A Grid Method for Predicting the Displacement and Central Pressure of East Coast Cyclones

E. C. Jarvis Meteorological Service of Canada, Toronto, Ontario

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Abstract

A prediction equation used in graphical prognosis is adapted to a grid for predicting the displacement of cyclones near the east coast of North America. The primary displacement, found using the mean 500-mb geostrophic wind over the grid area, is adjusted for secondary displacements resulting from the variation in height of terrain, the rate of exchange of sensible heat at the sea-air interface, and the variation of Coriollis force with latitude. Estimates of central pressure can be made by relating the primary and secondary displacements to initial and forecast 500-mb height fields.

24-hr forecasts were made by the grid method of fifty method for fifty randomly selected cases and results were compared with 24-hr forecasts made using the Ostby-Veigas point-value regression equations. The grid method incurred a rms displacement error of 2.5 degrees latitude and a rms error in the change of central pressure of 8.1 mb. The Ostby-Veigas method had a rms displacement error of 3.3 degrees latitude and a rms error in change of central pressure of 11.1 mb.

Abstract

A prediction equation used in graphical prognosis is adapted to a grid for predicting the displacement of cyclones near the east coast of North America. The primary displacement, found using the mean 500-mb geostrophic wind over the grid area, is adjusted for secondary displacements resulting from the variation in height of terrain, the rate of exchange of sensible heat at the sea-air interface, and the variation of Coriollis force with latitude. Estimates of central pressure can be made by relating the primary and secondary displacements to initial and forecast 500-mb height fields.

24-hr forecasts were made by the grid method of fifty method for fifty randomly selected cases and results were compared with 24-hr forecasts made using the Ostby-Veigas point-value regression equations. The grid method incurred a rms displacement error of 2.5 degrees latitude and a rms error in the change of central pressure of 8.1 mb. The Ostby-Veigas method had a rms displacement error of 3.3 degrees latitude and a rms error in change of central pressure of 11.1 mb.

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