Monsoon Summer 2015 Asia forecast may be affected by the temperature of the Pacific Ocean a few thousand miles away. The Indian weather office in New Delhi projects a 70% probability that El Niño will continue throughout the monsoon season. The recurrent phenomenon leads to dry spells throughout much of Asia and some forecasts are suggesting Below Normal rainfall after the June – September monsoon season. 2009’s El Niño dried the Indian monsoon, making it the weakest in four decades. Half of India’s farmland lacks adequate sustainable irrigation, so such droughts cripple her $280 billion farming industry. India consumes almost all of the food she produces and scant harvests lead to famine among her lower castes.
Marked by a warming of the Pacific Ocean, El Niño leads moisture-laden Lows that would otherwise affect India eastward into the Pacific. An El Niño event begins when the east-central Pacific Ocean endures three months of warming of at least 0.5°C (0.9°F.) Little is known about why El Niño comes and goes. It is presently very difficult to predict the longevity of an El Niño event but the typical observed span is nine to twenty-four months. Just as mysterious is the interval of time between events but two to seven years has been typical throughout documented history.
Monsoons are fueled by a seasonal land-sea thermal differential. Summertime insolation bakes the surface, which conducts heat into the air molecules that bombard it. These energized molecules then gradually mix with the air above and convect the heat upward. The hot air ascends and expands, which develops the semi-permanent Low that fuels the Indian monsoon. Moist, southeasterly winds over the southern Indian Ocean and the waters of Indo-Australia turn southwesterly when they cross the equator and hook storm systems eastward over southeast Asia, toward China and eventually the Northwest Pacific. Occasionally, wintertime bursts of cold air, nicknamed monsoon surges, interact with Lows that blow heavy rains toward eastern Malaysia and churn tall waves in the South China Sea.
Professor Yamagata, representing the Frontier Research Center for Global Change, recently proposed a new phase of El Niño called El Niño Modoki, characterized by warming in the central Pacific but cooling on the east and west coasts. The pattern is presently little understood but observations suggest that it funnels extra moisture to China and deprives Japan, among other less descriptive geographic generalizations. Presently, warm water lies near South America, typical of a normal El Niño event. Models suggest this warmth will remain for several months, inhibiting an El Niño Modoki.
Written by meteorologist Geoff Linsley