Weather Balloons Fly to the Frontlines of Forecasting
By Sarah Sipek
Medill News Service
I pull my jean jacket a little closer as I make my way across the deserted parking lot of the National Severe Storms Laboratory in Norman, Okla. Darkness still paints the sky and the cool air is heavy from last night’s thunderstorms—a novel occurrence during an Oklahoma July. It’s 5:30 a.m.
My destination is a small hut on the campus’s east side. Before I can knock on the door Forrest Mitchell opens it and ushers me inside.
“You must be here for the balloon launch,” said Mitchell, the observations program leader at the forecast office. “We’ve been expecting you.”
As my eyes adjust to the sudden change in light, the first thing that comes into view is a white sphere nearly the width of the small garage.
Mitchell’s bright turquoise collared shirt stands out in stark contrast to the white of the balloon. From my Yankee perspective, Mitchell emblemizes a Southern gentleman. His tanned skin and easy drawl hint at his Oklahoma roots, but it’s the way he tells a story that sets him apart. He doesn’t rush it. Deep breaths and thoughtful pauses provide a leisurely pace and make it seem as though he’s sharing an important piece of history with you—even if it’s just a simple response to how many years he has been launching weather balloons. His salt-and-pepper hair only adds to the persona.
This morning Mitchell is working with graduate student Carly Kovacik to prepare the first of two weather balloon launches that occur at the Norman site every day. Kovacik is learning the process and will eventually launch balloons on her own.
The first step is to fill the balloon with helium until it is approximately six feet wide. A radiosonde—a device that will measure temperature, air pressure, wind speed, wind direction, humidy and GPS location—will later be attached to the balloon. It transmits the data back to the Norman office where it will be used to prepare the local forecast.
Balloons are launched from 102 sites across the country twice daily to help create local and national forecasts. They have been used for 75 years to gather upper atmospheric weather data. The radiosonde is a modern addition to the process, miniaturizing the latest instrumentation needed to collect and disseminate streams of weather data.
After the device is calibrated and securely tied to the balloon, we step outside for the launch. Everything happens quickly. Kovacik walks to the end of a short driveway. In order to get the most accurate readings, she must anticipate the balloon’s position minutes after the launch. Mitchell instructs her to release it in a southwesterly direction so that it will float over the antennas that will pick up the radiosonde’s signals.
Once Kovacik lets go of the balloon it quickly begins its ascent—it’s the size of the still visible moon in less than ten seconds.
The balloon can reach an elevation of 20 miles before it pops and the radiosonde falls back to the ground. A parachute is released and controls the descent of the device. It can land as far as 200 miles from the launch site. After landing, it may start making strange noises and will likely smell like rotten eggs.
But don’t worry. It’s perfectly safe to handle.
The device is marked with instructions to return it to the National Weather Service for refurbishing, but Mitchell admits that less than 20 percent are sent back.
“Most people keep it as a souvenir,” he said. “It’s kind of cool to keep something that fell from the sky.”
Before that point the radiosonde will have collected data that will be used on to create forecasts and severe storm outlooks on both a local and national scale.
Partnering the weather balloon tradition with high-tech analysis
The technique that Mitchell is teaching Kovacik is laden with tradition.
“They’ve been launching these things long before I’ve been around,” Mitchell said.
Weather balloons have been a standard form of meteorological equipment since 1938. Previously, instruments were attached to military airplanes. Pilots were instructed to fly at specific elevations in order to create the most comprehensive view of the atmospheric environment.
“There were a lot of holes in this plan,” he said. “Pilots were often too busy, you know, flying the plane to note things like the elevation they were at when frost built up on the wings. Meteorology wasn’t their first priority.”
In addition, the lack of pressurized cabins at this time limited the elevations pilots could reach, so the technique quickly became obsolete.
Before that, monitoring devices were tethered to kites and flown during storms to record atmospheric conditions. Some meteorologists died from hypothermia and lack of oxygen while climbing mountain ranges to get readings at higher elevations.
Currently, information is transmitted via radio back to the forecast office where computers analyze the raw data. It is then “cleaned” by meteorologists who remove any anomalies before the data is input into forecast models.
“No data is better than bad data,” Mitchell said. Forecasters remove inconsistent data points to reflect trends in the larger data set. This can help prevent storms from being predicted in areas where the conditions will not support them.
Each balloon launch costs $200. This includes the price of the balloon, hydrogen and radiosonde.
“NOAA’s budget is $900 million,” he said. “I did the math one time and it works out to $8 a year per tax paying citizen, so it’s really not that bad. Imagine what we could do with $10.”
Searching the data for severe weather clues
After checking to make sure that the data is being transmitted back to the weather center, Mitchell, Kovacik and I head back across the parking lot to the Norman Forecast Office.
Kovacik tears open a bag of pop tarts and settles in front of a desk with multiple computer screens to begin monitoring and cleaning the data so that it can be input into the weather models used by the office’s forecast team. Meanwhile, Mitchell starts answering the phone. His first call is from the Oklahoma Department of Environmental Quality.
“They want to know if there’s a temperature inversion today,” Mitchell said.
A temperature inversion occurs when an area of warm air is trapped in between cool surface air and cool upper atmospheric air. Meteorologists monitor temperature inversions because they can help delay cloud formation and growth.
“On days when there is a possibility of severe weather, the inversion, sometimes referred to as a ‘cap,’ allows the air below it to warm and become more unstable, so that when the cap is broken the release of energy from the warm, humid air at the surface results in the explosive growth of thunderstorms,” he said.
The Oklahoma Department of Environmental Quality is concerned with something else. Temperature inversions can trap pollutants in the air and subsequently decrease air quality. The agency is responsible for issuing advisories when poor air quality poses a danger to the public’s health, so having quick access to daily readings is a necessity.
However, the phone calls are not always from government agencies. A significant portion of Mitchell’s time is spent talking with community members.
His next call is from a regular—a fifth grade student from Albion, Okla.
“He calls in every morning to see if there is going to be a tornado,” Mitchell said.
Mitchell takes a look at the incoming weather data and explains to the boy that conditions are not right for tornado formation. The conversation is brief, no more than three minutes, but it conveys the scope of a meteorologist’s job. It’s not just science. It’s public service.
Photo caption: Carly Kovacik lifts the weather balloon and prepares to bring it outside to launch. Weather balloons launch at a diameter of six feet and expand as they ascend into the atmosphere. They eventually pop while the weather monitoring devices parachute back to the ground. Sarah Sipek/MEDILL
A Carnegie Corp. grant for the development of science journalism programs at Medill supports the embedded reporting fellowships to work with field research teams such as those at the National Severe Storms Laboratory.