Weather Flashback

August 2022 - Tangled Weather Balloon (August 9, 2022)

Summary

This summer evening, I decided to take my daughter over to the National Weather Center (occasionally, informally, affectionately known as "Battlestar Norman") parking lot so that she could watch the 00-UTC weather balloon launch, while cautiously. The National Weather Service Office in Norman, which is housed at the National Weather Center, is responsible for launching these instrument-tethered balloons twice per day; once at 00-UTC, and again at 12-UTC. Data from instruments tethered to the balloon are used to create upper-air charts for meteorological analysis and prediction. The data is transmitted to a station by a radio in the instrument package. Collectively, the radio and meteorological instrumentation inside that make up the package are known as a radiosonde. Globally, there are about 1000 or so upper-air balloon sites. And every site is expected to launch their respective balloons at the same UTC time, irrespective of differences in local time from one site to another. Such that a 1pm British Summer Time launch at Camborne is a 7am Central Daylight Time launch at Norman. Additionally, lidar, radar and satellite are also capable of collecting data to generate upper-air profiles for various locations and times, as well as instrumentation onboard aircraft, including drones. However, here, I am only focused on balloon-based radiosondes, which remains the standard for upper-air measurements.

Most upper-air launches similar to the one in Norman on this summer evening are rather uneventful from a procedural perspective. A meteorologist prepares the balloon for launch, usually in an adjacent balloon barn or hanger, by going through a radiosonde checklist. The checklist includes inflating the balloon with a gas that is lighter than the surrounding air, so that it ascends. The checklist culminates with the release of the balloon and its radiosonde.

However, with the 00-UTC launch on this date, the dangling radiosonde became tangled with a nearby cedar tree; halting the balloon's ascent. What mechanism lead to the radiosonde getting caught up with the cedar tree was unclear to me. Maybe it was simply an unexpected gust of wind that blew the balloon and radiosonde more level with the ground for a while? Unfortunately, I did not have favorable view within the first second or two of the release to say. Basically, I did not want to get in the way of the National Weather Service's activities; so, I kept a safe (and courteous) distance, which unfortunately prevented me from seeing the first second or two of the launch. As the balloon whirled around, bobbing up and down several meters with just about every wind gust, my daughter become increasingly "fixated" on the situation. From that, I guessed that she wanted to have a closer look, so we got closer to the situation at hand. As I walked over to the cedar tree where the radiosonde was tangled up, I snapped a few photos of the situation, including the scene featured here. A closer inspection revealed that the radiosonde was "anchored" about 4-meters above ground in the tree. Not knowing whether the meteorologist noticed it was caught up, and also to satisfy my own curiosity, I decided to phone the Office for some clarity.

Apparently, the situation involving the balloon and radiosonde was well-known by those on shift that evening. So, in the interest of time, I decided not to probe about how the radiosonde got caught up. Instead, I focused on why it was still anchored. The person (I apologize here for not recalling the name of the person I spoke to) told me that it was because the balloon was filled with hydrogen, not helium! Apparently, radiosondes tethered to hydrogen-filled weather balloons are much more dangerous to retrieve than helium-filled ones. So, I erred on the side of caution and left the immediate area soon after. In the meantime, my spouse took our daughter over to a nearby Oklahoma Mesonet Station used for display purposes so that she could have a look at that instead.

Plate 1. Tangled Weather Balloon. Captured on August 9, 2022 at 8:06pm CDT. Looking north from 35.18°, -97.44°.