Yesterday’s severe event was active, but overall it was limited to a relatively small area. The grave threat today is quite different as it covers much of Central America.
However, this does not mean that the threat will be the same over the entire length of the identified risk area. Some of these threats are conditional, and some are potentially much stronger than others.
Before we get started, I’ll share my Capping Inversion infographic again. Hats will play a big part in at least part of today’s event. If you don’t know what a cap is, now is a good time to learn.
Now, let’s see if we can understand all the nuances of today’s potential event.
We start with a short wave trough. Notice the winds in the west. They are faster than those in the east. This suggests that the bottom will continue to deepen. This results in a bottom that is slightly positive to neutral.
At the surface, the lows associated with this system will continue to deepen.
As it does so, a fairly long dry line will sharpen and move east. This dry line will create a boundary that is expected to begin convection later this afternoon. At least for some, but much more in a minute.
An important note on shallows: as everyone who has ever driven storms off a coastline knows, the protrusion is where you want to target.
- Indicates stronger winds from WSW as the track moves ahead of the rest of the dry track.
- Forcing the surface wind in front of the dry line to reverse from the SE, increasing shear force in the direction.
- Provides lift to help break the cap/start convection.
So, if this particular bulge comes to fruition as HRRR suggests, it will really help regroup and concentrate the available components to give the area ahead a greater chance of a hurricane. Not surprisingly, this is where the SPC has mapped out its Medium risk for today, suggesting greater confidence that storms are forming and becoming severe here. The added courtesy of the proximity to the low surface (the triple point) is also really helpful here.
Due to all the components mentioned above, this area is home to the highest probability of all hazards – strong winds, tornadoes (some strong?) and heavy hail – which persist to date. now. Be ready.
As mentioned, the atmosphere is expected to remain off-limits. Therefore, convection initiation really depends a lot on who has enough lift and stability to overcome said limit?
We’ve discussed the components that are expected to come together to help parts of Iowa push the envelope, but what about the rest?
While daytime heating will add to the instability with CAPE exceeding 3500 J/kg in some places, there is little mechanical lift. Outside the triple point and away from the low surface, the only lift further south is the shallow line. The dry/unstable sugar combination may not be enough to break the bank in places like Oklahoma and Kansas.
This is not an easy method to understand, but cap strength can be estimated using a temperature of 700 mb.
In early/mid April, the 700 mb temperature of 8 to 9 degrees Celsius usually indicates a strong cut-off that will not be easily crossed by instability alone.
This map (via ECMWF) shows 700 mb temperatures in Kansas and Oklahoma around the 7 to 8 C mark. There is a strong possibility that these states, despite the strong uncertainty, will end ends with “broken blue skies” and no actual storms. However, hurricanes are still possible if a little more lift can be gained through a short wave or an inflated line.
So it’s not that there is no threat here today, just a highly conditional threat. Without more lift, the storm would most likely not materialize. However, prepare for the worst, hope for the best. If those storms do flare up, they can be very violent. Be ready regardless.
Farther south, from Texas to Louisiana and Arkansas, the short-wave impulse of the southern jet stream is expected to provide the lift that will be lacking in Kansas and Oklahoma.
Conditions are expected to favor supercells initially with superior growth into clusters. Heavy hail and strong winds will be the main threats to these storms, but the cuts also support a lower tornado threat, especially in areas with more moisture. east of the arid road.
So in a nutshell, we have a VERY complicated weather set up today. If you reside in the Central US, you need to pay attention to your local weather. Be prepared to act regardless of the “risk level” identified for your region.
As the risk area is so broad and difficult to detail in this blog, if you are concerned about your particular location, consult your local NWS or meteorologists for more details on what to expect for your area.
Wednesday will present another serious threat that we will discuss tomorrow morning. Keep stable!