To say that ballooning is a fair weather activity may be an understatement. It is common for the uninitiated to see what is otherwise a nice day, and be dumbfounded by a pilot’s decision to cancel the flight. Some of the most critical portions of the weather can not be easily seen and quantified while standing at one location. Here is a primer for what the pilot is looking at when the decision to fly or not is made.
Like any other aircraft, we are subject to minimum weather conditions as set by the FAA (Federal Aviation Administration). These limitations include-3 statute miles visibility,2000 ft. horizontal distance from clouds, 1000 ft distance above and 500 ft distance below clouds.
In addition to these legal restrictions, there are several practical requirements which come into play. Because balloons travel at the speed of the wind around them, fairly light and predictable wind speeds are required. As a rule of thumb, winds on the surface should not exceed 8 mph. Because wind speed generally increases as the morning progresses, surface wind speeds for morning flights need to be slower at launch time (4-5 mph) so that the speed has not surpassed the maximum when we land an hour or more later.
Winds aloft, the speed of air currents at higher elevations, also come into play. These speeds are measured at 3,000′, 6,000′, and 9,000′ above mean sea level. While it is desirable to have some amount of speed at the upper altitudes, here too there are limitations. Genereally the winds at 3,000′ need to be no more than 20-25 mph.
The final factor that comes into play is precipitation and convective activety. The balloon envelope is constructed from over one acre of fabric. If caught in a rain storm, this fabric will absorb many times it’s own weight in water, grossly degrading the performance of the aircraft. With rain often comes thunder. Thunderstorms can produce dangerous and eradict wind, the effects of which can be felt 50-100 miles away.
Here are some links to the internet weather sources we use