What do "wind chill warnings" mean?

[orogenicman]

If it's below freezing and your face is exposed to the wind here's a tip, cover your face or turn your head. The "wind chill" might be uncomfortable and it might take a bit of heat from the surface of your body until you do something about it but it can't be any more dangerous than the ambient temperature.

That is incorrect. Cold wind blowing across your skin increases the evaporation at the surface of your skin, drawing the heat out of your body, which lowers your body temperature, increasing the chances not only of hypothermia, but of frostbite.

 

[whitehall]

Wind Chill is the ambient temperature combined with the evaporative properties of the Wind.

Evaporation is how your Air Conditioner/Refrigerator/Freezer work. It is how your body cools itself, it is how scientists reach 'absolute zero'.

Evaporation is one of the more efficient and effective cooling methods there is.

Nope again. Your freezer works with a chemical that ....guess what...freezes your food. Evaporation does not change the ambient temperature. If you are in 35 degrees and the wind causes you to think that your skin will freeze you might be a low information liberal.

 

[BDBoop]

A couple of days at neg 57 and I guarantee you nobody gives a shit what it actually means.

 

[martybegan]

Wind Chill is the ambient temperature combined with the evaporative properties of the Wind.

Evaporation is how your Air Conditioner/Refrigerator/Freezer work. It is how your body cools itself, it is how scientists reach 'absolute zero'.

Evaporation is one of the more efficient and effective cooling methods there is.

Nope again. Your freezer works with a chemical that ....guess what...freezes your food. Evaporation does not change the ambient temperature. If you are in 35 degrees and the wind causes you to think that your skin will freeze you might be a low information liberal.

I'm angry it took me this long to figure it out.

 

[whitehall]

Most people should understand basic laws of physics when it pertains to their health and safety. You might feel colder but you can't get colder than the freaking thermometer which has been around longer than the "weather channel". What do "wind chill warnings" mean? They mean nothing but media hype and the ignorance of the basic news drones who read them. Low temperatures are dangerous. "Wind chill warnings" illustrate the ignorance of the pop culture media.

 

[orogenicman]

Most people should understand basic laws of physics when it pertains to their health and safety. You might feel colder but you can't get colder than the freaking thermometer which has been around longer than the "weather channel". What do "wind chill warnings" mean? They mean nothing but media hype and the ignorance of the basic news drones who read them. Low temperatures are dangerous. "Wind chill warnings" illustrate the ignorance of the pop culture media.

Perhaps you need a physics refresher:

Wind chill - Wikipedia, the free encyclopedia

The human body loses heat through convection, evaporation, conduction, and radiation.[1] The rate of heat loss by a surface through convection depends on the wind speed above that surface. As a surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts the boundary layer, allowing for new, cooler air to replace the warm air against the surface. The faster the wind speed, the more readily the surface cools.

The speed of cooling has different effects on inanimate objects and biological organisms. For inanimate objects, the effect of wind chill is to reduce any warmer objects to the ambient temperature more quickly. It cannot, however, reduce the temperature of these objects below the ambient temperature, no matter how great the wind velocity. For most biological organisms, the physiological response is to maintain surface temperature in an acceptable range so as to avoid adverse effects. Thus, the attempt to maintain a given surface temperature in an environment of faster heat loss results in both the perception of lower temperatures and an actual greater heat loss increasing the risk of adverse effects.[citation needed]

A surface that is wet, such as a person wearing wet clothes, will lose heat quickly because the wet cloth will conduct heat away from the body more rapidly, and because the evaporating moisture carries away heat.
[citation needed]

Conversely, humid air slows evaporation and makes a surface feel warmer, and this is incorporated into longer wind chill formulas. During warm months, this effect can be described in the heat index or humidex.

 

[martybegan]

Most people should understand basic laws of physics when it pertains to their health and safety. You might feel colder but you can't get colder than the freaking thermometer which has been around longer than the "weather channel". What do "wind chill warnings" mean? They mean nothing but media hype and the ignorance of the basic news drones who read them. Low temperatures are dangerous. "Wind chill warnings" illustrate the ignorance of the pop culture media.

