I am posting because of the significant potential for severe weather. However, I am not convinced the severe weather will materialize, at least on a widespread scale. Yet, the impacts, if they do occur, are significant enough to warrant posting. Severe weather is like cooking a wedding cake. The layers of the atmosphere have to be right, and you need enough energy to actually cook the cake. Absent the energy, you just have batter with potential.
Let’s start with the ingredients. You need moisture, and we have plenty of moisture. You need shear. Shear comes in two varieties, directional and speed. They are both important, but for different reasons. Speed shear is when the winds get faster as you go up in the atmosphere. Directional shear is when the wind direction changes as you go up in the atmosphere. Check, and check at least for the morning hours. While not absolutely necessary having some dry air mixed in aloft helps. Check. This gives us a nice batter.
However, the batter still has to cook. That’s where things get more dicey. In our case cooking the batter means the air rising high enough to take advantage of the ingredients. This can happen in two ways, either heating causing the air to rise, or something physically lifting the air such as a cold front or sea breeze. Tomorrow is a borderline situation. The rain will start at some point tonight, and that’s going to limit the ability for the air to warm tomorrow because of the preexisting cloud cover. The physical lifting is going to happen, but it’s not really lining up with the best ingredients.
So, what’s going to happen? Everyone – Houston and Triangle is going to see elevated winds. Now, this doesn’t mean damaging winds, but you will notice the increased winds. This increased “background” winds means the stronger storm cells/lines that develop don’t need to have terribly much impact to reach severe levels. Add to that local effects that can create wind tunnel effects, and at least isolated locations will see winds speeds capable of causing minor damage, irrespective of if a severe thunder storm warning is issued. The key word is isolated.
Now, beyond the background elevated wind, and obviously rain, the chance for significant severe weather can’t be ignored. While I don’t think the conditions will produce widespread severe weather, it would be mildly surprising if no severe storms happened. The only negative factor is the lift, and even something as simple as two cells moving in somewhat different directions would cause front flank winds to converge and rise. With everything else in place, it’s more likely than not that at least isolated severe thunderstorms will form.
Another hazard is hail. Some places are likely to see some hail. Now, it may not be large enough to damage roofs, but at least some scattered hail stones should mix in with the rain. If a cell can develop discrete from the main precipitation field the chance of hail there is pretty high.
Location wise, the threat for severe weather is much higher Houston than Triangle. The Storm Prediction Center has the category change from slight to enhanced running in between Houston and the Woodlands. The Triangle is well removed from the enhanced risk categorization.
Timing wise, the threat for the greatest impact severe weather is mid to late morning. As the day progresses the shear transitions more from directional to speed. This lowers the risk of severe weather overall. However, at the same time the cold front approaches. The cold front will cause lift and since lift is the big question mark raises the chance for wind and hail damage.
A simple way of saying the forecast is the potential for severe weather is very high. The actual severe weather occurrence is meh. But the potential consequences are so high that this has to be taken seriously for what very well could be a busted forecast. Two types of severe weather possibilities exist. In the morning all flavors of severe weather are on the table. In the afternoon, as the cold front approaches, the chance for tornadoes drops to almost nil, but the chance for damaging wind and hail increases since the missing lift will no longer be an inhibiting factor.
With all that in mind, I do expect at least a little severe weather tomorrow. Could we have a significant outbreak? You betcha, but it’s not terribly likely. However, when the cold front approaches things could get dicey with a wind threat.
I was going to add pictures and more scientific explanation, but this post is too long already.