Even with a severe lack of moisture, if you take a moment and look around the countryside, you will notice the 2018 wheat crop is greening up and even trying to grow. As the saying goes; “Wheat has nine lives.” Is it spotty, a bit thin, and behind schedule for March 11? Yes, Yes, and Yes. Was there likely winter kill in spots? Yes. Has the cooler than normal weather helped? Yes. Does the crop need moisture immediately? Yes. Is there any significant precipitation on the horizon? No. The why is the topic of today’s column – a La Nina in its second year.
Our weather/climate is part of the global weather system and so what happens half a world away impacts what happens in Kansas. It is helpful to remember all our weather/climate does is seek to eliminate the differences in temperature and air pressure from pole to equator to pole caused by the differential heating of the Earth’s surface that results from the 23.5 degree tilt of the Earth on its axis. And that our weather/environmental factors such as air pressure, precipitation, ocean currents and air temperatures are essentially cycles moving from higher to lower temperature, air pressure, humidity, etc. to eliminate these differences.
This effect is caused by the changes in temperatures off the coast of Peru in the Pacific Ocean between South America and Australia/Indonesia. There are three basic conditions off the coast of South America, normal, warmer than normal ocean temperatures at the surface (El Nino) and colder than normal conditions (La Nina). With limited space let’s explain it like this for Kansas:
- Normal temperatures result in a “normal” weather pattern, i.e. it doesn’t have an impact on our weather.
- The El Nino generally results in slightly to much above average precipitation and fairly mild winters in the Southern Great Plains and SE U.S. Kansas, is at the NW corner of this area so the effects may be severe or fairly mild.
- The La Nina, what we are in now, generally produces the opposite effect of an El Nino or what we are experiencing now – dry conditions. Briefly, this is caused by a shifting eastward of the jet stream and causing it to be in what is termed a “high amplitude” pattern. Simply, we receive most of our moisture from the Gulf of Mexico and this jet stream pattern shunts it to the east and we are dry.
These patterns shift back and forth. We are in the second year of the La Nina and what has made this one unusual is normally the effects weaken during the second year but for our part of the globe they haven’t. The good news is that forecasters are predicting its reversal. The bad news is that it may be several months.