El Niño is the warming of the water in the eastern tropical Pacific that often has global weather implications and for California has sometimes led to big rain and snow years. Federal weather scientists declared earlier this month that it looks as if an El Niño condition is forming. Since then, evidence has been gaining that the condition could be significant.
Based on recent developments, some scientists think this event may even rival the record El Niño event of 1997-1998. If that does happen, then 2015 would almost be guaranteed to set a record for the warmest year on Earth, depending on the timing of the El Niño conditions....
The Pacific Ocean exists in a constant state of unease, like an ocean badly in need of a mood stabilizer. Trade winds blow along and to the north of the equator from east to west, piling up warm ocean waters in the western Pacific, and causing sea levels to be higher in the west than they are in the east. Like a tipping bathtub, this setup can quickly be reversed with a reversal in trade winds and a sloshing of the warm sea surface temperatures from the western Pacific to the east, first at depth in a series of undersea waves known as Kelvin waves, and next toward the surface as the warm waters rise off the west coast of South America.
This complex chain of events, in which the atmosphere and the ocean act in concert to set up El Niño conditions, is well under way now. Starting in January of this year, there have been a series of strong bursts of winds coming out of the west in the equatorial tropical Pacific, and these have essentially replaced the typical easterly trade winds.
Partly as a result of these wind bursts, ocean buoys and satellites have detected the movement of unusually warm ocean waters from the western Pacific to the east. Ocean surface currents, which normally move westward across the Pacific basin, have reversed as well. El Niño forecasters have taken this as a further sign of a developing El Niño, and these conditions were a key reason why an El Niño Watch was issued on March 6.
Officially, NOAA says there is just over a 50 percent chance of an El Niño of any variety, weak, moderate or strong. (Note: the normal chance of an El Niño would be 33 percent, since its parent weather pattern known as the El Niño Southern Oscillation or ENSO, has three phases: El Niño, La Niña, and neutral).
Suppose a strong El Niño event does materialize later this summer or fall. What might it mean?
Large amounts of heat from the tropical Pacific ocean would be released into the atmosphere, likely raising global temperatures to record-setting levels.
Above normal rain would be favored in California.
Hurricane activity would likely be suppressed in the Atlantic
Washington, D.C. might see depressed snow next winter. Our two least snowy winters on record (0.1 inches at Reagan National Airport) coincided with two of the three strongest El Nino events on record (1997-1998 and 1972-1973).
On the question of whether El Nino brings more rain to California, there's this research.