TORNADOES IN THE MIDWEST

Weather Pattern Discussion

There has been increasing discussion about whether the developing El Niño is responsible for the recent outbreaks of thunderstorms, severe weather, and the potential for tropical development in the Gulf. However, it is important to remember that many of these weather events are quite typical for late spring and early summer.

Severe thunderstorms, tornadoes, large hail, and heavy rainfall are common across the Plains, Midwest, and eastern United States during this time of year. Likewise, occasional early-season tropical development in the Gulf or western Atlantic is not unusual. The mere presence of these weather events does not necessarily mean they are being driven by El Niño.

Historically, the strongest impacts from El Niño tend to occur during the fall and winter months when the southern branch of the jet stream becomes more active and shifts farther south. During late spring and summer, the jet stream is generally positioned farther north, which often limits the direct influence that El Niño can have on day-to-day weather patterns across much of the United States.

That does not mean El Niño has no influence at all, but its effects during the warm season are often subtle and can be difficult to separate from normal seasonal weather variability. As a result, it is important to be cautious about attributing every thunderstorm outbreak, heavy rain event, or tropical disturbance directly to El Niño. Many of the weather events occurring now are consistent with what is typically observed during late spring and early summer, regardless of the state of the tropical Pacific.

Bottom Line

• Severe thunderstorms and tornadoes are common during late spring.

• Early-season tropical development is not unusual.

• El Niño's strongest influence on U.S. weather typically occurs in fall and winter.

• Summer weather patterns are often driven more by seasonal storm tracks and regional conditions.

• Be cautious about linking every current weather event directly to El Niño.