The new tornado season and the meteorological spring in the United States are both here. A finally decrepit La Nina could result in increased severe weather events and well above-average tornado activity this year. The South and Southeast areas of the country could be hit with severe weather and tornadoes over the next week.
The meteorological spring officially began three weeks ago. Monday, January 20, 2022, marks the official start to the astronomical spring season. The United States’ tornado season will be the main focus of the next few months. Similar to last year’s, colder than usual Pacific waters are still present, with a decaying La Nina worldwide circulation which has an impact on the patterns across North America.
During the La Nina, and especially when it is transitioning to a neutral phase of the cycle, there is a potential for more severe weather events or above-average tornado activity. Although the recent winter season was quite active and cold, it didn’t slow down tornado activity at all. We can only recall the deadly tornadoes that hit Iowa a few months ago. Soon, thunderstorm activity will increase.
Recent weather model guidance confirms that there is a high probability of a strong weather system developing in large parts of the central and south United States. It will be active from Monday through Wednesday. It will bring spring snow on the north side and severe thunderstorms further south.
The statistics seem to be following the severe thunderstorm activity pretty closely this spring, with soon catching up to the long-term activity. The coming week’s forecast calls for a potentially dangerous severe weather and tornado outbreak with a significant threat across the South and the Southeast United States. There are increasing odds of a tornado outbreak developing as a strong, surface depression with a frontal storm rips through the central U.S. Moving into the Dixie Alley, with areas from Eastern Texas, Louisiana, Mississippi and Alabama in its prime zone, there are also areas from Mississippi, Louisiana, Mississippi and Alabama.
We are seeing an active start to the tornado activity this year and in spring, about 20% more than in a normal season. As we saw, severe weather activity started earlier than usual, especially when compared to recent years. The weather models show that the 2022 spring season could see a tornado season well above the average.
The Gulf of Mexico and Caribbean region have higher than average seawater temperatures. This is because they provide moist air mass to fuel the storms. The strong winds at the upper-levels of the atmosphere, along with the jet stream, are also important. The combination of the very moist and warm atmosphere at the lowest levels and the strong jet stream above it, creates organized severe thunderstorms.
While severe thunderstorms or tornadoes can occur at any time of day, they are most common in the central and south U.S. during March and April. This is why meteorologists consider spring to be severe weather or tornado seasons.
Let’s quickly go through the most important factors as their understanding is crucial for the forecasting of severe weather events.
TWO MAIN INGREDIENTS, INSTABILITY and WIND SHEAR
A thunderstorm is formed when surface heating results from an upward rising warm- and moist air mass. This occurs usually along a frontal boundary (e.g. This can be a cold front, dryline or other type of frontal boundary.), or mountain ranges for example. When air parcels rise, the condensed air creates precipitation. A thunderstorm is born when thunder and lightning are heard.
A more stable environment can result in more dangerous severe weather events. These are the times when severe thunderstorms become a problem. Supercell thunderstorms are the most dangerous type of storm. These storms are the most dangerous and can cause flooding, large hail and winds, as well as tornadoes.
Two main ingredients determine the intensity or type of potential severe weather (thunderstorms). These are the available energy, also known as instability, or the winds. Wind shear is caused by the difference in speed and direction between upper-level and lower-level winds. Severe thunderstorms are then caused by a combination of instability and winds.
To simplify: The higher the wind shear and instability, the more dangerous and robust thunderstorms could form.
Strong or extreme instability
We often refer to the unstable air mass InstabilityWhen we talk about the potential convectively available energy (or short: CAPE), the environment contains to fuel storms. The more energy that is present in the atmosphere, the more intense convection and storms are likely to develop. Sometimes, huge amounts of energy can lead to the explosive development and destruction of storms. The extreme events could see CAPE as high as 6000 to 1000 J/kg.
This is how we see the Gulf of Mexico’s seawater temperatures. The majority of the moisture in the U.S. comes from the Gulf of Mexico during the spring season. This is the key factor and directly influences the tornado season activity in the South, Southeast and Midwest U.S.A. due to higher energy levels in March and April. This region is also known locally as the Dixie Alley. It has been the scene of numerous deadly tornado outbreaks in the past.
