LEAD: NASA's satellites are tracking the developing El Niño across the Pacific Ocean.
1. Ocean conditions in 2015 bear some similarities to the powerful 1997 El Niño. This NASA visualization shows side-by-side comparisons of Pacific Ocean sea surface height anomalies measured by satellites in 1997 and 2015.
2. Red shows where the ocean is above the normal sea level.
3. Blue shades indicate areas of lower sea levels.
4. Sea surface height is an indicator of the temperature of the water below. Above normal levels indicate warmer temperatures, below normal colder temperatures.
5. El Niño events are characterized by a mass of warm water migrating from Southeast Asia toward South America.
TAG: Weather and climate forecasters are tracking El Niño closely because it could help steer beneficial rains to parts of drought-stricken California and the American West.