def plot_spot(fcst, variable_name=None):
"""
Takes a forecast that is assumed to hold a spot forecast and
infers the type of variable then uses the corresponding plot utilities.
"""
variable_name = variable_name or utils.infer_variable(fcst)
variable = query_utils.get_variable(variable_name)
if isinstance(variable, schemes.VelocityVariable):
spot.spot_velocity(fcst, variable)
else:
raise NotImplementedError("Only support velocity variables at "
"the moment.")
