Do you ever wonder about the weather? I do. Ever ask yourself why it’s hot today but it was cold yesterday? Why it’s sunny this morning but will rain this afternoon? Why it’s so windy today but calm yesterday? I’ve asked these questions all my life so I’ve decided to learn about the weather. The correct term for studying weather is, Meteorology. It seems Aristotle, the Greek philosopher came up with the name, and as you probably already figured out, weather doesn’t have much to do with meteors. In his time, studying anything above ground was considered Astronomy, and when he wanted to study weather, it couldn’t reasonably be called astronomy. Since meteors are visible to us in the sky he called studying weather, which happens in the sky, Meteorology. Apparently what’s good for Aristotle is good for us because the name stuck. Now as a disclaimer I’ll say this: I don’t have a degree of any kind in Meteorology. I have a degree in Medical Lab Science, Technician level, and that’s all. And that doesn’t have anything to do with Meteorology. So what I write here is my own opinion from what I’ve been studying. If I get something wrong, please feel free to let me know. I’m learning as I go along.
Did you know that all our weather happens because of the Sun? That’s right! The experts tell me that the heat of the Sun, combined with the roundness of the Earth, (attention Flat Earthers) and the Earths tilt in relation to the Sun, and the topography of the Earth, and gravity all come together to create all our weather. Even the Moon gets involved! What causes our weather is a very complicated process that takes years to understand. It is said that Meteorology is more complicated than rocket science! So the next time your local weather forecaster gets it wrong, give them a break. Forecasting the weather is a little like trying to hold wind in your hand. It’s a combination of science, magic, and voodoo, with a little witch doctoring thrown in!
These are some weather terms that I’ll be taking a closer look at on this page: Temperature, Humidity, Wind Direction, Wind Speed, Precipitation, Dew Point, and Barometric Pressure. These things are happening all around us, all the time. Weather affects everyone, every day. So wouldn’t it be nice to know something about it? I think so. If you stick with me, we’ll learn about this together!
Today’s Weather Observations
Thursday, June 25th, 2020 in Southern Minnesota at 1:00 pm
Temperature: 80 degrees F
Wind direction: SSW
Wind speed: 4 MPH
Dew point: 54 degrees F
Barometric Pressure: 29.93 inHg
(These weather observations are taken from my home weather station in my backyard.)
I am currently learning what all these terms mean, especially in relation to each other and I’ll be writing about all that soon. So if you have an interest in learning about the weather, this will be the place to do it!
Why does weather happen?
Weather happens because the Sun heats the atmosphere. However, it doesn’t heat the atmosphere evenly. Because the Earth spins on its axis, (Flat Earthers take note) half of the planet is in darkness half the time. Therefore our atmosphere is constantly heating and cooling. Also, in relation to the Sun, the Earth is tilted on its axis by 23.5 degrees so the Sun’s rays don’t hit the surface evenly. At the Equator, the full force of the Sun’s rays are felt all the time. As you move away from the equator, the Sun’s rays hit the surface at an angle, lessening their power. That is why temperatures are cooler, the further North or South of the equator you go. There are other reasons why weather happens as well. The Atmosphere only absorbs about 50% of the Sun’s rays. The rest get reflected back into space by surfaces like clouds, the ocean’s and lakes, mountains, ice crystals in the air, etc. Water, soil and other Earth features do absorb energy from the Sun and transmit that energy into the atmosphere by a process known as Convection. So all this heating and cooling, causes the atmosphere to be active, and that is why we get weather. This is a simplified explanation, I know. I will get into details as I go. Before I go any further though, I want to talk about the terms that weather forecasters use to describe weather. I’ll start with temperature.
Temperature is an easy one. It tells you how the air is going to feel, hot or cold. Thermometers are made to conform to the thermodynamic temperature scale which is an internationally agreed upon scale. So 70 degrees is 70 degrees no matter where you go. Temperature is not the only factor that contributes to how the air feels however, and each person feels temperature independently. Some think 70 degrees feels great while others think it’s too hot but it at least gives you an idea of how you are going to feel.
Usually it is referred to as just humidity but it is actually “relative” humidity. The definition goes like this: The amount of water vapor present in air expressed as a percentage of the amount needed for saturation at the current temperature. (Wikipedia) So at 100% humidity the air would be completely saturated with moisture. However, humidity is dependent on temperature. So 50% relative humidity at 70 degrees is not the same as 50% humidity at 90 degrees. That’s why relative humidity is not always a good indicator for how the air will feel.
