scholarly journals Effects of Air‐Sea Interaction on the Eyewall Replacement Cycle of Typhoon Sinlaku (2008): Verification of Numerical Simulation

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Lu Yang ◽  
Xiaoping Cheng ◽  
Xiaogang Huang ◽  
Jianfang Fei ◽  
Xiangcheng Li
Keyword(s):  
Numerical Simulation ◽  
Eyewall Replacement Cycle ◽  
Replacement Cycle

scholarly journals The Unconventional Eyewall Replacement Cycle of Hurricane Ophelia (2005)

2021 ◽  
Author(s):  
Muhammad Naufal Razin ◽  
Michael M. Bell
Keyword(s):  
Intensity Change ◽  
Wind Maximum ◽  
Low Level ◽  
Tangential Wind ◽  
Eyewall Replacement Cycle ◽  
Flight Level ◽  
Intensive Observation ◽  
Observation Period ◽  
Replacement Cycle

AbstractHurricane Ophelia (2005) underwent an unconventional eyewall replacement cycle (ERC) as it was a Category 1 storm located over cold sea surface temperatures near 23°C. The ERC was analyzed using airborne radar, flight-level, and dropsonde data collected during the Hurricane Rainband and Intensity Change Experiment (RAINEX) intensive observation period on 11 September 2005. Results showed that the spin-up of the secondary tangential wind maximum during the ERC can be attributed to the efficient convergence of absolute angular momentum by the mid-level inflow of Ophelia’s dominantly stratiform rainbands. This secondary tangential wind maximum strongly contributed to the azimuthal mean tangential wind field, which is conducive for increased low-level supergradient winds and corresponding outflow. The low-level supergradient forcing enhanced convergence to form a secondary eyewall. Ophelia provides a unique example of an ERC occurring in a weaker storm with predominantly stratiform rainbands, suggesting an important role of stratiform precipitation processes in the development of secondary eyewalls.

Doppler Radar Analysis of the Eyewall Replacement Cycle of Hurricane Matthew (2016) in Vertical Wind Shear

2021 ◽  
Author(s):  
Ting-Yu Cha ◽  
Michael M. Bell ◽  
Alexander J. DesRosiers
Keyword(s):  
Wind Shear ◽  
Doppler Radar ◽  
Vertical Wind Shear ◽  
Radar Data ◽  
Secondary Circulation ◽  
Vertical Wind ◽  
High Temporal Resolution ◽  
Radar Observations ◽  
Eyewall Replacement Cycle ◽  
Replacement Cycle

AbstractHurricane Matthew (2016) was observed by ground-based polarimetric radars in Miami (KAMX), Melbourne (KMLB), and Jacksonville (KJAX) and a NOAA P3 airborne tail Doppler radar near the coast of the southeastern United States during an eyewall replacement cycle (ERC). The radar observations indicate that Matthew’s primary eyewall was replaced with a weaker outer eyewall, but unlike a classic ERC, Matthew did not reintensify after the inner eyewall disappeared. Triple Doppler analysis was calculated from the NOAA P3 airborne fore and aft radar scanning combined with the KAMX radar data during the period of secondary eyewall intensification and inner eyewall weakening from 19 UTC 6 October to 00 UTC 7 October. Four flight passes of the P3 aircraft show the evolution of the reflectivity, tangential winds, and secondary circulation as the outer eyewall became well-established. Further evolution of the ERC is analyzed from the ground-based single Doppler radar observations for 35 hours with high temporal resolution at a 5-minute interval from 19 UTC 6 October to 00 UTC 8 October using the Generalized Velocity Track Display (GVTD) technique. The single-Doppler analyses indicate that the inner eyewall decayed a few hours after the P3 flight, while the outer eyewall contracted but did not reintensify and the asymmetries increased episodically. The analysis suggests that the ERC process was influenced by a complex combination of environmental vertical wind shear, an evolving axisymmetric secondary circulation, and an asymmetric vortex Rossby wave damping mechanism that promoted vortex resiliency despite increasing shear.

Are Eyewall Replacement Cycles Governed Largely by Axisymmetric Balance Dynamics?

2015 ◽  
Vol 72 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Sergio F. Abarca ◽  
Michael T. Montgomery
Keyword(s):  
Boundary Layer ◽  
Recent Work ◽  
Balance Model ◽  
Tangential Wind ◽  
Eyewall Replacement Cycle ◽  
Physics Simulation ◽  
Physics Model ◽  
Balance Dynamics ◽  
Eyewall Replacement Cycles ◽  
Replacement Cycle

Abstract The authors question the widely held view that radial contraction of a secondary eyewall during an eyewall replacement cycle is well understood and governed largely by the classical theory of axisymmetric balance dynamics. The investigation is based on a comparison of the secondary circulation and derived tangential wind tendency between a full-physics simulation and the Sawyer–Eliassen balance model. The comparison is made at a time when the full-physics model exhibits radial contraction of the secondary eyewall during a canonical eyewall replacement cycle. It is shown that the Sawyer–Eliassen model is unable to capture the phenomenology of secondary eyewall radial contraction because it predicts a net spindown of the boundary layer tangential winds and does not represent the boundary layer spinup mechanism that has been articulated in recent work.

scholarly journals Comparison of ARCHER MPERC to NHC Analysis

2021 ◽  
Vol 10 (3) ◽  
Author(s):  
Lorenzo Pulmano ◽  
Leya Joykutty
Keyword(s):  
Tropical Cyclones ◽  
Passive Microwave ◽  
Central Pacific ◽  
Atlantic Basin ◽  
Wind Speeds ◽  
Eyewall Replacement Cycle ◽  
Eyewall Replacement Cycles ◽  
National Hurricane Center ◽  
Joint Typhoon Warning Center ◽  
Replacement Cycle

Eyewall replacement cycles (ERCs) are events that occur in intense tropical cyclones (TCs) and are difficult to predict.  An ERC event involves a secondary outer eyewall that surrounds the inner eyewall.  The outer eyewall slowly moves towards the eye and weakens the inner eyewall, eventually replacing the inner eyewall.  During this process, wind speeds lower and the structure of a TC becomes disorganized, further weakening the storm.  TCs often restrengthen after an ERC.  Little is known about the process and as such, poses an obstacle to forecasters.  The Automated Rotational Center Hurricane Eye Retrieval (ARCHER) Microwave-based Probability of Eyewall Replacement Cycle (MPERC) is an algorithm that uses 89-95 GHz passive microwave imagery and intensity estimates from the National Hurricane Center (NHC), Central Pacific Hurricane Center (CPHC), or the Joint Typhoon Warning Center (JTWC) to predict the possibility of an ERC.  The effectiveness and ability of ARCHER MPERC was analyzed and compared to the NHC’s official reports on all Atlantic Basin tropical cyclones from 2017 to 2019.   MPERC ultimately predicted seventeen ERCs in nine tropical cyclones.  Of those, seven were valid ERCs.  The algorithm works well, predicting approximately 41% of the total number of predictions correctly.  However, MPERC did not predict five ERCs that were cited by the NHC.  It was further found that it was true that MPERC produces incorrect results in sheared and dry environments.

scholarly journals Evolution of the Warm-Core Structure during the Eyewall Replacement Cycle in a Numerically Simulated Tropical Cyclone

2019 ◽  
Vol 76 (8) ◽  
pp. 2559-2573
Author(s):  
Hui Wang ◽  
Yuqing Wang ◽  
Jing Xu ◽  
Yihong Duan
Keyword(s):  
Tropical Cyclone ◽  
Potential Temperature ◽  
Outer Edge ◽  
Core Structure ◽  
Upper Troposphere ◽  
Secondary Eyewall Formation ◽  
Warm Core ◽  
Eyewall Replacement Cycle ◽  
Upper Level ◽  
Replacement Cycle

Abstract This study examines the evolution of the warm-core structure during the secondary eyewall formation (SEF) and the subsequent eyewall replacement cycle (ERC) in a numerically simulated tropical cyclone (TC) under idealized conditions. Results show that prior to the SEF, the TC exhibited a double warm-core structure centered in the middle and upper troposphere in the eye region, and as the storm intensified with a rapid outward expansion of tangential winds, the warm core strengthened and a secondary off-center warm ring developed between 8- and 16-km heights near the outer edge of the eye. During the SEF, both the upper-level warm core and the secondary off-center warm ring rapidly strengthened. As the secondary eyewall intensified and contracted and the primary eyewall weakened and dissipated, the off-center warm ring extended inward and merged with the inner warm core to form a warm core typical of a single-eyewall TC. Results from the azimuthal-mean potential temperature budget indicate that the warming in the eye is due to subsidence and the warming above 14-km height outside the eye is largely contributed by radial warm advection in the outflow. The development of the off-center warm ring is largely due to the subsidence warming near the inner edge of the primary eyewall and in the moat area and the warming by diabatic heating in the upper part of the inner eyewall below 14-km height. Further analysis indicates that the eddy advection also played some role in the warming above 12-km height in the upper troposphere.

Essential Dynamics of Secondary Eyewall Formation

2013 ◽  
Vol 70 (10) ◽  
pp. 3216-3230 ◽  
Author(s):  
Sergio F. Abarca ◽  
Michael T. Montgomery
Keyword(s):  
Boundary Layer ◽  
Time Dependent ◽  
Layer Model ◽  
Mesoscale Simulation ◽  
Wind Maximum ◽  
Boundary Layer Model ◽  
Secondary Eyewall Formation ◽  
Tangential Wind ◽  
Eyewall Replacement Cycle ◽  
Replacement Cycle

Abstract The authors conduct an analysis of the dynamics of secondary eyewall formation in two modeling frameworks to obtain a more complete understanding of the phenomenon. The first is a full-physics, three-dimensional mesoscale model in which the authors examine an idealized hurricane simulation that undergoes a canonical eyewall replacement cycle. Analysis of the mesoscale simulation shows that secondary eyewall formation occurs in a conditionally unstable environment, questioning the applicability of moist-neutral viewpoints and related mathematical formulations thereto for studying this process of tropical cyclone intensity change. The analysis offers also new evidence in support of a recent hypothesis that secondary eyewalls form via a progressive boundary layer control of the vortex dynamics in response to a radial broadening of the tangential wind field. The second analysis framework is an axisymmetric, nonlinear, time-dependent, slab boundary layer model with radial diffusion. When this boundary layer model is forced with the aforementioned mesoscale model's radial profile of pressure at the top of the boundary layer, it generates a secondary tangential wind maximum consistent with that from the full-physics, mesoscale simulation. These findings demonstrate that the boundary layer dynamics alone are capable of developing secondary wind maxima without prescribed secondary heat sources and/or invocation of special inertial stability properties of the swirling flow either within or above the boundary layer. Finally, the time-dependent slab model reveals that the simulated secondary wind maximum contracts inward, as secondary eyewalls do in mesoscale models and in nature, pointing to a hitherto unrecognized role of unbalanced dynamics in the eyewall replacement cycle.

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