must not be treated as operational authorization.
Always defer to the S&TA, instructors, local procedures, and the pilot in command.

Safety thresholds, summaries, and predictions in the app are data-based outputs only. Always use local judgment and direct DZ weather evaluation before making a jump decision.