diff --git a/lib/xmet/thermo.py b/lib/xmet/thermo.py
index e06a7b5..c0fe75a 100644
--- a/lib/xmet/thermo.py
+++ b/lib/xmet/thermo.py
@@ -189,3 +189,9 @@ def follow_saturated_mixing_ratio(temp: float, pressure: float, step: float=1.0)
         p2 -= step
 
     return series
+
+def wind_u(speed: float, direction: float) -> float:
+    return speed * math.cos(rad(direction))
+
+def wind_v(speed: float, direction: float) -> float:
+    return -speed * math.sin(rad(direction))