Abstract
Shape fitting is a method of fitting mathematical equations representing a definite shape to a meteorological field. Here, a nine-parameter vortex representation is fitted to the sea-level pressure field of a strong midlatitude low. A severe winter storm case (26–27 January 1978 in eastern North America) is documented to illustrate the method and to show that it produces an accurate fit and meaningfully describes the storm. The residual difference between the fit equations and the pressure field of the low can be interpreted as finer scale detail of the field. Applications to analysis and verification am briefly demonstrated. Test forecasts using the shape fit itself are also shown, using different possible forecast assumptions.
