Ag Weather Forum

It has gotten hot across the middle of the United States this week, which is expected for the next several days. There could be some changes ahead to your local forecast for next week though, and they may be dramatic.

We should all be aware these big changes may occur in the second week of your 15-day forecast -- perhaps on a daily basis. It is typical during the fall and spring and we should take that into account when looking at the medium- and long-range forecasts.

With the change in the seasons getting deeper into fall, the atmosphere becomes a little more chaotic. Colder air is building up near the Arctic while it remains very hot in the Tropics. This major difference in temperature drives a lot of our local weather as the Earth does its best to even out the distribution in temperature. It happens every fall and spring to a greater degree than during the summer and winter, and more frequently we see big swings in temperature both higher and lower. Cold fronts are more effective at bringing in colder air southward while warm fronts are still able to shift warmer air northward during these months.

With such big swings in temperature possible and a lot of energy floating around in the upper atmosphere, models can sometimes do a poor job at forecasting changes in the pattern. Sometimes they let one side go on longer than it will, either too warm or too cold. Or they may not grab onto subtle changes very well. Sometimes they miss storm systems; or their impact goes a little less noticed. So, when you're looking at your 15-day forecast from your favorite weather company, you can probably expect to see some changes from day-to-day, especially in that second week's forecast.

It's a meteorologist's job to point out where these changes may happen and to what degree, even if models or their own official forecast aren't calling for it. I mentioned one possibility last week with a possible recurving typhoon in the Pacific Ocean. You can read about that here: https://www.dtnpf.com/…. That is still on the table as a change to the overall warm forecast. But models have tried to focus on another disruption at the same time, regardless of that typhoon.

In the last few days of both the European ECMWF and American GFS model runs, the two models are showing a cold front pushing through the U.S. On the European models, this is occurring next weekend, Oct. 10-12. On the GFS, it's a few days later. But both models are hinting at a big change to the weather, despite their forecasts still calling for mostly above-normal temperatures. Both of these individual model runs show the potential; but when we look at their ensembles, or groups of runs, those outcomes largely disappear, leaving behind warmer and drier weather for mid-October.

This is where a meteorologist can add some value to the discussion beyond a simple 15-day forecast. While there is some potential for big changes out there, models aren't really seeing it just yet, or have many differences in both the magnitude or timing of these changes. Being the fall season, that's not all that unusual. But it also means if these potential disruptions that both the ECMWF and GFS see are legitimate, some massive changes to the forecast may be warranted.

To find more weather conditions and your local forecast for free from DTN, head over to https://www.dtnpf.com/…

John Baranick can be reached at john.baranick@dtn.com

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