We had a cold core event produce tornadoes in Iowa in January of this year, so there is certainly greater focus on longshot cold core setups now as we start moving towards meteorological Spring. The Storm Prediction Centered issued a Marginal Risk tomorrow with a non-zero tornado threat in Eastern Kansas and Northwest Missouri.
Cold Core Tornado Events Are Rare in Cool Season
One of the secrets to employ while forecasting is to simply look at historical trends to see if certain types of setups produced in the past. While this doesn’t preclude setups doing completely unexpected things, they give you guardrails when considering a forecast. In this case, it is worth noting that tornadoes with the types of setups tomorrow are pretty rare! Lots of these happen every year but it seems like only a couple/few actually ‘get the job done’ so to speak.
Watch the Dewpoints Tomorrow
One thing to keep an eye on for upper-end potential tomorrow is what dewpoints do. Interestingly enough, and against its historical trends, the HRRR does not tend to mix out dewpoints across Eastern Kansas/Western Missouri despite dry air/southwest winds encroaching on what is a weak surface boundary extending SE from a surface low in Nebraska.
The HRRR not mixing out dewpoints in this surface regime is something that doesn’t typically happen. So I’m intrigued!
Conceptually, what makes more sense is a lot of mixing as dry air punches east through the day in the boundary layer as the FV3 shows here.
Longshot Cold Core Setups are Notoriously Fickle
With that said, there are numerous things which could really take tomorrow in one direction or another.
- As we just went over, will the dewpoints mix strongly through the afternoon or will they maintain in the upper 40s? This is a major difference in the degree of instability tomorrow.
- There will be a expansive rain shield move through during the night/morning hours. If temps are slightly cooler in either direction, tomorrow can really change.
- The timing of storm initiation is a big key too. Will storms hold off and allow the surface to heat longer?
A look at a sounding on the HRRR shows dramatically cool temps aloft under the 500mb low with storm tops only at or near 20,000’.
Conversely, the FV3 dries out the lower atmosphere by quite a bit which lowers the available moisture AND raises the cloud bases.
Don’t Count On It But Don’t Be Surprised If….
I have always used this saying for marginal risks, especially 2% tornado risks. Basically, tomorrow has a few ingredients that, if they go the ‘right’ way you could get a brief and weak tornado or two from very low topped supercells. If any one of the ingredients (surface temp, dewpoint, temps aloft, etc.) is not as favorable as shown today — then the threats of severe weather are greatly diminished. It’s a longshot, but that’s what sometimes works.