DAC Data Monitoring

It's very easy for us to say our forecasts are accurate. In fact, it's easy for any forecast site to say that their forecasts are accurate. But Metcheck do things a little differently to ensure we mean what we say.

What is DAC?
DAC or Data Assimilation Comparison is basically our way of ensuring forecast accuracy for thousands of locations around the world. In fact, we use rDAC which is a random version and will pick up to 10 locations around the UK and the world each week and then monitor each location hourly to compare WMO recorded data with the forecast data we provide on the site for that exact location.

Behind the scenes, the servers score and monitor each location and each forecast and any locations which consistently show an error of more than 10% are immediately investigated by coders to analyse further.

What do you compare?
Here is a chart of the Thames Estuary which we compare against Southend Airport every hour :-



Every day, our servers randomly pick locations then monitor them for a minimum of 7 days for temperature, wind speed, wind direction and sea level pressure. The server then marks each location every single hour based on what we forecast and what was observed and then scores each hour for every location.

Our benchmark for accuracy is 90%. Any location which falls below this is flagged up so our engineers can take a closer look and investigate.

We use DAC also for new parallel models which we develop in order to see whether a new model is more or less accurate than the current one.

The future of DAC?

All met agencies will have some form of monitoring forecast accuracy, whether this is upper level data or surface data. In late 2020 we will start putting all our DAC data online for various locations so you can see the accuracy for each location and also any new models we are developing behind the scenes.

Forecast accuracy is important to all met agencies. Not just because we are able to stand by the accuracy of our forecasts, but a poor forecast can also be a dangerous thing for certain activities and it's important that you can trust the forecast accuracy and make better decisions based on them.

Can I see a DAC job live now?

Sure! Below is a current live DAC job running at Metcheck on one of our stations. You can see over the last few days how the model, parallel and actual recordings are monitored for accuracy. Every week we will switch to another random station being monitored so you can see our process of maintaining forecast accuracy of the models here at Metcheck.

DAC JOB - 4/2025-CS-1262
DAC WMO - 4/2025-METCHECK-CS/2025/-1262
DAC LOC - EGGW (51.8747/-0.3683)
DAC ICAO - EGGW
DAC CLUSTER - AMZ-3/MET-3/SQL-4+3
DAC START - 06/05/2024 23:29:16
DAC END - 20/05/2024 23:29:16
Temperature at 2m (Kelvin)

Windspeed at 10m (m/s) Pressure at Sea Level (MB)