5th Season: Is tornado alley shifting east?
LAWTON, Okla. (KSWO) - Tornado alley is an area located in the central part of the United States where tornadoes are most frequent. Warm, moist air from the Gulf of Mexico meets dry, warm air from the west and cold dry air from the north. This becomes the ideal environment for tornadoes to form within strong thunderstorms and supercells.
The exact science on how tornadoes form are a bit more complex than that and before we talk about the other ingredients needed let’s first talk about what is needed for a thunderstorm to develop.
For a thunderstorm to happen you need: sufficient moisture, dew points in the 60s/70s, instability, will there be vertical motion within the atmosphere and some sort of lifting mechanism, usually a cold front. These 3 ingredients come together to form your day to day thunderstorm.
A tornado by definition is a violent rotating column of air extending from the ground to the base of a thunderstorm. In order for a tornado to form, it also needs moisture, instability, a lifting mechanism but also wind shear. Wind shear is the change in wind direction and speed with respect to height.
But its not just tornado alley that sees tornadoes, tornadoes happen all across the United States with Alabama, Mississippi and Arkansas also receiving their fair share of tornadoes each year.
While tornado alley remains king when it comes to frequency of tornadoes, a usurper has been rising in the ranks over the past couple of decades. Don’t take this the wrong way, tornado alley’s spot at the top of the mountain will continue to be uncontested, however they are not the leader when it comes to tornado frequency growth since the turn of the millennium.
There exists a second “tornado alley” in the United States. Located in the southeastern US encompasses the states of Mississippi, Alabama, Arkansas, Louisiana, and parts of Tennessee and Georgia.
Tornado alley is famed for its unobstructed views and flat environments for prime tornado viewing and chasing. The southeast is located in a region with lots of trees and hills, and the high amount of Gulf moisture in the Deep South causes most tornadoes that spawn from storms to be rain-wrapped, which limits tornado forecasting and identification. So while historically both tornado alley and the southeast have been active tornado hotspots, the southeast hasn’t been associated with the same accolades and perception due to the terrain and viewing difficulty that comes with the region.
But over the last couple of decades, with advancements in storm spotting and radar technology like the dual-pol radar, improvements in NWS severe weather practices, and the construction of more radar sites to limit blackout, data has shown that there has been an increase over-time with the frequency of tornadoes in the Deep South as opposed to a static & consistent tornado trend in the Great Plains. Does that mean that the tornado alley is shifting eastward?
The answer is no. Rick Smith, the warning coordinator for the National Weather Service Forecast Office in Norman describes how tornado activity across Oklahoma hasn’t changed.
“We haven’t really noticed any trends in severe weather, certainly not lower. We had a record number of tornadoes in Oklahoma just a few years ago, set an all time record. So, while the perception among some is that there’s not as much severe weather, not as many tornadoes, we certainly don’t find that to be the case. We’ve had no shortage of long days, active days, with lots of watches and warnings. That’s pretty much been a constant”
What the data has shown over the past couple of decades is that the region of the US that encompasses the greatest number of annual tornadoes is expanding in size to the east to include more of the Deep South, as well as parts of the Mid South & Midwest.
Smith also says its easy to get complacent if you haven’t had a bad storm or tornado in your area for a while but not to let your guard down.
“its easy to think “well we haven’t had it in a long time, so maybe we won’t have it again’ or there’s a myth that tornado alley has somehow shifted somewhere else. Just a reminder this time of year, that nothings changed in the atmosphere. We need to be ready for severe storms and tornadoes, its not a question of if we’re going to get more tornadoes in Texoma, it’s a question of when, how often and how bad they’re going to be. It takes just a few minutes to think about it this”
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