
Questions for meteorologists or mathematicians, or both
These are weatherrelated, but have to do with math:
1. When the outside temperature is five degrees below zero, and the person reading the weather report on air says it's "negative five degrees," is that correct?
2. When there is a slight chance of precipitation, and the person reading the weather report on air says there is a "one in five chance of precipitation," is that correct?
I say the answer to both questions is no. The onair person is making mathematical comparisons that aren't valid in regard to weather issues.
What are the scientific/accurate answers? Thanks in advance. (And please note I purposely wrote an "onair person reading the weather report," NOT a meteorologist giving the weather report.)

Re: Questions for meteorologists or mathematicians, or both
Math is a science that requires definitions. Once you've defined your terms, you seek to prove conclusions.
1. Five below zero is the same as negative five degrees. It's an acceptable English alternative.
2. It depends on what the definition of slight is. You define slight, and i'll tell you if 20% qualifies as slight. I know of no official mathematical definition of slight that relates to probability.

Re: Questions for meteorologists or mathematicians, or both
Originally Posted by Ms3r4ISU
These are weatherrelated, but have to do with math:
1. When the outside temperature is five degrees below zero, and the person reading the weather report on air says it's "negative five degrees," is that correct?
2. When there is a slight chance of precipitation, and the person reading the weather report on air says there is a "one in five chance of precipitation," is that correct?
I say the answer to both questions is no. The onair person is making mathematical comparisons that aren't valid in regard to weather issues.
What are the scientific/accurate answers? Thanks in advance. (And please note I purposely wrote an "onair person reading the weather report," NOT a meteorologist giving the weather report.)
1. Considering temperature is based on a scale where zero is not an endpoint (at least not on the Fahrenheit scale  the Kelvin scale has zero as an endpoint and nothing can get colder than 0 K), then anything that occurs on one side of zero is going to be positive and anything on the other side is going to be negative. "Below zero" indicates that it is in the "negative" part of the range, so five below zero would be the same thing as 5 degrees.
2. A "1 in 5" chance of rain is the same thing as saying a 20% chance of rain (1/5 = 20%), and a 20% chance of rain is generally not considered good odds of rain occurring, so someone saying that 1/5 chance slight would be correct (although I never hear anyone call it anything but an X% chance of rain).
By the way, I'm no professional meteorologist, but I am pretty good with practical math.
"That's what I do. I drink, and I know things."  Tyrion Lannister
"Success is just failure that hasn't happened yet."  life advice from Latrell Spreewell

Re: Questions for meteorologists or mathematicians, or both
There is only a 'slight' chance that they are right either way.
Sometimes you win, sometimes you lose, sometimes it rains.

Re: Questions for meteorologists or mathematicians, or both
When you see 20% chance of rain in the forecast, it is technically a 20% probability of precip (POPS).
Another weather item that routinely is mucked up by the media is the once a century flood. Technically, the statistic is that there is a 1% probability that a flood of that type will occur in any given year .

Re: Questions for meteorologists or mathematicians, or both
Originally Posted by drmwevr08
There is only a 'slight' chance that they are right either way.
wow, that never gets old.

Re: Questions for meteorologists or mathematicians, or both
Yeah, thats why I added it. Thanks for noticing.
Sometimes you win, sometimes you lose, sometimes it rains.

Re: Questions for meteorologists or mathematicians, or both
Originally Posted by drmwevr08
Yeah, thats why I added it. Thanks for noticing.
Figured so I thought I should play along

Re: Questions for meteorologists or mathematicians, or both
1. Considering temperature is based on a scale where zero is not an endpoint (at least not on the Fahrenheit scale  the Kelvin scale has zero as an endpoint and nothing can get colder than 0 K), then anything that occurs on one side of zero is going to be positive and anything on the other side is going to be negative. "Below zero" indicates that it is in the "negative" part of the range, so five below zero would be the same thing as 5 degrees.
I understand your explanation, but I remember learning in math classes quite some time ago that any negative number was the "opposite" of the same positive number. If this scale's lowest point is 0 degrees Kelvin, then is "negative 5" still accurate?
Last edited by Ms3r4ISU; 04092009 at 12:18 PM.

