scholarly journals Large Roll Vortices Exhibited by Post-Tropical Cyclone Sandy during Landfall

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 259
Author(s):  
James A. Schiavone ◽  
Kun Gao ◽  
David A. Robinson ◽  
Peter J. Johnsen ◽  
Mathieu R. Gerbush
Keyword(s):  
Tropical Cyclone ◽  
Doppler Radar ◽  
Surface Wind ◽  
Weather Research And Forecasting ◽  
Wind Fields ◽  
Horizontal Scale ◽  
Vortex Model ◽  
Roll Vortices ◽  
O 10 ◽  
Horizontal Wavelength

Roll vortices are frequent features of a hurricane’s boundary layer, with kilometer or sub-kilometer horizontal scale. In this study, we found that large roll vortices with O (10 km) horizontal wavelength occurred over land in Post-Tropical Cyclone Sandy (2012) during landfall on New Jersey. Various characteristics of roll vortices were corroborated by analyses of Doppler radar observations, a 500 m resolution Weather Research and Forecasting (WRF) simulation, and an idealized roll vortex model. The roll vortices were always linear-shaped, and their wavelengths of 5–14 km were generally larger than any previously published for a tropical cyclone over land. Based on surface wind observations and simulated WRF surface wind fields, we found that roll vortices significantly increased the probability of hazardous winds and likely caused the observed patchiness of treefall during Sandy’s landfall.

Global Scatterometer Observations of the Structure of Tropical Cyclone Wind Fields

2020 ◽  
Vol 148 (11) ◽  
pp. 4673-4692
Author(s):  
Ali Tamizi ◽  
Ian R. Young ◽  
Agustinus Ribal ◽  
Jose-Henrique Alves
Keyword(s):  
Tropical Cyclone ◽  
Surface Wind ◽  
Radial Distance ◽  
Wind Fields ◽  
Forward Movement ◽  
Left Right Asymmetry ◽  
The Right ◽  
Very Large Database ◽  
Left Front ◽  
Tropical Cyclone Center

AbstractA very large database containing 24 years of scatterometer passes is analyzed to investigate the surface wind fields within tropical cyclones. The analysis confirms the left–right asymmetry of the wind field with the strongest winds directly to the right of the tropical cyclone center (Northern Hemisphere). At values greater than 2 times the radius to maximum winds, the asymmetry is approximately equal to the storm velocity of forward movement. Observed wind inflow angle (i.e., storm motion not subtracted) is shown to vary both radially and azimuthally within the tropical cyclone. The smallest observed wind inflow angles are found in the left-front quadrant with the largest values in the right-rear quadrant. As the velocity of forward movement increases and the central pressure decreases, observed inflow angles ahead of the storm decrease and those behind the storm increase. In the right-rear quadrant, the observed inflow angle increases with radius from the storm center. In all other quadrants, the observed inflow angle is approximately constant as a function of radial distance.

scholarly journals Evaluation of the Hurricane Research Division Doppler Radar Analysis Software Using Synthetic Data

2013 ◽  
Vol 30 (6) ◽  
pp. 1055-1071 ◽  
Author(s):  
Sylvie Lorsolo ◽  
John Gamache ◽  
Altug Aksoy
Keyword(s):  
Doppler Radar ◽  
Three Dimensional ◽  
Synthetic Data ◽  
Vertical Component ◽  
Radar Data ◽  
Weather Research And Forecasting ◽  
Analysis Software ◽  
Wind Fields ◽  
Research Division ◽  
Tangential Wind

Abstract The Hurricane Research Division Doppler radar analysis software provides three-dimensional analyses of the three wind components in tropical cyclones. Although this software has been used for over a decade, there has never been a complete and in-depth evaluation of the resulting analyses. The goal here is to provide an evaluation that will permit the best use of the analyses, but also to improve the software. To evaluate the software, analyses are produced from simulated radar data acquired from an output of a Hurricane Weather Research and Forecasting (HWRF) model nature run and are compared against the model “truth” wind fields. Comparisons of the three components of the wind show that the software provides analyses of good quality. The tangential wind is best retrieved, exhibiting an overall small mean error of 0.5 m s−1 at most levels and a root-mean-square error less than 2 m s−1. The retrieval of the radial wind is also quite accurate, exhibiting comparable errors, although the accuracy of the tangential wind is generally better. Some degradation of the retrieval quality is observed at higher altitude, mainly due to sparser distribution of data in the model. The vertical component of the wind appears to be the most challenging to retrieve, but the software still provides acceptable results. The tropical cyclone mean azimuthal structure and wavenumber structure are found to be very well captured. Sources of errors inherent to airborne Doppler measurements and the effects of some of the simplifications used in the simulation methodology are also discussed.

