A TUTORIAL ON LATERAL BOUNDARY-CONDITIONS AS A BASIC AND POTENTIALLY SERIOUS LIMITATION TO REGIONAL NUMERICAL WEATHER PREDICTION

Limited-area models (LAMs) are presently used for a wide variety of re search and operational forecasting applications, and such use will lik ely expand greatly as the rapid increase in the performance/price rati o of computers and workstations makes LAMs more accessible to novice u sers. The robustness of these well-tested and documented models will m ake it tempting for many to consider them as turn-key systems that can be used without any experience or formal training in numerical weathe r prediction. This paper is intended as a tutorial and caution for suc h prospective model users, with the specific purpose of illustrating t hat, in spite of advanced physical-process parameterizations and high resolutions permitted by faster computers, and modern mesoscale data f or initial conditions, there is still a basic limitation to predictabi lity with a LAM-lateral boundary conditions (LBC). Illustrations are p rovided of previous work that show the serious negative effects of LBC s, and guidelines are provided for helping to minimize their negative impact on forecast quality.