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An idealized, three‐dimensional, numerical simulation of tropical cyclone evolution in a quiescent environment on an f‐plane is used to explore aspects of the cyclone's life cycle in the context of the rotating‐convection paradigm. In the 20‐day simulation, the vortex undergoes a life cycle including a gestation period culminating in genesis, a rapid intensification phase, a mature phase, a transient decay and re‐intensification phase, a second mature phase and a rapid decay phase. During much of the life cycle, the flow evolution is highly asymmetric, although important aspects of it can be understood within an azimuthally averaged framework, central to which are a boundary‐layer control mechanism and a new ventilation diagnostic. The boundary‐layer control mechanism provides an explanation for the gradual expansion of the inner core of the vortex. The ventilation diagnostic characterizes the ability of deep convection within a given radius to evacuate the mass of air ascending out of the boundary layer within that radius. The transient decay and re‐intensification phase is not associated with an eyewall replacement cycle, but rather with a hitherto undescribed process in which the eyewall becomes fragmented as a rainband complex forms beyond it. This process is interpreted as an interplay between the boundary layer and ventilation. The final rapid decay of the vortex results from the ever increasing difficulty of deep convection to ventilate the air exiting the boundary layer. Any unventilated air flows radially outwards in the lower troposphere and leads to spin‐down because of the approximate conservation of mean absolute angular momentum. If found in real cyclones, such transience or final decay might be erroneously attributed to ambient vertical wind shear. The results support the hypothesis that, even in a quiescent environment, isolated tropical cyclone vortices are intrinsically transient and never reach a globally steady state., A three‐dimensional, idealized numerical simulation of tropical cyclone evolution on an f‐plane is used to explore aspects of the cyclone's life cycle in the framework of the rotating‐convection paradigm. In the simulation, which lasts for 20 days, the vortex undergoes a life cycle that includes a gestation period cultimating in genesis, a rapid intensification period, a mature stage followed by a transient decay and re‐intensification stage, a second mature stage and a final rapid decay stage. The results support the hypothesis that, even in a quiescent environment on an f‐plane, isolated tropical cyclone vortices are intrinsically transient and never reach a globally steady state., U.S. Office of Naval Research http://dx.doi.org/10.13039/100000006, German Research Council

This review article summarizes recent (2014–2019) advances in our understanding of tropical cyclogenesis, stemming from activities at the ninth International Workshop on Tropical Cyclones. Tropical cyclogenesis involves the interaction of dynamic and thermodynamic processes at multiple spatio-temporal scales. Studies have furthered our understanding of how tropical cyclogenesis may be affected by external processes, such as intraseasonal oscillations, monsoon circulations, the intertropical convergence zone, and midlatitude troughs and cutoff lows. Additionally, studies have furthered our understanding of how tropical cyclogenesis may be affected by internal processes, such as the organization of deep convection; the evolution of the “pouch” structure; the role of friction; the development of the moist, warm core; the importance of surface fluxes; and the role of the mid-level vortex. A relatively recent class of idealized, numerical simulations of tropical cyclogenesis in radiative-convective equilibrium have highlighted the potential importance of radiative feedbacks on tropical cyclogenesis. We also offer some recommendations to the community on future directions for tropical cyclogenesis research.

Tropical cyclone formation and evolution at, or near, the Equator is explored using idealized three‐dimensional model simulations, starting from a prescribed, initial, weak counterclockwise rotating vortex in an otherwise quiescent, nonrotating environment. Three simulations are carried out in which the maximum tangential wind speed (5 m surn:x-wiley:qj:media:qj3701:qj3701-math-0001) is specified at an initial radius of 50, 100, or 150 km. After a period of gestation lasting between 30 and 60 hr, the vortices intensify rapidly, the evolution being similar to that for vortices away from the Equator. In particular, the larger the initial vortex size, the longer the gestation period, the larger the maximum intensity attained, and the longer the vortex lifetime. Beyond a few days, the vortices decay as the cyclonic vorticity source provided by the initial vortex is depleted and negative vorticity surrounding the vortex core is drawn inwards by the convectively driven overturning circulation. In these negative vorticity regions, the flow is inertially/centrifugally unstable. The vortex evolution during the mature and decay phases differs from that in simulations away from the Equator, where inertially unstable regions are much more limited in area. Vortex decay in the simulations appears to be related intimately to the development of inertial instability, which is accompanied by an outward‐propagating band of deep convection. The degree to which this band of deep convection is realistic is unknown.

