WHERE ARE YOU EL NIÑO ?
By Matt Makens Atmospheric Scientist
The most frequently asked question this summer , and so far this fall , has been , “ Where ’ s my rain ? Shouldn ’ t El Niño have helped us out already ?” The easiest answer to that question is , “ Patience .” The weather is a constant evolution and migration of wet and dry areas . When it comes to El Niño , the biggest impacts are typically noticed late in the year through mid-spring . Plus , I hate to say it and have before , no two El Niños will be identical and that makes clumping all El Niños together a bad idea .
The evolution or migration of an El Niño weather pattern begins when we get the ocean temperatures to warm above average in the Central Pacific Ocean along the Equator . However , each El Niño can be a bit different depending on where the warmest water sits . For example , so far , this El Niño event has been an east-based one meaning the warmest temperatures where we look for them in the Pacific are to the far east , right by South America . Some El Niño events in the past have been similar , while others had their warmest water central or western-based . Why does this matter ?
Think of these warmer-than-normal oceans as a source of heat and energy for the atmosphere , like a burner on a stove top . Which burner you turn on changes which pot you are adding heat / energy to . If we are turning on the east-based ocean burner , if you will , then we are applying a lot more energy to the atmosphere right by South America . If we apply that energy here , it will ripple downstream and impact the atmosphere ’ s flow differently than if we applied all the energy in the Western Pacific Ocean . Where we apply the energy makes this El Niño event unlike many others , and that creates differences in how our storms will flow across the U . S .
We started turning up energy in this part of the ocean several months ago and continue adding energy to the atmosphere . Go back to our stovetop example ; the second you turn on the burner the water does not instantly boil — it takes time to collect that heat and get the pot to boil . The oceans have been warm for months and sending a lot of that energy to the atmosphere , but it takes time for the atmosphere to respond . It was a few months after the
oceans signaled an El Niño was here that the atmosphere began to behave like it too . This is part of the reason you may or may not see a quick impact once you hear that we are in an El Niño event .
The regions of the country that will classically notice an impact first are the Northwest and Southeast corners . Through the fall to winter into spring , impacts will be increasing for the Southern and Southwestern states as well as the Great Lakes and Upper Midwest . In general , those Northern states have a drier pattern develop , whereas the Southern states have a wetter pattern develop . This image gives a general idea as to the timing of El Niños biggest influence . One could argue the dryness El Niño brings to the Midwest has been in place for months already .
In a very general sense , Image 1 is the timing of an El Niño . We must consider , too , the other part which is the type of El Niño and its strength . I described what makes each El Niño event different in terms of where the warmest ocean temperatures are , which adds fuel to our atmosphere . The strength of that warm ocean is also a factor ( strength in terms of how much warmer than average it is ). We are talking about a difference of 1 degree Celsius between a strong versus weak event . The August National Cattlemen had images showing just how different the precipitation and temperature pattern can be across the country between weaker and stronger events ; it is quite remarkable to think about a degree Celsius difference in the ocean that far away can make for significant weather pattern changes across the country .
There is a lot more to it than just El Niño . The Arctic pattern and amount of cold air , the behavior of the North Pacific and North Atlantic oceans can change the storm flow , too . The biggest influence is El Niño , and then we create more subtle changes to that overall pattern depending on these other oscillations or heat sources ( like different stove top burners being on or off , if you will ). You can see how a lot of factors go into each El Niño event , and why it is not fair to clump all El Niños together . So , have we seen this type of event before ? Yes and no .
18 NATIONAL CATTLEMEN www . NCBA . org