El Nino to bring cooler summer


The weather pattern known as El Nino will likely form this summer, and it could mean cooler than average temperatures for Japan, the Meteorological Agency said Monday.

El Nino, which is characterized by a warming of the central Pacific Ocean, will likely last through the fall, the agency said. It last developed between the summer of 2009 and the spring of 2010, and broke out briefly in the summer of 2012. A prolonged El Nino can cause abnormal weather worldwide.

The weather agency said in a three-month forecast late last month that temperatures in Hokkaido and the Tohoku region may be lower than average in June and July because of El Nino. It also expected that rainfall across the country, outside of Okinawa and the adjacent Amami region, could be above average in July. The agency will announce a new three-month weather forecast on May 23.

In the eastern equatorial Pacific off South America, trade winds normally allow cold water to upwell, and cold currents prevail from east to west. But during El Nino trade winds weaken, allowing warmer water from the western Pacific to move eastward. Marine waters that often give rise to cumulonimbus clouds also move eastward.

If El Nino forms this summer, it would likely cause high-pressure systems in the Pacific to extend over Japan to a lesser extent, weakening the Tibetan high-pressure system in southern Asia. That means subtropical westerly winds around Japan would blow southward.