Severe weather experts at AccuWeather.com are forecasting the intense weather outbreaks in the U.S. to continue beyond April into much of May.
According to Severe Weather Expert Meteorologist Henry Margusity, "We see no let-up in the weather pattern that has led to the outbreaks this month."
A pronounced temperature contrast often produces strong storm systems.
May is notorious for severe weather and tornadoes in its own right as warmth builds from the strengthening sun, while the upper atmosphere and the low-level air over the northern latitudes remain chilly.
The jet stream tends to hover close to the temperature contrast.
We cannot say that there is a direct correlation between La Nina and a particular outbreak. However, the ocean water temperature anomaly in the Pacific tends to lead to a strong polar jet stream.
While a strong jet stream is a common occurrence in the spring, the presence of a strong, ongoing La Nina has that strong jet stream on steroids.
A strong jet stream is a key contributor to severe weather and tornado outbreaks.
While the ongoing La Nina may weaken slightly in the coming months, it is still rather strong at present. It could continue to fuel, in an indirect way, frequent strong storm systems and the severe thunderstorms they often breed.
As the chilly air around the Great Lakes, Northeast U.S. and neighboring Canada retreats northward, the risk of severe weather will increase in these areas.
While this too is part of the normal northward progression of severe weather in the spring, the strong La Nina driving the strong jet stream may continue to make severe weather matters much worse than normal.
Two other factors, such as warm, moist air from the Gulf of Mexico and intrusions of dry air from the West, are always players in severe thunderstorms.
The Gulf of Mexico is much warmer than average this spring. The extra warmth translates to higher moisture levels (higher dew points) over downwind areas of the land.
In contrast, the air is extremely dry (low dew points) over southern High Plains as evidenced by the drought and wildfires in the region.
Both of these secondary factors, combined with the strong jet stream may be cranking up the potential energy to be released in the form of violent storms.
It is possible that smoke from the wildfires may be limiting severe weather incidents (and tornadoes) over the favored area of southern High Plains.
However, it may be that the air is just too dry and too extensive in that area, pushing the boundary of the dry and moist air (dry line) farther east, closer to the middle and lower Mississippi Valley.
This boundary is often the fuse for severe thunderstorms and tornadoes.
Throw in the strengthening sun and building warmth to the mix during May and we could really have some ferocious storms on our hands.
From AccuWeather.com (find the original story here); reprinted with permission.