1-a, 2-a, 3- -, 4-a, 5- a, 6- -, 7- -, 8-an, 9- -, 10- -, 11- -, 12- -, 13-an, 14- -, 15- -.
Countable nouns, singular: a rainbow, a barometer, a cup, a forecast, a disaster, a journey
Countable nouns, plural: weathermen, habitats, people, children, hedges.
Uncountable nouns: sunshine, knowledge, weather, scenery.