World Grain - September 2020 - 59

Driest
Region

Credit for map

There are two problems with that
thinking. First, if the prevailing
weather pattern is already drier than
usual and La Niña comes along to
further reduce precipitation, there
will still be a shortage of moisture despite the long-term trend
in precipitation patterns in recent
decades. The second problem is
that, despite most seasons having a
greater precipitation trend because
of global warming, there are two
periods where the opposite is true.
October through December and
November through January are the
only two three-month seasons that
the NOAA suggests the long-term
trend in precipitation is actually
downward. In other words, during
the latter parts of autumn and early
winter there is not a trend toward
greater precipitation in the western
Corn Belt, but rather a decreasing
precipitation trend. When that is
blended with La Niña, there is a
greater decrease in precipitation.
If Iowa and neighboring states in
WKH 0LGZHVW GR QRW JHW VX൶FLHQW
rain in September or October to
adequately recharge the soil with
moisture, there is a growing potential that with La Niña around the
GULHUELDVZLOOODVWWKURXJKWKH¿UVW
half of winter.
HOW LONG WILL LA NIÑA LAST?
Another NOAA correlation with La
Niña and western Corn Belt weather (as well as parts of the central
and southern Great Plains) is that
the periods February through April
and March through May tend to be
more notably drier biased for Iowa
and some neighboring areas in the
central and southern Plains. If that
correlation proves correct and La
Niña lasts into late winter and early
spring (as it may), there may be a
further narrowing in the "window
of opportunity" for replenishing
rainfall for Iowa and the central
and southern Plains, raising more
anxiety for producers who will be
looking for moisture replenishment

in the driest areas prior to the start
of 2021 crop weather.
One of the biggest unknowns is
in regard to the duration of this La
Niña event. World Weather, Inc.
is of the opinion that La Niña will
only last for several months and
then dissipate temporarily. A La
1LxD RI JUHDWHU VLJQL¿FDQFH PLJKW
then evolve later in 2021 and 2022,
which might have a greater lasting impact on mid-latitude weather
around the world. The break in La
Niña during the spring and summer
 PLJKW EH VX൶FLHQW IRU FURSV
to perform favorably, but that is
pure speculation at this point and
a close watch on La Niña, autumn
and winter weather patterns as well
as spring and summer weather for
next year is warranted.
Studies for 2021 weather are just
beginning and it will take a few
months to determine the weather
potential for next year's crops. In
the meantime, there will be much
concern and some anxiety for farmers as they worry over the lower
moisture in the soil today.
7KH ¿UVW KDOI RI 6HSWHPEHU ZLOO
not provide much moisture to the
drier areas in the western Corn Belt,
although temperatures will be cooler
biased. That may help to conserve
soil moisture, but most of the rain
advertised for early September will
not be nearly as great as the outlook
charts imply and there is a very strong
probability that the second half of

www.World-Grain.com / World Grain / September 2020

August 2020
percent of
normal
rain

September will trend dry and warmer
than usual, once again reversing the
moisture gained from the cooler conditions in early September. October
R൵HUV VRPH KRSH IRU WHPSRUDU\
improvements and then November
through March may not prove to be
real fruitful for moisture improvements, although there will be some
lift in topsoil moisture.
In the meantime, dryness in the
Black Sea region will be closely
monitored this autumn and winter
for the same reasons. Their moisWXUH SUR¿OH LV DOVR TXLWH OLPLWHG
and without greater precipitation
over the winter there could be a
serious shortage in the spring that
might threaten production. As long
as La Niña goes away for a while
in 2021, all of these drier biased areas may have a better chance to get
VLJQL¿FDQW PRLVWXUH ZKHQ QHHGHG
But if La Niña prevails too long,
there could some greater production concerns.
Drew Lerner is senior agricultural
meteorologist with World Weather, Inc.
He may be reached at worldweather@
bizkc.rr.com. World Weather, Inc. forecasts
and comments pertaining to present, past
and future weather conditions included
in this report constitute the corporation's
judgment as of the date of this report and
are subject to change without notice.
We want to hear from you - Send comments
and inquiries to worldgrain@sosland.com.
For reprints of WG articles, e-mail
reprints@sosland.com.

59
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