scholarly journals High-Resolution Simulation of the Electrification and Lightning of Hurricane Rita during the Period of Rapid Intensification

2011 ◽  
Vol 68 (3) ◽  
pp. 477-494 ◽  
Author(s):  
Alexandre O. Fierro ◽  
Jon M. Reisner
Keyword(s):  
High Resolution ◽  
Latent Heat ◽  
Functional Relationship ◽  
Doppler Radar ◽  
Propagation Speed ◽  
Radar Data ◽  
Lightning Activity ◽  
Rapid Intensification ◽  
Hurricane Rita ◽  
Resolution Simulation

Abstract In this paper, a high-resolution simulation establishing relationships between lightning and eyewall convection during the rapid intensification phase of Rita will be highlighted. The simulation is an attempt to relate simulated lightning activity within strong convective events (CEs) found within the eyewall and general storm properties for a case from which high-fidelity lightning observations are available. Specifically, the analysis focuses on two electrically active eyewall CEs that had properties similar to events observed by the Los Alamos Sferic Array. The numerically simulated CEs were characterized by updraft speeds exceeding 10 m s−1, a relatively more frequent flash rate confined in a layer between 10 and 14 km, and a propagation speed that was about 10 m s−1 less than of the local azimuthal flow in the eyewall. Within an hour of the first CE, the simulated minimum surface pressure dropped by approximately 5 mb. Concurrent with the pulse of vertical motions was a large uptake in lightning activity. This modeled relationship between enhanced vertical motions, a noticeable pressure drop, and heightened lightning activity suggests the utility of using lightning to remotely diagnose future changes in intensity of some tropical cyclones. Furthermore, given that the model can relate lightning activity to latent heat release, this functional relationship, once validated against a derived field produced by dual-Doppler radar data, could be used in the future to initialize eyewall convection via the introduction of latent heat and/or water vapor into a hurricane model.

Retrieved Thermodynamic Structure of Hurricane Rita (2005) from Airborne Multi-Doppler Radar Data

2021 ◽  
Author(s):  
Annette M. Boehm ◽  
Michael M. Bell
Keyword(s):  
Wind Shear ◽  
Doppler Radar ◽  
Three Dimensional ◽  
Vertical Wind Shear ◽  
Vertical Motion ◽  
Radar Data ◽  
Vertical Wind ◽  
Vertical Acceleration ◽  
Hurricane Rita ◽  
Doppler Radar Data

AbstractThe newly developed SAMURAI-TR is used to estimate three-dimensional temperature and pressure perturbations in Hurricane Rita on 23 September 2005 from multi-Doppler radar data during the RAINEX field campaign. These are believed to be the first fully three-dimensional gridded thermodynamic observations from a TC. Rita was a major hurricane at this time and was affected by 13 m s−1 deep-layer vertical wind shear. Analysis of the contributions of the kinematic and retrieved thermodynamic fields to different azimuthal wavenumbers suggests the interpretation of eyewall convective forcing within a three-level framework of balanced, quasi-balanced, and unbalanced motions. The axisymmetric, wavenumber-0 structure was approximately in thermal-wind balance, resulting in a large pressure drop and temperature increase toward the center. The wavenumber-1 structure was determined by the interaction of the storm with environmental vertical wind shear resulting in a quasi-balance between shear and shear-induced kinematic and thermo-dynamic perturbations. The observed wavenumber-1 thermodynamic asymmetries corroborate results of previous studies on the response of a vortex tilted by shear, and add new evidence that the vertical motion is nearly hydrostatic on the wavenumber-1 scale. Higher-order wavenumbers were associated with unbalanced motions and convective cells within the eyewall. The unbalanced vertical acceleration was positively correlated with buoyant forcing from thermal perturbations and negatively correlated with perturbation pressure gradients relative to the balanced vortex.

scholarly journals The Role of Observed Environmental Conditions and Precipitation Evolution in the Rapid Intensification of Hurricane Earl (2010)

2015 ◽  
Vol 143 (6) ◽  
pp. 2207-2223 ◽  
Author(s):  
Gabriel Susca-Lopata ◽  
Jonathan Zawislak ◽  
Edward J. Zipser ◽  
Robert F. Rogers
Keyword(s):  
Structural Changes ◽  
Doppler Radar ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Radar Data ◽  
Rapid Intensification ◽  
Low Level ◽  
Upper Level ◽  
Wind Retrievals

