Barotropic instability during eyewall replacement

Prior to landfall in Puerto Rico, Hurricane Maria (2017) underwent an eyewall replacement cycle. The National Oceanic and Atmospheric Administration (NOAA) San Juan (TJUA) radar captured a robust outer convective ring with an inner ring first distorted into an ellipse and then disintegrated. To understand the dynamical processes during eyewall replacement, this work interprets the eyewall replacement event using the non-divergent barotopic model with a linear stability analysis and non-linear numerical simulations. For the linear stability analysis, the model’s axisymmetric basic state vorticity distribution is piece-wise uniform in five regions: eye, inner eyewall, moat, outer eyewall, and far field. The stability of such structures is investigated by solving a simple eigenvalue/eigenvector problem. For the non-linear model, the evolution into a more stable structure is simulated using the non-linear barotropic model. Three types of instability and vorticity rearrangement are identified: (1) instability across the outer ring of enhanced vorticity, (2) instability across the low vorticity moat, and (3) instability across the inner ring of enhanced vorticity. This dataset includes (1) a loop of the NOAA TJUA radar during the landfall of Hurricane Maria (2017) in GIF format to show the convective evolution, (2) the output from the five-region linear stability analysis in NetCDF format, and (3) the output from the non-divergent barotropic model in NetCDF format and GIF format to show the vortex evolution. These data are provided without restrictions for further exploration into understanding barotropic instability during eyewall replacement.

Methods
Five-region linear stability analysis

Nondivergent barotropic model linear stability analysis results for a two-dimensional family of vortices, each having an axisymmetric basic state vorticity with a five-region piecewise uniform distribution. These results are for understanding which azimuthal wavenumber(s) will become unstable for each vortex in the family.

Nondivergent barotropic model

Output from a finite difference nondivergent barotropic model for tropical cyclones that uses high-order accurate discretization and MUDPACK. These results are for three specific vortices in which instability develops in the inner-eyewall region (Vortex B), in the outer-eyewall region (Vortex C), or across the moat between the two eyewalls (Vortex A).

NOAA NEXRAD TJUA radar

A loop from the NOAA NEXRAD TJUA radar centered on the position of Hurricane Maria (2017). The radar reflectivity (dBz) imagery includes every base scan starting at 05:42:01 UTC and ending at 09:50:00 UTC on 20 September 2017.