MODIFICATION OF THE FJORTOFT GRAPHICAL PROGNOSIS METHOD.

• Main Authors: Clark, Stanley Davis, Sr., Langemo, James Carroll
• Other Authors: NAVAL POSTGRADUATE SCHOOL MONTEREY CA
• Format: Text
• Language: English
• Published: 1966
• Subjects: Meteorology; Cartography and Aerial Photography; *WEATHER FORECASTING); (*METEOROLOGICAL CHARTS; ATMOSPHERIC MOTION; CYCLONES; ANTICYCLONES; ATMOSPHERE MODELS; INTENSITY; ALTITUDE; BAROMETRIC PRESSURE; VORTICES; WIND; NUMERICAL ANALYSIS; NORTH AMERICA; PACIFIC OCEAN; NORTHERN HEMISPHERE; ATLANTIC OCEAN; EQUATIONS; GRAPHICS; DIURNAL VARIATIONS; NORTH ATLANTIC; NORTH PACIFIC OCEAN; Pacific; North Atlantic
• Online Access: http://www.dtic.mil/docs/citations/AD0803354; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0803354

This paper presents a relatively simple method for producing a 24-hour prognostic 500-mb chart by graphical means. It modifies the Fjortoft graphical method by incorporating a technique to include the intensification and weakening of systems. That is, it uses factors which allow intensification of poleward-moving cyclones and weakening of equatorward-moving cyclones and the converse for anti-cyclones. The theoretical development of the so-called 'geostrophic model' used, the research procedure, and a number of illustrative charts are all discussed and a table of chart verification scores is presented to assist in the reader's evaluation of the method. It is concluded that this method does provide a simple prognostic procedure which includes some intensity change for systems. The results showed an average 24.9% improvement over persistence for the charts analyzed using a height-gradient verification scheme. Appendix 1 outlines the specific procedure for utilizing the method on a practical basis and is included as such for the convenience of potential users. (Author)