The main goal of weather forecasting is to provide information to the public so informed life or business decisions can be made. This could range from using sunscreen when going out or getting prepared for severe weather entering the area. To provide this support, forecasters have to look through a myriad of different maps and charts all providing different information to create an effective forecast. Maps can range from satellite imagery, surface pressure maps, or numerical modeling. Forecasters must choose which information is best applicable to the situation involved. For example, an area under a high-pressure system could expect calmer conditions, so looking at an Energy Helicity Index map wouldn't be applicable. To do this, forecasters can use a concept called a forecast tunnel to create a forecast. This process describes how meteorologists can start from the top of the atmosphere to the surface to develop a succinct forecast.
Planetary and Hemispheric scales start this process and this could involve parameters like Rossby Waves. They are on the scale of tens of thousands of kilometers, in respect of size of the system. Afterward, you move to the synoptic-scale which is on the scale of several hundred to several thousand kilometers. This would typically involve features like high and low-pressure systems. Lastly, the smallest scale for the forecast tunnel is mesoscale. These are smaller-scale features on the order of a few to several hundred kilometers. An example of these features would be sea breeze and squall lines. These scales are interconnected and using the forecast tunnel helps forecasters see these features and how they relate dynamically.
Furthermore, it is imperative that meteorologists make forecasts promptly so that the forecast remains relevant to the public. Traditionally, the larger the scale, the fewer time forecasters will spend working on the specific features within that time scale. Planetary scale features are on such a large magnitude that they shouldn’t experience significant changes during a traditional forecast period, so monitoring it should take the least amount of time. Conversely, mesoscale features require more time because the nature of the size scale is smaller. These features are harder to examine if they are going to impact the forecast area and how they will evolve with time.
Photo Creds: The Comet Program
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©2020 Weather Forecaster Dakari Anderson
Photo Credit: New York Times
It’s well known that acid rain causes damage to plant and animal life. When acid rain flows through an environment, it can break down aluminum from its surroundings in the soil and carry the metal with it, consequentially, lowering the pH of the water nearby and underground. Both effects can cause a great deal of damage to plant and animal life by making the water intolerable to certain species. Since plants and animals are interconnected by food chains, animals resistant to pH changes are adversely affected when their food supply consumes their own tainted food supply. For example, many plants may die in an area due to acid rain, causing an herbivore that can withstand the pH changes to die as well because its source of food is gone.
What’s not as well known is how exactly acid rain originates. Most of it comes from harmful pollutants made by humans, especially those from burning fuel in factories or cars. When fuel is burned, it releases energy as well as byproducts including carbon dioxide (CO2), sulfur dioxide (SO2), and nitrogen oxides (NOx). By observation, one can tell that water mixes well with a lot of compounds. The water in the atmosphere is no exception. When water in the atmosphere meets these byproducts, they can mix and create potentially hazardous compounds such as carbonic acid (H2CO3), sulfuric acid (H2SO4), or even nitric acid (HNO3). While these compounds are greatly distilled by the water, they are still harmful to plant and animal life. Additionally, gases from burning fuels don’t even have to mix with rain to reach the ground. They can sink into the ground in their original forms and stick to objects near the surface, adding to the adverse effects from gas pollutants.
Since carbon dioxide is a relatively abundant trace gas in the atmosphere, virtually all rainwater is at least slightly acidic because of the presence of carbonic acid. Thankfully, carbonic acid is a weak acid that doesn’t affect the pH of rainwater to the point of making it harmful. The same could not be said for sulfuric acid or nitric acid. These acids are quite powerful in comparison to carbonic acid. They can cause the pH of water to swing down and create acid rain, which has an average pH of 4.3. For comparison, the pH of pure water is 7 and the pH of regular rain is 5.6. It’s important to note that the pH scale is not linear, but logarithmic. That is, it doesn’t increase and decrease at a constant rate. Instead, it increases and decreases exponentially the farther it gets from the neutral pH of 7. As a result, acid rain is over 10 times more acidic than regular rain on average!
