« Giant warm up expected ahead of storm with near record temps! | Main | A Late Look At Late Data From AdvanceTrak For Severe Weather Potential Early Wednesday! »


Severe Weather Risk For Wednesday Morning! My Thoughts In This Blog!

Last week I warned about the potential for severe weather Tuesday night / Wednesday morning and unfortunately it looks like we are going to have some problems. In this blog, we will discuss the storm system and I will have my full thoughts on this setup. Let's jump right in.


Storm Prediction Center Severe Weather Risk


SPC is playing this one a bit odd. They have part of our area in a slight risk of severe weather tomorrow night, but call it off for the east part of our area. I can't say I completely agree.


SPC Categorical Severe Weather Risk Tuesday 7 AM - Wednesday 7 AM

Notice SPC has most areas through I-65 in the slight risk including Louisville.


Severe Risk 1


SPC Probabilistic Severe Weather Risk Tuesday 7 AM - Wednesday 7 AM

Notice SPC has a 15% chance of severe weather through Louisville and a 5% chance of the eastern part of our area.


Spc 2 prob


SPC Categorical Severe Weather Risk Wednesday 7 AM - Thursday 7 AM

Notice SPC only includes Columbia, KY in this slight risk for Wednesday.


Severe Risk 2


SPC Categorical Severe Weather Risk Wednesday 7 AM - Thursday 7 AM

Notice SPC does extend the 5% chance into the eastern part of our area on Wednesday.


Spc 3 prob



Wednesday Morning Severe Weather Discussion


Since we haven't had many severe weather discussions in the month of January, I wanted to remind you of the parameters I look for when I analyze a severe weather risk.


Severe Weather Ingredients



The forcing for storms Tuesday night through Wednesday morning is very strong. We will have a powerful upper level low / front move right across our area. Notice the very deep upper level low moving across our area near dawn on Wednesday.


Nam_500_vort 1


In addition, the front is a titanic front that will bring considerably colder weather early Thursday. Notice the very cold blues and purples moving in our direction late Wednesday.




Wind Energy...

The wind energy is not just strong early Wednesday but it borders on obscene. From the surface through the important layers, the wind energy is absolutely brutal. In addition, there is a directional change from the surface through 1 mile above the ground labeling this as "directional wind shear". Remember "directional wind shear" is the kind that can and does produce tornadoes in the presence of instability. Notice the winds as we start at the surface and go upward in the atmosphere.


NAM Surface Winds Early Wednesday

Notice the surface winds are south-southeast at nearly 20 mph.


NAM Winds 1000 Feet Above The Ground Early Wednesday

Notice the winds increase FAST to near 50 knots or 60 mph just 1000 feet above the ground and shift to the south-southwest.


NAM Winds 1 Mile Above The Ground Early Wednesday

Notice the winds 1 mile above the ground are simply brutal. They are 80 - 90 knots or 90 - 100 mph out of the southwest. This is mega speed shear and shows directional change.

It is clear that we have extremely strong winds early Wednesday and there is directional shear.



It is winter and the cold season, so warmth is not something that is normally in abundance. We traditionally see cold weather in the winter and cold is the anti-instability. With that said, both the NAM and GFS show instability for our area.


NAM Instability Early Wednesday

Notice the NAM shows nearly 500 units in our area.




NAM Instability Early Wednesday

Notice the GFS shows about 250 units for Louisville and a little higher in the southern part of the area.


Gfs CAPE 1


Looking into the raw data can help us determine if the instability is legit or we should plan on more or less. The raw grids place the NAM temperature late tomorrow at 63 while the GFS has 61 and I have 71. That means I have considerably warmer temperatures in our area. I don't think we will release all of that warmth with the strong winds Tuesday night, so I think these instability values could be underdone.


With these values, the NAM and GFS both show an explosion of storms moving across our area on Wednesday morning. The first is the GFS computer model and the second is the NAM computer model.







My Thoughts On Wednesday Morning


The bottom line is that a major upper level low moving across our area Wednesday morning with a powerful front that moves through during the afternoon on Wednesday. This will create intense rising motion and forcing is more than sufficient for severe weather. The wind energy is simply brutally strong. The winds increase to near 90 - 100 mph just a mile above the ground early Wednesday which is just incredible. The winds do change direction with height and we have the more dangerous directional wind shear. The instability is low but unquestionably there. I also think the computer models are underestimating the instability Wednesday morning and that could be a problem. I would not be surprised to see up to 750 units of instability early Wednesday. In my opinion, we will see severe weather in our area early Wednesday.