Re: Questions for meteorologists or mathematicians, or both
Originally Posted by ce1
Math is a science that requires definitions. Once you've defined your terms, you seek to prove conclusions.
1. Five below zero is the same as negative five degrees. It's an acceptable English alternative.
2. It depends on what the definition of slight is. You define slight, and i'll tell you if 20% qualifies as slight. I know of no official mathematical definition of slight that relates to probability.
I used the word "slight" because I didn't want to prejudice how the rest of my question was viewed. The 20% chance was an arbitrary choice. Also, my question was whether 20% and oneinfive chance were the same thing.
And to add another: do oneinfive chance and twointen chance mean the same thing when it comes to weather forecasts?
I think the person reading the forecast simply didn't want to say 20% chance, and substituted his own interpretation of that phrase.

Re: Questions for meteorologists or mathematicians, or both
Originally Posted by Ms3r4ISU
I used the word "slight" because I didn't want to prejudice how the rest of my question was viewed. The 20% chance was an arbitrary choice. Also, my question was whether 20% and oneinfive chance were the same thing.
And to add another: do oneinfive chance and twointen chance mean the same thing when it comes to weather forecasts?
I think the person reading the forecast simply didn't want to say 20% chance, and substituted his own interpretation of that phrase.
1/5 = 2/10 = 20/100 = .2 = 20%
Don't confuse hope for a plan.

Re: Questions for meteorologists or mathematicians, or both
Originally Posted by Ms3r4ISU
1. Considering temperature is based on a scale where zero is not an endpoint (at least not on the Fahrenheit scale  the Kelvin scale has zero as an endpoint and nothing can get colder than 0 K), then anything that occurs on one side of zero is going to be positive and anything on the other side is going to be negative. "Below zero" indicates that it is in the "negative" part of the range, so five below zero would be the same thing as 5 degrees.
I understand your explanation, but I remember learning in math classes quite some time ago that any negative number was the "opposite" of the same positive number. If this scale's lowest point is 0 degrees Kelvin, then is "negative 5" still accurate?
I suppose it would be accurate, but not physically possible. 0 K is the point where all molecular vibration stops. Since temperature is essentially a measurement of this vibration, it's impossible to go below 0 K.

Re: Questions for meteorologists or mathematicians, or both
Originally Posted by aeroclone08
I suppose it would be accurate, but not physically possible. 0 K is the point where all molecular vibration stops. Since temperature is essentially a measurement of this vibration, it's impossible to go below 0 K.
Kelvin is also just a function of the Celsius scale. Essentially Kelvin is just Celsius +273. So the freezing point, which is 0 degrees C, is 273 K. The boiling point, which is 100 degrees C, is 373 K. Absolute zero, the absolute lowest temperature you could possibly get, which is 0 K, is 273 degrees C.
"That's what I do. I drink, and I know things."  Tyrion Lannister
"Success is just failure that hasn't happened yet."  life advice from Latrell Spreewell

Re: Questions for meteorologists or mathematicians, or both
Originally Posted by Ms3r4ISU
I understand your explanation, but I remember learning in math classes quite some time ago that any negative number was the "opposite" of the same positive number. If this scale's lowest point is 0 degrees Kelvin, then is "negative 5" still accurate?
Yes, a negative number is opposite number, but you have to understand that a scale is just a set of numbers. A scale does not have to include every number that exists, just the set of numbers that define the measurement. For instance, the set of numbers that define the Kelvin scale include any number greater than zero. Any number less than zero is not a definition of the Kelvin scale. The same thing with Celsius  the numbers that define the Celsius scale are any number that is greater than 273, and the numbers that define the Fahrenheit scale is any number greater than 459.4.
"That's what I do. I drink, and I know things."  Tyrion Lannister
"Success is just failure that hasn't happened yet."  life advice from Latrell Spreewell

Re: Questions for meteorologists or mathematicians, or both
Remember that "temperature" is actually a measure of thermal energy, which is not measured on an infinite scale. You can have zero energy, but you cannot have negative energy. Kelvin is the absolute scale for temperature, so 0 K is eqiuvalent to zero thermal energy. All the other temperature scales (Fahrenheit, Celcius, Rankine) are just relative to the Kelvin scale. 0 K = 459.67°F
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