La Niña impacts on the world’s weather are less predictable than the effects wrought by El Niño. This is mainly because of the big differences in the jet stream and the storm track. El Niño causes the Pacific storm track to become stronger, to drop farther south than usual, and to straighten out like a necklace of weather extending more-or-less straight across the ocean. The La Niña storm track is weaker and loopy and irregular, like a piece of wet and wiggly spaghetti, more changeable — so the behavior and direction of the storms it carries are more difficult to accurately forecast – More and charts at – http://www.dummies.com/WileyCDA/DummiesArticle/id-1852.html

The causes of this kind of severe natural phenomenon are hidden in the major fluctuations of temperature in the surface of waters of the Equatorial Pacific Ocean. La Nina occurs when the difference between atmospheric pressures in South America and Indonesia increases to a certain level. La Niña usually occurs just after an El Nino has occurred. In fact due to the change of the air pressures, trade winds are produced. These strong trade winds blow the hot water from the surface of the oceans to the Southeast Asia. Then the inner cold water that is there in the depth of the ocean comes upward. The temperature of this water surface is much cooler than the normal temperature of the ocean.

http://www.mapsofworld.com/referrals/weather/severe-weather-conditions/la-nina.html

something is conceivable while it comes right down to the climate, right here in the Midwest component of the U.S. we get precipitation each each now and then different than that that could be a drought united states of america.