We have been in a dominant wet, cooler pattern without a lot of violent severe outbreaks or drought since 2014. We have been in a solar minimum with positive PDO, positive PNA & weak ENSO events mostly.
We are in a cycle to revert back to pattern more like that of 2010-12 or 1999-2001 (increasing sun activity after Solar Cycle 24, flip to negative PNA, negative PDO & warm phase AMO) feature greater severe weather outbreaks in the Midwest in spring with repeated outbreaks, some violent with greater potential of drought in summer & fall (example.....1886 spring was very violent & we saw violent weather in the fall, but it actually turned droughty in summer to fall).
Often such periods have a sequence of outbreaks where you see severe weather over a region day after day for a week or two on-end, often with higher risks like ENHANCED, MODERATE day after day with occasionally an apex of HIGH RISK.
We have not had a sequence of severe weather outbreaks in a row over a period of time on a substantial scale since 2010 & 2011. In 2010 I worked 21 consecutive days in June with severe weather events & outbreaks every few days.
We have not seen a significant drought in the area since 2012, though we have had a few pockets of Moderate Drought over the past 7 years. We are seeing that right now.
1973-75 & 1987-89 La Ninas also come to mind with violent outbreaks of severe weather in 1973, with the big two outbreaks in 1974 & a big winter outbreak in the 1974-75 winter. Drought occurred in the summer of 1974 & there was a lack of intense cold in the winters of that period.
Overall................
La Nina should return quickly in summer 2020 & ramp up for 2020-21 winter & last into 2021 summer & fall. Looks to be the strongest & lengthiest since 2010-12 or 1999-2001.
Despite more violence & greater severe weather episodes in both springs (we have not had an F4/EF4 tornado in the viewing area since 1994 & we average one in the viewing area every 14 years so we are overdue. We are currently in our longest F4/EF4 tornado drought since the 1930s, widespread drought should return to our area with varying intensity 2020-22.
We average 2 HIGH RISK days per decade & I think 2021 could be the first occurrence for our area of the decade. They often coincide with strong La Ninas.
We already have this semi-permanent upper ridge in the Southeast with heat & dryness & La Nina will enhance & expand that ridge.
Significant drought may occur Texas to the Southeast & it will pulse & engross the area at times. Other times we may be under that pattern of lots of storms & heavy rainfall (with tornado risk).
However, I do see more drought & sustained drought here.
We should see 100 or greater again, something we have not seen in the area since 2012. We have been close on a couple of occasions, but we did not reach or exceed it in the area in any of the summers & falls of the past 7 years.
Interestingly, we nearly reached it in May 2018!
Also, I see less of the cold, wet springs that linger on for years on end. We have had to deal with wet, wet, wet springs for years now & I do think that may abate somewhat as we get into this La Nina.
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So...........
2019-20 Winter neutral - Colder, snowier, wetter than normal
2020 Spring just starting to trend to La Nina - Cooler, wetter than normal
2020 Summer La Nina developing - Normal temperatures, wetter, then developing flash drought
2020 Fall La Nina - Warmer, Normal precipitation
2020-21 Winter strong La Nina - Warmer than normal, wetter, drought quashed, severe weather possible
2021 Spring strong La Nina - Warmer, very active severe weather, slightly wetter
2021 Summer La Nina - Developing drought again, intense heat
2021 Fall La Nina - Drought, heat
Winter 2021-22 Trend to neutral, then weak El Nino - Normal temperatures, normal snowfall, normal rainfall
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Strong La Nina:
Greater potential of wet winter with random severe weather in winter.
More violent, more frequent severe outbreaks in spring
Warmer springs
Increased frequency of summer & fall drought
Increased likelihood of 100 degrees or greater & increased likelihood of intense significant heat waves.
Winters..............weak vs. strong La Nina:
