Page 45 - COPA_July2023

Coastal Weather
Flying
by Karsten Shein
Instead of turning onto the airport road, Tony drove past the airport to a small diner. His out-of-town guests were puzzled. “We might as well have lunch before your sightseeing flight up the coast. The thunderstorms will be here at 11:45,” he told them. His guests, itching to get in the air, glanced at the largely clear sky and protested. “Just wait,” was all Tony would say. When the first thunderclap resonated through the diner at exactly 11:45, both guests stared at Tony in awe.
Coastal flying brings with it weather considerations that may be unfamiliar to many pilots. What Tony knew from years of flying out of his airport just a few miles from the coast was that at this time of year, the sea breeze front moved inland just before noon. Although he guessed at the precise time, Tony knew he wouldn’t be off by more than a few minutes and that once the storms passed, he’d have several hours of clear air before the front migrated back out to sea.
Sea breeze circulation is like a heat pump. In any atmospheric circulation system, surface heat is transferred to the atmosphere, causing the air to rise. Surface air from cooler surroundings is drawn into the area of the surface low pressure created by the rising air, and cool air from aloft descends to replace the surface air drawn toward the thermal low. In a coastal area, there is a diurnal heating of the land surface adjacent to a relatively thermally stable ocean surface. From sunrise on, the increasing land surface heating strengthens and expands the sea breeze circulation inland, creating an onshore breeze and the potential for towering cumulonimbus and thunderstorms
VOLUME 18, NUMBER 7 43
PILOT POINTERS