Actually maybe you are serious. What you are leaving out of the equation is biology. Frostbite is primarily caused by a lack of circulation in chilled areas. As the wind increases the temperature gradient at the surface AND causes more rapid evaporation of moisture, the body constricts blood flow quicker to maintain core body heat.

Biology is what you leave out.

 

[whitehall]

Most people should understand basic laws of physics when it pertains to their health and safety. You might feel colder but you can't get colder than the freaking thermometer which has been around longer than the "weather channel". What do "wind chill warnings" mean? They mean nothing but media hype and the ignorance of the basic news drones who read them. Low temperatures are dangerous. "Wind chill warnings" illustrate the ignorance of the pop culture media.

Perhaps you need a physics refresher:

Wind chill - Wikipedia, the free encyclopedia

The human body loses heat through convection, evaporation, conduction, and radiation.[1] The rate of heat loss by a surface through convection depends on the wind speed above that surface. As a surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts the boundary layer, allowing for new, cooler air to replace the warm air against the surface. The faster the wind speed, the more readily the surface cools.

The speed of cooling has different effects on inanimate objects and biological organisms. For inanimate objects, the effect of wind chill is to reduce any warmer objects to the ambient temperature more quickly. It cannot, however, reduce the temperature of these objects below the ambient temperature, no matter how great the wind velocity. For most biological organisms, the physiological response is to maintain surface temperature in an acceptable range so as to avoid adverse effects. Thus, the attempt to maintain a given surface temperature in an environment of faster heat loss results in both the perception of lower temperatures and an actual greater heat loss increasing the risk of adverse effects.[citation needed]

A surface that is wet, such as a person wearing wet clothes, will lose heat quickly because the wet cloth will conduct heat away from the body more rapidly, and because the evaporating moisture carries away heat.
[citation needed]

Conversely, humid air slows evaporation and makes a surface feel warmer, and this is incorporated into longer wind chill formulas. During warm months, this effect can be described in the heat index or humidex.

Hypothermia is a compelling issue but you can't get freaking colder than the 300 year old thermometer says.

 

[Delta4Embassy]

Winc chill temps only apply to living things, mostly about whether frostbite is a risk or not. Watching the Weather Channel as us old guys do (heh) they've talked about it every year.

Saw it at -9 here day before yesterday at about 6pm. Lowest I've ever seen, dunno what the wind chill was but -30 at least.

Toasty today though, 34F when I went to bed

 

[The Professor]

Most people should understand basic laws of physics when it pertains to their health and safety. You might feel colder but you can't get colder than the freaking thermometer which has been around longer than the "weather channel". What do "wind chill warnings" mean? They mean nothing but media hype and the ignorance of the basic news drones who read them. Low temperatures are dangerous. "Wind chill warnings" illustrate the ignorance of the pop culture media.

Perhaps you need a physics refresher:

Wind chill - Wikipedia, the free encyclopedia

The human body loses heat through convection, evaporation, conduction, and radiation.[1] The rate of heat loss by a surface through convection depends on the wind speed above that surface. As a surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts the boundary layer, allowing for new, cooler air to replace the warm air against the surface. The faster the wind speed, the more readily the surface cools.

The speed of cooling has different effects on inanimate objects and biological organisms. For inanimate objects, the effect of wind chill is to reduce any warmer objects to the ambient temperature more quickly. It cannot, however, reduce the temperature of these objects below the ambient temperature, no matter how great the wind velocity. For most biological organisms, the physiological response is to maintain surface temperature in an acceptable range so as to avoid adverse effects. Thus, the attempt to maintain a given surface temperature in an environment of faster heat loss results in both the perception of lower temperatures and an actual greater heat loss increasing the risk of adverse effects.[citation needed]

A surface that is wet, such as a person wearing wet clothes, will lose heat quickly because the wet cloth will conduct heat away from the body more rapidly, and because the evaporating moisture carries away heat.
[citation needed]

Conversely, humid air slows evaporation and makes a surface feel warmer, and this is incorporated into longer wind chill formulas. During warm months, this effect can be described in the heat index or humidex.

