ATPL Meteorology Question 3: In the Northern Hemisphere, where is the area of most significant divergence aloft relative to a jet streak?

“1013 hectopascals,” she replied immediately. “But the surface wind is 210 at 18 knots, gusting 28.”

“What’s the QNH from ATIS again, Maya?” Jim asked.

Twenty minutes later, they broke out of the overcast at 2,500 feet over Naples. The runway lights were bright and steady. No freezing drizzle. Visibility 10 kilometers. As Maya flared for landing, she glanced at the outside air temperature: +6°C.

As Maya reprogrammed the FMS, she asked, “Captain, what made you pull the trigger?”

“But here’s the kicker,” Jim said, pointing to the satellite imagery overlay. “Look at the 300 hPa chart. The jet stream core is 150 knots, and we’re on the left exit sector. What does that give us?”

“Drinks are on me,” Jim said, unstrapping his harness. “But first: what’s the definition of a warm occlusion, and how does it differ from a cold occlusion?”