Severe Weather Risk Today ... My Assessment In This Blog!
The Storm Prediction Center continues with the slight risk of severe weather across our area today. In this blog, I want to discuss that severe weather threat and give you a timeline on when we will see storms in our area.
Storm Prediction Center Severe Weather Risk Today
SPC has placed our entire area under a slight risk of severe weather. They have lowered the tornado probabilities in the last update, so I want to get you the latest.
SPC Categorical Severe Weather Risk Today
Notice the slight risk of severe weather covers our entire area.
SPC Hail Risk Today
Notice SPC has less than a 2% chance of hail producers in our area today.
SPC Damaging Wind Risk Today
Notice SPC has a 15% chance of damaging winds today.
SPC Tornado Risk Today
Notice SPC has a 2% chance of tornados in our area today.
Severe Weather Discussion
The bottom line is everyone knows there is wind energy today. The winds have already gusted to 43 MPH in Louisville this afternoon and there is a wind advisory in effect for the entire area through 8 pm.
The latest wind gusts across the area as of 2 PM are impressive. Many have seen wind gusts over 30 mph already.
The fact is that wind energy is in abundance. The wind just 1 mile above the ground is nearly 50 - 55 knots or 56 - 62 mph right now.
The data also suggests the winds are favorable for rotating storms. The value below is called "helicity" and it gives you a good idea if the wind energy supports rotating storms or tornadoes. Notice the high values across our area late this afternoon and evening.
I have always said that wind energy with no instability is like a corvette engine with water in it's gas tank. Sure the engine has the potential to go very fast, but it needs the correct fuel to run. Without instability, the winds will simply shear off the tops of the storms or just blow them over and we will have limited severe weather potential. Let's look at the instability for today.
The instability is simply a combination of warm, humid air at the surface and very cold air aloft. Well we have air that is not that warm, the dewpoints are not that high, but the air aloft is somewhat cool. This kind of describes instability that is not that high. Looking at the latest data, we see there is quite frankly no instability in our area.
The NAM suggest some better instability might develop later this afternoon with values maxing near 750 units. The very reliable HRRR computer model does back these numbers from the NAM. Notice the slight higher instability values south of the river.
Let's put this together...
My Thoughts On Severe Weather Tonight
The setup has strong wind energy, weak instability, and acceptable forcing. Other than the wind energy, the other 2 key ingredients do not look impressive at all. We would expect this to only support shallow t-storms at best. StormView3D shows the storms that were near Seymour about 30 minutes ago only penetrated to about 14,000 feet into the atmosphere. These are VERY low top showers and t-storms.
With that said, we know the strong winds are only about 5,000 feet above the ground and in my opinion this does need a low end severe weather risk. The slight risk is justified by SPC, but the data suggests this will be no outbreak at all. The main threats from any storms that can briefly go severe would be damaging winds and there is a very isolated / brief tornado threat. We have seen odd ball quick spin-ups in setups like this and I will be watching things very closely this afternoon. It is still a low end threat, but the 2% from SPC seems justified.
The latest runs of AdvanceTrak suggest the storms will last through around 6 pm - 8 pm, then the threat will drop quickly as the front moves through and the wind energy exits to our east. AdvanceTrak is capturing the weak, lop topped storms in our area for the next few hours. Keep in mind the timestamp is on the top right of each image.
I am in the weather center today, and if you ever have any questions, please remember I can be reached on facebook easily! Just follow the link below to my facebook page and click "LIKE"!