scholarly journals Evolution of Dynamic and Thermodynamic Structures before and during Rapid Intensification of Tropical Cyclones: Sensitivity to Vertical Wind Shear

2019 ◽  
Vol 147 (4) ◽  
pp. 1171-1191 ◽  
Author(s):  
Dandan Tao ◽  
Fuqing Zhang
Keyword(s):  
Wind Shear ◽  
Inner Core ◽  
Vertical Wind Shear ◽  
Onset Time ◽  
Vertical Wind ◽  
Asymmetric Structure ◽  
Rapid Intensification ◽  
Background Flow ◽  
Budget Analysis ◽  
Axisymmetric Structure

Abstract This study explores the spatial and temporal changes in tropical cyclone (TC) thermodynamic and dynamic structures before, near, and during rapid intensification (RI) under different vertical wind shear conditions through four sets of convection-permitting ensemble simulations. A composite analysis of TC structural evolution is performed by matching the RI onset time of each member. Without background flow, the axisymmetric TC undergoes a gradual strengthening of the inner-core vorticity and warm core throughout the simulation. In the presence of moderate environmental shear (5–6 m s−1), both the location and magnitude of the asymmetries in boundary layer radial flow, relative humidity, and vertical motion evolve with the tilt vector throughout the simulation. A budget analysis indicates that tilting is crucial to maintaining the midlevel vortex while stretching and vertical advection are responsible for the upper-level vorticity generation before RI when strong asymmetries arise. Two warm anomalies are observed before the RI onset when the vortex column is tilted. When approaching the RI onset, these two warm anomalies gradually merge into one. Overall, the most symmetric vortex structure is found near the RI onset. Moderately sheared TCs experience an adjustment period from a highly asymmetric structure with updrafts concentrated at the down-tilt side before RI to a more axisymmetric structure during RI as the eyewall updrafts develop. This adjustment period near the RI onset, however, is found to be the least active period for deep convection. TC development under a smaller environmental shear (2.5 m s−1) condition displays an intermediate evolution between ensemble experiments with no background flow and with moderate shear (5–6 m s−1).

The Intensity- and Size-Dependent Response of Tropical Cyclones to Increasing Vertical Wind Shear

2021 ◽  
Author(s):  
Peter M. Finocchio ◽  
Rosimar Rios-Berrios
Keyword(s):  
Wind Field ◽  
Wind Shear ◽  
Diabatic Heating ◽  
Inner Core ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Vertical Coupling ◽  
Tangential Wind

AbstractThis study describes a set of idealized simulations in which westerly vertical wind shear increases from 3 to 15 m s−1 at different stages in the lifecycle of an intensifying tropical cyclone (TC). The TC response to increasing shear depends on the intensity and size of the TC’s tangential wind field when shear starts to increase. For a weak tropical storm, increasing shear decouples the vortex and prevents intensification. For Category 1 and stronger storms, increasing shear causes a period of weakening during which vortex tilt increases by 10–30 km before the TCs reach a near-steady Category 1–3 intensity at the end of the simulations. TCs exposed to increasing shear during or just after rapid intensification tend to weaken the most. Backward trajectories reveal a lateral ventilation pathway between 8–11 km altitude that is capable of reducing equivalent potential temperature in the inner core of these TCs by nearly 2°C. In addition, these TCs exhibit large reductions in diabatic heating inside the radius of maximum winds (RMW) and lower-entropy air parcels entering downshear updrafts from the boundary layer, which further contributes to their substantial weakening. The TCs exposed to increasing shear after rapid intensification and an expansion of the outer wind field reach the strongest near-steady intensity long after the shear increases because of strong vertical coupling that prevents the development of large vortex tilt, resistance to lateral ventilation through a deep layer of the middle troposphere, and robust diabatic heating within the RMW.

