Secondary eyewalls in idealized HWRF simulations

Secondary eyewalls are common in nature, with about 80% of Saffir-Simpson Category 3 hurricanes and equivalent in the Atlantic and western Pacific exhibiting them. In contrast they are rare in mesoscale numerical simulations. The Hurricane Weather Research and Forecasting Model (HWRF) is one of the best performing hurricane forecast guidance models. We investigate secondary eyewall structures in idealized HWRF simulations. Our focus is both on the 2015 version of the model and in model versions with changes that have a strong potential to be included as part of the 2016 HWRF version. The idealized model setup we use includes constant sea surface temperature and absence of environmental flow. Preliminary results use the 2015 version of the model and that same model setup but with the modified 2015 GFS planetary boundary layer parameterization. Comparisons of these model setups indicate that vortex structure and evolution are dramatically sensitive to the choice of planetary boundary layer scheme. Discussion on the physical processes behind the vortex structure differences will be presented.