How to Register Your Weather Station with CWOP

The Citizen Weather Observer Program — CWOP — is a joint project between NOAA, the National Weather Service, and amateur weather observers. When you register your station, it receives an official call sign and begins feeding observations directly into the models that NWS meteorologists use to build local forecasts. Your data matters most during rapidly developing severe weather, when the spacing between official ASOS stations (typically 20–40 miles) is simply too coarse to capture what's happening in between.

The CWOP documentation available from NOAA is a PDF dating from 2016. Much of the software it references — APRS+SA, UI-View — is obsolete. This guide uses the current registration process and the software actually in use in 2025.

Understanding CWOP Call Signs

Every CWOP station gets a unique call sign. There are two formats:

• CW-format: CW followed by 4 digits (e.g., CW1234). Issued to stations without an amateur radio license.
• EW-format: EW followed by 4 digits (e.g., EW4567). Also issued to non-licensed observers — this is the more recently issued format and what most new registrations receive in 2024–2025.
• Ham radio call sign: If you hold an amateur radio license, you can use your actual call sign (e.g., W5XYZ) instead. This is optional but many ham operators prefer it.

Your call sign is permanent. It's tied to your station's geographic coordinates, not to any specific hardware — so if you upgrade your station, the same call sign continues. If you move, you contact CWOP to update your coordinates.

Step 1 — Register at the CWOP Website

Go to weatherunderground.com/weatherstation/submitws.asp or the CWOP registration page at wxqa.com (the CWOP quality assurance site maintained by program volunteers). The registration form asks for:

• Your name and email address
• Station latitude and longitude (decimal degrees, to 4 decimal places — use Google Maps to find this precisely)
• Station elevation in feet above sea level (use a GPS app or topographic map — not elevation from a weather app, which is often rounded)
• Equipment type (manufacturer and model)
• Antenna/sensor height above ground in feet

After submitting, you'll receive an email with your CWOP call sign within a few minutes to a few hours (usually faster during business hours). Save this — it's your permanent station identifier.

Step 2 — Understand the APRS-IS Protocol

CWOP uses the Automatic Packet Reporting System Internet Service (APRS-IS) to receive data. This is a ham radio data protocol that was adapted for internet use. You don't need a ham radio license or any radio equipment — your station sends weather data packets over the internet to APRS-IS servers, which then forward them to CWOP and MADIS.

The key server details for CWOP submissions in 2025:

The passcode -1 is correct for unlicensed (CW/EW) stations. Licensed amateur operators use a numeric passcode derived from their call sign — but CW and EW stations always use -1.

Step 3A — Configure Ecowitt (WSView Plus)

Ecowitt gateways can push CWOP data directly without any additional software. In WSView Plus:

1. Go to your gateway's settings → Weather Services

   Same location as the Weather Underground setup. Scroll to find "Weather Observation Website" or "WOW/CWOP" — the label varies by firmware version.

2. Look for the "Customized" upload option

   Some Ecowitt firmware versions don't have a native CWOP toggle. Use the Customized server option with the CWOP server address.

3. Enter server: cwop.aprs.net, Port: 14580

   In the Station ID field, enter your CWOP call sign (e.g., EW4567). Leave the password field as -1 for CW/EW stations.

4. Set upload interval to 5 minutes (300 seconds)

   NWS MADIS systems expect 5-minute observations. More frequent uploads are not harmful but don't provide additional value to the forecast models.

5. Save and verify

   Wait 10 minutes, then check your station at findu.com/cgi-bin/find.cgi?call=YOURCWOPID to confirm data is arriving.

Step 3B — Configure Ambient Weather

Ambient Weather consoles (WS-2902 series) push CWOP data through the Ambient Weather Network dashboard rather than through a local app. Log in to ambientweather.net, go to your device settings, and look for "CWOP" under "Data Sharing." Enter your CWOP call sign. The Ambient Weather Network handles the APRS-IS connection on your behalf — you don't configure the server directly.

Step 3C — Configure WeeWX

WeeWX has a built-in CWOP extension. In your weewx.conf file, find the [StdRESTful] section and add or uncomment the CWOP block:

[[CWOP]]
    enable = true
    station = EW4567
    passcode = -1
    server_list = cwop.aprs.net:14580, cwop2.aprs.net:14580
    post_interval = 300
    stale = 600

Replace EW4567 with your actual call sign. Restart WeeWX with sudo systemctl restart weewx and check the WeeWX log for CWOP upload confirmations.

Step 4 — Verify Your Station Is Reporting

The easiest verification method is findu.com — type your call sign into the search and it shows the last received observation with a timestamp. If your station is reporting correctly, you'll see a temperature, pressure, wind, and rain reading within 10 minutes of configuring the upload.

A second verification tool is wxqa.com, the CWOP quality assurance site. It analyzes your station's data against nearby NWS stations and flags outliers. Your station will likely show a quality score within 24–48 hours of first reporting. Don't be alarmed by an initial low score — it takes a few days of data for the statistical comparison to stabilize.

What CWOP Data Is Used For

Your observations feed into NOAA's Meteorological Assimilation Data Ingest System (MADIS) every 5 minutes. From there:

• NWS forecast offices can query individual stations to cross-check model output against observed conditions
• Storm Prediction Center forecasters use CWOP density during severe weather to see exactly where temperature and dew point boundaries are tracking
• The Hydrometeorological Prediction Center uses CWOP rain gauge networks to calibrate NEXRAD radar rainfall estimates
• Your data is archived permanently in NOAA's climate record — it will be there long after your station is gone

During tornado outbreaks and major winter storms, dense CWOP networks in affected areas have directly improved warning lead times by giving forecasters fine-scale boundary data that official airport stations can't provide. Your station in your backyard contributes to this.