The Convective Evolution and Rapid Intensification of Hurricane Earl (2010)

2014 ◽  
Vol 142 (11) ◽  
pp. 4364-4380 ◽  
Author(s):  
Stephanie N. Stevenson ◽  
Kristen L. Corbosiero ◽  
John Molinari
Keyword(s):  
Wind Shear ◽  
Inner Core ◽  
Rare Event ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Lightning Strikes ◽  
Warm Core ◽  
Core Convection

Abstract The relationship between an inner-core (r < 100 km) lightning outbreak and the subsequent rapid intensification (RI) of Hurricane Earl (2010) is examined using lightning strikes recorded by the World Wide Lightning Location Network (WWLLN) and in situ observations from various aircraft missions. Moderate (8.4 m s−1) northeasterly deep-layer (850–200 hPa) vertical wind shear, caused by outflow from Hurricane Danielle, existed over Earl at the beginning of a prolonged period of RI. Over 70% of the lightning strikes within a 500-km radius occurred downshear, with a preference toward downshear right in the outer rainbands, in agreement with previous studies. The location of inner-core strikes in Earl differed markedly from previous studies. The inner-core lightning activity precessed from left of shear to upshear, an extremely rare event, beginning just prior to the onset of RI. Diagnosis of the vortex tilt midway through the lightning precession showed this convection was occurring downtilt in the upshear-left quadrant; however, limited observations could not confirm if the vortex tilt was precessing with the lightning. Elevated values of low-level relative humidity and CAPE were also found upshear and supported the inner-core convection, which was found to occur within the radius of maximum wind (RMW). Previous studies have shown that convection located inside the RMW promotes intensification. It is hypothesized that intensification may have occurred in part because the vertical wind shear acted to reduce the upshear tilt, and the occurrence of convection inside the RMW helped to enhance the warm core.

Rapid Intensification of a Sheared, Fast-Moving Hurricane over the Gulf Stream

2012 ◽  
Vol 140 (10) ◽  
pp. 3361-3378 ◽  
Author(s):  
Leon T. Nguyen ◽  
John Molinari
Keyword(s):  
Gulf Stream ◽  
Wind Shear ◽  
Inner Core ◽  
Vertical Wind Shear ◽  
Vertical Motion ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Warm Core ◽  
Hurricane Irene ◽  
Sufficient Intensity

Abstract Hurricane Irene (1999) rapidly intensified from 65 to 95 kt (~33.4 to 48.9 m s−1) in 18 h. During the rapid intensification (RI) period, the northeastward storm motion increased from 10 to 18 m s−1, the ambient southwesterly vertical wind shear increased from 6–7 to 10–13 m s −1, and the downshear tilt of the inner core vortex increased. The azimuthal wavenumber-1 asymmetric convection that developed was consistent with a superposition of shear-induced and storm motion–induced forcing for vertical motion downshear and ahead of the center. Although the diabatic heating remained strongly asymmetric, it was of sufficient intensity to dramatically increase the azimuthally averaged heating. This heating occurred almost entirely inside the radius of maximum winds, a region known to favor rapid warm core development and spinup of the vortex. It is hypothesized that asymmetric forcing from the large vertical wind shear and rapid storm motion were responsible for RI. An unanswered question is what determines whether the heating will develop within the radius of maximum winds. Extraordinarily deep cells developed in the inner core toward the end of the RI period. Rather than causing RI, these cells appeared to be an outcome of the same processes noted above.

scholarly journals The Relationship between Convective Bursts and Warm-Core Intensification in a Nonhydrostatic Simulation of Typhoon Lionrock (2016)

2019 ◽  
Vol 147 (5) ◽  
pp. 1557-1579 ◽  
Author(s):  
Ryo Oyama ◽  
Akiyoshi Wada
Keyword(s):  
Wind Shear ◽  
Inner Core ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Maximum Temperature ◽  
Short Time Scale ◽  
Warm Core ◽  
Budget Analysis ◽  
Convective Bursts ◽  
Monsoon Gyre

