Weather For Weather Geeks August 17

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Meteorologists Are Very Accurate (Yes, Really)

I’ve heard a version of this joke roughly 7,234,519 times in my life. The most common iteration is “must be nice to be wrong half the time and still get paid!”. Ugh.  All I ask is that people be original when half-insulting me and my profession!

The truth is, meteorologists…those on TV, in the private sector, at the National Weather Service, are really good.  Weather forecasts have never been more accurate. The lead time on tornado warnings is (on average) around 13-15 minutes. The accuracy of hurricane track forecasts is excellent.

But of course, we aren’t always right. And never will be. A lot of people have trouble with this. I get it. If your picnic/graduation/golf outing is ruined by weather, it’s maddening. Especially if the forecast led you astray.

Let’s pull back the curtain on our internal accuracy numbers

I take accuracy very seriously and it drives me crazy when a forecast is off. Especially if it’s an impactful situation like a snow storm or severe weather.  If it’s August and my forecast high was 81 and it ends up being 86 it irks me but that kind of “bust” doesn’t really impact anyone significantly. That said, temperatures are the easiest thing to track so let me show you how we are doing so far this year. I keep very detailed records on our temperature accuracy dating back 5 years. The spreadsheet I use is pretty slick; I enter the forecast highs and lows as well as the actual observations and the spreadsheet produces easy-to-read accuracy numbers.

Let’s dig into a few of these numbers. So far in 2018, our high temperature forecast for the following day is within TWO degrees 70% of the time and within 3 degrees 84% of the time.

Skip ahead to DAY 7: We get the temperature right within 2 degrees 38% of the time and within 5 degrees 64% of the time.  Not bad for 7 days out and I suspect these numbers would surprise some.

Meteorologists vs. Atheletes

Professional athletes are incredible and I would love to have even a shred of their talent. But here’s what they aren’t doing: predicting the future! Let’s look at the “success” rate of athletes at the top of the major sports.

MLB

Mookie Betts of the Red Sox leads the majors in hitting right now with a batting average of .350. That’s a very impressive number but means he is still failing to get a hit 65% of the time! If my forecast busted 65% of the time i would be in a world of hurt. Yet in baseball this is succeeding at very high level.

NBA

Clint Capela of the Rockets led the league in field goal percentage last season at about 65%. A great number but below our rate of getting the temperature right within 2 degrees (for the following day) of 70%. And again we are predicting the future!

NFL

Drew Brees led the NFL in completion percentage last year but still threw an incompletion 28% of the time. If I failed on snowfall forecasts at a rate of 28% I think I’d need to reconsider my career choices.

In Conclusion

The point of this post is not to brag. We’re accurate but I’d like to be a LOT more accurate and I am always trying to get these numbers higher. Every “bust” is a learning opportunity. Meteorologists who don’t learn from their mistakes don’t typically have a long career in this profession.  This can be said of nearly every profession but it’s especially true in a line of work that places a premium on accuracy. Sometimes I compare our job to referees/umpires. Most referees at the top of their profession get FAR more calls right than wrong. Yet their reputation is that they “are all blind” and what not. It’s especially bad if they blow a very important call at the end of a very big game. A ref could have gotten every call right up until that point but it doesn’t matter if he affected the outcome of the game by making a high-profile screw up. In our job, all these accuracy numbers are great and everything but in January if I say there will be 1-2″ of snow and there ends up being 10″ and people’s days are severely impacted, it’s very easy for the old “meteorologists are always wrong” cliches to come out. It’s part of the reason I don’t sleep much before big storms! That’s ok…I love it. Couldn’t imagine doing anything else!

Best Meteor Shower Of Year Peaks This Weekend

This is the weekend in which the best (well, certainly the most popular) meteor shower of the year reaches it’s peak. A couple of other meteor showers, such as the Geminids in December may have a somewhat higher number of visible meteors but the Perseids occur in August, which features nice, warm nights to sit outside and enjoy the show.

What’s a meteor?

A meteor is a big space rock that has been shed by a comet.  Comets leave behind a trail of debris that Earth occasionally passes through.  As these rocks enter our atmosphere, they “burn” up, creating a bright streak of glowing hot air.

Where to look?

You can see a meteor anywhere in the sky but the “tails” of the meteors all seem to come from about the same spot. or “radiant”.  Meteor showers are named after the constellation that is home to their radiant. The Perseids come from the constellation Perseus, which will be in the northeast sky for much of the night.

 

When to look?

You can spot some meteors in the evening after it gets completely dark but the most numerous will be after midnight.

What to expect

Meteor showers tend to be somewhat disappointing for those who 1) don’t stay up late enough 2) don’t get to a dark enough spot 3) aren’t patient enough to allow their eyes to adjust to the darkness.  Be patient. It will be possible to see a meteor every minute if you are in a good dark spot and….

Will the weather cooperate?

This is the big question. The trends for the weekend have been good but the forecast is still a bit tricky. On average, the most accurate computer model in our arsenal is the European. It has a significantly cloudier forecast for both Saturday and Sunday night than it’s American counterparts, the NAM and GFS.

Saturday night European:

Saturday night NAM:

Sunday night European:

Sunday night GFS:

So, we will hope the European model is being too pessimistic!

The Perseids tend to be especially colorful. The color depends on the chemical composition of the meteor; different chemicals give off different colors as they burn up high in the atmosphere.  

 

Debunking The Myth Of Heat Lightning

There are many, many weather myths…nuggets of “wisdom” that have been passed down from generation to generation. Many people hold on to these tightly; their dad or grandma or great aunt insisted these things were true! Believe me, I understand. My grandmother was largely responsible for getting me interested in weather and many of her weather-related anecdotes and pearls of wisdom, as it turns out, were not exactly filled with scientific rigor. And that’s ok! Some weather myths are harmless fun and others (such as a few related to tornado safety) can actually be dangerous.

At this time of the year, one of the most common weather myths that gets some play is “heat lightning”. This is a term that many people associate with warm summer evenings in which you can see lightning in the distance but don’t hear any associated thunder. Often the sky directly overhead is clear. The general idea behind heat lightning is that, well, it’s really warm and sometimes that just makes lightning form. I guess?

Well the truth is, lightning is lightning and it all forms by the same processes.  An electric charge is formed in a tall cloud by chunks of ice (some big, some tiny) bumping into and rubbing against each other.  When the charge grows large enough, a giant spark-lightning- occurs between positive and negative charges.  That discharge can occur within a cloud, from cloud-to-cloud or from the cloud and the ground.

WHERE’S THE THUNDER?

All lightning produces thunder, it’s just that sometime we can’t hear it. Lightning can be seen from as much as 100 miles away. But thunder can usually only be heard from a distance of about 10 miles away.

The curvature of the earth plays a role. A distant thunderhead may be mainly below the horizon from your vantage point. But the lightning at the top of the storm may still be seen.

Finally, don’t forget: every time someone spells lightning “LIGHTENING”, a meteorologist’s blood pressure ticks upward.