Observations and Photographs of a Cold Front Made from an Airplane

Abstract

The purpose of presenting the following diagrams and cloud photos made in connection with an airplane flight over and through a cold front is to show cloud formations associated with a weak cold front. Such information is lacking in textbooks where only the more severe cold fronts are portrayed. Over land the front here described was preceded by daytime cumulus, their tops rising as the front approached. Some pileus was observed above them where later on Ac cumulogenitus (cug) formed as the tops reached that level. The layer became solid over the position of the cold front at the surface, and there was an upward bulge into the temperature inversion found at 8,000 feet. Over the sea, remains of the Ac cug in the form of lenticulars were found farthest ahead of the front. It is important to note that all the clouds were found some distance above the frontal discontinuity, within the warm air. This was owing to the dryness of the warm air. Detailed observations from the surface were made at Blue Hill Observatory, near by, during the flight.