Abstract Typhoon Lionrock (2016) was unusual among tropical cyclones (TCs) in that it formed east of the monsoon gyre in the western North Pacific, and moved counterclockwise. It rapidly intensified in the monsoon gyre in an environment of weak upper-tropospheric winds and vertical wind shear. This study used a 3-km mesh nonhydrostatic model to examine the warm-core intensification of Typhoon Lionrock, which was associated with cyclone-scale vigorous convection [i.e., convective bursts (CBs)]. The simulation reproduced the multiple CBs at intervals of 1 day or shorter, which were related to the diurnal cycles and other short time-scale variations in the TC convection. Each CB tended to precede peak temperature anomalies near the TC center by 0–12 h, indicating that the warm-core intensification occurred due to diabatic heating released by the vigorous eyewall convection. Notably, updrafts due to convection during the intensification phase were stronger than those occurring during the mature and decay phases, and the maximum temperature anomaly of the upper-tropospheric warm core rapidly increased during eyewall formation. In addition, this study indicated that most of the asymmetric inner-core vigorous convection associated with CBs, which was induced by the vertical wind shear, contributed to the warm-core intensification. Furthermore, the budget analysis of potential temperature within the TC inner core showed that adiabatic heating due to subsidence from near the tropopause within the eye, often following CBs, was essential in developing the eye. The lag correlation suggested the lag time between the CBs and the subsidence within the eye was 3–9 h.

Effects of Vertical Wind Shear on Inner-Core Thermodynamics of an Idealized Simulated Tropical Cyclone

2015 ◽  
Vol 72 (2) ◽  
pp. 511-530 ◽  
Author(s):  
Jian-Feng Gu ◽  
Zhe-Min Tan ◽  
Xin Qiu
Keyword(s):  
Wind Shear ◽  
Inner Core ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Intensity Change ◽  
Eddy Flux ◽  
Radial Gradient ◽  
Budget Analysis ◽  
Eddy Fluxes ◽  
Low Entropy

Abstract A suite of idealized simulations of tropical cyclones (TCs) with weak to strong vertical wind shear (VWS) imposed during the mature stage was employed to examine the effects of VWS on the inner-core thermodynamics and intensity change of TCs using a three-dimensional full-physics numerical model as well as a budget analysis of moist entropy. For sheared TCs with shear-induced convective asymmetries, VWS tends to reduce moist entropy within the midlevel eyewall and the boundary layer (BL) but supply moist entropy outside the eyewall above the BL. Such changes in moist entropy reduce the radial gradient of moist entropy across the eyewall, resulting in weakening of the TC. Budget analysis showed that the intense eddy fluxes are mainly responsible for the reduction and/or increase in entropy in the sheared TCs. The entropy reduction within the midlevel eyewall is a result of both the radial eddy flux and the vertical eddy flux. These eddy fluxes are effective at introducing low-entropy air into the midlevel eyewall. Accompanying the flushing of midlevel low-entropy air into the BL, there is an increase in moist entropy outside the eyewall above the BL due to the upward transport of moisture from the BL by shear-induced convection. This represents a new potential pathway to further restrain the radial gradient of moist entropy across the eyewall and hence TC intensity in the sheared environmental flow.

Observed Processes Underlying the Favorable Vortex Repositioning Early in the Development of Hurricane Dorian (2019).

2021 ◽  
Author(s):  
George R. Alvey ◽  
Michael Fischer ◽  
Paul Reasor ◽  
Jonathan Zawislak ◽  
Robert Rogers
Keyword(s):  
Wind Shear ◽  
Inner Core ◽  
Doppler Radar ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
In Situ Data ◽  
Upper Level

AbstractDorian’s evolution from a weak, disorganized tropical storm to a rapidly intensifying hurricane is documented through a unique multi-platform synthesis of NOAA’s P-3 tail-Doppler radar, airborne in situ data, and Meteo-France’s Martinique and Guadeloupe ground radar network. Dorian initially struggled to intensify with a misaligned vortex in moderate mid-tropospheric vertical wind shear that also allowed detrimental impacts from dry air near the inner core. Despite vertical wind shear eventually decreasing to less than 5 m/s and an increasingly symmetric distribution of stratiform precipitation, the vortex maintained its misalignment with asymmetric convection for 12 hours. Then, as the low-level circulation (LLC) approached St. Lucia, deep convection near the LLC’s center dissipated, the LLC broadened, and precipitation expanded radially outwards from the center temporally coinciding with the diurnal cycle. Convection then developed farther downtilt within a more favorable, humid environment and deepened appreciably at least partially due to interaction with Martinique. A distinct repositioning of the LLC towards Martinique is induced by spin-up of a mesovortex into a small, compact LLC.It is hypothesized that this somewhat atypical reformation event and the repositioning of the vortex into a more favorable environment, farther from detrimental dry mid-tropospheric air, increased its favorability for the rapid intensification that subsequently ensued. Although the repositioning resulted in tilt reducing to less than the scale of the vortex itself, the pre-existing broad mid-upper level cyclonic envelope remained intact with continued misalignment observed between the mid-level center and repositioned LLC even during the early stages of rapid intensification.

scholarly journals Simulation of Rapid Intensification of Super Typhoon Lekima (2019). Part I: Evolution Characteristics of Asymmetric Convection Under Upper-Level Vertical Wind Shear

2021 ◽  
Vol 9 ◽  
Author(s):  
Qijun Huang ◽  
Xuyang Ge ◽  
Melinda Peng
Keyword(s):  
Wind Shear ◽  
Inner Core ◽  
Thermal Structure ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Super Typhoon ◽  
Storm Center ◽  
Upper Level

The role of the upper-level vertical wind shear (VWS) on the rapid intensification (RI) of super typhoon Lekima (2019) is investigated with a high-resolution numerical simulation. Our simulation shows that under moderate upper-level easterly VWS, the tilting-induced convective asymmetry is transported from the initially downshear quadrant to the upshear quadrant and wrapped around the storm center by the cyclonic flow of the storm while moving inward. This process enhances upward motions at the upshear flank and creates upper-level divergent flow. As such, the establishment of outflow acts against the environmental flow to reduce the VWS, allowing vertical alignment of the storm. The organized outflow plays an important role in sustaining the inner-core deep convection by modulating the environmental upper-level thermal structure. Accompanying deep convective bursts (CBs), cold anomalies are generated in the tropopause layer due to the adiabatic cooling by the upward motion and radiative process associated with the cloud anvil. Physically, cold anomalies at the tropopause locally destabilize the atmosphere and enhance the convections and the secondary circulation. The CBs continue to develop episodically through this process as they wrap around the storm center to form a symmetric eyewall. The results suggest that deep convections are capable of reducing the upper-level VWS, promoting the development of upper-level outflow. Lekima overcame the less favorable environment and eventually intensified to become a super typhoon.

scholarly journals The Unexpected Rapid Intensification of Tropical Cyclones in Moderate Vertical Wind Shear. Part I: Overview and Observations

2018 ◽  
Vol 146 (11) ◽  
pp. 3773-3800 ◽  
Author(s):  
David R. Ryglicki ◽  
Joshua H. Cossuth ◽  
Daniel Hodyss ◽  
James D. Doyle
Keyword(s):  
Tropical Cyclones ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Convective Cloud ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Brightness Temperatures ◽  
Idealized Modeling ◽  
Hurricane Prediction ◽  
Upper Level

Abstract A satellite-based investigation is performed of a class of tropical cyclones (TCs) that unexpectedly undergo rapid intensification (RI) in moderate vertical wind shear between 5 and 10 m s−1 calculated as 200–850-hPa shear. This study makes use of both infrared (IR; 11 μm) and water vapor (WV; 6.5 μm) geostationary satellite data, the Statistical Hurricane Prediction Intensity System (SHIPS), and model reanalyses to highlight commonalities of the six TCs. The commonalities serve as predictive guides for forecasters and common features that can be used to constrain and verify idealized modeling studies. Each of the TCs exhibits a convective cloud structure that is identified as a tilt-modulated convective asymmetry (TCA). These TCAs share similar shapes, upshear-relative positions, and IR cloud-top temperatures (below −70°C). They pulse over the core of the TC with a periodicity of between 4 and 8 h. Using WV satellite imagery, two additional features identified are asymmetric warming/drying upshear of the TC relative to downshear, as well as radially thin arc-shaped clouds on the upshear side. The WV brightness temperatures of these arcs are between −40° and −60°C. All of the TCs are sheared by upper-level anticyclones, which limits the strongest environmental winds to near the tropopause.

scholarly journals Simple kinematic models for the environmental interaction of tropical cyclones in vertical wind shear

2011 ◽  
Vol 11 (17) ◽  
pp. 9395-9414 ◽  
Author(s):  
M. Riemer ◽  
M. T. Montgomery
Keyword(s):  
Numerical Experiment ◽  
Limit Cycle ◽  
Wind Shear ◽  
Inner Core ◽  
Point Vortex ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Horizontal Flow ◽  
Manifold Structure ◽  
Environmental Air

Abstract. A major impediment to the intensity forecast of tropical cyclones (TCs) is believed to be associated with the interaction of TCs with dry environmental air. However, the conditions under which pronounced TC-environment interaction takes place are not well understood. As a step towards improving our understanding of this problem, we analyze here the flow topology of a TC immersed in an environment of vertical wind shear in an idealized, three-dimensional, convection-permitting numerical experiment. A set of distinct streamlines, the so-called manifolds, can be identified under the assumptions of steady and layer-wise horizontal flow. The manifolds are shown to divide the flow around the TC into distinct regions. The manifold structure in our numerical experiment is more complex than the well-known manifold structure of a non-divergent point vortex in uniform background flow. In particular, one manifold spirals inwards and ends in a limit cycle, a meso-scale dividing streamline encompassing the eyewall above the layer of strong inflow associated with surface friction and below the outflow layer in the upper troposphere. From the perspective of a steady and layer-wise horizontal flow model, the eyewall is well protected from the intrusion of environmental air. In order for the environmental air to intrude into the inner-core convection, time-dependent and/or vertical motions, which are prevalent in the TC inner-core, are necessary. Air with the highest values of moist-entropy resides within the limit cycle. This "moist envelope" is distorted considerably by the imposed vertical wind shear, and the shape of the moist envelope is closely related to the shape of the limit cycle. In a first approximation, the distribution of high- and low-θe air around the TC at low to mid-levels is governed by the stirring of convectively modified air by the steady, horizontal flow. Motivated by the results from the idealized numerical experiment, an analogue model based on a weakly divergent point vortex in background flow is formulated. The simple kinematic model captures the essence of many salient features of the manifold structure in the numerical experiment. A regime diagram representing realistic values of TC intensity and vertical wind shear can be constructed for the point-vortex model. The results indicate distinct scenarios of environmental interaction depending on the ratio of storm intensity and vertical-shear magnitude. Further implications of the new results derived from the manifold analysis for TCs in the real atmosphere are discussed.

scholarly journals The Unexpected Rapid Intensification of Tropical Cyclones in Moderate Vertical Wind Shear. Part III: Outflow–Environment Interaction

2019 ◽  
Vol 147 (8) ◽  
pp. 2919-2940 ◽  
Author(s):  
David R. Ryglicki ◽  
James D. Doyle ◽  
Daniel Hodyss ◽  
Joshua H. Cossuth ◽  
Yi Jin ◽  
...  
Keyword(s):  
Wind Shear ◽  
Vertical Wind Shear ◽  
Environmental Flow ◽  
Vertical Wind ◽  
Environment Interaction ◽  
Rapid Intensification ◽  
Field Matching ◽  
Upper Level ◽  
Bernoulli Flow ◽  
Dynamic High Pressure

Abstract Interactions between the upper-level outflow of a sheared, rapidly intensifying tropical cyclone (TC) and the background environmental flow in an idealized model are presented. The most important finding is that the divergent outflow from convection localized by the tilt of the vortex serves to divert the background environmental flow around the TC, thus reducing the local vertical wind shear. We show that this effect can be understood from basic theoretical arguments related to Bernoulli flow around an obstacle. In the simulation discussed, the environmental flow diversion by the outflow is limited to 2 km below the tropopause in the 12–14-km (250–150 hPa) layer. Synthetic water vapor satellite imagery confirms the presence of upshear arcs in the cloud field, matching satellite observations. These arcs, which exist in the same layer as the outflow, are caused by slow-moving wave features and serve as visual markers of the outflow–environment interface. The blocking effect where the outflow and the environmental winds meet creates a dynamic high pressure whose pressure gradient extends nearly 1000 km upwind, thus causing the environmental winds to slow down, to converge, and to sink. We discuss these results with respect to the first part of this three-part study, and apply them to another atypical rapid intensification hurricane: Matthew (2016).

Sign in / Sign up

Export Citation Format

Share Document