Ag Weather Forum

No La Nina, But Still Hot

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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A broad ridge of high pressure over the Southern Plains and southern Midwest is forecast to be a hot and dry weather maker during the middle of July. (Tropical Tidbits graphic)

It's been a tumultuous week in the ag weather world; quite a bit different than we've had for a number of years. Instead of concern and fretting because of wet ground and late planting, we had concern and fretting over hot and dry conditions. Heat advisories were featured in the Midwest and at least on Friday, July 10, covered the Southern Plains along with the Delta and Southeast. Timing of the heat is ominous with corn entering the pollination stage.

We're not used to this in recent history. This kind of heat has not been a part of the U.S. midsummer weather scene since 2012; I don't have to remind you of what a year that was for heat and dryness. And this episode of dry and hot conditions is going to be around for a while, although forecast models differ in the location and intensity of the bubble of hot air -- a ridge, in meteorological terms -- that gets the spotlight in forecast discussions.

Regarding the placement of the ridge: I favor a depiction with the ridge's northern boundary in the corridor between Interstates 70 and 80. On the northern side of that boundary, shower and thunderstorm formation is more likely, along with some periods of slightly cooler temperatures (I use cooler as a descriptor; values in the mid to upper 80s would still be likely). South of that boundary, hot and dry conditions like we have seen this week would be prone to continue.

My colleague Stephen Strum, DTN vice president of long-range forecasting, is looking for a fair amount of back and forth with the ridge core and thus its northern boundary. "The core of the ridge will likely meander back and forth from the Southwest to the Appalachians," Strum said in an email discussion. "When the ridge center is farther west, there will be better chances for MCS (mesoscale convective system -- thunderstorms) development across the eastern Plains and Midwest, but when that ridge center is farther east during the week two period (July 17-24), much of the Corn Belt should stay drier. (The) Upper Midwest could stay active on the northern perimeter of the ridge, however."

In other words, there could be some periods of heat and dryness in the western Midwest during mid-July. "That (storm) activity should be pushed north of there ... after the middle of next week ... more North Dakota to Wisconsin," Strum said. So, the heat and dryness outlook is set to be a forecast headliner through the prime time of pollination 2020.

This is all happening in the absence of a Pacific Ocean La Nina temperature event -- an indication that summertime heat and dryness can occur with the Pacific in a neutral phase. "Absolutely no (La Nina) connection," said NOAA Central Region Forecast Office Director Doug Kluck in response to an email question. A Pacific Ocean update issued by the NOAA Climate Prediction Center (CPC) Thursday, July 9, made the same reference. "Overall, the combined oceanic and atmospheric system is consistent with ENSO-neutral. ENSO-neutral is favored to continue through the summer, with a 50-55% chance of La Nina development during Northern Hemisphere fall 2020 and continuing through winter 2020-21," said the CPC in a Pacific El Nino-Southern Oscillation update. That means that there is a 45-50% chance of La Nina not developing during the coming fall season.

Bryce Anderson

Twitter: @BAndersonDTN


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