So the source of very moist air actually comes from the deep southern tropical region as well as from the Caribbean Sea. The following chart shows that the sea surface temperatures are around 1-2 degrees Celsius more than the average. The higher the water level, the more moisture (dewpoints), are present.
This is a crucial signal to watch for the spring tornado season. The high moisture gradually spreads into the United States from March into April and then increases through May and Juni further north across the Great Plains, Midwest, and Midwest. This indicates that the energy could increase rapidly if there is a stronger warming in April.
This is why it is important to remember that the more energy is accumulated, the higher the humidity and temperature. This means that spring is more likely to see stronger convection and severe thunderstorms.
Jet stream and wind Shear
The wind throughout the atmosphere is the second ingredient, which is also crucial for thunderstorms to organize and get moving. From the lowest levels to the highest-level parts. Winds at higher levels are stronger and are known as the jet stream.
The temperature difference between large-scale systems at the upper levels of our troposphere is what creates the jet stream. The jet stream will be stronger if the systems are stronger. The speed of wind increases with height. However, the direction of the wind changes. This is known as the Wind shear.
Wind shear is an important ingredient for severe thunderstorm environments. A rotating updraft tower is created when the wind changes with height. This helps thunderstorms to live longer and sustain themselves. These are called the Supercell thunderstorms.
As the winter transitions into spring, the upper-level winds start to retreat towards the east every year. The effects of the La Nina degrading will make the jetstream stronger than ever in 2022. This is also amplifying the winds closer to the ground, which helps to pump the fuel for storms – moist and very warm air mass – from the Gulf of Mexico to the north.
The chart shows the typical late-winter/early-spring season climatological activity of severe weather across the United States. The frequency of severe weather events in the South and Southeast United States tends to increase as the jet stream is amplified.
These tornadoes are stronger in the spring season, according to studies of the Tornado and Dixie Alley tornado events environment. When the Pacific waters are colder, March and April tends to produce more tornadoes than usual. This is why it is important that we study global patterns and how they can help us predict what to expect during a tornado-season this spring.
2022 TORNADO SEESON NEAR NORMAL SO FOR
As of this weekend’s March 18th, 140 tornadoes had been reported in the United States. An average year produces around 170 tornado reports between January 1st and mid-March. So 2022 tornado season is not far off. It runs at about 80% of the long term normal this spring.
This does not mean that the season could see below-normal activity. However, the general spring season forecasts point to an increase in activity. La Nina will be ending its last weakening this year. This normally leads to higher severe weather events, and above-average tornado activity, from March through June.
This spring season could see an above-average number tornadoes due to the below-average tropical central Pacific water temperatures. Statistics are likely to catch up in the coming weeks. The forecast conditions are favorable for higher tornado counts than in recent years.
The chart above shows the most recent ENSO forecast for central Pacific ocean water temperatures. Cooler Pacific waters can lead to more severe weather, including the notorious Tornado Alley and Dixie Alley. There is a greater chance of tornado outbreaks. La Nina tends not to produce tornado outbreaks, even though one day or event could lead to many dangerous twisters.
DANGEROUS SERIOUS WEATHER WITH TORNADO OUTBREAK TEXAS & LOUISIANA ON MONDAY
The weather pattern across the United States will rapidly change on Monday with a deep upper wave forming in the southwestern regions of the country. As it moves towards the southern Plains, the low will continue to deepen. Due to the strong upper High in the eastern US, plenty of moisture and warm weather will spread northwards towards the western Gulf Coast.
An upper wave that emerges from the west across the southern Rockies will cause a rapid moisture recovery in Texas and Louisiana. The associated frontal waves and fronts will then bump into very warm and moist Gulf of Mexico air, which can lead to severe weather.
High-level thunderstorms will be supported by strong, moist advection from the southerly wind through Monday morning hours in central Texas. The persistent southerlies moving northward with high Gulf moisture will cause a gradual increase in thunderstorm activity.
The possibility of thunderstorm development in central Texas will be most prevalent by afternoon.
Supercells will benefit from the combination of high flow and significant veering at the lowest 3km.
Large hail is possible in central Texas from storms, while tornadoes are more likely to strike further east.
