”We need 3 mph (4.8 kph) or less at 800 feet (244 meters). We are going to stick it out for another couple of hours. We’ve got everyone here. We are going to wait and see if we can take advantage of it.”

The Importance of Weather for Red Bull Stratos and Felix Baumgartner

Calm Winds: To avoid the balloon tearing during launch, take-off will not be authorized if winds exceed 2 miles / 3 kilometers per hour anywhere from ground level to 800 feet / 244 meters in altitude. Winds are also a concern at the border of the stratosphere where turbulence is common.

Clear skies: To comply with Federal Aviation Administration regulations, Felix’s balloon will not ascend if skies are more than 5 /10 overcast or if the horizontal visibility is under 3 miles / 4.8 kilometers. Any precipitation will also prevent launch.

Cooler is better. The speed of sound is dependent on temperature. The warmer it is, the faster sound waves travel – and the faster Felix will have to travel to catch up. To ensure supersonic freefall, cooler weather is preferable.

Knowing air density at various altitudes during Felix’s freefall helps the team understand how much drag he will encounter from air resistance. The stratospheric temperature readings on the day of his jump will determine if his velocity surpassed the speed of sound.

However, the best indicator that Felix has broken the speed of sound will come from ‘radiosonde’ weather balloon data.

A crew member launches a weather balloon up to the stratosphere during the preparation for thefinal manned flight for Red Bull Stratos in Roswell, New Mexico, USA on October 4, 2012 (c) Joerg Mitter /Red Bull Content Pool

RADIOSONDES AND OTHER EQUIPMENT

The team relies on the expertise of meteorologist Don Day whose computer weather models determine launch windows and create projections of Felix’s flight and landing patterns.

Meteorologist Don Day of the United States stands in front of the capsule during the preparation of the final manned flight for Red Bull Stratos in Roswell, New Mexico, USA on October 5, 2012 (c) balazsgardi.com /Red Bull Content Pool

To make accurate forecasts, Don Day:

– Releases radiosondes at the Red Bull Stratos launch site. A mini stratospheric balloon 10 feet/3 meters in size and made of Latex, a radiosonde looks like an oversized birthday balloon with a small half-pound/quarter kilogram package dangling beneath. The equipment in that package samples wind speed and direction, temperature, humidity, and atmospheric pressure every 500 feet/152 meters potentially all the way up to Felix’s target jump altitude of 120,000 feet/36,576 meters – and transmits the information back to Don on the ground.

Taking readings specifically in the area where Felix will ascend provides the most accurate, relevant data possible. Don will launch up to 10 radiosondes in the days prior to the mission, including the final hours before countdown.

– Analyzes readings from an “aerostat” balloon at the launch site. This balloon, which resembles a miniature blimp, provides real-time temperature and wind speed data for a particular altitude at which it’s tethered, up to 800 feet/244 meters.

– Observes the movements of a trio of PIBALs (pilot balloons) that are strung one above the other at the launch site. Watching the direction in which these balloons align, or whether they strain against each other on the tether, provides another indication of how winds and cross winds are behaving.

– Examines data on upper-level conditions received twice daily from radiosondes launched by the U.S. National Weather Service. These launches take place at El Paso, Texas, and Albuquerque, New Mexico, USA, to altitudes around 100,000 feet/30,480 meters.

Fingers crossed the wind’s in the right direction…

Read more on the Mission to the Edge of Space here and other attempts at this dangerous feat.