LOS ANGELES, June 11 (Xinhua) -- The U.S. National Oceanic and Atmospheric Administration (NOAA) announced Thursday that El Nino has developed in the tropical Pacific and issued an El Nino Advisory.
NOAA forecasts that the climate pattern could strengthen to a moderate or strong event this fall. Forecasters estimate a 63 percent chance that sea surface temperatures in the Nino-monitored region of the Pacific will exceed 2.0 degrees Celsius. If that threshold is reached, NOAA would classify the event as a "very strong" El Nino.
NOAA declares an El Nino event when sea surface temperatures in the equatorial Pacific remain at least 0.5 degrees Celsius above average for several consecutive months. The agency also monitors atmospheric conditions over the region, including the Walker Circulation, a large-scale east-to-west airflow driven by temperature and pressure differences across the Pacific Ocean.
According to NOAA, El Nino is declared when the Walker Circulation weakens and warmer ocean waters shift eastward toward South America.
NOAA said that El Nino tends to be strongest during winter, and its global impacts are typically most significant in the Northern Hemisphere. It often leads to a warmer-than-usual winter over the northern United States.
"Every El Nino is not the same; each one is unique with its own imprint on our weather," said Ken Graham, director of NOAA's National Weather Service (NWS).
"Advanced monitoring and an improved understanding of El Nino patterns allow the NWS to better predict and better prepare the public and our core partners for what is to come." ■