Tropical Cyclone Inner-Core Kinetic Energy Evolution

2008 ◽  
Vol 136 (12) ◽  
pp. 4882-4898 ◽  
Author(s):  
Katherine S. Maclay ◽  
Mark DeMaria ◽  
Thomas H. Vonder Haar
Keyword(s):  
Tropical Cyclone ◽  
Kinetic Energy ◽  
Inner Core ◽  
Surface Wind ◽  
Statistical Testing ◽  
Vertical Shear ◽  
Structure Evolution ◽  
Wind Fields ◽  
Secondary Eyewall Formation ◽  
Wind Structure

Abstract Tropical cyclone (TC) destructive potential is highly dependent on the distribution of the surface wind field. To gain a better understanding of wind structure evolution, TC 0–200-km wind fields from aircraft reconnaissance flight-level data are used to calculate the low-level area-integrated kinetic energy (KE). The integrated KE depends on both the maximum winds and wind structure. To isolate the structure evolution, the average relationship between KE and intensity is first determined. Then the deviations of the KE from the mean intensity relationship are calculated. These KE deviations reveal cases of significant structural change and, for convenience, are referred to as measurements of storm size [storms with greater (less) KE for their given intensity are considered large (small)]. It is established that TCs generally either intensify and do not grow or they weaken/maintain intensity and grow. Statistical testing is used to identify conditions that are significantly different for growing versus nongrowing storms in each intensification regime. Results suggest two primary types of growth processes: (i) secondary eyewall formation and eyewall replacement cycles, an internally dominated process, and (ii) external forcing from the synoptic environment. One of the most significant environmental forcings is the vertical shear. Under light shear, TCs intensify but do not grow; under moderate shear, they intensify less but grow more; under very high shear, they do not intensify or grow. As a supplement to this study, a new TC classification system based on KE and intensity is presented as a complement to the Saffir–Simpson hurricane scale.

scholarly journals Development and Testing of Tropical Cyclone Parametric Wind Models Tailored for Midlatitude Application—Preliminary Results

2006 ◽  
Vol 45 (9) ◽  
pp. 1244-1260 ◽  
Author(s):  
Allan W. MacAfee ◽  
Garry M. Pearson
Keyword(s):  
Tropical Cyclone ◽  
Surface Wind ◽  
Angular Size ◽  
Absolute Error ◽  
Parametric Models ◽  
Wind Fields ◽  
Low Latitude ◽  
New Techniques ◽  
Qualitative And Quantitative ◽  
Using Data

Abstract Over the years, researchers have developed parametric wind models to depict the surface winds within a tropical cyclone (TC). Most models were developed using data from aircraft flights into low-latitude (south of 30°N) TCs in the Atlantic Ocean, Gulf of Mexico, and Caribbean Sea. Such models may not adequately reproduce the midlatitude TC wind field where synoptic interaction and acceleration are more pronounced. To tailor these models for midlatitude application, latitude-dependent angular size and shape details were added by using new techniques to set values for model input parameters and by incorporating additional field-shaping procedures. A method to assess the different techniques and field-shaping procedures was developed in which qualitative and quantitative assessment was performed using five parametric models and samples of buoy and 2D surface wind data. Contingency tables and statistical scores such as mean absolute error and bias were used to select the techniques and procedures that create the most realistic depiction of low- and midlatitude TC surface wind fields.

scholarly journals Tropical Cyclone Destructive Potential by Integrated Kinetic Energy

2007 ◽  
Vol 88 (4) ◽  
pp. 513-526 ◽  
Author(s):  
Mark D. Powell ◽  
Timothy A. Reinhold
Keyword(s):  
Wind Speed ◽  
Tropical Cyclone ◽  
Kinetic Energy ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Wind Loading ◽  
Wind Fields ◽  
Damage Potential ◽  
Spatial Coverage ◽  
Destructive Potential

