Launch Decision with Marginal Surface Wind
At 06:00 the surface wind at the launch site is 190°/10 kt, gusting to 16 kt. The site is a small field surrounded by a 4 m hedge on the south and west sides and a line of trees 80 m to the north. The forecast is for the wind to veer to 250° and increase to 15 kt gusting 22 kt by 08:00. Your balloon is 77,000 cubic feet and you have 3 passengers. The nearest alternate launch site is 25 km away and has no shelter from the forecast wind. A NOTAM indicates parachute activity 5 km north-east from 07:00 to 09:00.
1. Assess the launch site conditions and the effect of the hedge and trees on the launch.
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The surface wind is from 190°, which is roughly from the south, so the hedge on the south and west sides will create turbulence and a lee eddy in the launch field. The trees 80 m north will also disturb the airflow, especially as the wind veers to 250° and increases. Gusts to 16 kt, rising to 22 kt, are marginal for a 77,000 cubic foot balloon with three passengers, because the balloon will be difficult to control on the ground and the initial climb may be turbulent. The pilot should consider launching only if the wind is steady and the field allows a clean inflation and ascent away from the obstacles. If the wind is already gusting, the launch should be delayed or moved.
2. Explain how the NOTAM and the forecast wind change affect the go/no-go decision.
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The NOTAM places parachute activity 5 km north-east between 07:00 and 09:00. With the wind veering to 250°, the balloon would drift towards the north-east, potentially into the active area. The pilot should either launch early enough to be clear before 07:00 or choose a track that avoids the area. The forecast increase to 15 kt gusting 22 kt makes the launch marginal, and the alternate site offers no shelter, so moving there does not improve conditions. The decision should be to cancel or delay unless the pilot can launch immediately with a clear plan to remain south and west of the activity. Passenger safety and the inability to guarantee clearance from the parachute area justify a no-go.