Abstract An investigation into the possible causes of the rapid intensification (RI) of Hurricane Earl (2010) is carried out using a combination of global analyses, aircraft Doppler radar data, and observations from passive microwave satellites and a long-range lightning network. Results point to an important series of events leading to, and just after, the onset of RI, all of which occur despite moderate (7–12 m s−1) vertical wind shear present. Beginning with an initially vertically misaligned vortex, observations indicate that asymmetric deep convection, initially left of shear but not distinctly up- or downshear, rotates into more decisively upshear regions. Following this convective rotation, the vortex becomes aligned and precipitation symmetry increases. The potential contributions to intensification from each of these structural changes are discussed. The radial distribution of intense convection relative to the radius of maximum wind (RMW; determined from Doppler wind retrievals) is estimated from microwave and lightning data. Results indicate that intense convection is preferentially located within the upper-level (8 km) RMW during RI, lending further support to the notion that intense convection within the RMW promotes tropical cyclone intensification. The distribution relative to the low-level RMW is more ambiguous, with intense convection preferentially located just outside of the low-level RMW at times when the upper-level RMW is much greater than the low-level RMW.

An Axisymmetric View of Concentric Eyewall Evolution in Hurricane Rita (2005)

2012 ◽  
Vol 69 (8) ◽  
pp. 2414-2432 ◽  
Author(s):  
Michael M. Bell ◽  
Michael T. Montgomery ◽  
Wen-Chau Lee
Keyword(s):  
Boundary Layer ◽  
Diabatic Heating ◽  
Doppler Radar ◽  
Radar Data ◽  
Intensity Change ◽  
Latent Heating ◽  
Areal Extent ◽  
Hurricane Rita ◽  
Observation Period ◽  
Vorticity Structure

Abstract Multiplatform observations of Hurricane Rita (2005) were collected as part of the Hurricane Rainband and Intensity Change Experiment (RAINEX) field campaign during a concentric eyewall stage of the storm’s life cycle that occurred during 21–22 September. Satellite, aircraft, dropwindsonde, and Doppler radar data are used here to examine the symmetric evolution of the hurricane as it underwent eyewall replacement. During the approximately 1-day observation period, developing convection associated with the secondary eyewall became more symmetric and contracted inward. Latent heating in the emergent secondary eyewall led to the development of a distinct toroidal (overturning) circulation with inertially constrained radial inflow above the boundary layer and compensating subsidence in the moat region, properties that are consistent broadly with the balanced vortex response to an imposed ring of diabatic heating outside the primary eyewall. The primary eyewall’s convection became more asymmetric during the observation period, but the primary eyewall was still the dominant swirling wind and vorticity structure throughout the period. The observed structure and evolution of Rita’s secondary eyewall suggest that spinup of the tangential winds occurred both within and above the boundary layer, and that both balanced and unbalanced dynamical processes played an important role. Although Rita’s core intensity decreased during the observation period, the observations indicate a 125% increase in areal extent of hurricane-force winds and a 19% increase in integrated kinetic energy resulting from the eyewall replacement.

Observations of Atypical Rapid Intensification Characteristics in Hurricane Dorian (2019)

2021 ◽  
Author(s):  
David R. Ryglicki ◽  
Christopher S. Velden ◽  
Paul D. Reasor ◽  
Daniel Hodyss ◽  
James D. Doyle
Keyword(s):  
Vortex Flow ◽  
Doppler Radar ◽  
Vertical Wind Shear ◽  
Radar Data ◽  
Environmental Flow ◽  
Rapid Intensification ◽  
Spatiotemporal Resolution ◽  
Atmospheric Motion ◽  
Upper Level ◽  
Atmospheric Motion Vectors

AbstractMultiple observation and analysis datasets are used to demonstrate two key features of the Atypical Rapid Intensification (ARI) process that occurred in Atlantic Hurricane Dorian (2019): 1) precession and nutations of the vortex tilt and 2) blocking of the impinging upper-level environmental flow by the outflow. As Dorian came under the influence of an upper-level anticyclone, traditional methods of estimating vertical wind shear all indicated relatively low values were acting on the storm; however, high-spatiotemporal-resolution atmospheric motion vectors (AMVs) indicated that the environmental flow at upper levels was actually impinging on the vortex core, resulting in a vertical tilt. We employ a novel ensemble of centers of individual swaths of dual-Doppler radar data from WP-3D aircraft to characterize the precession and wobble of the vortex tilt. This tilting and wobbling preceded a sequence of outflow surges that acted to repel the impinging environmental flow, thereby reducing the shear and permitting ARI. We then apply prior methodology on satellite imagery for distinguishing ARI features. Finally, we use the AMV dataset to experiment with different shear calculations and show that the upper-level cross-vortex flow approaches zero. We discuss the implication of these results with regards to prior works on ARI and intensification in shear.