What can be done to prevent acid rain or decrease its impact? The primary answer is to decrease the number of harmful byproducts coming from factories, since it’s not possible to get the gases out of the atmosphere once they’re up there. Many factories have methods of extracting harmful products out of their emissions and international treaties exist to limit certain types of emissions from factories. It’s essential for those who wish to decrease the prevalence of acid rain to understand where it comes from so the sources of these pollutants can be targeted and limited. By having a full comprehension of how acid rain is formed people can work towards limiting their harmful impacts.
© 2020 Weather Forecaster Cole Bristow
Another beautiful sight for the eyes, Mackerel Skies and Mares Tails are cloud formations that have distinctive patterns and displays of beauty in our atmosphere. These cloud formations are rather common and can hint at inclement weather as they are often seen during specific weather patterns. So, if you see these beautiful cloud formations you will be aware of the weather that is expected to precede.
Characterized by rows of clouds arranged in a pattern of ripples or waves often resembling fish scales, a mackerel sky is quite a crowd pleaser of beautiful sky displays. This type of cloud formation is created by two different types of cloud formations: altocumulus and cirrocumulus clouds. Altocumulus are mid level clouds that are made up of mostly water droplets that form at elevations around 2000 meters to 7000 meters. These clouds are puffy and can be dense at times, blocking out most of the sunlight making the day look almost overcast. Cirrocumulus clouds are higher level clouds. They are mostly made up of ice crystals and take the form of small puffy white tufts. These are not likely to block out most of the sun like altocumulus can. They are rather thin in nature and more scattered.
Although these clouds are fair weather clouds, meaning they are often seen during times of calm weather, these clouds most often prelude to unsettled weather. Altocumulus and cirrocumulus clouds are usually an indication of rising air and are seen ahead of a warm front. When warm air rises you can expect moisture to condense into rain. Most of the time when altocumulus clouds are spotted in the morning during a humid summer, pop-up thunderstorms can be expected by late afternoon that same day.
Mares tails are characterized by clouds that are long, thin and wispy. They are called mares tails because they resemble the long flowing tails of horses. Cirrus clouds form like this.They are thin, high-level clouds solely made up of ice crystals. They are so high in the atmosphere they are influenced by strong upper level winds called prevailing winds that flow in a specific direction depending on the region. You can also spot these clouds on a clear fair weather day out ahead of a warm front.
Sailors used to use clouds as weather predictors during their trips across seas when technology and weather predictions were not as advanced as they are today. Whenever a combination of mackerel skies and mares tails was spotted, it meant that the weather was deteriorating and a low pressure system was on its way. This was typical of these clouds, being ahead of a warm front meant a cold front was to follow. Both warm and cold fronts are associated with low pressure systems that can produce wind, heavy rain and unsettled seas.
© 2020 Meteorologist Alex Maynard
For more education on the atmosphere click here.
Ahrens, C. Donald., and Robert Henson. Meteorology Today: an Introduction to Weather, Climate, and the Environment. Cengage, 2019.
“Cirrocumulus Clouds.” Met Office, www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/clouds/high-clouds/cirrocumulus.
“Clouds Form Due to Weather Fronts.” UCAR Center for Science Education, scied.ucar.edu/cloud-form-weather-fronts.
“Weather Lore That's A Bit Fishy.” Farmers' Almanac, 5 Jan. 2020, www.farmersalmanac.com/what-is-a-mackerel-sky-26275.
One of the most beautiful additions to a sunset, Jacob’s Ladder, also known as crepuscular rays, sunbeams, light shafts or God’s fingers can be seen quite often in the sky. Usually on a cloudy day when the sun peeks through, near twilight, beams of light will flow from the clouds to the ground or spread out into the sky. It delivers a dramatic experience to the onlooker as they gaze at the display of light. Many describe this scene as something out of a bible, as if angels were ascending to heaven from earth on beams of light or that the sun was drawing up water from the ocean.
