In-depth view of precipitation inside the storm as seen by TRMM's precipitation radar. A line of thunderstorms can be seen in the taller red areas. Red colors indicate rain rates in excess of 2 inches per hour. Strong rainfall in the central Pacific are the signature of El Nino. The red areas indicate more than one inch per day.
Energy is used to evaporate water.
Water vapor rises in atmosphere. Condensation releases energy into atmosphere. Water drops fall back to Earth. Rain cycle repeats itself. We still do not understand all the reasons why.