a first look at the structure of the wave pouch during the 2009 predict grip dry runs over the atlantic abstractin support of the national science foundation pre depression investigation of cloud systems in the tropics nsf predict and national aeronautics and space administration genesis and rapid intensification processes nasa grip dry run exercises and national oceanic and atmospheric administration hurricane intensity forecast experiment noaa ifex during the 2009 hurricane season a real time wave tracking algorithm and corresponding diagnostic analyses based on a recently proposed tropical cyclogenesis model were applied to tropical easterly waves over the atlantic the model emphasizes the importance of a lagrangian recirculation region within a tropical wave critical layer the so called pouch where persistent deep convection and vorticity aggregation as well as column moistening are favored for tropical cyclogenesis distinct scenarios of hybrid wave vortex evolution are highlighted it was found that easterly waves without a pouch or with a shallow pouch did not develop although not all wav

observations and predictability of a nondeveloping tropical disturbance over the eastern atlantic abstracta strong african easterly wave aew left the west african coast in early september 2014 and operational global numerical forecasts suggested a potential for rapid tropical cyclogenesis of this disturbance in the eastern atlantic despite the presence of a large region of dry air northwest of the disturbance analysis and in situ observations show that after leaving the coast the closed circulation associated with the aew trough was not well aligned vertically and therefore low level or midlevel dry air was advected below or above respectively areas of closed circulation gps dropwindsonde observations highlight the dry air undercutting the midlevel recirculation region in the southwestern quadrant this advection of dry air constrains the spatial extent of deep convection within the aew trough leading to the vortex decaying as the column continues to be displaced horizontally losing vertical alignment this enables increased horizontal advection of dry air into the system further limiting

coupled dynamic thermodynamic forcings during tropical cyclogenesis part i diagnostic framework abstracta diagnostic framework to investigate the role of processes around and during tropical cyclogenesis is presented the key framework metric is the ratio of bulk differences of moist entropy over differences of angular momentum between an inner and outer region of a tropical disturbance or cyclone this ratio is hypothesized to decrease and become negative as both the high entropy core and low level vortex in the inner region amplify during tropical cyclogenesis the time tendency of this ratio can be split into two forcings a moist entropy forcing and an angular momentum forcing each forcing can be further divided into components comprising differences in net advective fluxes and nonadvective boundary fluxes of moist entropy or angular momentum between each region the framework provides a comprehensive way to compare the relative importance of processes leading to tropical cyclogenesis in a tractable consistent manner suggestions on how to apply the framework to numerical model output are given

a unified view of tropical cyclogenesis and intensification idealized high resolution numerical simulations of tropical cyclogenesis are presented in a model that represents deep convection by a warm rain process only starting with an initially weak cloud free axisymmetric warm cored vortex maximum wind speed 5 m s 1 at a radius of 100 km rapid vortex intensification begins after a gestation period on the order of 2 days from a three dimensional perspective the genesis process is similar to that in the rotating convection paradigm for vortex intensification starting with a much stronger initial vortex vmax 15 m s 1 the patterns of deep convection and convectively amplified cyclonic relative vorticity are far from axisymmetric during the genesis period moreover the organization of the cyclonic relative vorticity into a monopole structure occurs at relatively low wind speeds before the maximum local wind speed has increased appreciably barotropic processes are shown to play an important role in helping to consolidate a single signed vorticity monopole within a few hours near the intensification begin time the rotating convection paradigm appears adequate to explain the basic genesis process within the weak initial vortex providing strong support for a hypothesis of montgomery and smith that the genesis process is not fundamentally different from that of vortex intensification in particular genesis does not require a trigger and does not depend on the prior existence of a mid level vortex

secondary eyewall formation in an idealized tropical cyclone simulation balanced and unbalanced dynamics abstractthe secondary eyewall formation sef in an idealized simulation of a tropical cyclone tc is examined from the perspective of both the balanced and unbalanced dynamics and through the tangential wind vt budget analysis it is found that the expansion of the azimuthal mean vt above the boundary layer occurs prior to the development of radial moisture convergence in the boundary layer the vt expansion results primarily from the inward angular momentum transport by the mid to lower tropospheric inflow induced by both convective and stratiform heating in the spiral rainbands in response to the vt broadening is the development of radial inflow convergence and the supergradient flow near the top of the inflow boundary layer results from the vt budget analysis show that the combined effect of the mean advection and the surface friction is to spin down vt in the boundary layer while the eddy processes eddy radial and vertical advection contribute positively to the spinup of vt in the sef region

