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| Meteorologist Jim Woodmencey |
From where I sit, thunderstorm forecasting during the summer season is quite challenging, and on par with snowfall forecasting in the winter. Nailing down where, when and how strong the thunderstorms might be is as difficult a task as deciding where, when and how much snow will fall in the winter season, throughout the Jackson Hole area.
By definition, if there is thunder, there is lightning. And with any thunderstorm, it is implied that there could also be heavy downpours, and/or gusty winds, and/or hail involved. Or, all of the above!
In this week’s column, I will give you some insight into how those forecasts are made, and what they really mean. Maybe that will help you when planning your next outdoor activity.
PoP
Most weather forecasts will provide you with a “probability of precipitation”, or PoP, which might say something like: “30-percent chance of showers today”. That is often interpreted to mean, “it is going to rain for 30-percent of the day”, or “30-percent of the area will get precipitation”. Actually, neither of those is totally accurate.
The correct meteorological translation of “Probability of Precipitation” is: “The likelihood of occurrence of a measurable amount of precipitation (at least 0.01 inches) at any given point within the forecast area.” The same could be said for the probability of thunderstorms occurring.
From the National Weather Service, PoP is defined mathematically as follows:
PoP = C x A where "C" = the Confidence that precipitation will occur somewhere in the forecast area, and where "A" = the Percent of the Area that will receive measureable precipitation, if it occurs at all.
A “30-percent PoP” could be calculated one of two ways, as per these examples:
1) There is 100-percent confidence that precipitation will occur, but only 30-percent of the area will get it. (PoP= 1 x .30 = .30 or 30-percent chance).
2) There is only 30-percent confidence that precipitation will occur, but if it does occur, it will produce precipitation over 100-percent of the area. (PoP = .30 x 1 = .30 or 30-percent).
Either way, you should interpret a 30-percent chance to mean: there is a 30-percent chance precipitation (or thunderstorms) will occur at any given point within the forecast area.
You could also interpret that to mean that there is a 70-percent chance there won’t be any precipitation (or thunderstorms) where you are.
Using the Forecast
Nowadays, computer models generate the POP’s and chances for thunderstorms. In some cases, the local forecaster’s experience will get factored into the equation, as well.
What you should look for in the forecast before heading out the door for the day is how certain or uncertain the forecast sounds to you. In other words, if the POP or thunderstorm probability is quite high, 70-percent or greater, that means the computer model, and/or the forecaster is highly certain about what will happen during the forecast time period, and the odds are good that the forecasted weather will materialize.
“Slight chance”, “Chance”, “Possible”, or “Likely” are all uncertain descriptive terms that can be used interchangeably for the percent probability in the text of the forecast. (See the table).
If no uncertain terms or probability numbers are used, then certainty is high, such as, “Thunderstorms today”, or “Showers this afternoon”. Take that to mean the probability of occurrence is greater than 80 percent.
Final Check
Arm yourself with the latest weather forecast before you launch on your next outdoor adventure this summer, then keep an eye on the sky to see how well those probabilities are panning out, I guarantee it will be different everyday. Precipitation or thunderstorms can happen when the POP is 20-percent, and they can miss you completely or never materialize when the POP is 70-percent.
Especially in the mountains, I would treat any mention of showers or thunderstorms in the forecast to mean, “be-on-the-lookout” that day. The higher the percentage, the more likely you will get wet, but I still carry my raincoat on a 20-percent PoP day.
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Probability of Precipitation (POP)
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Probability Value
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“Uncertain” Term
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10 to 20 %
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Slight Chance
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30 % to 50 %
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Chance
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60 % to 70 %
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Possible or Likely
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80 % to 100 %
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(usually no term used,
certainty is high)
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Jim is the chief meteorologist at mountainweather.com and has been forecasting the weather in Jackson Hole and the Teton Mountains for over 20 years.
Most weather predictions will give you a "probability of precipitation," or PoP, which may be something like: "30 percent chance of showers today." This is frequently understood to indicate "it will rain for 30% of the day" or "30% of the area will receive precipitation". Actually, neither of those are quite accurate. Thank you for sharing your insight! Keep up the great work! Continue sharing. Please feel free to browse my website.
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Your insights are both valuable and thought-provoking. Looking forward to reading more from you!
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This article on Probability of Precipitation offers a clear and informative explanation of what PoP really means. It breaks down common misconceptions and provides useful insights into how meteorologists calculate rain chances. A must-read for anyone who wants to better understand weather forecasts and plan accordingly!
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I love how you explain things step by step. It makes it easy to understand for someone like me who's new to this topic.
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Ever wondered what the Probability of Precipitation (PoP) really means when you check the weather forecast? In this blog post, "What Does Probability of Precipitation Mean?" we break down this common term to help you understand how likely it is that rain, snow, or other precipitation will occur.
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Interesting breakdown of PoP! Many misinterpret it, thinking it's area coverage. I appreciate the clear explanation and formulas. Makes weather forecasting much clearer. Reminds me of the challenge of Wordle Unlimited – probabilities and possibilities! Understanding those odds is key. Thanks for sharing!
ReplyDeleteThis article provides a really clear explanation of what probability of precipitation actually means—much more detailed than most weather apps offer. I always thought a 30% chance meant the whole day would be rainy for sure! The unpredictability of thunderstorms sounds like Cookie Clicker , where outcomes always keep you guessing.
ReplyDeleteThis article provides a really clear explanation of what probability of precipitation actually means—much more detailed than most weather apps offer. I always thought a 30% chance meant the whole day would be rainy for sure! Thanks for sharing!
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So, precipitation probability isn't as straightforward as we think. Is it about area or time? Turns out, it’s about the likelihood at a single point. I remember once planning a picnic, the forecast said 40% chance of rain. We thought it was low enough. But it poured! Ruined the sandwiches, the mood, everything! This article would have been useful then. Sharing is caring, a real block breaker move!
ReplyDeletePredicting summer thunderstorms definitely keeps meteorologists on their toes, much like forecasting snowy blizzards in winter. It’s fascinating how unpredictable nature can be, with thunder, lightning, and sudden downpours all mixing unpredictably. I recall a time when I planned a picnic, only to have a surprise thunderstorm crash the event—feeling like time spent chatting on Omegle while waiting for the skies to clear. Understanding these forecasts better surely makes planning outdoor activities less stressful.
ReplyDeleteI always thought a 30% chance meant only part of the day would be rainy, but understanding it's about the likelihood at a specific point makes a big difference in how I plan my activities. It's a bit like trying to predict the behavior of something unpredictable, and it reminds me of this one time I saw this funny animation, this crazy cattle 3d video where the cows were running all over the place reacting to the rain. It would be nice if weather forecasting was as predictable as some of those animations.
ReplyDeleteWeather forecasts can be tricky to interpret, especially when probabilities fluctuate. Understanding terms like slight chance or likely helps us plan better yet leaves room for surprises. Once, during a hiking trip, I relied heavily on a 30-percent chance of rain and got soaked—lesson learned! Always check the forecast from reliable sources, just like I trust Monkey Mart for timely updates. Staying prepared beats getting caught off guard every time.
ReplyDeleteInteresting point about forecast certainty! A high probability percentage definitely helps decide whether to brave the outdoors. It's like checking the "Parts and Service" status in FNAF Security Breach - a low score, you're taking a risk! Seeing that 70%+ makes me feel a lot less anxious about the day ahead. Thanks for the clear explanation!
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