Synoptic Structure and evolution of a kona low

A subtropical cyclone or kona low affected the island of Hawaii on 24 - 27 February, 1997 and brought with it record winds at Hilo, large hail, blizzard conditions at upper elevations, and high surf. Damage estimates for the storm due to crop loss, property damage, and electricity and phone line outages exceed four million dollars. A detailed case study of the storm was conducted using all available operational and NCEP/NCAR reanalysis data. The kona low formed on 23 February 1997 along a stalled trough northeast of the Hawaiian Islands and is investigated during five evolutionary stages (i) incipient, (ii) intensifying, (iii) mature, (iv) weakening, and (v) dissipating. The system's initial development is linked to quasi-geostrophic dynamics at the 250-mb level. The maximum circulation, maximum absolute vorticity, and the maximum height anomalies occurred at 250 mb. Cold anomalies occurred in a deep layer between 850 - 250 mb. Cloud bands with embedded convective cells formed on the low's eastern side and propagated eastward, eventually leaving the area of synoptic scale ascent and losing their convective properties. Areas where the best-lifted index values were less than zero and areas of positive low-level advection of equivalent potential temperature coincided with regions of deep convection, as inferred from satellite imagery. The Rossby wave dispersion relationship predicted the zonal propagation speed of the kona low. The vorticity tendency in the lower troposphere is dominated by the divergence term, especially during the incipient and intensifying stages. Horizontal vorticity advection plays an equal role with the divergence term in the upper tropospheric vorticity tendency for all stages.