case studies of developing east pacific easterly waves this paper contains a study of developing east pacific easterly waves observed during the summer of 1991 with aircraft in situ and radar data and geosynchronous infrared satellite imagery the circulation and divergence profiles surface momentum and entropy fluxes as well as 700 mb and 975 mb saturated and actual equivalent potential temperatures were measured repeatedly for three disturbances that evolved into east pacific hurricanes as the disturbances develop the level of maximum updraught mass flux decreases which leads to increased convergence at low levels this process appears to be coupled to an increase in the mid level relative humidity which in turn suppresses the development of convective downdraughts comparison of the respective tendencies of convergence and surface friction to spin up and spin down a developing disturbance suggests that friction is unimportant in the early stages of development however as the surface circulation develops the two effects become comparable in magnitude if surface friction is deposited through a fairly deep layer of the troposphere the observations appear to rule out boundary layer ekman balance in these developing systems though more accurate observations of the eddy fluxes of absolute vorticity into such systems are needed to answer this question with certainty

effects of vertical shears and midlevel dry air on tropical cyclone developments abstracta set of idealized experiments using the weather research and forecasting model wrf were designed to investigate the impacts of a midlevel dry air layer vertical shear and their combined effects on tropical cyclone tc development compared with previous studies that focused on the relative radial position of dry air with no mean flow it is found that the combined effect of dry air and environmental vertical shear can greatly affect tc development moreover this study indicates the importance of dry air and vertical shear orientations in determining the impact the background vertical shear causes the tilting of an initially vertically aligned vortex the shear forces a secondary circulation fsc with ascent descent in the downshear upshear flank hence convection tends to be favored on the downshear side the fsc reinforced by the convection may overcome the shear induced drifting and restore the vertical alignment when dry air is located in the downshear right quadrant of the ini

the role of vortical hot towers in the formation of tropical cyclone diana 1984 abstract a high resolution 3 km horizontal grid spacing near cloud resolving numerical simulation of the formation of hurricane diana 1984 is used to examine the contribution of deep convective processes to tropical cyclone formation this study is focused on the 3 km horizontal grid spacing simulation because this simulation was previously found to furnish an accurate forecast of the later stages of the observed storm life cycle the numerical simulation reveals the presence of vortical hot towers or cores of deep cumulonimbus convection possessing strong vertical vorticity that arise from buoyancy induced stretching of local absolute vertical vorticity in a vorticity rich prehurricane environment at near cloud resolving scales these vortical hot towers are the preferred mode of convection they are demonstrated to be the most important influence to the formation of the tropical storm via a two stage evolutionary process i preconditioning of the local environment via diabatic production of mul

dynamics of lower tropospheric vorticity in idealized simulations of tropical cyclone formation abstractidealized simulations are conducted using the cloud model version 1 cm1 to explore the mechanism of tropical cyclone tc genesis from a preexisting midtropospheric vortex that forms in r

the wyoming gold deposits volcanic hosted lode type gold mineralisation in the eastern lachlan orogen australia the eastern lachlan orogen in southeastern australia is noted for its major porphyry epithermal skarn copper gold deposits of late ordovician age whilst many small quartz vein hosted or orogenic lode type gold deposits are known in the region the discovery of the wyoming gold deposits has demonstrated the potential for significant lode type mineralisation hosted within the same ordovician volcanic stratigraphy outcrop in the wyoming area is limited with the ordovician sequence largely obscured by clay rich cover of probable quaternary to cretaceous age with depths up to 50 m regional aeromagnetic data define a north south trending linear belt interpreted to represent the ordovician andesitic volcanic rock sequence within probable ordo silurian pelitic metasedimentary rocks drilling through the cover sequence in 2001 to follow up the trend of historically reported mineralisation discovered extensive alteration and gold mineralisation within an andesitic feldspar porphyry intrusion and adjacent volcaniclastic sandstones and siltstones subsequent detailed resource definition drilling has identified a substantial mineralised body associated with sericite carbonate albite quartz chlorite pyrite arsenopyrite alteration the wyoming deposits appear to have formed as the result of a rheological contrast between the porphyry host and the surrounding volcaniclastic rocks with the porphyry showing brittle fracture and the metasedimentary rocks ductile deformation the mineralisation at wyoming bears many petrological and structural similarities to orogenic lode style gold deposits although the timing of alteration and mineralisation in the wyoming deposits remain problematic a relationship with possible early to middle devonian deformation is considered likely