Kinematics of the Secondary Eyewall Observed in Hurricane Rita (2005)

2011 ◽  
Vol 68 (8) ◽  
pp. 1620-1636 ◽  
Author(s):  
Anthony C. Didlake ◽  
Robert A. Houze
Keyword(s):  
Doppler Radar ◽  
Three Dimensional ◽  
Heavy Precipitation ◽  
Radar Data ◽  
Outer Edge ◽  
Vorticity Field ◽  
Wind Maximum ◽  
Comparable Rate ◽  
Hurricane Rita ◽  
Tangential Wind

Abstract Airborne Doppler radar data collected from the concentric eyewalls of Hurricane Rita (2005) provide detailed three-dimensional kinematic observations of the secondary eyewall feature. The secondary eyewall radar echo shows a ring of heavy precipitation containing embedded convective cells, which have no consistent orientation or radial location. The axisymmetric mean structure has a tangential wind maximum within the reflectivity maximum at 2-km altitude and an elevated distribution of its strongest winds on the radially outer edge. The corresponding vertical vorticity field contains a low-level maximum on the inside edge, which is part of a tube of increased vorticity that rises through the center of the reflectivity tower and into the midlevels. The secondary circulation consists of boundary layer inflow that radially overshoots the secondary eyewall. A portion of this inflowing air experiences convergence and supergradient forces that cause the air to rise and flow radially outward back into the center of the reflectivity tower. This mean updraft stretches and tilts the vorticity field to increase vorticity on the radially inner side of the tangential wind maximum. Radially outside this region, perturbation motions decrease the vorticity at a comparable rate. Thus, both mean and perturbation motions actively strengthen the wind maximum of the secondary eyewall. These features combine to give the secondary eyewall a structure different from the primary eyewall as it builds to become the new replacement eyewall.

scholarly journals Assimilating C-Band Radar Data for High-Resolution Simulations of Precipitation: Case Studies over Western Sumatra

2021 ◽  
Vol 14 (1) ◽  
pp. 42
Author(s):  
Bojun Zhu ◽  
Zhaoxia Pu ◽  
Agie Wandala Putra ◽  
Zhiqiu Gao
Keyword(s):  
High Resolution ◽  
Data Assimilation ◽  
Doppler Radar ◽  
Weather Prediction ◽  
Wrf Model ◽  
Active Phase ◽  
Radar Data ◽  
Skill Score ◽  
Moist Convection ◽  
Simulated Precipitation

Accurate high-resolution precipitation forecasts are critical yet challenging for weather prediction under complex topography or severe synoptic forcing. Data fusion and assimilation aimed at improving model forecasts, as one possible approach, has gained increasing attention in past decades. This study investigates the influence of the observations from a C-band Doppler radar over the west coast of Sumatra on high-resolution numerical simulations of precipitation around its vicinity under the Madden–Julian oscillation (MJO) in January and February 2018. Cases during various MJO phases were selected for simulations with an advanced research version of the weather research and forecasting (WRF) model at a cloud-permitting scale (~3 km). A 3-dimensional variational (3DVAR) data assimilation method and a hybrid three-dimensional ensemble–variational data assimilation (3DEnVAR) method, based on the NCEP Gridpoint Statistical Interpolation (GSI) assimilation system, were used to assimilate the radar reflectivity and the radial velocity data. The WRF-simulated precipitation was validated with the Integrated Multi-satellitE Retrievals for GPM (IMERG) precipitation data, and the fractions skill score (FSS) was calculated in order to evaluate the radar data impacts objectively. The results show improvements in the simulated precipitation with hourly radar data assimilation 6 h prior to the simulations. The modifications with assimilation were validated through the observation departure and moist convection. It was found that forecast improvements are relatively significant when precipitation is more related to local-scale convection but rather small when the background westerly wind is strong under the MJO active phase. The additional simulation experiments, under a 1- or 2-day assimilation cycle, indicate better improvements in the precipitation simulation with 3DEnVAR radar assimilation than those with the 3DVAR method.