The air-sea exchanges of momentum which are often parameterized by the variation of drag coefficient (CD) and wind speed (un), is largely uncertain at typhoon-fo...

Three idealized high‐resolution simulations of tropical storm formation from a weak vortex are analyzed. The three simulations include a case using warm rain microphysics, a similar case in which surface friction is omitted, and a case in which ice microphysics is used. The goal is to understand the mechanisms controlling the intensity and distribution of convection in the formation process in each of these cases. Simulations of convection in weak temperature gradient convective models show that a combination of low to middle tropospheric moist convective instability, the saturation fraction or column relative humidity, and the surface moist entropy flux explain a high percentage of the variance in precipitation and lower tropospheric vertical mass flux. Tropical cyclones differ from other convective environments in that intense frictional convergence occurs in the boundary layer. Adding a measure of convective inhibition to account for this process enables the lower tropospheric mass flux to be predicted even in the core regions of the simulated tropical cyclones. These results are pertinent to the development of more accurate convective parameterizations for large‐scale models.

Four idealized, high‐resolution (500 m horizontal grid spacing), numerical simulations are used to investigate the evolution of convective structures during tropical cyclogenesis. The simulations all begin with a weak initial axisymmetric cloud‐free vortex in a quiescent environment, but differ in the moisture level of the initial sounding and whether or not ice microphysical processes are considered. Irrespective of experimental setup, there is only a short period where shallow or congestus clouds dominate. The shallow cloud phase is slightly extended with the drier initial environmental sounding. The composite structure of the convective elements sampled changes markedly throughout the genesis period. For much of the genesis phase, vertical profiles of the mean convective cell show significant amounts of anticyclonic vorticity produced in cells in the inner core. Towards the end of the genesis phase, there is a large increase in the production of cyclonic vertical vorticity in inner‐core convection, and cyclonic vorticity becomes dominant at low‐mid levels. The evolution from roughly equal strength vertical profiles of cyclonic/anticyclonic vorticity at low‐mid levels to profiles where cyclonic vorticity dominates occurs at relatively low system wind speeds (Vmax less than 10 m·s−1). This finding indicates a change in the structure of vortical convection prior to rapid intensification. In outer‐core convection, there are roughly equal strength vertical vorticity dipoles produced throughout the genesis period., Four idealized, high‐resolution (500 m horizontal grid spacing), numerical simulations are used to investigate the evolution of convective structures during tropical cyclogenesis. The composite structure of the average convective element sampled changes markedly throughout the genesis period, and towards the end of the genesis phase there is a large increase in the production of cyclonic vertical vorticity in inner‐core convection, which becomes dominant at low‐mid levels. Irrespective of microphysical scheme and environmental sounding used, there is a short period where cumulus congestus clouds dominate, that is, when the mean cloud top is between 5 and 9 km height, a finding which is at odds with a prior theory claiming that tropical cyclogenesis can be viewed as a two‐stage process in which congestus clouds have a large dynamical and thermodynamical contribution at early stages., German Research Council (Deutsche Forschungsgemeinschaft) http://dx.doi.org/10.13039/501100001659

Three high-resolution numerical simulations are carried out to investigate the effects of initial vortex size on tropical cyclogenesis and intensification, starting with a relatively weak initial vortex with a maximum tangential wind speed of 5 m s(-1), but located at different radii. In all simulations, there is a progressive organization of convectively induced, cyclonic relative vorticity into a monopole structure. As the initial vortex size is increased, the organization occurs later. In addition, the size of the vorticity monopole, the sizes of the inner and outer core tangential wind circulations and the lifetime intensity of the vortex all become larger. An explanation for this behaviour is offered in terms of a boundary-layer control of the overturning circulation. The findings are consistent with those of previous studies that bypass the genesis stage and start with appreciably stronger initial vortices.