role of cumulus congestus in tropical cyclone formation in a high resolution numerical model simulation abstractthe role of cumulus congestus shallow and congestus convection in tropical cyclone tc formation is examined in a high resolution simulation of tropical cyclone fay 2008 it is found that cumulus congestus plays a dominant role in moistening the lower to middle troposphere and spinning up the near surface circulation prior to genesis while deep convection plays a key role in moistening the upper troposphere and intensifying the cyclonic circulation over a deep layer the transition from the tropical wave stage to the tc stage is marked by a substantial increase in net condensation and potential vorticity generation by deep convection in the inner wave pouch region this study suggests that tc formation can be regarded as a two stage process the first stage is a gradual process of moisture preconditioning and low level spinup in which cumulus congestus plays a dominant role the second stage commences with the rapid development of deep convection in the inner pouch region after the air colum

mesoscale interactions in tropical cyclone genesis with the multitude of cloud clusters over tropical oceans it has been perplexing that so few develop into tropical cyclones the authors postulate that a major obstacle has been the complexity of scale interactions particularly those on the mesoscale which have only recently been observable while there are well known climatological requirements these are by no means sufficient a major reason for this rarity is the essentially stochastic nature of the mesoscale interactions that precede and contribute to cyclone development observations exist for only a few forming cases in these the moist convection in the preformation environment is organized into mesoscale convective systems each of which have associated mesoscale potential vortices in the midlevels interactions between these systems may lead to merger growth to the surface and development of both the nascent eye and inner rainbands of a tropical cyclone the process is essentially stochastic but the degree of stochasticity can be reduced by the continued interaction of the mesoscale systems or by environmental influences for example a monsoon trough provides a region of reduced deformation radius which substantially improves the efficiency of mesoscale vortex interactions and the amplitude of the merged vortices further a strong monsoon trough provides a vertical wind shear that enables long lived midlevel mesoscale vortices that are able to maintain or even redevelop the associated convective system the authors develop this hypothesis by use of a detailed case study of the formation of tropical cyclone oliver observed during toga coare 1993 in this case two dominant mesoscale vortices interacted with a monsoon trough to separately produce a nascent eye and a major rainband the eye developed on the edge of the major convective system and the associated atmospheric warming was provided almost entirely by moist processes in the upper atmosphere and by a combination of latent heating and adiabatic subsidence in the lower and middle atmosphere the importance of mesoscale interactions is illustrated further by brief reference to the development of two typhoons in the western north pacific

merger of african easterly waves and formation of cape verde storms there are two easterly wave tracks over west africa one to the south and the other to the north of the african easterly jet aej a northern wave sometimes merges with a southern wave near the coast of west africa the dynamic and thermodynamic evolution of the waves during the merger and the impacts of the merger on subsequent storm development are examined in this study three groups of storms are identified non merger developers merger developers and merger non developers relative to non merger developers merger developers have a weaker circulation near the surface prior to the merger but the merger leads to a stronger and deeper wave pouch which is more conducive to tropical cyclogenesis the dryness of the northern disturbances does not seem to hinder the storm development composite analysis shows that merger developers are associated with a warmer and broader heat low over west africa and a more extensive aej which helps to maintain the northern waves over the east atlantic merger developers and non developers resemble each other prior to the merger but dry air intrusion west of the wave trough in the middle and upper troposphere contributes to the non development of some mergers the dry air in non developers is related to a strong and broad upper tropospheric trough and the associated subsidence west of the low level wave pouch the trough advects dry air from the extratropical atlantic in the middle and upper troposphere and also induces a strong westerly vertical shear composites of aerosol optical depth suggest that the saharan air layer has a limited contribution to the dryness in the vicinity of the non developers

a dynamically based method for forecasting tropical cyclogenesis location in the atlantic sector using global model products 1 a real time forecast method is developed for prediction of the tropical cyclogenesis location over the atlantic using global model operational products the method is based on the marsupial theory for tropical cyclogenesis proposed in a recent observational study a moisture front is usually found ahead of the precursor wave trough which separates the relatively dry air outside of the wave pouch a region of closed circulation from the relatively moist air inside the wave pouch the propagation speed of the pouch can be determined by tracking the propagation of this moisture front and the intersection of the critical surface and the trough axis pinpoints the predicted genesis location using the global model operational products the genesis location can be predicted up to three days in advance with an error less than 200 km which can provide useful guidance for forecasters and flight planning

genesis of hurricane julia 2010 within an african easterly wave low level vortices and upper level warming abstractwhile a robust theoretical framework for tropical cyclogenesis tcg within african easterly waves aews has recently been developed little work explores the development of low level meso scale vortices llvs and a meso scale surface low in relation to deep convection and upper tropospheric warming in this study the development of an llv into hurricane julia 2010 is shown through a high resolution model simulation with the finest grid size of 1 km the results presented expand upon the connections between llvs and the aew presented in previous studies while demonstrating the importance of upper tropospheric warming for tcg it is found that the significant intensification phase of hurricane julia is triggered by the pronounced upper tropospheric warming associated with organized deep convection the warming is able to intensify and expand during tcg owing to formation of a storm scale outflow beyond the rossby radius of deformation results confirm previous ideas by demonstrating that th