Tropical cyclone damage potential, as currently defined by the Saffir-Simpson scale and the maximum sustained surface wind speed in the storm, fails to consider the area impact of winds likely to force surge and waves or cause particular levels of damage. Integrated kinetic energy represents a framework that captures the physical process of ocean surface stress forcing waves and surge while also taking into account structural wind loading and the spatial coverage of the wind. Integrated kinetic energy was computed from gridded, objectively analyzed surface wind fields of 23 hurricanes representing large and small storms. A wind destructive potential rating was constructed by weighting wind speed threshold contributions to the integrated kinetic energy, based on observed damage in Hurricanes Andrew, Hugo, and Opal. A combined storm surge and wave destructive potential rating was assigned according to the integrated kinetic energy contributed by winds greater than tropical storm force. The ratings are based on the familiar 1–5 range, with continuous fits to allow for storms as weak as 0.1 or as strong as 5.99.

An Automated, Objective, Multiple-Satellite-Platform Tropical Cyclone Surface Wind Analysis

2011 ◽  
Vol 50 (10) ◽  
pp. 2149-2166 ◽  
Author(s):  
John A. Knaff ◽  
Mark DeMaria ◽  
Debra A. Molenar ◽  
Charles R. Sampson ◽  
Matthew G. Seybold
Keyword(s):  
Tropical Cyclone ◽  
Input Data ◽  
Surface Wind ◽  
Information Service ◽  
Wind Fields ◽  
Central Pacific ◽  
Wind Retrieval ◽  
Research Division ◽  
Satellite Platform ◽  
Wind Analysis

AbstractA method to estimate objectively the surface wind fields associated with tropical cyclones using only data from multiple satellite platforms and satellite-based wind retrieval techniques is described. The analyses are computed on a polar grid using a variational data-fitting method that allows for the application of variable data weights to input data. The combination of gross quality control and the weighted variational analysis also produces wind estimates that have generally smaller errors than do the raw input data. The resulting surface winds compare well to the NOAA Hurricane Research Division H*Wind aircraft reconnaissance–based surface wind analyses, and operationally important wind radii estimated from these wind fields are shown to be generally more accurate than those based on climatological data. Most important, the analysis system produces global tropical cyclone surface wind analyses and related products every 6 h—without aircraft reconnaissance data. Also, the analysis and products are available in time for consideration by forecasters at the Joint Typhoon Warning Center, the Central Pacific Hurricane Center, and the National Hurricane Center in preparing their forecasts and advisories. This Multiplatform Tropical Cyclone Surface Wind Analysis (MTCSWA) product is slated to become an operationally supported product at the National Environmental Satellite Data and Information Service (NESDIS). The input data, analysis method, products, and verification statistics associated with the MTCSWA are discussed within.

scholarly journals Tropical Cyclone Wind Retrievals from the Advanced Microwave Sounding Unit: Application to Surface Wind Analysis

2006 ◽  
Vol 45 (3) ◽  
pp. 399-415 ◽  
Author(s):  
Kotaro Bessho ◽  
Mark DeMaria ◽  
John A. Knaff
Keyword(s):  
Tropical Cyclone ◽  
Wind Direction ◽  
Surface Wind ◽  
Wind Fields ◽  
Directional Bias ◽  
Wind Speeds ◽  
Research Division ◽  
Microwave Sounding Unit ◽  
Microwave Sounding ◽  
Advanced Microwave Sounding Unit

Abstract Horizontal winds at 850 hPa from tropical cyclones retrieved using the nonlinear balance equation, where the mass field was determined from Advanced Microwave Sounding Unit (AMSU) temperature soundings, are compared with the surface wind fields derived from NASA's Quick Scatterometer (QuikSCAT) and Hurricane Research Division H*Wind analyses. It was found that the AMSU-derived wind speeds at 850 hPa have linear relations with the surface wind speeds from QuikSCAT or H*Wind. There are also characteristic biases of wind direction between AMSU and QuikSCAT or H*Wind. Using this information to adjust the speed and correct for the directional bias, a new algorithm was developed for estimation of the tropical cyclone surface wind field from the AMSU-derived 850-hPa winds. The algorithm was evaluated in two independent cases from Hurricanes Floyd (1999) and Michelle (2001), which were observed simultaneously by AMSU, QuikSCAT, and H*Wind. In this evaluation the AMSU adjustment algorithm for wind speed worked well. Results also showed that the bias correction algorithm for wind direction has room for improvement.

