Most of the proposed transport vessels were barges from rivers such as the Rhine, converted for the invasion. Their poor suitability for an English Channel crossing made weather particularly important. Atlantic weather generally reached Allied areas before moving over Europe. That gave the Allies an advantage in forecasting conditions.
Notable Point · 26:56-27:50
River barges facing Channel weather
Converted river barges made the invasion dependent on suitable weather, while Atlantic weather patterns favored Allied forecasting.