appraisal of recent theories to understand cyclogenesis pathways of tropical cyclone madi 2013 the present study aims to examine the new understanding of cyclogenesis by analyzing the genesis sequence of formation of a very severe cyclonic storm madi 6 13 december 2013 that occurred over the bay of bengal we have generated a high resolution 18 km 6 km and 2 km analysis using three dimensional variational data assimilation technique and weather research and forecasting model the genesis sequence of madi cyclone is analyzed using the concepts in the marsupial theory and other theories of tropical cyclone formation major results are as follows the developed analysis is found useful for tracking the movement of westward moving parent disturbance from 15 days prior to the genesis identifying developed pouch region in the lagrangian frame of reference understanding the evolution of the pouch and convection within the pouch region and for the study of intensification inside the pouch region also large scale priming of environment concurs with the hypotheses of the marsupial theory of tropical cyclogenesis the analysis of dynamical and thermodynamical processes within the pouch region showed gradual moistening uplifting of moisture diabatic heating causing buoyant convection in the vorticity rich environment followed by vortex tube stretching development of convection heavy precipitation strengthening of lower level convergence and hence spin up during a day or two preceding the genesis of madi cyclone in general it is concluded that intensification within pouch region during the cyclogenesis phase followed the marsupial paradigm and bottom up mechanism

three dimensional kinematic and microphysical evolution of florida cumulonimbus part ii frequency distributions of vertical velocity reflectivity and differential reflectivity abstract high resolution radar data collected in florida during the convection and precipitation electrification experiment are used to elucidate the microphysical and kinematic processes occurring during the transition of a multicellular storm from convective to stratiform stages a statistical technique is employed to examine the evolving properties of the ensemble small scale variability of radar reflectivity vertical velocity and differential reflectivity over the entire storm differential radar reflectivity data indicate that the precipitation at upper levels was nearly glaciated early in the storm s lifetime dual doppler radar data show that throughout the storm s lifetime both updrafts and down drafts were present at all altitudes and that most of the volume of the radar echo contained vertical velocities incapable of supporting precipitation size particles thus the ensemble microphysical properties of the storm were increasingly dominated by particles falling in an environment of weak vertic

the formation of moist vortices and tropical cyclones in idealized simulations abstractthe upscale aggregation of convection is used to understand the emergence of rotating coherent midtropospheric structures and the subsequent process of tropical cyclone formation the cloud model version 1 cm1 is integrated on an f plane with uniform sea surface temperature sst and prescribed uniform background flow deep convection is maintained by surface fluxes from an ocean with uniform surface temperature convection begins to organize simultaneously into moist and dry midtropospheric patches after 10 days after 20 days the patches begin to rotate on relatively small scales moist cyclonic vortices merge eventually forming a single dominant vortex that subsequently forms a tropical cyclone on a realistic time scale of about 5 days radiation that interacts with clouds and water vapor aids in forming coherent rotating structures using the path to genesis provided by the aggregated solution the relationship between thermodynamic changes within the vortex and changes in the character

influence of the north pacific victoria mode on western north pacific tropical cyclone genesis the victoria mode vm is defined as the second empirical orthogonal function mode eof2 of sea surface temperature anomalies sstas in the north pacific north of 20 n this study examines the influence of the spring vm on the tropical cyclone tc genesis over the western north pacific wnp during summer may august for the period 1960 2016 our analysis demonstrates that the spring vm exhibits a good relationship with the following summer tropical cyclone frequency tcf over the wnp characterized by positive correlations over the eastern wnp ewnp and negative correlations over the western wnp wwnp during strongly positive vm cases the sstas in the north pacific 5 20 n associated with the spring vm persist until summer via the wind evaporation sst wes feedback the low level convergence divergence caused by the vm related sstas combined with a strengthened weakened wnp monsoon trough as well as a weakened strengthened west pacific subtropical high wpsh result in the enhanced suppressed tc genesis over the ewnp wwnp it appears that the spring vm may be a useful predictor for the wnp tcs in summer