Jacob's Ladder is an optical phenomenon made by sunlight that is scattered by particles of haze or dust in the sky. The dust, tiny water droplets or haze scatters the light making a certain area of the sky appear brighter. Light scattering is when a beam of light hits an object of imperfect shape and gets redirected or reflected back in many different directions. Most of the time, the beams of light scattered from the cloud are a blue or yellow tint. This is due to the type of particle that is scattering the light. Some particles are selective scatterers, meaning that when a beam of light hits them, they tend to absorb certain wavelengths of that light and scatter the other wavelengths. Different colors of light have different wavelengths. For example, reds, yellows and oranges have larger waves then blues, purples and greens. So, if you spot Jacob's ladder, and the beams of light are yellow, you can tell that the particles scattering them are absorbing shorter wavelengths and scattering longer wavelengths of light.
The name Jacobs ladder originates from a biblical story about a patriarch that had a dream about a stairway to heaven. Although it has many versions, the story is simplified. During a quarrel with his brother over their birthright to the family inheritance Jacob fled from his brothers rage. During his escape, he stopped for the night and slept on a rock. When he slept he had a dream about a ladder or stairway to heaven shrouded in golden light where he saw God at the top and angels ascending it from earth. It's easy to see where this optical phenomenon may resemble the description in Jacobs dream. Most of the time, crepuscular rays that shine down and touch the earth are so golden and breathtaking that they look as if they are coming from the open doors of heaven.
© 2020 Meteorologist Alex Maynard
For more information about the atmosphere, click here.
Ahrens, C. Donald., and Robert Henson. Meteorology Today: an Introduction to Weather, Climate, and the Environment. Cengage, 2019.
Ancient-Origins. “Stairway to Heaven: The Story of Jacob's Ladder.” Ancient Origins, Ancient Origins, www.ancient-origins.net/myths-legends-europe/stairway-heaven-story-jacobs-ladder-006173.
Baker, Jess. “Science Behind the Optical Illusion of Crepuscular Rays (PHOTOS).” The Weather Channel, The Weather Channel, 4 Aug. 2015, weather.com/news/news/fingers-of-god-crepuscular-rays-20130220.
Many of us see weather forecasts and hear the terms “European models” and “American models” within them. But do we know what the difference is between these models and what they both mean? The main differences between the two models involve accuracy and time frame of predictions; however, both are global models.
The American model, also known as the Global Forecast System model (GFS), is operated by the National Weather Service (NWS). Forecasts are produced four 4 times a day, and can predict up to 16 days in advance. The computing power used to create these models can process eight 8 quadrillion calculations every second. According to the National Oceanic and Atmospheric Association (NOAA), the computer that runs these calculations is in the top 30 fastest computers in the world.
The European model, known as the European Center for Medium-Range Weather Forecasts (ECMWF), is more powerful than the American model, and generally a better model. The main reasoning for this is the organization and processing of the data, as well as the power of the supercomputer itself. In fact, the European model was able to accurately predict when Hurricane Sandy would turn into the northeastern section of the United States before the American model could. While the American model can predict up to 16 days in advance, the European model can only predict up to 10 days in advance. Although the time frame is shorter, 10 days is typically seen as the “practical limit” of forecasting, and thus is more accurate than the American model. Forecasts are only so reliable, and the farther in advance one wants to forecast, the less accurate a forecast becomes.
©2020 Weather Forecaster Sarah Cobern
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The difference between Small Craft Advisory, Gale Force and Storm Warnings and Watches (Photo Credit: NWS Brownsville)
DISCUSSION: If you live in the coastal regions, likely you have heard the forecast on the news or read the forecast on social media outlets, even hearing the terms such as “Small Craft Advisory”, “Gale Watch” or “Storm Warnings” but have no indication on meaning. These three warnings are based on wind speeds over the ocean or lakes so those who go boating or fishing can be safe due to the winds.
