A World of Weather Balloons, and We’re Just Living In It! - Joel’s Weather Corner

Hey Michigan, your MSC chief meteorologist Joel Fritsma here with my first ever blog post. I’ve moved over to more of a blog style of writing, which will feature anything from weather, to a day in the life, to even complex technical weather discussions, which I’ll do my best to explain in occasional parentheses. In high school I did weekly blog posts as well, so this should be familiar territory, but bear with me as I shake off the rust.

Today, we dive into the world of SKEW-T’s and weather balloons. You’ll see these SKEW-T’s get referenced a lot more as we return into the severe weather season. For those who have followed us for a while, you’ll remember them as the charts with the red and green lines. In a nutshell, that’s what we look at the most. The calculations of the atmosphere are then done using a series of equations that dabble in calculus, logarithms, and differential equations. These were some classes I also had the pleasure of taking while in college at Central Michigan University. Yes, meteorology isn’t just taking one semester of college trigonometry and calling it good. Thankfully, a lot of the calculus I had to learn in college isn’t used as much on a daily basis. Back to SKEW-T’s, these are generated each day on dozens of different model runs. Weather forecasting would cease to exist actually if we didn’t have meteorologists stationed around the world. This is because twice a day, at 00z and 12z (yes that’s zulu time, also known as GMT), weather balloons are launched from select offices. This is also a two-person job typically. An instrument package known as a radiosonde is attached to a string that’s hooked to a massive balloon. This balloon is filled with helium, and sometimes hydrogen to help the radiosonde package accelerate quickly into the sky to get faster results. After floating up to over 10 miles, sometimes 15 miles, the balloon expands so much, it pops, and the instrument falls back to the surface. When I was at Central Michigan University, I was able to hold and help launch a couple special balloons. The worry brought up by the public was always, what if they hit you? Thankfully, the odds of that happening are extremely low, given that balloons are only launched twice a day, and not by every NWS office either. Plus, with the changing atmosphere above us, no two launches are ever the same, especially since these radiosondes measure temperature, dew point, and wind speeds primarily. Even if one were to land on you, the package itself is less than a pound. The popped balloon weighs more than the package. If you’ve ever seen one of those Chinese-food containers, the radiosondes kind of look like that, but much smaller.

Once the full atmosphere profile is seen, bad data is filtered out, then uploaded as soon as possible for all the model runs that use this data world wide. Some models specialize in certain layers of the atmosphere, often in different resolutions too (example: 3 km, 6 km, 12 km), so often, when we use these models to make a meteorological conclusion, we have to figure out some biases. Yes, meteorology does not use freedom units, so you’ll hear a lot of talk about values not often taught in American schools. It’s an entire process, but we wouldn’t be anywhere close to knowing what’s coming when, thanks to balloon launches, and the meteorologists, engineers, and mathematicians who came before us to create such complex and yet accurate formulas for calculating values for measurements of our atmosphere.

Looking at a SKEW-T I attached, it’s no secret that these are very complex to learn. In fact, a fellow CMU Chippewa Cameron Nixon had an entire atmospheric journal dedicated to the complexities of these SKEW-T’s and the supporting hodographs (the loopy lines you see in the top right) on just hail-producing storms alone. It can be read about here: https://journals.ametsoc.org/view/journals/wefo/38/11/WAF-D-23-0031.1.xml

This is a forecasted SKEW-T off the NAM3k model. The NAM, or North American Mesoscale model is used primarily for medium-range forecasting typically in that 2-4 days out period, mainly since the data for the 3k model only goes out 60 hours, and the 12k goes out 84 hours. The “3k” is the resolution size of each area of land it reads from, so quite small. I’ll clear one thing up right away, the values on the bottom bar would take a while to learn, but you can find things like helicity (spin), CAPE totals (storm fuel), CINH (negative fuel that hurts storm formation), LCL height (the base level at which clouds form), and of course shear (wind speeds at certain heights) in number form only. The charts show more of a physical, and fun side of things, although intimidating upon first glance. The SKEW-T itself is the main area in the top left that takes up at least a third of the photo. Two things, green line is your dew point with height, red line is temperature with height, all measured in celsius. You can see the 0°C line indicated by a thin cyan-colored dashed line that extends from the ground (bottom of the SKEW-T) up to the top right. Why not go straight up? Well, it’s no secret that the atmosphere gets colder as you move up through the troposphere, so in order to not have the SKEW-T profile extremely stretched across the page, lines are drawn diagonal to better fit the data. On the right side of the SKEW-T, you have what are called wind barbs, which are the feathery looking things that indicate wind speed in knots as you move from the surface on up. Each little line on the wind barb is 10 knots, unless it’s a short line, in which case it’s 5 knots. At 50 knots, you introduce the triangle. You can see those triangles on the wind barbs above the 5 km height limit, indicating there’s a fairly strong mid to high-level jet stream over our heads for this forecast period, which happens to be this Wednesday in Central Michigan. By the way, you can see how high up you are by checking out the heights on the left side of the screen, measured in both millibars, and kilometers. Again, not miles, but that’s the way the world works. The hodograph in the top right is more of a top down view of the winds as you travel up. It’s a little harder to understand, but the heights of the atmosphere are also colored-coded, so pink is the lowest kilometer, red being 1-3 km up, and so on. Essentially, the further the line is away from the center at that level of the atmosphere, the stronger the winds are. This is how we measure helicity values as well, imperative to forecasting tornadic weather.

What does this SKEW-T tell us? Given that the temperature and dew point are fairly close together through a decent majority of the atmosphere, all below 32°F except for really close to the surface, this  shows us that precipitation is likely Wednesday morning in the form of mainly snow, with perhaps a little drizzle or sleet mixed in. We’d need that red line to be further to the right of that freezing line if we’d want to see any major sleet accumulations, or worse, freezing rain. You’ll also notice that the red temperature line turns yellow for a brief period. That is our bullseye for winter weather forecasting known as the dendritic growth zone. This is the temperature at which dendrites (snowflakes) form the best and quickest, especially when completely saturated. The longer that yellow line, and/or the closer to the ground it is, the better for major snowfall. This dendritic growth zone appears a little too elevated for now, as the mid-levels and low-levels are impeded by slightly warmer air. The wind barbs don’t have too many lines on them either, so winds on Wednesday appear light to start, but anytime a clipper moves through, those pressure gradients from the low pressure can really kick up those winds. Again, this was just a forecast SKEW-T. A raw data one looks the same, but sometimes a lot less pretty.

There you have it, balloons, SKEW-T data, and a little dosage of a forecast all in one! I hope you enjoyed the read. If there’s anything you’d like to know more about, you can always reach out to Michigan Storm Chasers on messenger, my private email, or my Meteorologist Joel Fritsma Facebook page and I’ll try my best to answer your questions in blog form. See you next time.