A Columbia University study has found that El Niño and La Niña have an impact on severe weather in Tornado and Dixie alleys. THE RELATIONSHIP BETWEEN EL NINO, LA NINA, AND UNITED STATES The Storm Prediction Center's archive of United States tornadoes from The El Niño/Southern Oscillation (ENSO) is characterized by changes However, the strength of the relationship to intense tornadoes was not.
Keep in mind that any sort of comparison using the full record is going to be extra problematic when it comes to tornado counts. Population and observation capabilities have increased since when the modern record began, in some cases quite dramatically. Fortunately, ENSO phase changes are fairly common. El Ninos have a bit of the short end of the stick thanks to a bunch early in the record. In all cases below, except for the general tornado fatality figures, I have grouped moderate and strong El Ninos or La Ninas together.
How does El Nino, La Nina or La Nada impact the following tornado season? - U.S. Tornadoes
Is there any impact on timing? Tornadoes happen all year most years. That said, over half of the tornadoes on record have come in a three month span from April-June. That percentage rises to about 75 percent looking at March through July.
So tornado season is only something of a misnomer. In this phase, May and June are basically identical over the years, but June holds a very slight — two tenths of a percent — edge. Above it is easy to see that post El Nino years tend to start slower but hold on a bit longer than other years. Moderate to strong La Ninas have placed on April and early-season compared to normal.
Over 19 percent of moderate or strong La Nina tornadoes have occurred in April compared to the non-Nina average of 12 percent. The moderate and strong La Ninas have a higher percentage of tornadoes than other phases from January through April in the sample, then fall behind the rest in May and stay there through the year.
The rollover likely loses impact once we get into the back half of the year, but there are typical transitions from El Ninos like we may see in It lasts at least into the middle of the year and probably longer depending on strength and other factors. So the question arises: Starting with the whole record back to delivers some potential leads. Moderate and strong El Ninos took up their fair share of real estate as well, especially up north and out west.
Neutral was the third most likely to be favored. The weak El Ninos and La Ninas were generally barely noticed comparatively.
El Niño Can Predict Tornado Season's Severity
Interestingly, a number of the Plains states tended to favor years coming out of neutral winter when it comes to upside tornado risk. This is also around the time higher standards for F2 tornadoes were captured in surveying.
Maybe an argument not to sleep on a moderate to strong El Nino despite some studies indicating quieter years coming out of an El Nino. Currently, the National Weather Service's Storm Prediction Center issues tornado outlooks up to eight days in advance.
In contrast, hurricane outlooks come several months ahead of the summer storm season. However, though the Columbia University research team plans to issue its own forecast as soon as next year, optimistically, an official forecast is at least five years away, said Ashton Simpson Cook, a meteorologist at the Storm Prediction Center who was not involved in the research.
The authors did not use historical tornado records, which are fraught with reporting biases. Instead, they analyzed the environmental conditions that favor severe weather, such as temperature, atmospheric moisture and wind shear, which is different wind directions and speeds at different elevations above the surface.
Cool sea surface temperatures dominate in the eastern tropical Pacific.
These temperature shifts have a ripple effect on wind patterns around the world, which, in turn, affects where storms form.
So far, the tornado season is off to a slow start, with 28 tornados reported, according to the Storm Prediction Center. For instance, the southerly flow brings cool, dry air from the plains and Canada. This brings warm, moist air into Tornado Alley, the twister-prone regions of the United States.