Answers to El Nino Questions

By: Shane Motley Email
By: Shane Motley Email

We love viewer questions...if you have any, be sure to send them in. In addition, if you have any questions on specific topics you would like us to address here the Blog, please let us know. The last Blog received a few great comments that I’d like to talk about. The first is:

“Do you guys really believe the Nino stuff?"

Do I believe the Nino stuff? Since there are two possible questions being asked here, I'll go ahead and address them both. First off: do I believe the waters of the equatorial Pacific go through warm and cool phases? The answer to that is a definite “yes.” We have instrumentation on buoys, ships, and satellites that constantly monitor the ocean temperatures and they all show that the waters oscillate between warmer and cooler than normal phases. However, I actually believe this question is asking: do I believe that the warming and cooling of waters in the equatorial Pacific can influence the global weather patterns? The answer to that question is also a definite “yes.” Temperature changes are what drive the winds that steer weather systems around the globe. Think about what happens when you open the door to your house on a hot summer day. If your A/C is on, you are pleasantly greeted by a refreshing blast of cool air. On the other hand, very little wind hits you as you open your door on a day like today when the temperature inside the house is almost the same as it is outside. The point is temperature changes lead to changes in the winds and changes in the winds will lead to changes in the steering currents that bring us our weather. Therefore, as ocean temperatures increase over the equatorial Pacific the southern branch of the jetstream becomes more active leading to a higher possibility of precipitation (key word being: possibility).

The big error I often see is when folks say: “this storm is caused by El Nino.” Although El Nino conditions may enhance the conditions that lead to the formation of a storm, an El Nino is never completely responsible for a single storm. This is actually one of my bigger meteorological pet peeves since blaming El Nino on, say, the lack of a significantly active 2006 hurricane season is only half the story. In addition, simply accepting “El Nino” (and only El Nino) as the answer and moving on could cause meteorologists to miss out on the bigger picture of what actually happened. Granted, the El Nino surely plays a major role, but there are many other factors that came into play.

The next question asks: “Did we also have an El Nino last summer when we had a drought?”

Last year we were actually moving in from a neutral period (average water temperatures) to an El Nino period. El Nino typically has a bigger impact on Texas precipitation during the winter months. In addition, the strength of an El Nino is extremely important and some research has shown that weak El Nino’s may promote drought in the same locations that a strong El Nino would promote flooding (e.g. southern California this year is in a serious drought due to this year’s relatively week El Nino).

Another question received was: “In (the previous article) you speak of potential drier conditions due to La Nina and in another article you say that La Nina conditions are better suited for Hurricanes which bring more moisture. Is there an inconsistency here as far as your comments are concerned?”

This is a great question and it is certainly true that a tropical system would bring abundant rainfall to the area. However, even though increased hurricane activity is typically expected during a La Nina, the chance of a hurricane making landfall in Texas is too small to suggest that it would contribute to our rainfall totals. Thankfully, the majority of Atlantic hurricanes recurve back into the Atlantic and never make landfall; therefore, chances are that our rainfall would be lower than normal. I think the questions proposed here, however, make a very good point: we are talking about probabilities of rainfall rather than the definite value. The water temperatures of the Pacific do provide us with increased confidence on these probabilities, but other factors can always get in the way.

Shane Motley
KBTX News 3

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