HRD Monthly Science Meeting of July 2014

July’s Science meeting had 4 presentations:

  1. Kelly M. Núñez Ocasio:  An Extreme Event in the Eyewall of Hurricane Felix
  2. Robert Nystrom:   Storm-Relative Correlation Structures
  3. Joseph Patton:  Extratropical Transition of Hurricane Sandy
  4. Robert Rogers:  Deep convection and its role in RI

The presentations are available on the anonymous ftp site at:

HRD Debrief for missions into Tropical Storm/Hurricane Arthur – 11 July 2014

HRD researchers discussed the results from the 5 P-3 and 4 G-IV missions into Tropical Storm/Hurricane Arthur. The agenda for the discussion was:

  • Missions Overview (Reasor)
  • Science Discussions
    • N42: TDR (Rogers/Bucci)
    • N43: TDR (Aberson/Zhang)
    • G-IV: TDR/ET (Gamache/Aberson)
  • Field Program Issues

HRD welcomes summer students



Left to right: Robert Nystrom, Joseph Patton, Kelly Nuñez Ocasio, and Michael Maier-Gerber.

HRD is hosting four students this summer as part of various NOAA programs and collaborations with research partners.

Robert Nystrom is a NOAA Hollings Scholar from the University of Illinois at Urbana-Champaign.  He is working with Altug Aksoy to investigate storm-relative correlation structures in ensembles of idealized hurricane simulations.

Joseph Patton is also a NOAA Hollings Scholar, and hails from the University of Oklahoma.  He is working with Sim Aberson to study the extratropical transition of Hurricanes Sandy using HEDAS analyses.

Kelly Nuñez Ocasio is a NOAA Education Partnership Program Scholar from the University of Puerto Rico-Mayagüez.  She is working with Jun Zhang and Sim Aberson on data from the P-3 flight into Hurricane Felix that was aborted due to turbulence.

Michael Maier-Gerber is an undergraduate student at the Institute for Meteorology and Climate Research at the Karlsruhe Institute of Technology, Karlsruhe, Germany.  He is examining the structure and evolution of Hurricane Ingrid (2013) to elucidate how Ingrid was able to intensify under the influence of sustained shear.

We hope you all enjoy your time at HRD and learn a lot about hurricanes to take with you in your future careers.

HRD seminar – Jun Zhang, CIMAS and AOML/HRD – 29 May 2014

Jun presented a seminar on “A Developmental Framework for Improving Hurricane Model Physical Parameterizations using Aircraft Observations”


As part of NOAA’s Hurricane Forecast Improvement Program (HFIP), this paper addresses the important role of aircraft observations in hurricane model physics validation and improvement. A model developmental framework for improving the physical parameterizations using quality-controlled and post-processed aircraft observations is presented, with steps that include model diagnostics, physics development, physics implementation and further evaluation. Model deficiencies are first identified through model diagnostics by comparing the simulated axisymmetric multi-scale structures to observational composites. New physical parameterizations are developed in parallel based on in-situ observational data from specially designed hurricane field programs. The new physics package is then implemented in the model, which is followed by further evaluation. The developmental framework presented here is found to be successful in improving the surface layer and boundary layer parameterization schemes in the operational Hurricane Weather Research and Forecast (HWRF) model. Observations for improving physics packages other than boundary layer scheme are also discussed.

A video recording of the presentation is available on the anonymous ftp site:

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HRD seminar – Jun Zhang, CIMAS and AOML/HRD – 15 May 2014

Jun presented a seminar on “Asymmetric hurricane boundary layer structure relative to the  wind shear from dropsonde composites