scholarly journals Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework

2019 ◽  
Vol 19 (4) ◽  
pp. 2477-2487 ◽  
Author(s):  
Liguang Wu ◽  
Qingyuan Liu ◽  
Yubin Li
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Large Scale ◽  
Surface Wind ◽  
Wrf Model ◽  
Surface Wind Speed ◽  
Horizontal Scale ◽  
Lower Altitude ◽  
Near Surface ◽  
Research Aircraft

Abstract. A tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL) has been observed in intense hurricanes and the associated intense turbulence poses a severe threat to the manned research aircraft when it penetrates hurricane eyewalls at a lower altitude. In this study, a numerical experiment in which a TC evolves in a large-scale background over the western North Pacific is conducted using the Advanced Weather Research and Forecast (WRF) model by incorporating the large-eddy simulation (LES) technique. The simulated tornado-scale vortex shows features similar to those revealed with limited observational data, including the updraft–downdraft couplet, the sudden jump of wind speeds, the location along the inner edge of the eyewall, and the small horizontal scale. It is suggested that the WRF–LES framework can successfully simulate the tornado-scale vortex with grids at a resolution of 37 m that cover the TC eye and eyewall. The simulated tornado-scale vortex is a cyclonic circulation with a small horizontal scale of ∼1 km in the TCBL. It is accompanied by strong updrafts (more than 15 m s−1) and large vertical components of relative vorticity (larger than 0.2 s−1). The tornado-scale vortex favorably occurs at the inner edge of the enhanced eyewall convection or rainband within the saturated, high-θe layer, mostly below an altitude of 2 km. In nearly all the simulated tornado-scale vortices, the narrow intense updraft is coupled with the relatively broad downdraft, constituting one or two updraft–downdraft couplets, as observed by the research aircraft. The presence of the tornado-scale vortex also leads to significant gradients in the near-surface wind speed and wind gusts.

scholarly journals Tornado-Scale Vortices in the Tropical Cyclone Boundary Layer: Numerical Simulation with WRF-LES Framework

2018 ◽  
Author(s):  
Liguang Wu ◽  
Qingyuan Liu ◽  
Yubing Li
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Large Scale ◽  
Surface Wind ◽  
Wrf Model ◽  
Surface Wind Speed ◽  
Horizontal Scale ◽  
Lower Altitude ◽  
Near Surface ◽  
Research Aircraft

Abstract. The tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL) has been observed in intense hurricanes and the associated intense turbulence poses a severe threat to the manned research aircraft when it penetrates hurricane eyewalls at a lower altitude. In this study, a numerical experiment in which a TC evolves in a large-scale background over the western North Pacific is conducted using the Advanced Weather Research and Forecast (WRF) model by incorporating the large eddy simulation (LES) technique. The simulated tornado-scale vortex shows the similar features as revealed with the limited observational data, including the updraft/downdraft couplet, the sudden jump of wind speeds, the favorable location, and the horizontal scale. It is suggested that the WRF-LES framework can successfully simulate the tornado-scale vortex with the grids at the resolution of 37 m that cover the TC eye and eyewall. The simulated tornado-scale vortex is a cyclonic circulation with a small horizontal scale of ~ 1 km in the TCBL. It is accompanied by strong updrafts (more than 15 m s−1) and large vertical components of relative vorticity (larger than 0.2 s−1). The tornado-scale vortex favorably occurs at the inner edge of the enhanced eyewall convection or rainband within the saturated, high-θe layer, mostly below the altitude of 2 km. Nearly in all the simulated tornado-scale vortices, the narrow intense updraft is coupled with the relatively broad downdraft, constituting one or two updraft/downdraft couplets or horizontal rolling vortices, as observed by the research aircraft. The presence of the tornado-scale vortex also leads to significant gradients in the near surface wind speed and wind gusts.

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