Mississippi’s first tornadoes of 2021
By Skip Rigney
After a slow start, Mississippi’s 2021 tornado season came to life Wednesday when five twisters hit the state. These were the first tornadoes in Mississippi since December 23rd.
The most intense of Wednesday’s tornadoes touched down 15 miles west of Waynesboro. Meteorologists from the National Weather Service in Mobile surveyed the damage in Wayne County on Thursday. They found the tornado was on the ground for nearly 13 miles and estimated its maximum winds at 135 miles per hour.
The closest tornado to Pearl River County occurred 12 miles west of Purvis in Lamar County. Surveyors from the NWS in Jackson reported that its 80 mph winds destroyed a couple of sheds, took most of the roof off of a home, and blew a tree through a mobile home.
Forecasters at the NWS’s Storm Prediction Center predicted Mississippi would be the epicenter for Wednesday’s severe weather outbreak, but even more tornadoes hit Alabama where preliminary reports indicate at least a dozen touched down. Additionally, there were 166 separate damage reports across the South associated with straight line winds from severe thunderstorms. One of those reports was of damage to several homes near Highway 43 in Marion County less than five miles north of the Pearl River County line.
The main catalyst for the severe weather was a strong low pressure system, which moved eastward through Oklahoma on Wednesday and by Friday morning was pushing off the eastern Atlantic seaboard. Thunderstorms developed in the southeastern quadrant of the low’s counterclockwise swirl of winds, as warm, moist air was rapidly lifted upward.
Unlike hurricanes, which get stronger when wind shear is weak, non-tropical thunderstorms are most likely to produce tornadoes when they are embedded in an environment with large wind shear.
With the wind direction changing with height, updrafts into a thunderstorm can begin to rotate producing what is called a supercell thunderstorm. The rotation of the supercell sometimes becomes concentrated enough that a tornado forms.
The wind shear also tilts the storm. This allows the updrafts into and downdrafts out of the storm to be nearly balanced, helping the system stay alive for hours.
That is what happened Wednesday afternoon in east central Mississippi and Alabama. To the south and west here in Pearl River County, wind shear was weaker. Instead of forming discrete supercells, the thunderstorms developed into a solid line that moved through the area Wednesday evening. Lightning detection networks estimated over 1,000 lightning discharges over the county. Radar-estimated rainfall totals ranged from one inch to over two and one-half inches with some of the heaviest rain falling near Crossroads.
No rain is forecast for the next several days as high pressure dominates the eastern one-third of the United States.
However, several rounds of rain, some heavy, are possible Tuesday through Friday as multiple disturbances move eastward across the area.
In addition to heavy rainfall, forecasters are also monitoring the potential for these systems to produce strong thunderstorms.
It will be a good week to keep up on the latest forecasts from the NWS in Slidell, available online at www.weather.gov/LIX.