Type safe generic Java observer. Compile time error?

Requirements

I am trying to write an Observer / Observable pair of classes. I want to parametrize the Observer so that a type safe update call is possible. Imagine this version:

class View implements Observer<Model> {
    @Override
    public void update(Model model) { render(model); }  // no casting:)
}

Instead of this version that needs casting:

class View implements Observer {
    @Override
    public void update(Object model) { render((Model) model); }  // casting:(
}

Attempt

Here's what I have so far. My Observer interface:

public interface Observer<T extends Observable> {
    public void update(T observable);
}

and my Observable abstract class:

import java.util.List;

public abstract class Observable {
    private List<Observer<? extends Observable>> observers;

    public Observable() {
        System.out.println(this.getClass());
    }

    public void addObserver(Observer<? extends Observable> obs) {
        observers.add(obs);
    }

    public void removeObserver(Observer<? extends Observable> obs) {
        observers.remove(obs);
    }

    protected <E extends Observable> void updateObservers(E self) {
        for (Observer<? extends Observable> obs : observers) {
            obs.update(self);  // <-------------------- COMPILER ERROR!!!
        }
    }
}

Problem

The line labeled "COMPILER ERROR" has a problem with the .update():

The method update(capture#4-of ? extends Observable) in the type Observer is not applicable for the arguments (E)

So even though the self argument passed to update() is of type E extends Observable, it does not satisfy the interface method signature update(T observable); where T extends Observable. Why is that? I really expected those to be compatible.

Is there I can fix this to meet my requirements?

Thanks.