KSN Storm Track 3 Digital Extra: Climatological pattern impacts on fall corn harvest

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Believe it or not, the fall season is just right around the corner which means the fall harvest is quickly approaching! Climatological patterns can help to dictate, on average, how a growing and harvest season may turn out. Of course, it is important to remember that day-to-day storm systems, severe weather and significant swings in temperatures can ultimately play a huge role in how crops turn out by harvest. However, setting the stage by understanding what drives these storm systems from season to season is important to know and what changes the overall pattern may experience by the time the crops are ready to be harvested. To understand these patterns we have to understand El Nino-Southern Oscillation or ENSO.

You have likely heard the terms El Nino and La Nina which represent either warmer than average or cooler than average sea surface temperatures respectfully in the central and eastern tropical Pacific Ocean just off the western coast of South America. If these ocean waters remain closer to average, it is what we call ENSO Neutral. The reason understanding this climatological pattern is important is because these ocean temperatures have a huge influence on how our jet stream behaves not only here in the United States but across the globe. The jet stream is the highway our storms systems travel along and can greatly impact whether we are talking about a dome of high heat or bitterly cold temperatures. This summer, we have been in an ENSO Neutral. A typical ENSO Neutral pattern has only subtle shifts both above and below-average expected for corn crops in Kansas.

These subtle shifts will be greatly impacted by moisture and temperature fluctuations during the growing season leading up to harvest. So, what does ENSO Neutral mean in terms of temperature and precipitation for Kansas? We are going to break it down looking at July to see if we have been on track in terms of that standard range. From there, we will break down what could be expected as we wrap up the summer season and head into the fall harvest season. To start, we will look at temperatures.

If you were to take all of the daytime highs and overnight lows and create one average overall temperature, during an ENSO Neutral July, that temperature should range between 76° and 82° based on our different growing zones here in the Sunflower State. July started off with some rather cool temperatures for summertime standards before the heat really started to settle in as we wrapped up the month.

Given all of our cooler weather to start, it did in fact keep that average temperature overall between 75° and 80° which is on par for where we should be in a typical ENSO Neutral July pattern. Precipitation was another story as we entered the heart of the summer season. On average, when ENSO Neutral is in place in July, rainfall ranges between 2.5″ to 4.5″.

However, July told a very different story across our four zones. Many struggled to scrape up 2″ of rainfall with Dodge City meeting the lower end of that threshold. The heat that started to build in by the end of July that has stuck with us into the first several days of August could mean soil moisture problems unless organized storm systems can provide a healthy drink of water for Kansas crops.

Soil moisture continues to dry out and shows a continued drying trend even 50 cm (19.6 inches) below the surface where the roots really start to take hold. Taking into account the week or so of August over the past 30 days, many areas in Kansas are experiencing a rainfall deficit to the tune of almost 3.5″ or more.

Given this general lack of rainfall and warming afternoon temperatures, drought conditions have popped up across the state with the latest Drought Monitor put out on August 5th.

Farmers may start to see stresses on crops as a result of the drought starting to take hold in parts of the state. Signs that the plants are starting to experience these drought conditions could be leaves on the corn stalk starting to roll under earlier in the day, kernels not filling out completely on the ear, or overall growth becoming stunted due to a lack of moisture available.

In an ENSO Neutral July, we do see rainfall drop off on average from May and June. A lot of this has to do with the seasonal shift of the jet stream farther to the north steering more organized rain chances away from the Sunflower State. However, by August, if ENSO Neutral holds, slightly more rainfall can start to become the trend as we near the end of summer. Forecasts at this time favor ENSO Neutral holding into the fall season, but changes are on the way and how early they take hold could impact fall crops.

While ENSO Neutral is currently in place, we also have a La Nina Watch in effect. This means we could see those sea surface temperatures turn cooler than average which would greatly start to influence the behavior of our jet stream. La Nina could take hold as early as September or as late as November. A La Nina pattern here in Kansas would favor increased chances at both warmer and drier than average conditions.

It will be interesting to see how long ENSO Neutral can hold on before we make that forecast change, but hopefully, it can hold on long enough to make some improvements on the drought to give Kansas farmers a favorable harvest season!

— Meteorologist Erika Paige

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