There are differences in the timing from the computer models, but I think we are seeing them shake out  quite a bit in the data today. The GFS brings the storms into the western part of our area around 2 am, then I-65 around 4 am, then the eastern part of our area around 7 am. The NAM is about 2-3 hours slower. Regardless, the timing is late Tuesday / early Wednesday. AdvanceTrak shows the storms along the I-65 corridor around 7 am. Keep in mind the timestamp is on the top right part of each image and notice the appearance of a mature and intense squall line.


AdvanceTrak 1



AdvanceTrak 2


AdvanceTrak 3


AdvanceTrak 4


AdvanceTrak 5


The wind energy is really exceptional early Wednesday and the direction change is concerning. The instability is being underestimated by the computer models in my opinion and this means we have a mix of wind shear and lower level instability. The NAM suggests there is a very good chance that we will see some rotating storms in our area. The NAM supercell index shows us the likelihood of rotating storms and you can see the values are high in our area and VERY high over TN/AR/MS.


Nam supercell index


All of the data has me concerned. I think we will see a lot of damaging wind reports early Wednesday and I wouldn't rule out destructive winds over 70 mph. This is a real concern. The line of storms will definitely have breaks in it based on the profile in the atmosphere and these breaks in the line can produce tornadoes. The main threat will be damaging winds (I cannot rule out some destructive winds) and isolated tornadoes. The wind energy absolutely supports all modes of severe weather, but the instability will be the key in determining how bad it gets. I absolutely think the entire area should be under a slight risk of severe weather. This is a storm that we need to watch and this could be an outbreak of severe weather. We will be watching this one VERY closely.






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"!




Feed You can follow this conversation by subscribing to the comment feed for this post.

I suppose the SPC thinks the storms will diminish in intensity overnight. I'm with you in that a slight risk is warranted for the entire area.
Thanks for the details.

jds, they do almost overlap with their risk for Wednesday, but not entirely. I would like to see a full overlap.

Marc, any concerns of renegade storms that might develop ahead of the main line? I know the primary threat will be damaging winds and isolated spin-ups. Will hail be a big concern? Also reading in the NWS discussion that a Wind Advisory will be a given winds will be strong enough without the severe storms. Storms that tap into that insane wind field spells real bad news. NWS is very concern with the very likely hood of wide spread wind damage.

Danny, the forcing is very linear, so I don't see a big concern for renegades. You need forcing ahead of the line for that and I am not sure that is there unless the trough goes negative.

Hail is a concern when there is high instability, so I don't see it as a huge concern right now.

Marc, like I said before what we lack in the snow department we make up for in severe weather unfortuantely that can be a very bad and sometimes sad thing.

Danny, anytime there is warm in a cold season you can have problems. Baroclinic zones inherently reside where there are large temperature contrasts and warm this time of the year can create big storms.

Marc, I fully agree and looks like were facing that situation. Bad timing for this possible outbreak of severe weather. Most people will be asleep including myself but I can assure you between my big baby rotweiler who literally hates storms and my weather radio I will be on guard.

Danny, you know you can trust us. We will be here for you no matter what time it is. If you follow me on twitter or facebook, then you can stay plugged in.

It is sort of unnerving to me the forecast similarities from March of last year. I am fully aware that the threat isn't as severe as last march but it's unnerving that we are having a sever weather threat and snow all in the same week. Same as march of 2012. Don't like the forecast but feel very blessed to be able to follow you and all the wonderful work you do. I feel very prepared when it comes to your forecasts I feel informed and prepared and that is comforting to someone who has anxiety when it comes to these things. Thank you Marc for all of your wonderful work!!!

Trista, thank you very much. It is very comforting to me knowing that we can make a difference in your lives. My entire team works very hard to earn the respect of our community.

You guys have more than earned my respect!!!! You and your team have gone above and beyond. Your love and passion for the safety of your community shows everytime you guys come on!!!! Again thank you all for the amazing work you do and Louisville would not be the same without you guys!!!!

Trista, thanks! I hope to be here a long time and continue to made a difference in our community.

The comments to this entry are closed.