Ag Weather Forum

For weeks, model forecasts beyond the next seven days have been hard to trust. Small variations in the upper-level forecasts have meant that forecasts for the following week have been all over the place. It has been difficult to trust anything that models have been saying, because they have been wrong. They always latch onto the right solution, but do not give forecasters a lot of lead time.

That has meant that forecasters, myself included, have been looking deeper to try and find the clues that unlock which model solutions may be closer to the eventual truth. I admit that I might not have had the best track record at pinning down these forecasts during the last couple of weeks. But it appears that models are finally working out of their relative funk. It also stands to reason that they could go right back into it.

Part of the reason of their inconsistency may be due to the tropical season picking back up in the western Pacific Ocean. Tropical storms and cyclones have been increasing off the coast of China, with a couple of these getting caught up in the jet stream that brings them over to the United States.

These tropical systems add energy to the upper-level pattern and can cause bigger storms down the line. The problem is that they are also small. Large, global models do not get their details right. Small changes with the initialization of these storms could mean big differences down the line. Sort of like the chaos that comes with weather forecasting that I mentioned in a previous blog here: https://www.dtnpf.com/…. And considering it takes several days for storms to move from one side of the Pacific to the other, the six- to 10-day forecast can be quite challenging when one of these is involved.

The remnants of Tropical Storm Jongdari that is currently moving off the Korean Peninsula is combining with a storm system there. In the models, you can track its remnants as it moves across the northern Pacific Ocean through the weekend, then as it combines with another trough in the Gulf of Alaska.

What follows is that large trough moving through Canada next week. It does not look all that imposing on the model forecasts. But if you look at the ridges on those same graphics, you can see them moving around quite a bit. The trough will mean big changes to the weather situation over the U.S. next week, likely resulting from a big storm. You can find maps of these upper-level images for free here: https://www.tropicaltidbits.com/….

Watch for the "lack of color" moving across Canada next week and how the red ridges seem to disappear across the U.S. and Canada. The likely reason for the lack of blue coloring, or the indication of the trough, is due to the uncertainties in the timing of Jongdari being wrapped up into the trough. The European model shows this a little better than the GEFS I linked above, but those images are not available for free.

Regardless, the tropical feature is important here, as that added energy could bring about a bigger storm system and a bigger change to the weather we feel at the surface, not just the upper-level pattern. Because ahead of this trough and storm, an upper-level ridge will be spreading from its current location in the Rockies throughout the eastern half of the U.S. and Canada. Heat will be returning to the Midwest this weekend and will sit there until the ridge is forced to leave. The trough that comes through next week will likely be that force to move it.

The result should be a strong storm system capable of producing widespread rain and potential severe weather, followed by a burst of cooler air. The timing is likely to be between Aug. 28 and Aug. 30 across the Corn Belt, with the cooler air filtering in a day behind it.

The details still need to be figured out, and the models may not be incorporating Jongdari's remnants well, so changes to the forecast are likely. But I would be surprised if the storm and burst of cool conditions do not verify for next week.

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

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

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