This talk presents the asymmetric structure of the hurricane boundary layer in relation to the environmental vertical wind shear in the inner core region. GPS dropsonde data deployed by research aircraft in 19 hurricanes are analyzed in a composite framework. Kinematic structure analyses based on Doppler radar data from 96 eyewall penetration legs are compared with the dropsonde composites. Shear-relative quadrant-mean composite analyses indicate that both the kinematic and thermodynamic boundary layer height scales tend to decrease with decreasing radius, consistent with previous axisymmetric analyses. There is still a clear separation between the kinematic and thermodynamic boundary layer heights. Both the thermodynamic mixed layer and the height of maximum tangential wind speed are within the inflow layer. The inflow layer depth is found to be deeper in quadrants down shear, with the downshear right (DR) quadrant being the deepest. The mixed layer depth and height of maximum tangential wind speed are alike at the eyewall, but are deeper outside in quadrants left of the shear. The results suggest also that air parcels acquire equivalent potential temperature (θe) from surface fluxes as they rotate through the upshear right (UR) quadrant from the upshear left (UL) quadrant. Convection is triggered in the DR quadrant in the presence of asymmetric mesoscale lifting coincident with a maximum in θe. Energy is then released by latent heating in the downshear left (DL) quadrant. Convective downdrafts bring down cool and dry air to the surface and lower θe again in the DL and UL quadrants. This cycling process may be directly tied to shear-induced asymmetry of convection in hurricanes.

An audio recording of the presentation is available on the anonymous ftp site:

and a copy of the presentation is also available at:

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HRD seminar – Paul Reasor & Altug Aksoy, AOML/HRD – 15 May 2014

Paul and Altug each presented a seminar:

  • “Evaluation of shear-relative hurricane structure from the HWRF model” – Paul Reasor


This talk will present a composite-based analysis of shear-relative hurricane structure from the HWRF model. The model’s representation of shear-relative precipitation and kinematic structure are evaluated using a recently-published composite of such structure diagnosed from airborne Doppler radar. Results stratified by shear magnitude, motion direction and vortex intensity are examined in addition to the total-case composite. Differences between the model and observed shear-induced asymmetries, including the vortex tilt, are interpreted in the light of differences in the typical environmental and symmetric vortex properties of the respective databases. Given the availability of HWRF model output at regular intervals, the talk is concluded with a composite-based examination of the relationship between temporal changes in vortex tilt and changes in hurricane structure and intensity.

A video recording of Reasor’s presentation is available on the anonymous ftp site:

  • “Model Sensitivity in Idealized, Ocean-Coupled Hurricane Simulations: Perturbations of Environment, Structure, and Model Physics Parameters” – Altug Aksoy


Idealized simulations are important tools to investigate in detail the dynamical evolution of a tropical cyclone for various environmental and/or structural characteristics. We present here a systematic sensitivity analysis using an idealized version of the Hurricane Weather Research and Forecasting (HWRF) model. The tropical cyclone environment is initialized with the tropical moist sounding of Dunion (2011, J. Climate). The westerly 850-200-hPa vertical wind shear is thermally balanced in the meridional direction. The zonal wind field is adjusted to yield a vertically integrated westward mean flow typical of Tropical Atlantic hurricanes. Lateral boundaries are forced with the same initial environmental profiles as in the computational domain interior to minimize imbalances. Coupling with a one-dimensional column ocean model introduces ocean cooling due to surface wind stress and modifies surface fluxes. The ocean column is initialized with prescribed temperature and salinity profiles that exhibit hurricane-season Tropical Atlantic characteristics with a deep, well-mixed upper ocean. The initial vortex is a wavenumber-0 composite of thousands of hurricane reconnaissance (dropwindsonde and tail Doppler radar) observations and historical height-radius cross-sections of steady-state, category-one Tropical Atlantic hurricanes over water. An analysis of the 5-day control simulation obtained in this manner will be presented first.

Model sensitivity to perturbations in parameters that include magnitude of zonal shear, vertically integrated atmospheric mean flow (storm speed), initial SST, environmental low-level and mid-level moisture and temperature, initial intensity, initial radius of maximum wind (RMW), as well as model parameters that control horizontal diffusion, vertical eddy diffusivity, and exchange coefficients of surface momentum and heat flux is then investigated, especially focusing on the quasi-steady-state regime that is observed in the 48-96 hours of the control simulation. Detailed analyses of parameter-model correlations, simulation spread, and response function will be presented for a systematic evaluation of model sensitivity. Suggestions will be made for calibrating the range of parameter values to improve the signal-to-noise ratio for the possibility of multiple, simultaneously perturbed parameters. Implications for ensemble-based data assimilation will be discussed.

A video recording of Altug’s presentation is available on the anonymous ftp site:

A video recording of the Q&A of both presentations is available on the anonymous ftp site: