Some people may look at this map and see “pretty colors” and “nifty shapes.” When meteorologists look at it, we see what is likely the end of El Nino this year as well as the end of our very rainy pattern for Texas.
What does the map mean? The map shows the difference between normal ocean surface temperatures in the Pacific Ocean versus the temperature of the ocean water as of May 4, 2016. The areas of yellow and orange mean that the water is still ABOVE NORMAL (meaning an El Nino pattern). However, notice all the white and light blue colors! That means the ocean is COOLING DOWN, the classic indication of the beginning of a La Nina year.
How does this happen? Why does the ocean surface temperature change? Off the coast of South America, the prevailing trade winds flow from east to west. In a normal (La Nina) year, those trade winds are strong. During an El Nino year, for some unexplained reason, those trade winds slow down… way down. The strong trade winds “PULL” the ocean water away from the coast, causing an up-welling of COLDER water. When those winds become light, the “PULL” on the ocean water is weak, and water warms up. El Nino=Warm Pacific La Nina=Cold Pacific
According to the Climate Prediction Center of NOAA, La Niña is favored to develop during the Northern Hemisphere summer 2016, with about a 75% chance of La Nina during the fall and winter 2016-17.
So is that good or bad for weather? In a classic La Nina year, Texas will generally have LESS rainfall. Sometimes, significant droughts can form during a La Nina year. Also, the Atlantic Ocean becomes more active for hurricanes and tropical storms.
2015 brought record rainfall for Texas. Let’s see what this coming La Nina year means for our state.