Dew point, which is expressed as a temperature, is the point at which condensation occurs. (Condensation in this case is the point where water vapor in the air becomes liquid water/dew) It is a more direct measure of moisture in the air than humidity because it is not dependent on air temperature. Therefor you know that a 70 degree dew point is going to make it feel humid outside no matter what the temperature but a 50 degree dew point will feel much more comfortable even when the temperature is high.
Wind speed and direction
Wind speed and direction are important factors to consider when determining how comfortable you will be outside. They can also tell you what kind of weather may be coming your way. Wind has a cooling effect so a hot day will feel cooler with a strong wind blowing and a cool day will fell colder. The direction of the wind will generally tell you about comfort as well. A South wind (here in the Mid-West U.S.) will generally bring warm breezes and a North wind will be cooler. Because of the spin of the Earth and the heating of the atmosphere by the Sun, most of our storms and weather comes from the West. When we have an East wind it is usually because of a weather formation that is circling as it moves West which means there is a high probability of storms.
Precipitation is what falls from the sky. The atmosphere absorbs moisture from the oceans, lakes, rivers, and the soil through evaporation. The moisture in the air forms clouds and when clouds become saturated it rains or snows, sleets or hails, depending on a number of factors.
Barometric or atmospheric pressure is the weight of the atmosphere over the measurement point. Everything has weight because of gravity. Even air molecules have weight. The atmosphere exerts a pressure of approximately 14.696 pounds per square inch at sea level. Which means that one square inch of your skin has over 14 pounds of pressure all the time. So if you hold your arms out level to the ground you’re holding up a lot of weight. You don’t feel that weight however, because atmospheric pressure is exerted from all points at once. So that 14 pounds per square inch of pressure is felt under your arms pushing up at the same time it’s pushing down on top of your arms.
Air is denser at lower altitudes. So the atmospheric pressure at sea level will be higher than at say, Denver, Colorado. A lot of our weather is influenced by pressure. Cold fronts are generally called low pressure systems and are areas of cooler air moving into areas of warmer air. Cold air is denser than warm air so cold fronts push under warm air and lift it higher. Cold fronts generally have lower atmospheric pressure than warm fronts. Warm fronts that move into cooler air push down on the cooler air, squeezing it out of the way and have higher atmospheric pressure. Cold fronts are associated with cloudiness and therefore have steadier temperatures. Warm fronts usually have clear skies behind them with higher pressure and have greater temperature fluctuations.
So if you have a barometer in your house you’ll notice a steady barometer means steady weather, whatever that weather happens to be. As soon as the barometer begins to change you can expect a change in the weather.
The heating of the atmosphere around the Equator is almost constant. The equator faces the Sun more directly than any other part of the planet. As warm air is less dense than cold air this warming causes the air to move upward. In the sub tropical regions above and below the equator (Between the Tropic of Cancer and the Tropic of Capricorn, imaginary lines 23.5 degrees North and South of the equator) air is pulled toward the equator in an East to West direction. This happens because of the warming of the air by the Sun and the spin of the Earth (Flat Ear–Oh never mind!). These almost constant winds are called, the Trade Winds, so named because back in the days when getting around the World required sailing ships, these winds were used by sailors to carry their ships on trading missions. In the Northern hemisphere (specifically around the U.S.) these East to West winds circulate and are pushed Westward and Northward by winds from the Pacific Ocean. Also, winds from the Polar regions travel West to East and collide with the sub tropical winds coming from the South and then move West to East across the U.S.. Whew!
Did you know that the U.S. gets more violent weather than anywhere else on Earth? That’s right, it does. Mainly because of these North and South winds coming together and also from sub tropical winds out of the Gulf of Mexico, and North winds coming across Canada. We are right in the convergence zone of all these winds! So we get slapped around by storms more often than anywhere else on the planet. Yay for us!
These patterns of wind circulation are pretty constant. The trade winds and polar winds pretty much act the same way all the time. That’s not to say that things can’t change, and they do from time to time but because of the heating from the Sun and the spin of the Earth you can pretty much count on these winds blowing our weather here in the U.S. from West to East across the country. Weather observers know that darkening skies to the West and a falling barometer means you are in for rough weather.
Friday, June 26th, Southern Minnesota at 12:30 pm.
Temperature: 76 degrees F
Wind direction: SW
Wind speed: 4 MPH
Dew Point: 68 degrees F
Barometric pressure: 29.85 inHg
You can see by comparing today with yesterday that there is a much higher humidity and dew point today. Everything else is pretty much the same which means that there’s more moisture in the air, making it feel more uncomfortable. Unless of course you like that stickiness. I’m not a big fan of it myself.