World Grain - March 2022 - 70

FEATURE: BAD OMEN FOR CENTRAL US WEATHER
the past, but there are certain times in weather history
in which the presence of strongly negative PDO and a
multi-year La Niña event can work together to produce
notable dryness in the middle of North America, and
this year may be one of those times.
The times in which these features have come together
to reinforce the dry bias seem to occur between
the solar minimum and solar maximum in the sunspot
cycle. Sunspots have been monitored for hundreds of
years, and they are well correlated with some anomalous
weather around the world.
One of those highly ranked correlations is with
drought in the middle of North America and in parts of
Russia during the period between the solar minimum
and the solar maximum, which is usually a five-year
period, and it is normally associated with a La Niña
event relatively close to the solar minimum. That La
Niña event tends to last many times longer in every
other solar cycle, which is normally 10 to 12 years in
length.
Since multi-year La Niña is most common to every
other 11-year solar cycle, that cycle is referred to as a
22-year solar cycle instead of the 11-year cycle.
What will La Niña do?
This year (2022) is in that 22-year solar cycle, and
the minimum of sunspots was recorded in 2020 and
La Niña began in that same year and has prevailed 19
months with a brief two-month pause last summer.
Most La Niña events in this 22-year solar cycle have
lasted 23 to 36 months, and that helps add some support
for computer forecast models predicting La Niña
will continue through spring and possibly into summer
this year. If that occurs while PDO is still significantly
negative, the potential for drought in the central United
States becomes much greater because that is what has
happened in the past when these three patterns work
together.
La Niña creates a dry bias in the central and southwestern
Plains in the winter, and if it is allowed to prevail
through spring it will perpetuate that dryness into
summer and allow it to expand into the western US
corn and soybean production areas.
La Niña events in this cycle also tend to dry out
the southeastern United States while keeping the
southwestern states, including central and southern
California, drier biased as well. As the warm season
unfolds and the jet stream in North America weakens
and shifts farther to the north, the dry bias in the Plains
continues to be influenced by dry weather, not only because
of La Niña but due to the negative PDO as well.
PDO will have much to say about the positioning for
this year's spring and summer ridge of high pressure in
North America, but with La Niña already drying out the
70
US central and southwestern Plains and possibly the
western Corn Belt, the potential for ridge building will
be greatest over the already dry areas in the central US.
Once the ridge of high pressure establishes, it (and
the trough of low pressure in the western US) will support
rainy weather from the northern Rocky Mountain
region into Canada's Prairies and a part of the northern
US Plains while the central and southern Plains, western
Corn Belt and parts of the Mississippi River Basin
trend drier and warmer than usual.
A correlation study showing this relationship puts
it all into perspective. In the fourth quarter of 2021,
the PDO index was strongly negative. Correlations
between strongly negative PDO in the fourth quarter
of any year and drought in the central United States is
moderately high.
The correlation is also high between below-normal
precipitation and the strongly negative fourth quarter
PDO index for the eastern Midwest.
The implications of this are that 1) drought has a high
potential of prevailing in the Plains and western Corn
Belt this summer and 2) below-average precipitation
is likely in the eastern Midwest during the same period.
It is important to also note that while La Niña and
negative PDO promote dryness in the central US in the
post 22-year solar minimum years, they also promote
wet-biased weather in the winter and spring across the
northern Delta, the lower and eastern Midwest and a
part of the Tennessee River Basin.
The wet winter and spring in the eastern Midwest
and northern Delta should delay planting. Once crops
get planted, they will reproduce later than usual, and
that is when the highly correlated negative PDO suggests
dryness will evolve during June, July and August.
That implies a tough summer in the Plains and western
Corn Belt because of drought and a tough growing season
in the eastern Midwest and Delta because of a wet
spring and then a drier summer.
It is all about cycles, but a meteorologist with 43
years of experience only gets to see this pattern twice
in his/her lifetime, which takes all of their knowledge
and experience and puts it on the line for a rare time
such as this when these patterns co-exist. Past weather
performance is no guarantee of the future, but after all,
these are interesting times.
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,
email reprints@sosland.com.
March 2022 / World Grain / World-Grain.com
http://www.World-Grain.com
World Grain - March 2022

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