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Simulated radar — how to read it

The radar map shows simulated radar reflectivity in dBZ — what a weather radar would see if it scanned the ICON-D2 forecast atmosphere. It captures convective cell structure and intensity gradients much more sharply than the smooth precipitation field.

ClearToFly simulated radar forecast for Wed Jul 15 at 16:45 CEST covering the Swiss / Southern German border region (Basel, Zürich, Bodensee, Bregenz, Immenstadt). A large organised system stretches east across northern Switzerland: multiple magenta / red / dark-red cores (55–65+ dBZ, severe cells with hail signature) embedded in a broader shield of yellow / green (20–40 dBZ, moderate rain). A hover tooltip near Ebingen shows 66 dBZ. The slider maximum is 14 h — a hint that this is a RUC-only product with a 15-minute time step. The right-side legend runs from light blue (0–10 dBZ, drizzle) through green / yellow / orange / red into magenta (> 60 dBZ, severe cells).
Simulated radar around Lake Constance, Wednesday afternoon. An organised multi-cell system with clearly-visible convective cores (magenta 55–65+ dBZ near Ebingen, tooltip 66 dBZ) embedded in a wider stratiform shield of moderate rain. This is the structure the precipitation map smooths away — the compact cores are exactly the “route around, don't cross” features. Note the slider's 14 h maximum: radar is RUC-only, so it doesn't extend to 48 h or 120 h like most other products.
This is not a live radar feed. It's the model's projection of where storms will be at the selected forecast hour. Radar is a RUC-only product on ClearToFly: the ICON-D2-RUC model publishes it hourly at 15-minute time steps out to +14 hours. There is no simulated-reflectivity field in the standard ICON-D2 output past that horizon, so the radar map does not extend to 48 or 120 hours the way most of the other maps do. For actual observed cells and their next-60-min tracks, use the Storms (KONRAD3D) map — DWD's radar observations rather than the ICON-D2 model. Close to flight time, always cross-check against actual ground radar (DWD Wetter- und Klimavorhersage, MeteoFrance, etc.).

Reading dBZ

Virga is not benign

If simulated radar shows a bright cell but the precipitation map is dry underneath, you're looking at virga — rain that evaporates before reaching the ground. Not a runway problem, but avoid it: virga sits near a convective cell (usually on the downshear side), and the evaporation cooling drives strong downdrafts and surface outflow winds. Flying underneath the virga trail can put you in the outflow gust front. If you see virga on a summer afternoon near a thunderstorm signature on CAPE, treat the whole area with the same caution as the cell itself.

Why simulated radar beats plain precipitation for storms

Precipitation maps show the smoothed water flux to the ground. Simulated radar shows the structure: a compact 50-dBZ core embedded in a 30-dBZ shield of stratiform rain — a shape that says "cell embedded in an area of weaker rain" — is instantly obvious on the radar map and hard to see on the precipitation map. That structure is what determines whether you can route around a cell.

Combining with convection and cross-section

For convective days, use three products together: