Can we train a Keras Model in Stages?
Yes, you can, but the concept is not called "stages" but batches and it is the most common method to train neural networks. You just need to make a generator function that loads batches of your data one at a time and use model.fit_generator to start training it.
I have a huge NumPy matrix of dimension (1919090, 140, 37). Now it is not easy to fit something that large anywhere in the memory local or on a server.
So I was thinking of splitting the NumPy matrix into smaller parts say of (19,000, 140, 37) and then training a Keras model on it. I store the model, then loading it again and continue training on the next matrix portion. I repeat this until the model is trained on all the 100 or so matrix bits. 
Is there a way of doing it?