A small craft advisory is an advisory when the winds over the body of the water are forecasted to be or are currently between 25 and 38 miles per hour. This advisory is generally used for those in small boats as those boats are prone to being tipped and sunk in high winds compared to larger boats. A small craft advisory is indicated to boaters by one red pennant at the docks and piers. Waves during a small craft advisory are around 9 and 19 feet.
A gale watch and warning are when the winds are between 39 and 54 mph. The difference between a gale watch and a gale warning is that a watch is when the winds are expected to be gale force while a warning is when the wind is at gale force. A gale watch or warning are mainly issued during non-tropical conditions as the wind speeds for a gale match the criterion of a tropical storm. A gale is indicated by two red pennants. In a gale wind, the waves increase to between 18 and 32 feet.
The final watch and warning for maritime winds during non-tropical situations is Storm Watches and Warnings. A storm watch, like a gale watch, when the winds are forecasted to be 55 mph or above and a warning is when the wind is at or exceeds 55 mph. A storm watch/warning is indicated by a red square flag with a black square in the middle. Waves in a storm force wind are generally 30 feet or higher. If the storm was tropical based then it would be classified as a tropical storm instead of a storm.
Generally, these warnings and watches are issued due to an approaching trough of low pressure especially at coastal regions. We at the Global Weather and Climate Center would like to remind that if you are going to be in the water when the NWS issues any of the aforementioned warnings to be cautious especially when boating as the enhanced waves from the winds can be dangerous and even deadly.
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©2020 Meteorologist JP Kalb
Sun Halo. Source: https://sites.google.com/site/thebrockeninglory/
Sun halos are some of the most interesting and frequent atmospheric optical effects, and along with sun dogs and glories, are the results of physical properties that occur in the atmosphere.
Sun Halo. Source: Wunderground
In order to understand how these optical effects occur in the sky, it’s important to recognize that light is radiation that travels across the universe at certain wavelengths. Our eyes are able to intersect all the wavelengths that fall within what’s referred to as the visible spectrum, and they range from around 400nm (nanometers) to 700nm. Blue light exists around 400nm and wavelengths below that it exist in the ultraviolet spectrum while red light exists around 700nm and any and all wavelengths beyond it exist in the infrared. The rest of the colors we say in day to day life all exist somewhere within that range!
The EM spectrum. Source: newgradoptometry.com
All of that light travels from the sun and enters our atmosphere, where it interacts with everything from the molecular level all the way up to the synoptic (large-scale) level. It’s during this stage that light will experience some degree of reflection or refraction. While reflection is a commonly used term in our day-to-day lives, refraction isn’t so much.
Refraction from a prism. Source: annisaidris.wordpress.com
Refraction refers to when light changes its speed and the direction. Another way to think about it is to visualize a prism, which forces light to slow down and bend towards a new direction, resulting in light “breaking” and appearing as a rainbow once it makes it to our eyes. And much like the prism’s effect on incoming light, water droplets and ice crystals also bend light as it travels through the atmosphere. In fact, it’s when these particles refract light at certain angles that we end up getting all of our atmospheric optical effects!
For sun halos, we need light to be refracted off ice crystals in high cirrus clouds:
For sun dogs, we need for there to be refraction off ice crystals at an angle of around 22-24 degrees from the sun in any direction. Depending on where you’re standing and if the conditions are right, you may be able to see the entire sun dog from your field of vision!
For glories, you’ll likely have to be either on a hill or up in the air looking towards a thin layer of clouds or fog and facing away from the sun, given that this phenomenon occurs via the scattering of light from behind the observer. Other descriptions for this phenomenon include fog bows and Brecken specters.
And there you have it. The next time you’re in an environment that’s ripe with these conditions you might just get lucky enough to see some of these atmospheric optical effects first-hand. As always, feel free to share any and all of your pictures of any of the effects we discussed here or any that we might have missed!
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©2020 Meteorologist Gerardo Diaz Jr.