Through the night and into the morning, the favorablely unstable airmass will expand to the east across the Sabine River into Louisiana. There will be very strong shear.
This will increase tornado risk, especially in East Texas, Louisiana, and beyond.
SEVERE WEATHER – TORNADO THREAT LIKELY TO CONTINUE INTO MISSISSIPPI & ALABAMA TUESDAY
There is the possibility of another severe weather event and a tornado outbreak in parts of the Dixie Alley the day after.
On Tuesday and Wednesday, the upper wave disturbance will be intensifying as it moves further east across the central United States. Its deep core suggests that it could pose a serious threat to the air masses in the South U.S. Severe storms are expected to intensify on Tuesday afternoon, and again on Tuesday evening.
The jet stream, which is very strong, develops aloft and is the main reason for the increased chance of large tornado outbreaks. It is associated with the eastward moving deepening upper core and it couples with the unstable air mass below.
The core of the upper low will be surrounded by strong upper-level winds, which will provide a very favorable source for a lifting mechanism that allows thunderstorms to continue and expand their coverage on Tuesday and Wednesday.
The jet stream will experience very strong winds speeds (100-130 knots), which will increase the wind shear and create a volatile environment that allows storms to form. These conditions support the development of tornadic hurricanes.
Below is the Storm Relative Helicity Chart (SREH), which measures the amount of wind shear available to the ground from the lowest levels in the atmosphere. If values are higher than 250 m2/s2, it indicates a greater risk of supercells or tornadoes. These are very concerning numbers and could indicate the potential for strong tornadoes.
The Gulf of Mexico is a hot spot for high moisture (surfaces dewpoints in the 60s) that moves northward into the prefrontal warm sector. This area includes Louisiana, Mississippi and central Alabama. The central Gulf Coast states are likely to have a high-end environment that is conducive to dangerous twisters. This area could lead to a significant outbreak or severe thunderstorms.
The tornado threat should be increased in eastern Louisiana and central Mississippi by the afternoon, then moving eastward into Alabama. These conditions are extremely concerning and could cause a dangerous tornado outbreak in part of Mississippi and Alabama on Tuesday. There is a high likelihood of tornadoes and severe damaging winds, as well as significant flooding.
The severe weather threat will likely persist into Wednesday, but the upper wave may become somewhat longer as the upper low shifts northeastward through the Ohio Valley. This will create an unstable and humid environment with strong shear in parts of South Carolina, Georgia, Florida Panhandle, and southeastern Alabama. Continued potential for severe thunderstorms, including a few more tornadoes.
You should tune in to your local National Weather Office for the most recent updates and warnings, especially if storms are forecast for Tuesday.
ABOVE-AVERAGE SLIGHT WEATHER TORNADO ACTIVITY LIKE THIS SPRING SEASON
The warming of the United States during the spring season increases from south-to-north. The Gulf of Mexico’s moist atmosphere is becoming increasingly unstable as it mixes in with warmer areas to the north. We can get a sense of what is possible for the tornado season if we consider the still-existing La Nina, which normally boosts activity. It’s not so simple, but it is likely that we will encounter a very tornado active spring season this year.
Similar to the season 2021 the main activity may shift again this year, possibly into the low-mid Mississippi Valley, and the central Gulf Coast. Although this does not necessarily mean that there will be fewer tornadoes in Tornado Alley, the activity may keep them below average.
The Midwest and southern United States should still have the highest frequency of tornadoes or severe weather hazards each year.
The Southeast United States region is best known for its Dixie Alley tornado outbreaks. When tornadoes do occur, it is often a difficult area to live in. The Mississippi Valley is filled with trees and high humidity so tornadoes are more dangerous than in the Great Plains.
With the weakening upper level winds and the high temperature contrast below, the south-central US states around the Mississippi river may be at greater risk through April. Then, you should expect a shift towards traditional Tornado Alley.
The strong jet stream pattern will likely continue into May. This will ensure that storm chasers throughout the country will be busy this year.
*** The images used in this article were provided by Wxcharts, PivotalWeather, and Windy.
Also see: A strong Polar Vortex collapse event is now underway, causing the stratospheric winter circulation to be disrupted
Source: Severe Weather