A recent idealized, high-resolution, numerical model simulation of tropical cyclogenesis is compared with a simulation in which the surface drag is set to zero. It is shown that, while spin up occurs in both simulations, the vortex in the one without surface drag takes over twice as long to reach its intensification begin time. When surface friction is not included, the inner core size of the simulated vortex is considerably larger and the subsequent vortex intensity is significantly weaker than in the case with friction. In the absence of surface drag, the convection eventually develops without any systematic organization and lies often outside the radius of azimuthally-averaged maximum tangential winds. The results underscore the crucial role of friction in organizing deep convection in the inner core of the nascent vortex and raise the possibility that the timing of tropical cyclogenesis in numerical models may have an important dependence on the boundary layer parameterization scheme used in the model.

Idealized numerical model simulations are used to investigate the generation and evolution of vertical vorticity by deep convection in a warm-cored vortex of near-tropical-storm strength. Deep convective updraughts are initiated by thermal perturbations located at different radii from the vortex axis. It is found that, as the location of the thermal perturbation is moved away from the axis of rotation, the updraught that results becomes stronger, the cyclonic vorticity anomaly generated by the updraught becomes weaker, the structure of the vorticity anomaly changes markedly and the depth of the anomaly increases. For an updraught along or near the vortex axis, the vorticity anomaly has the structure of a monopole and little or no anticyclonic vorticity is generated in the core. Vorticity dipoles are generated in updraughts near or beyond the radius of maximum tangential wind speed and this structure reverses in sign with height. In all cases, the vorticity anomalies persist long after the initial updraught has decayed. Implications of the results for understanding the vorticity consolidation during tropical cyclogenesis are discussed. The effects of eddy momentum fluxes associated with a single updraught on the tangential-mean velocity tendency are investigated and a conceptual framework for the interpretation of these eddy fluxes is given. The simulations are used to appraise long-standing ideas suggesting that latent heat release in deep convection occurring in the high inertial stability region of a vortex core is more efficient' than deep convection outside the core in producing temperature rise in the updraught.

The dependence of tropical cyclone intensification rate on the sea-surface temperature (SST) is examined in the prototype problem for tropical cyclone intensification on an f-plane using a three-dimensional, non-hydrostatic numerical model. The effects of changing the SST are compared with those of changing the latitude examined in a recent article. It is found that the dependence of intensification rate on latitude is largest when the SST is marginal for tropical cyclone intensification (26 degrees C) and reduces in significance as the SST is increased. Further, at a given latitude, intensification begins earlier and the rate of intensification increases with increasing SST, on account of a significant increase of surface moisture fluxes from the warmer ocean. These higher fluxes result in higher values of near-surface moisture and equivalent potential temperature, leading to a larger radial gradient of diabatic heating rate in the low to middle troposphere above the boundary layer. This larger radial gradient leads to a stronger overturning circulation, which in turn leads to a stronger radial import of absolute angular momentum surfaces and therefore more rapid spin-up. These arguments invoke the classical axisymmetric spin-up mechanism. Non-axisymmetric issues are touched upon briefly.

The long term behaviour of tropical cyclones in the prototype problem for cyclone intensification on an f -plane is examined using a nonhydrostatic, three-dimensional, numerical model. After reaching a mature intensity, the model storms progressively decay while both the inner core size, characterized by the radius of the eyewall, and size of the outer circulation, measured for example by the radius of gale force winds, progressively increase. This behaviour is explained in terms of a boundary-layer control mechanism in which the expansion of the swirling wind in the lower troposphere leads through boundary-layer dynamics to an increase in the radii of forced eyewall ascent as well as to a reduction in the maximum tangential wind speed in the layer. These changes are accompanied by changes in the radial and vertical distribution of diabatic heating. As long as the aggregate effects of inner-core convection, characterized by the distribution of diabatic heating are able to draw absolute angular momentum surfaces inwards, the outer circulation will continue to expand. The quantitative effects of latitude on the foregoing processes are investigated also. The study provides new insight on the factors controlling the evolution of size and intensity of a tropical cyclone. It provides also a plausible, and arguably simpler, explanation for the expansion of the inner-core of Hurricane Isabel (2003) than that given previously. German Research Council National Science Foundation NASA Naval Postgraduate School NOAA Grant no. SM30-23 (GRC) Grant no. N62909-15-1-N021 (NSF) AGS-1313948 (NSF) HFIP Grant no. N0017315WR00048 (NOAA) NNG11PK021 (NASA)