There is no doubt you are correct. If you Google “survival and wind chill” you will find over 24 million sites, including the U.S. Army Survival Manual, Chapter 5, which states in part:

“Windchill increases the hazards in cold regions. Windchill is the effect of moving air on exposed flesh. For instance, with a 27.8-kph (15-knot) wind and a temperature of -10 degrees C, the equivalent windchill temperature is -23 degrees C. Figure 15-1 gives the windchill factors for various temperatures and wind speeds., you will create the equivalent wind by skiing, running, being towed on skis behind a vehicle, working around aircraft that produce wind blasts.”

The reference gives a chart which details the effects of wind at various temperatures upon the human body. The chart shows that increased wind speeds increase the risk of frostbite.

SAS Survival Manual - 15 - Cold Weather Survival

Other sites explains why winds increase the risk of frost bite:

“Wind chill is a measure of the combined effects of wind and temperature. Temperature alone does not give a true indication of the impact of cold. The human body loses heat through convection, evaporation, conduction, and radiation. Wind chill has a direct affect on convection. As your body surface heats the air around it, it forms an insulating layer of warm air against the surface. Moving air or wind disrupts this layer, allowing for new, cooler air to replace the warm air against the surface. The faster the wind speed, the quicker you lose heat and the faster the surface cools.”

Wind chill | TheSurvivalPlaceBlog

“Wind doesn’t change temperature, but it does blow away the thin layer of warm air that surrounds the skin, hastening frostbite and hypothermia. The problem is that the actual chilling effect of the wind varies with sunshine and each layer of clothing, every shifting gust or wind-breaking building or tree.”

Love it or hate it, ?wind chill? here to stay - The Globe and Mail

It is certainly true that if you hung a thermometer in an open field, the temperature would not decrease no matter how hard the wind blew. However, the human body responds differently. For the reasons already stated, heat loss is increased and the surface freezes more quickly. This is not just a scam perpetrated by the weathermen. The millions of sites on the subject of wind chill include meteorologists, scientists, physicists and survivalists. Every survival book I have read confirms the effects of wind chill on the human body. However, I have not been able to find a single site which says that wind chill does not have any effect on frost bite and other cold-caused injuries.

The wind chill temperatures given by the weathermen may not be completely accurate, and they may be misleading in that the actual temperature does not change as a result of the wind; however, there is no doubt that wind contributes to the total effects of cold upon the human body.

 

[MeBelle]

The weather people and the news drones rattle off phrases like "dangerous wind chill" but the laws of physics dictate that the ambient temperature will remain the same no matter how hard the wind is blowing. In other words if it is 20 degrees out it will be 20 degrees with no wind or 30 mph wind. Some nerdy calculation might claim that "it feels like 10 below zero" but it isn't 10 below zero. It might be damn cold but the wind doesn't make it colder.

NWS Wind Chill Index

http://www.nws.noaa.gov/om/windchill/wind-chill-brochure.pdf

Are you claiming noaa is bunk?

Hubby wants to know what law of physics you refer to.

Have you lived in a very cold climate for any length of time?

tia

 

[orogenicman]

Most people should understand basic laws of physics when it pertains to their health and safety. You might feel colder but you can't get colder than the freaking thermometer which has been around longer than the "weather channel". What do "wind chill warnings" mean? They mean nothing but media hype and the ignorance of the basic news drones who read them. Low temperatures are dangerous. "Wind chill warnings" illustrate the ignorance of the pop culture media.

Perhaps you need a physics refresher:

Wind chill - Wikipedia, the free encyclopedia

The human body loses heat through convection, evaporation, conduction, and radiation.[1] The rate of heat loss by a surface through convection depends on the wind speed above that surface. As a surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts the boundary layer, allowing for new, cooler air to replace the warm air against the surface. The faster the wind speed, the more readily the surface cools.

