diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1174b3f..f33a333 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- Pass down number of ensembles from configurations to `ProbabilisticAdvection`. This gives a roughly 3x speedup in the no ensembles case [!12](https://github.com/dmidk/sunflow/pull/12), @JoachimKoenigslieb
+
 ## [v1.1.0]
 
 ### Added
diff --git a/sunflow/forecast.py b/sunflow/forecast.py
index 27eadf3..3abe325 100644
--- a/sunflow/forecast.py
+++ b/sunflow/forecast.py
@@ -62,9 +62,7 @@ def preprocess_data(
 
 
 def simple_advection_forecast(
-    ratio_data: np.ndarray,
-    motion_field: np.ndarray,
-    n_steps: int,
+    ratio_data: np.ndarray, motion_field: np.ndarray, n_steps: int, ens_members: int
 ) -> np.ndarray:
     """Run a deterministic advection forecast on solar irradiance ratios.
 
@@ -90,6 +88,7 @@ def simple_advection_forecast(
         alpha=0.0,  # No Gaussian noise on motion field norm
         beta=0.0,  # No von Mises noise on motion field angle
         return_motion_field=False,
+        ens_members=ens_members,
     )
     # Run probabilistic advection using the correct method name
     forecast = pa.maps_forecast(n_steps, ratio_data, motion_field)
diff --git a/sunflow/main.py b/sunflow/main.py
index e7402b2..5ac6f63 100644
--- a/sunflow/main.py
+++ b/sunflow/main.py
@@ -273,7 +273,10 @@ def run_nowcast(
 
     # Simple forecast (ratio forecast)
     ratio_forecast = simple_advection_forecast(
-        ratio_data, motion_field, nowcast_config.future_steps
+        ratio_data,
+        motion_field,
+        nowcast_config.future_steps,
+        ens_members=nowcast_config.ens_members,
     )
 
     # Generate previous day time steps for clearsky lookup