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Quarterly Journal of the Royal Meteorological Society The article of record as published may be found at http://dx.doi.org/10.1002/qj.3332 Many previous diagnoses of the global kinetic energy for a tropical cyclone have given prominence to a global integral of a pressure-work term in the generation of kinetic energy. However, in his erudite textbook of atmospheric and oceanic dynamics, Gill (1982) derives a form of the kinetic energy equation in which there is no such explicit source term. In this paper we revisit the interpretations of the generation of kinetic energy given previously in the light of Gill's analysis and compare the various interpretations, which are non-unique.Further, even though global energetics provide a constraint on the flow evolution, in the context of the kinetic energy equation, they conceal important aspects of energy generation and consumption, a finding that highlights the limitations of a global kinetic energy budget in revealing the underlying dynamics of tropical cyclones. Of?ce of Naval Research Global Grant No. N62909-15-1-N02 1. NSF grant AGS-1313948, NOAA HFIP grant N0017315 WR00048, NASA grant NNG11PK021, ONR grant N0001417WX00336, and the U.S. Naval Postgraduate School. Office of Naval Research Global Grant No. N62909-15-1-N02 1. NSF grant AGS-1313948, NOAA HFIP grant N0017315 WR00048, NASA grant NNG11PK021, ONR grant N0001417WX00336, and the U.S. Naval Postgraduate School.

Edmund Campion arrived in Dublin on August 25, 1570, on a travelling fellowship from St. John’s College, Oxford. This five-year leave of absence enabled him to postpone ordination in the Elizabethan church. Campion was invited to stay with the Recorder of Dublin, James Stanihurst, whose library was to satisfy his academic needs, and who was hoping that Campion might help with the university that formed a key part of the program of reform in Ireland. Campion had ignored calls from friends already at the English college in Douai to join them. Dublin was meant to be a quiet pause, allowing Campion to stay quietly within the establishment. It was not to be like that. This article argues that Ireland was the beginning and, thanks to the disastrous invasion in July 1579 by Nicholas Sander, the end of Campion’s troubles; that the rebellion stirred by Sander in Munster created such fear of an invasion in England that the Jesuit missionaries were doomed from the moment they landed at Dover one year later; that the radical arguments in favor of papal power to depose monarchs expressed in De visibili monarchia (1571), not the theological arguments for the Catholic and apostolic church in Rationes decem (1581), were at the center of Campion’s interrogations on the rack; and that the parallel lives of Campion and Sander reveal two completely contrasting views of the papacy, and of Rome.

We describe idealized numerical model experiments to study the effects of a vortex boundary-layer wind profile on the generation of vertical vorticity in tropical deep convection. Situations are considered in which there is either no vertical shear above the boundary layer or negative vertical shear appropriate to a warm-cored vortex. Deep convection growing in these environments develops dipole structures of vertical vorticity in which the cyclonic gyre is favoured and persists longer than the anticyclonic one. The orientation of the dipole at a particular height is determined partly by that of the ambient horizontal vortex lines, which rotate with height, and also by the vertical advection of vertical vorticity from below. An increase in the magnitude of boundary-layer shear enhances the distortion of the initial thermal, weakening its subsequent ascent rate. This effect is detrimental to vertical vorticity production by stretching but, because the increase in shear implies an increase in the magnitude of horizontal vorticity that can be tilted, its net effect on the vertical vorticity production by tilting cannot be foreseen. In the calculations described, the effect of the increased horizontal vorticity dominates, so that updraughts rising in stronger vertical shear have larger vertical vorticity maxima, despite smaller vertical velocity maxima. With negative vertical shear above the boundary layer, the vorticity dipole reverses in sign with height, as in a recent study of the effects of unidirectional shear. The results provide a basis for appraising a recently proposed conceptual model for the inward contraction of eyewall convection in tropical cyclones, as well as a starting point for developing an improved understanding of the formation of a vorticity monopole during tropical cyclogenesis.

