Using the Lagrangian method to track trajectories of fog and mist in the Monterey Bay

Abstract

The military forecaster is challenged with predicting the outcome of the operational atmospheric environment for the warfighter on a daily basis. The caveat is that most operational forecast professionals complete their task without the benefit of an advanced meteorology or atmospheric science degree. One of the most difficult weather conditions to predict is the onset and the dissipation of fog and low stratus. Coastal California in the summer has one of the highest rates of fog and low stratus in the world, and the United States Navy possesses a large fleet concentration area that operates in the gloomy Eastern Pacific throughout the year. From May through August, training and mission requirements become problematic due to low marine layer cloud decks and diminishing visibility due to fog and mist; all the while, the operational forecaster is expected to provide the best forecast possible during these grim weather conditions. To assist the operational forecaster, this study collects data in the fog-rich environment of Monterey Bay for June and July 2016. Backtracking trajectories via the Lagrangian method provided significant insight as to how air parcels can change characteristics from warm and dry to cool and moist and vice versa. By gathering over 3,500 weather observations for Monterey Bay, the Monterey airport and the Salinas airport, along with tracking 48-hour trajectory data, patterns were identified, and fog formation and dissipation hypotheses were developed.