Is El Nino Coming? And If It Is What Does It Mean?

17/08/12 -- The US drought-bringing plague that is La Nina finally seems to be giving way to her illustrious little brother El Nino. But what is El Nino, and what are some of the weather effects it often brings? Here's a few pointers from my US weather friend Gail Martell of Martell Crop Projections:

Changes in the tropical Pacific Ocean winds, air pressure the sea temperatures indicate an emerging El Nino. Presently an "El Nino watch" in place. Sea surface temperatures across the eastern equatorial Pacific Ocean are currently 0.8 C above normal, and slightly above the 0.5 C threshold for El Nino. The Climate Prediction Centre anticipates the development of El Nino as the large-scale winds and air pressure patterns in the Pacific Basin are taking on El Nino characteristics.

The probability of El Nino forming is 70%, based on a consensus of scientists polled by the Climatic Prediction Centre. Virtually all the dynamical models predict a developing El Nino in August-September prevailing through the Northern Hemisphere winter.

What sort of weather does El Nino produce?

The ENSO signal is a see-saw pattern causing exceptional wetness at the eastern end of the Pacific Basin, but drought at the western end in the Indonesian Basin.

Argentina is one of the world’s most sensitive regions to the ENSO signal. With El Nino, conditions are wet and favourable for crops. Twice-normal rains have developed this month in Buenos Aires, southern Santa Fe and La Pampa. The forecast continues wet with predictions for another .75 to 3 inches in the next 5 days.

Australia is strongly impacted by El Nino, but in a negative way, experiencing drought in New South Wales, Victoria and South Australia. Conditions this month have been cold and dry. Field moisture has deteriorated sharply with below-average rains the past 3-4 weeks.

In the American Midwest, El Nino causes a wet signal. August rainfall has increased in the corn- and soybean belt, though not all farms have received generous showers. The average rainfall this month is 1.3 inches against 1.63 normally, and 80% of average. A fresh round of showers has developed overnight in Iowa and Wisconsin.

The El Nino signal is also very cool in the Midwest. The new forecast calls for the coolest weather of the season and 5-10 degrees F below normal in the heartland.

Insight on US crops

Field conditions were so dry to begin with that increased August rainfall has largely soaked into parched fields, not improving crop potential much. Soybeans have benefited somewhat. Had the rainy weather pattern started a month earlier, corn and soy potential would have significantly improved.