scholarly journals Assimilation of High-Resolution Tropical Cyclone Observations with an Ensemble Kalman Filter Using HEDAS: Evaluation of 2008–11 HWRF Forecasts

2015 ◽  
Vol 143 (2) ◽  
pp. 511-523 ◽  
Author(s):  
Sim D. Aberson ◽  
Altuğ Aksoy ◽  
Kathryn J. Sellwood ◽  
Tomislava Vukicevic ◽  
Xuejin Zhang
Keyword(s):  
Kalman Filter ◽  
High Resolution ◽  
Tropical Cyclone ◽  
Ensemble Kalman Filter ◽  
Doppler Radar ◽  
Radar Data ◽  
Doppler Radar Data ◽  
Flight Level ◽  
Airborne Doppler Radar ◽  
Aircraft Data

Abstract NOAA has been gathering high-resolution, flight-level dropwindsonde and airborne Doppler radar data in tropical cyclones for almost three decades; the U.S. Air Force routinely obtained the same type and quality of data, excepting Doppler radar, for most of that time. The data have been used for operational diagnosis and for research, and, starting in 2013, have been assimilated into operational regional tropical cyclone models. This study is an effort to quantify the impact of assimilating these data into a version of the operational Hurricane Weather Research and Forecasting model using an ensemble Kalman filter. A total of 83 cases during 2008–11 were investigated. The aircraft whose data were used in the study all provide high-density flight-level wind and thermodynamic observations as well as surface wind speed data. Forecasts initialized with these data assimilated are compared to those using the model standard initialization. Since only NOAA aircraft provide airborne Doppler radar data, these data are also tested to see their impact above the standard aircraft data. The aircraft data alone are shown to provide some statistically significant improvement to track and intensity forecasts during the critical watch and warning period before projected landfall (through 60 h), with the Doppler radar data providing some further improvement. This study shows the potential for improved forecasts with regular tropical cyclone aircraft reconnaissance and the assimilation of data obtained from them, especially airborne Doppler radar data, into the numerical guidance.

scholarly journals Verification of a High-Resolution Model Forecast Using Airborne Doppler Radar Analysis during the Rapid Intensification of Hurricane Guillermo

2010 ◽  
Vol 49 (4) ◽  
pp. 807-820 ◽  
Author(s):  
X. Zou ◽  
Yonghui Wu ◽  
Peter Sawin Ray
Keyword(s):  
High Resolution ◽  
Inner Core ◽  
Doppler Radar ◽  
Mesoscale Model ◽  
Radial Profile ◽  
Initial Time ◽  
Rapid Intensification ◽  
Model Forecast ◽  
Research Division ◽  
Airborne Doppler Radar

Abstract The NOAA Hurricane Research Division (HRD) P-3 aircraft provided airborne radar observations during the period of rapid intensification of Hurricane Guillermo on 2 August 1997. The inner core structure and evolution of Hurricane Guillermo (1997) over a 120 km by 120 km square area, centered on the storm, was observed by the P-3 aircraft during 10 flight legs at half-hour intervals during a 6-h period from 1800 UTC 2 August to 0000 UTC 3 August 1997. A high-resolution short-term model forecast initialized at 1800 UTC 2 August 1997 was made using the fifth-generation Pennsylvania State University–NCAR nonhydrostatic, two-way interactive, movable, triply nested grid Mesoscale Model (MM5). The weak vortex at the initial time in the NCEP analysis was replaced by a tropical storm–like vortex generated by a 4D variational data assimilation (4D-Var) vortex initialization experiment. The modeled Guillermo followed the observed track with less than a 12-km track error at any time during the 6-h forecast period. The modeled eye is smaller than the observed eye and the modeled vortex is more upright than shown by the radar analysis. The minimum pressure, maximum wind (intensity), and radial profile of tangential winds are close to the radar analysis after 2–3 h of model spinup. A spectral decomposition further reveals that (i) large differences between the model simulation and radar analysis of the asymmetric features are mostly caused by azimuthal phase errors; (ii) the wavenumber 1 component dominates the asymmetric features and remains stationary within the inner core region, as is also observed by airborne Doppler radar; and (iii) although being significantly different from radar analysis, the azimuthal phase of the wavenumber 1 component of modeled reflectivity does not vary greatly with time as the radar data suggest.

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