Winter 2019-2020 will be remembered as warm and wet for most of the US. A strong polar vortex plus split flow in the jet stream in the North Pacific Ocean only allowed for brief interludes of cold air leading Missouri to have is 10th warmest and 18th wettest winter on record. The southern states have been extremely wet which has limited spring fieldwork from Texas to South Carolina while drought has gripped California (despite above normal March precipitation). As we move into Spring the big questions are about flooding threat in the corn belt and if sizable planting windows will open throughout April and May. Here are the details.
- March 2020 will finish just as wet as it began. An "Omega Block" is setting up over Alaska which is displacing cold air into a trough off the west coast of the US. That pattern leads to frequent low-pressure systems that track from the 4-corners states to the Northeast. The south will remain wet as will parts of the Midwest while snow covers the ground in parts of Nebraska, South Dakota, and Montana after melting away in February.
- Saturated soils in the Missouri, Mississippi, and Ohio River Valleys will increase the likelihood of spring flooding along these main river systems. Soil moisture anomalies are not as high as they were in 2019, but they are elevated over the 30-year average. We must watch for large low-pressure systems that can transport a lot of moisture and warmth north from the Gulf Of Mexico that melts the snow and adds several inches of rainfall. That would be the worst-case scenario for spring flooding in 2020 (and is exactly what we saw in 2019).
- A strong southern branch to the jet stream has lead to the 3rd most active start to the severe weather season over the last 15 years. The probability of keeping on track with an active severe weather season is very high at this point.
- One major driver of the early spring activity in our weather systems has been anomalously high global winds. We measure the net wind speed of the atmosphere and compare it to normal and to the rotation of the earth. When these winds are faster than normal, we see a lot of weather systems - just like winter and early spring this year. This same phenomenon happened in 2019, but the big difference is in timing. The global winds seem to have peaked early and if they calm down throughout March and April this will lead to more favorable precipitation patterns for planting. Watch this closely.
- Unlike 2019, Spring of 2020 does not have a weak El Nino in the central Pacific Ocean. El Nino springs and summers are often wet and without that feature this year, many are investigating the possibility of a weak La Nina forming. La Nina's are accompanied by cool water of the west coast of the Americas and strong trade winds. This tends to lead toward hotter and drier summers in the Midwest. Currently, the ocean temperatures are cooling along the coast of both North and South America and if the atmosphere responds by increasing trade winds and slowing the polar jet stream, this could increase the chances for summer heat.
- Brazil and Argentina have had a largely benign year in terms of weather issues. Both countries are expecting very large crops of soybeans, corn, and cotton. Lately, heat and dryness in Argentina has curtailed some of the bigger numbers on yield for full season corn while a delay in soybean harvest efforts in Brazil pushed about 40% of the safrinha corn crop to be planted outside of the ideal planting window. If the monsoon slows early this year, April conditions could turn very dry for parts of Brazil just as safrinha corn hits pollination. This needs to be monitored closely.
Recapping these ideas, early spring weather looks wet, but there are several indicators pointing toward a more "normal" planting time period. Remember that there is a lot of excess water still in the soil which will limit early fieldwork. We need to watch global winds as well as the Pacific Ocean for clues on summer's weather patterns and the potential for hotter and drier conditions. Weather patterns are different enough from early spring 2019 to suggest that 2020 will not be as anomalous, but we need to watch for a more active severe storm season this year.
