DIAGNOSIS OF OCEANIC CYCLOGENESIS USING SURFACE-BASED Q-VECTORS

The use of quasigeostrophic Q-vector diagnosis for marine cyclogenesis is examined for two cases from the Experiment on Rapidly Intensifying Cyclones over the Atlantic. Surface observations plus aircraft observ ations and satellite imagery are used to objectively analyze these cas es, and Q vectors are calculated from these surface analyses. Although application of omega equation diagnosis at the surface stretches the theory, the relationship between vertical motion in cyclones and Q vec tors suggests that a useful diagnosis can be made. The accuracy and us efulness of these surface-based Q vectors for the two cases are examin ed subjectively through comparisons tb satellite imagery and cyclone c onceptual models as well as objectively through statistical comparison with future pressure tendencies. Results of these comparisons suggest that useful representations of the synoptic-scale vertical motion can be determined from a surface Q-vector diagnosis. This Q-vector diagno sis can be used to help assess the numerical model guidance routinely available to operational forecasters by highlighting regions of signif icant low-level forcing and providing insight into the future track of a developing cyclone.