Mesoscale Eddy Development over South Auckland—A Case Study

Abstract

Evidence is presented confirming the existence of a late-afternoon mesoscale eddy primarily caused by local diabatic heating. Simulations with the Colorado State University (CSU) mesoscale model show that the eddy forms in a zone of strong sea-breeze convergence under light southeasterly gradient flow. Although showing good agreement with simulations in respect to the timing and location of eddy development, observations from two days demonstrate that eddy formation may be complicated by mesoscale interactions that result in concurrent cloud development and precipitation in the vicinity of eddy genesis. The ability of the CSU model to capture the salient mesoscale features in the region, and the association of the cyclonic eddy and sea-breeze convergence in south Auckland with a preferred synoptic regime give cause for optimism in forecasting such phenomena.