‘Official’ First Fall Frost Forecast

‘Official’ First Fall Frost ForecastThe sun was totally set on March 19 when lightning flashed to the south of our residence in Hartwick. What caused this electrical storm was the occurrence of the southern branch of the northern jet stream jutting north. This allowed a southern moisture-laden air mass to slam into a drier cold air mass. This merger caused huge amounts of condensation and similarly great electrical activity – and a rapid drop in air temperature. Exactly a half-year later, the jet stream is supposed to do the exact opposite, allowing frigid air masses into our region. What made this meteorological drama particularly interesting this year is the fact that this process repeated itself in other parts of our region on March 25. It appears sensible to me to consider these two events as parts of the same weather happening. That said, it’s logical to use an average date of March 22 as the launch point for forecasting the end of the summer annual crop growing season, 183 days hence.

Here’s the science supporting my annual springtime prediction. The climatological factor calling the shots here is known as the jet stream polar drift rule. It states that the first serious electrical storm of spring in latitudes near the 45th parallel (which is halfway between the equator and the North Pole and runs near Canton) will be followed a half-year later by autumn’s first killer frost. Thus, we can expect our first killer frost to impact much of the Northeast on or about Sept. 21. That’s exactly how the jet stream phenomenon is supposed to play out unless El Niño or La Niña “misbehave.”

El Niño is said to take place when the Pacific Sea surface temperature (PSST) rises by more than 1.5º C above normal for that particular time of year. La Niña is said to occur when PSST drops by more than 1.5º C below normal for that time of year. What’s occurring now, PSST-wise, is described as a mild La Niña, bouncing between 0.6º and 0.9º C below normal. With my judgment of La Niña’s behavior as being more normal than not, I’m comfortable making my Sept. 21 forecast.

Does my comfort level pertaining to the end-of-summer forecast mean that between now and then weather and climate are going to be smooth sailing? Absolutely not. Even a mild La Niña has already started to drive away boredom. Weather, of course, is a key factor with La Niña conditions impacting South America’s growing regions. For the second year in the row, the Little Girl is influencing widespread weather events. Those cooler than usual waters in the eastern Pacific Ocean often affect the tropical rainfall in the southern hemisphere. The Little Girl also pushes the jet stream farther north, which has weather impacts in the U.S. and Canada. This year, the ongoing La Niña pattern is delivering excessively dry hot conditions to Paraguay, Brazil and Argentina – all heavily planted to corn and soybean. This in turn is forcing U.S. growers to attempt bumper crops in anticipation of higher commodity prices, despite drought and high fertilizer costs.

If you can accept the probability that the Northeast won’t have a nicely delayed first fall killer frost, here are management pointers pertaining to corn: Try to plant as much of your corn ground to short season varieties as possible. Although the following sounds like a no-brainer, long-season corns don’t outyield short-season corns to the extent that they used to 40 and 50 years ago. During my agronomist Extension days in the 1970s, a 100-day corn didn’t outperform an 80-day variety by 25%, but the performance gap likely was still in the 10% – 15% superiority range.

What’s closed this gap is the skill of plant breeders, both land grant and proprietary, in helping the shorter season varieties catch up to the performance of the longer season ones – even if the latter do receive the extra growing degree days they require. Thus, the gap between longer season corns and shorter season has shrunk down to the 5% – 8% range. As a result, many growers have opted to shorten the growing season of varieties they select, particularly for silage. Taking this one step further, with the large swings in more modern weather patterns, i.e., climate change, corn crops that successfully reach optimum maturity are a more cautious approach to economically sensible forage production. Variety trials in the last dozen years have shown that corn breeders’ efforts have produced higher yields from traditionally shorter-season varieties. Longer-season varieties don’t necessarily guarantee the grower significantly higher yields.

Certified Crop Advisor Tom Kilcer has a good use for the additional growing season in September given to us by shorter season corns. He admitted we lose about three-quarters of a ton of silage for every five-day reduction in growing season requirement. But that the difference between varieties of the same maturity can be greater than that. Shortening the season from 95- to 100-day down to an 85-day variety would theoretically lose three tons of silage per acre (roughly one ton of dry matter). But he said that if we get the mature crop harvested before Sept. 10 in the Albany area, winter triticale can be planted on time and yield over three tons of dry matter, gaining over eight tons of silage (or baleage) to replace corn dry matter yield loss due to shorter season varieties. Quoting Kilcer: “The slight decrease in corn yield is more than offset by a threefold increase in total yield of winter forage that is far superior in supporting high milk, compared to the corn silage you are giving up. Slightly shorter season corn varieties allow you to maximize the winter forage potential.”

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