Model Initialisation Bias – Why 00Z Runs Beat 12Z for 24-Hour Wingfoil Accuracy
Weather models run four times a day (00Z, 06Z, 12Z, 18Z). You might assume the latest run is always the best. For wingfoil wind planning, this is not always true.
The 00Z run (Midnight UTC) often holds a "Data Superiority" that makes it the most reliable tool for planning your day's session.
The Radiosonde Advantage
Weather models live on data. The most critical data comes from Radiosondes—weather balloons released simultaneously around the world.
These balloons are expensive. Most stations only launch them twice a day: at 00:00 UTC and 12:00 UTC.
- 00Z Run: Ingests the full global balloon data.
- 06Z / 18Z Runs: "Intermediate" runs. They rely heavily on satellite data and estimates because no fresh balloons were launched.
The "Freshness" for Planning
For a rider in Europe or the Americas, the 00Z run arrives in the early morning. It contains a complete, data-rich snapshot of the atmosphere taken just hours before your session.
The 12Z run arrives in the afternoon. By then, the thermal wind cycle has already started. The model is playing catch-up.
Furthermore, the 00Z data is collected at night (in many western time zones). The atmosphere is stable and "quiet" at night. This allows the balloons to measure the baseline pressure gradients without the noise of daytime convection. A cleaner starting picture leads to a cleaner forecast.
When to Trust 12Z
The 12Z run is useful for "course correction." If the morning 00Z predicted 15 knots, but the 12Z update suddenly drops it to 10 knots, pay attention. The model has ingested the morning satellite data and noticed that the sea breeze clouds are not forming as expected.
Summary
For your primary flight plan, trust the 00Z (Morning check). It is built on the hard data of thousands of weather balloons. Treat the intermediate runs (06Z/18Z) with skepticism—they are often just mathematical guesses filling the gap.