We present a series of idealized numerical model experiments to investigate aspects of deep convection in tropical depressions, including the effects of boundary-layer wind structure on storm structure, especially on vertical vorticity production and updraught splitting, and the combined effects of horizontal and vertical shear on vertical vorticity production, with and without background rotation. In warm-cored disturbances such as tropical depressions, the vertical shear and horizontal vorticity change sign at some level near the top of the boundary layer so that, unlike in the typical middle-latitude ‘supercell’ storm, the tilting of horizontal vorticity by a convective updraught leads not only to dipole patterns of vertical vorticity, but to a reversal also in sign of the updraught rotation with height. This finding has implications for understanding the merger of convectively induced vorticity anomalies during vortex evolution. Ambient cyclonic horizontal shear and/or cyclonic vertical vorticity favour amplification of the cyclonically rotating gyre of the dipole. Consistent with an earlier study, storm splitting occurs in environments with pure horizontal shear as well as pure vertical shear, but the morphology of splitting is different. In both situations, splitting is found to require a relatively unstable sounding and relatively strong wind shear.

The Queen's visit to Oxford in 1566 has been viewed largely through the prism of John Nichols’ The Progresses of Queen Elizabeth. This article returns to the manuscript sources, all of which survive. All make the disputations central; all but one were written by Catholics who subsequently suffered for their faith: Thomas Neale, John Bereblock and Miles Windsor. The Queen's visit clearly represented for Catholics in Oxford the last chance to try to win her favour. This article explores the complex tensions that existed in early Elizabethan Oxford: between the Calvinists who dominated Christ Church and Magdalen, and those still committed to the ‘old religion’. It highlights the continuities with pre-Reformation and Marian Oxford, arguing that Sir Thomas Pope and Sir Thomas White had engaged, with the Owens of Godstow, in a coherent programme to preserve as many of the monastic houses as they could. An exploration of the background of the three main witnesses reveals the presence of a determined Catholic resistance to the Earl of Leicester and his Vice-Chancellor, and the beginnings of alternative centres of learning in an ‘underground’ university of halls, taverns and farms that soon included many of the leading scholars: Thomas Neale, George Etheridge, Edmund Rainolds and John Case. It was while moving along this network that Edmund Campion was captured.

We present idealized numerical model experiments to investigate the convective generation of vertical vorticity in a tropical depression. The ambient vertical vorticity is represented by a uniform solid-body rotation. The calculations are motivated by observations made during the Pre-Depression Investigation of Cloud-systems in the Tropics (PREDICT) experiment. A specific aim is to isolate and quantify the effects of low- to mid-level dry air on convective cells that form within a depression and, in particular, on the generation of vertical vorticity in these cells. The results do not support a common perception that dry air aloft produces stronger convective downdraughts and more intense, cold-air outflows therefrom. Indeed, we find that dry air aloft weakens both updraughts and downdraughts, corroborating the recent results of James and Markowski. As in the recent calculations of Wissmeier and Smith, the growing convective cells locally amplify the ambient rotation at low levels by more than an order of magnitude and this vorticity, which is produced by the stretching of existing ambient vorticity, persists long after the initial updraught has decayed. Moreover, significant amplification of vorticity occurs even for clouds of only moderate vertical extent. The maximum amplification of vorticity is relatively insensitive to the maximum updraught strength, or the height at which it occurs, and it is not unduly affected by the presence of dry air aloft. Thus the presence of dry air is not detrimental to the amplification of low-level vorticity, although it reduces the depth through which ambient vorticity is enhanced. Results for a limited number of different environmental soundings indicate that the maximum amplification of vorticity increases monotonically with the strength of the thermal perturbation that initiates the convection, but the amount of increase depends also on the thermodynamic structure of the sounding.