A Weather Aware Day

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MAIN THREATS

Today: isolated storms that could be severe

Tonight: A line of severe storms with damaging winds

Saturday: Strong to severe storms

SUMMARY

The main focus for this forecast period is the threat for severe storms tonight. Let me say this, our chance for a storm this afternoon and evening is low. HOWEVER, if any storm develops you will need to take it very seriously. Our atmosphere is very unstable and any storm that can get fired off will be capable of producing large hail, damaging winds, and a tornado. Again, the chance of that happening is on the low end, but it’s something worth mentioning. If you have travel plans that take you west of the plateau today, the threat is even higher the farther west you go in TN.

Tonight we’ll have the main event pass through. A squall line of strong to severe storms will take shape later today to our northwest and will surge southeast. The main brunt of this line looks to heavily impact most of West and Middle TN. This is why the Storm Prediction Center upgraded our risk to an enhanced risk for severe storms for tonight. The main time frame looks to be between 9:00 p.m. and 3:00 a.m. All modes of severe weather are again possible, including tornadoes, but damaging straight-line winds will be the main concern.

And yes, there is the possibility that the main line will push just to our west and spare us the brunt of the impact. I’ll keep you posted.

On Saturday, our atmosphere will remain very unstable and we will once again have to keep our guard up for any strong to severe storms. The SPC has placed all of us in the slight risk for severe storms on Saturday.

Anyone with outdoor plans today, tonight, or Saturday should pay close attention to the weather. Keep an eye on the radar and make sure you have a way of getting watches and warnings as they are issued.

Below is a threat map put out by the NWS Nashville. The moderate risk (level 4 out of 5 on the threat levels) is back west of Nashville. But, notice we are now in the enhanced risk (level 3 out of 5). The moderate risk area will see activity by this afternoon. Then, it all swings east for us overnight. I expect the threats to only expand as we go through the day.

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As always, I’ll be watching it all and keeping you informed, no matter how late into the night the threat goes. That’s why God gave us coffee, right? 🙂

For those of you reading this on TAP Talk you should know by now that you can get my blog updates after hours at https://meteorologistmark.com/ and on Facebook (/thunderchaser).  I’ll update, as needed, throughout the day.

DISCUSSION

The system that will be bringing us the threat of severe weather has already wrecked havoc across the Plains. Yesterday evening I watched as supercells tracked across Iowa. The damage is incredible to look at this morning.

The pattern that gave rise to those violent storms will not set up over us here on the plateau. I do worry, however, that West TN and western KY will have some tornadoes today and I’m worried about how intense some of those may become. If you know anyone out in those areas you may need to remind them to watch the weather today. Tornadoes in July in Tennessee are not common and people are probably not looking out for them like they should.

All that mess will translate into a squall line tonight. It’s never easy determining who will be most heavily impacted by these systems. Just a glancing blow from one of these lines can wreck havoc. Plus, there’s the risk of embedded tornadoes in these lines. Thankfully for us, the worst of the worst may stay just to our west today. But, it certainly bears watching and that’s just what I’ll be doing.

I’ll send out updates on the forecast as needed. Don’t rely on my for warnings. That’s for your NOAA weather radio or your reliable apps that warn you (weatherTAP has just what you need for that!). But, I am here if you have any questions and I’m here to prepare you.

Go ahead and review your severe weather safety plan right now. Does everyone in your family know where to meet or who to call to check in? If the power goes out are you prepared for that? If cell phones don’t work do you still have a way of getting in touch with your kids/family? Do they know this plan? Even if today’s storms miss us, it’s always a good idea to go over your severe wx safety plan ever once in while. You just never know when you might need it.

I will leave you today with an article I had published this week in the Fentress Courier. I also want to mention that the Livingston Enterprise has now been publishing my stories every week now for over a month! I am so proud to see that and to see that my articles are gaining popularity. I’m just a nervous wreck that the New York Times will call any minute now….. (haha).

So, here’s my article. I hope you enjoy it and learn something.

What are the Chances?

We often hear forecasters say there is a certain chance of rain, especially this time of year. It seems like every day we have at least a 20% chance of an afternoon storm.

But, do you know exactly what that percentage means?

I cannot begin to count how many times I have heard folks say, “It rained at my house and there was only a 20% chance of rain. Why can’t you meteorologists get the forecast right?”

But, there was a 20% chance of rain. It wasn’t zero. Clearly, there is a breakdown in communication for some folks when they hear percentages for rain chances.

The definition of rain chances is, “Probability of precipitation = Confidence in rain multiplied by Area covered by rain (C x A).”

That means if a forecaster is 100% certain that rain will occur in the area (C= 100%), he/she then has to figure out how much of a percentage of the area will see rain (A). So, if the forecaster knows precipitation is sure to occur (confidence (C) is 100%)), he/she is ultimately expressing how much of the area will receive rain.

That is the formula that many of us stick with. A 20% chance of precipitation means that 20% of the plateau is expected to pick up some precipitation.

The problem is that folks rarely stay in one spot all day. For example, if you drive from Livingston to Cookeville you increase your chances of driving into that “20% chance of rain”. This may lead you to believe the forecast was a bust.

Getting a forecast right is difficult and communicating that forecast to the public adds another challenge. But, with more articles like this we can make the latter a little less challenging!

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