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Did SPC F up ?


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Re: outlooks and the general public, I agree that there are some issues. I almost never use the slight, moderate, or high wording when I tell people about possible severe weather and certainly not probabilities. I might say "decent" or "heightened" chance on some moderate or high risk days.

Our station is big on using the SPC outlooks on air but we don't use the word slight (which I hate when relaying information to the public) as it sounds very misconceiving, therefore we use "Elevated" and Moderate and High.

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Considering I was chasing and well in the loop about the behind the scenes events on Tuesday, let me go ahead and brief you on what exactly came into play.

....

WOW.

My condolences about your grandmother.

The narrative you shared is incredible. I didn't see the Tarrant County tornado personally but I did track the Dallas County tornado across the city; it was not an easy chase as it kept wrapping itself in rain, lifting and repositioning itself over the less than complete road network in that part of town. I never found myself that close to it though, that's just ridiculous. Especially considering you really didn't mean to be that close to it either.

Regarding your editorial, I agree and was also impressed by the way every agency handled the event. I'll admit, I expected a typical broken squall line event and went about doing yardwork before the rain Tuesday morning. Came back inside around noon a bit surprised the rain hadn't arrived yet, saw the tornado warnings, fiddled around a bit with radar and reading updated SPC and NWS products, then saw WFAA's live shot of the tornado near 35-E, put batteries in my camera and got in my car. I knew conditions had become favorable for tornadoes, but I seriously doubted we'd actually see any tornadoes until the proof appeared on television, because, well, we have had a lot of false alarms lately. There were many reasons why nobody died Tuesday, and chief among them is definitely sheer luck, when you look at all the cases of near-death experiences survivors endured. Ultimately though I think had there not been live video of these tornadoes on television before they entered the contiguous suburbs, we would have had casualties. Once the threat became real, so to speak, most people got to their safe places - bathtubs and interior closets, the only rooms that survived the EF-2 and EF-3 hits many of their houses took. Then there are people like ourselves who went out chasing the tornadoes on the roads in urban traffic, but I guess you can't fix that. :drunk:

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Elevated, moderate and high is a much better way. 10% is 10%, can manipulate the parameter of that as you see fit like saying it's 10X of Zero percent therefore meaningful. It's not meaningful as 10% means highly unlikely. Weather does not get special consideration in math nor does a tornado. 10% chance of showers in Ft Benning area and we get 2" is a busted prediction.

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Elevated, moderate and high is a much better way. 10% is 10%, can manipulate the parameter of that as you see fit like saying it's 10X of Zero percent therefore meaningful. It's not meaningful as 10% means highly unlikely. Weather does not get special consideration in math nor does a tornado. 10% chance of showers in Ft Benning area and we get 2" is a busted prediction.

The probabilities do have a specific meaning, though: the probability of the hazard in question occurring within 25 miles of a point. Because tornadoes are climatologically far rarer and more isolated than rain with far larger consequences, the user must adjust his/her perception accordingly. I'm quite certain most of the public would take it seriously if they were told there's a 10% chance of a nuclear meltdown within X miles of their house today, so clearly 10% does not always mean to go about your business.

Also, I don't really have an issue with the SLGT label, either. If you follow the convective outlooks for any length of time, you'll probably find that somewhere in the ballpark of half the days in a given year have a SLGT risk out somewhere. To call it "elevated" or anything similarly aggressive cheapens the message of the higher two categories. At the very least, doing that would require changing MDT to something like "significant" in order to keep things consistent and avoid further confusion.

Clearly, the categorical outlook was never intended for mass consumption, but rather for NWSFO operations and other decision-making parties. For example, the OP in this thread complained that there was a SLGT risk out, despite the fact the tornado probabilities themselves were fairly elevated (10%). If the categorical outlook were truly a public product, I'd probably advocate for 10% tornado probabilities warranting a higher category, since it indicates a fairly substantial threat to life and property. But because it's meant more for internal use, it's very coverage-biased; it's possible that the coverage implied by the 10% tornado contour warrants less concerns about NWSFO staffing than, say, a 45% hail contour (MDT) might.

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Actually, 10% chance of rain resulting in 2" of rain is not a busted prediction, unless the same thing happens 10 days in a row. If you forecast 10% chances of something on 20 days, and it actually happens on 2 days, you're doing perfectly fine. I'm not a probabilities expert, just stating something that seems obvious here.

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This might be a perfect time to pull up your thread about SPC probabilities and what they mean and such.

Wiz it isn't about those that are on this forum understanding it. Most here have at least some understanding about how the risks work, the general public however doesn't.

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Wiz it isn't about those that are on this forum understanding it. Most here have at least some understanding about how the risks work, the general public however doesn't.

The general public wouldn't know about SPC probs if the media didn't start showing them a few years ago. Anyway, they don't need to know as I'm sure they see those areas and assume the risk is higher there for severe storms.

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The general public wouldn't know about SPC probs if the media didn't start showing them a few years ago. Anyway, they don't need to know as I'm sure they see those areas and assume the risk is higher there for severe storms.

I think you hit it right here though when you mention the media. Locally every news station's weather will make light of severe risks when we get them.

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Most of the general public probably doesn't even know what a severe storm is. A storm with lots of lightning and heavy rain is probably a severe storm in their mind.

Yes, I know this to be true just from my internship at NWS DTX and taking spotter reports...

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I think you hit it right here though when you mention the media. Locally every news station's weather will make light of severe risks when we get them.

One of the stations here takes a bar graph and shows relative probabilities of severe weather. I like it better than the arbitrary maps. I'm sure you could start a discussion about use of the word "low" but I think it still conveys it better.

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Our station is big on using the SPC outlooks on air but we don't use the word slight (which I hate when relaying information to the public) as it sounds very misconceiving, therefore we use "Elevated" and Moderate and High.

I love to hear this, as this is exactly how the process should work. Meteorologists who understand the outlooks convey the risk to the public in a way that gets the message across.

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Elevated, moderate and high is a much better way. 10% is 10%, can manipulate the parameter of that as you see fit like saying it's 10X of Zero percent therefore meaningful. It's not meaningful as 10% means highly unlikely. Weather does not get special consideration in math nor does a tornado. 10% chance of showers in Ft Benning area and we get 2" is a busted prediction.

This is about the only part of this post I agree with.

There is no manipulation going on, and weather is not changing considerations when it comes to probabilities. Every probability has context, whether you think so or not.

If I tell you a quarter flips tails only 10% of the time, there is a low risk of getting tails as the probability should be 50/50. On any given April day the chance of a tornado within 25 miles of Dallas is roughly 1%. If all of a sudden that probability changes to 10% there is a significant increase in the probability of a tornado within 25 miles of Dallas. Same probability for each event (coin toss or tornado, 10%), but it is saying completely different things based on context.

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