Ag Weather Forum

Rinse And Repeat

Bryce Anderson
By  Bryce Anderson , DTN Senior Ag Meteorologist
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Near-identical placement of hot upper-atmosphere high pressure ridging over the southeastern U.S. has been a key factor in keeping storm systems parked over the Plains and Midwest. (Graphics from Tropical Tidbits and NOAA)

There was one thing the Corn Belt -- especially the Western Corn Belt -- did not need going into the fall season of 2019 and that was a revisiting of the heavy rain-producing upper air pattern that brought the heavy, harvest-delaying precipitation of fall 2018.

But, here we are. The phrase "rinse and repeat" may sound harsh, but in many respects that's what has happened. The weather pattern right now is remarkably similar to last fall, when the northern and Western Corn Belt was wet with extensive harvest delays.

A primary feature of this pattern is strong high pressure in the upper atmosphere -- a ridge -- over the southeastern half of the contiguous U.S. The strength of upper-air ridging over the Ohio Valley, Delta and Southeast is impressive, to say the least. The height of the ridge Wednesday morning, Oct. 2, was 5,940 decameters over Tupelo, Mississippi. This is a hot and dry feature; if it were to have shown up in midsummer, it would very possibly be known as a "Dome of Doom" by producing damaging heat and dryness.

But, that high pressure ridge has another feature that has helped to soak the western and northern Midwest. The circulation around that high, going clockwise in the Northern Hemisphere, has led to a consistent stream of moisture out of the Gulf of Mexico heading northward and into a cold frontal boundary in the north-central Plains and the western and north-central Midwest. The circulation around that heat dome also allowed Pacific Ocean moisture to trail inland northeastward from action around former Tropical Storm Mario in the Gulf of California, between Baja, California, and the Mexican coast. With all these elements in synch, the heavy rain mechanism was set in place.

The big question now is how long this pattern will continue. The forecast over the next ten days does indicate the southeastern ridge flattening and running east-west, rather than southwest-northeast. That may allow for reduced Gulf moisture inflow, and a more west-to-east air flow over the central U.S. A little drier trend would be the big feature, along with warmer temperatures.

However, crop impact is notable, to offer an understatement. Corn maturity is running very slow -- only 43% of the corn nationally is mature, which is in the same ballpark as 2009 when corn maturity was at 37% at the end of September. That is one feature 2018 offered; a year ago, corn maturity was at 84%. It may have been hard to get the crop out of the field, but at least things were farther along than producers are putting up with now.

Hard-freeze conditions still seem at least a couple weeks out yet. So much for the idea that cold temperatures will seal up the wet ground to allow machinery to work.

Bryce Anderson can be reached at Bryce.anderson@dtn.com

Follow him on Twitter @BAndersonDTN

(CZ)

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Meral Martin
10/3/2019 | 1:28 PM CDT
Question: So this has happened for two years in a row, but the last 5 seasons here have also been very wet. I know not remember this much moisture in the fall in the fields I have farmed for 40 years and the soils here this wet.. For that matter the springs either .Are there larger reasons that have made it easier to set up wet patterns in the atmosphere, or is is it just just simply bad luck ? Thanks