The speed of cooling has different effects on inanimate objects and biological organisms. For inanimate objects, the effect of wind chill is to reduce any warmer objects to the ambient temperature more quickly. It cannot, however, reduce the temperature of these objects below the ambient temperature, no matter how great the wind velocity. For most biological organisms, the physiological response is to maintain surface temperature in an acceptable range so as to avoid adverse effects. Thus, the attempt to maintain a given surface temperature in an environment of faster heat loss results in both the perception of lower temperatures and an actual greater heat loss increasing the risk of adverse effects.[citation needed]

A surface that is wet, such as a person wearing wet clothes, will lose heat quickly because the wet cloth will conduct heat away from the body more rapidly, and because the evaporating moisture carries away heat.
[citation needed]

Conversely, humid air slows evaporation and makes a surface feel warmer, and this is incorporated into longer wind chill formulas. During warm months, this effect can be described in the heat index or humidex.

Hypothermia is a compelling issue but you can't get freaking colder than the 300 year old thermometer says.

Well, it is a good thing we use more modern thermometers then, eh?

 

[jon_berzerk]

The weather people and the news drones rattle off phrases like "dangerous wind chill" but the laws of physics dictate that the ambient temperature will remain the same no matter how hard the wind is blowing. In other words if it is 20 degrees out it will be 20 degrees with no wind or 30 mph wind. Some nerdy calculation might claim that "it feels like 10 below zero" but it isn't 10 below zero. It might be damn cold but the wind doesn't make it colder.

it means its frikkin cold outside + windy

--LOL

no it isnt colder however

your exposed skin to the wind

will reach ambient temp quicker

 

[jon_berzerk]

All I know is most everything outdoors is shut down for the day around here. Nobody in the stores, nobody on the streets. Very few vehicles and many businesses closed down. No outdoor construction going on today. Guys got the day off. Good day to be in the fixing broken down vehicles business. Lots of cars not starting. Mother nature is asserting her will. Not worth risking one's safety to make a buck or spend it today.

All I know is most everything outdoors is shut down for the day

during the height of the cold scare

i had to run to ace hardware to pick up a couple of parts for a job

as i got there they were putting a closed for due to the cold sign in the door

i asked the manager -really

he responded with

we are a bunch of pussies

--LOL

 

[MeBelle]

i had to run to ace hardware to pick up a couple of parts for a job

as i got there they were putting a closed for due to the cold sign in the door

i asked the manager -really

he responded with

we are a bunch of pussies

--LOL

 

[SwimExpert]

If it's below freezing and your face is exposed to the wind here's a tip, cover your face or turn your head. The "wind chill" might be uncomfortable and it might take a bit of heat from the surface of your body until you do something about it but it can't be any more dangerous than the ambient temperature.

You seem to be thinking that there is only one way in which heat transfer occurs. In this case, you seem to be thinking about diffusion, a.k.a. conduction. Diffusion is the transfer of kinetic energy between molecules, in the form of heat, from one object to another, or from one system to another. An example is when a heated piece of metal is dunked into a bucket of water. When the wind is generally still, transfer of a person's body heat to the surrounding air will occur by diffusion and will happen at a rate based on the difference between body temp and the air's ambient temperature, as you describe.

On the other hand, when the wind is moving, a person will lose heat via convection. Convection is the transfer of heat due to the motion of a fluid. It is essentially diffusion + movement, and from that alone it should already be pretty clear that convection will always result in greater heat transfer. An example of convection is blowing on hot food before you eat it.


Diffusion:

Convection:

 

[Abraham3]

The weather people and the news drones rattle off phrases like "dangerous wind chill" but the laws of physics dictate that the ambient temperature will remain the same no matter how hard the wind is blowing. In other words if it is 20 degrees out it will be 20 degrees with no wind or 30 mph wind. Some nerdy calculation might claim that "it feels like 10 below zero" but it isn't 10 below zero. It might be damn cold but the wind doesn't make it colder.

it means its frikkin cold outside + windy

--LOL

no it isnt colder however

your exposed skin to the wind

will reach ambient temp quicker

And the ambient temperature is a really bad one for your face to be at.