As we approach the time of year when severe threats turn to be more frequent in the Delta states than in the South/Southeast, it is important to understand the role of limit reversals and how it can serve to enhance severe weather or induce “blue sky busts”.
You are probably also familiar with this term. If not, I have prepared a homemade explanatory image to illustrate the concept.
Limit inversion occurs when there is a layer of warmer air overhead. This typically occurs in the Plains states when warm, dry air from the desert Southwest is brought into the area.
As the atmosphere warms, the heated air at the surface begins to rise. If there is enough moisture, it will create clouds when it reaches the air saturation point. When there is a limit reversal, this level is usually found just below the limit.
The rising, now saturated air finally hits the limiting inversion layer, a layer that is, sometimes significantly, warmer than the air below it. Air cannot enter another layer of air warmer than it, so it is forced to sink. In a situation like this, you’ll often see rows of cumulus clouds in fine weather overhead with clear grooves between them.
This process continues until enough instability builds up underneath, the underlying air is heated past the temperature of the lid, or a lifting mechanism (such as a cold front or dry line) appears to push the air. gas through the cap.
After the cap is eroded or broken, if all other atmospheric conditions are true, then deep convection can occur.
In situations where there is not enough added instability, heating during the day, or no forcing mechanism, the lid remains in place and no deep convection occurs – hence the term “break”. blue sky”.
We’re seeing this problem today in the Southern Plains, where there was a very strong cutoff this morning, as seen on the 12Z observed emitting from Norman, OK.
Farther north in the Central Plains into the Missouri River Valley, the cap, although also quite strong, is not considered an overwhelming problem.
The latest modeling data from HRRR shows the limit is somewhat weaker in the Southern Delta this afternoon while it has mostly eroded over parts of the Central Plain.
The Central Plains region is located closer to the lower region and is better affected by both hot and cold fronts coming. The Southern Plains region is far from the good force and is relying on the dry line as an additional lifting resource.
The question is, will that dry line provide enough thrust to push through the limit before it builds up again stronger as night falls and the boundary layer becomes more stable?
As of now, not much is happening in the Southern Delta. However, if you examine the Central Plains in Nebraska/Kansas, you can see a faint return that seems to indicate cold air is moving. We’ll likely see some action developing east of here shortly.
While the cap could leave us bust blue skies further south, if hurricanes MAY form, they could be very powerful.
Heavy hail and a few tornadoes are possible for both areas of concern, but the Central Plains/Central Missouri Valley presents a risk of significant wind damage in addition to the other two hazards.
- Severe weather is forecast today across the Central Plains/Mid-Missouri Valley and possible in parts of the Southern Plains (primarily Western Oklahoma and North-Central Texas).
- Turn on your weather radio and get ready to go along with at least one other reliable way of getting alerts.
- Although tornadoes are not the primary risk, they can still happen. Be prepared to take shelter if necessary.
- Consider taking shelter during severe thunderstorm warnings, especially in the northern part of the high wind risk area.
- Heavy hail is expected. Park under a roof if possible.
- Raise awareness. If you know anyone in the area at risk, make sure they are aware of the possibility of severe weather this evening.
About the author
Meteorologist – ’22 Mississippi State Writer for Weather.us and Weathermodels.com. Focus on weather communication. BoyMom x1, CatMom x5. Twitter: @MegGulledgeWX