development and nondevelopment of binary mesoscale vortices into tropical cyclones in idealized numerical experiments abstractthe evolution of two symmetric midlevel mesoscale vortices situated above a warm ocean is examined with a basic cloud resolving model idealized numerical experiments provide insight into how the evolution may vary with the initial vortex separation distance d and other parameters that influence the time scale for an isolated vortex to begin rapid intensification the latter parameters include the ambient middle tropospheric relative humidity rh and the initial midlevel wind speed of each vortex at relatively low rh there exists an interval of d where binary midlevel vortex interaction prevents tropical cyclone formation while tropical cyclones generally develop at high rh similar values of d can delay the process if the vortices are initially weak prevention or inhibition of tropical cyclone formation occurs in association with the outward expulsion of lower tropospheric potential vorticity anomalies as the two vortices merge in the middle troposphere it is proposed that the primary mecha

thermodynamic aspects of tropical cyclone formation abstractthe thermodynamic aspects of tropical cyclone tc formation near the center of the wave pouch a region of approximately closed lagrangian circulation within the wave critical layer are examined through diagnoses of a high resolution numerical simulation and dropsonde data from a recent field campaign it is found that the meso area near the pouch center is characterized by high saturation fraction small difference in equivalent potential temperature e between the surface and the middle troposphere and a short incubation time scale updrafts tend to be more vigorous in this region presumably because of reduced dry air entrainment while downdrafts are not suppressed the thermodynamic conditions near the pouch center are thus critically important for tc formation the balanced responses to convective and stratiform heating at the pregenesis stage are examined using the sawyer eliassen equation deep convection is concentrated near the pouch center the strong radial and vertical gradients o

a vortical hot tower route to tropical cyclogenesis abstract a nonhydrostatic cloud model is used to examine the thermomechanics of tropical cyclogenesis under realistic meteorological conditions observations motivate the focus on the problem of how a midtropospheric cyclonic vortex a frequent by product of mesoscale convective systems during summertime conditions over tropical oceans may be transformed into a surface concentrated warm core tropical depression as a first step the vortex transformation is studied in the absence of vertical wind shear or zonal flow within the cyclonic vorticity rich environment of the mesoscale convective vortex mcv embryo the simulations demonstrate that small scale cumulonimbus towers possessing intense cyclonic vorticity in their cores vortical hot towers vhts emerge as the preferred coherent structures the vhts acquire their vertical vorticity through a combination of tilting of mcv horizontal vorticity and stretching of mcv and vht generated vertical vorticity horizontally localized and exhibiting conve

gradient balance in tropical cyclones abstract analysis of a large inventory of in situ observations from research aircraft shows that the gradient wind approximates the axisymmetric swirling flow in the free atmosphere within 150 km of the centers of atlantic hurricanes and tropical storms in the middle and lower troposphere the rms difference between the azimuthal cream swirling and gradient winds is typically lt 1 5 m s 1 with zero bias this balance prevails only for the azimuthal mean not locally nor is balance to be expected in either the surface friction layer or the upper tropospheric outflow layer where the radial flow is comparable with the swirling flow it is theoretically possible that axisymmetric supergradient flow may occur in response to rapid radial acceleration where the radial flow slows in the friction layer beneath the eyewall or where it converges into intense diabatically forced updrafts nevertheless the observations in the free lower and midtroposphere show that systematic departures of the azimuthal mean vorte

understanding the vertical structure of potential vorticity in tropical depressions author s murthy vs boos wr abstract 2019 royal meteorological society potential vorticity pv has been used to understand the intensification and motion of a variety of tropical vortices here atmospheric reanalyses and idealized models are used to understand how the vertical structures of moist convective heating and adiabatic advection jointly shape the vertical structures of pv in tropical depressions observationally based estimates reveal a top heavy pv structure in tropical depressions contrasting with bottom heavy structures of absolute vorticity and diabatic pv generation these distinct vertical structures are reproduced in an axisymmetric model which employs the weak temperature gradient approximation for conceptual simplicity and is forced by stratiform and deep convective heating when applied in isolation the stratiform and deep convective heatings produce pv maxima at 500 hpa and near the surface respectively when these two heatings are applied simultaneously interactions between the stratiform and deep convective modes enhance the adiabatic advective tendencies produced by the transverse circulation making the pv distribution more top heavy in the lower and middle troposphere radial advection also greatly reduces the radius of the pv structure relative to that of the imposed heating consistent with structures in observed tropical depressions the implications of these differences in radial structures for using the flux form of the relevant conservation equations e g for pv substance or absolute vorticity are discussed

genesis of pre hurricane felix 2007 part i the role of the easterly wave critical layer abstract the formation of pre hurricane felix 2007 in a tropical easterly wave is examined in a two part study using the weather research and forecasting wrf model with a high resolution nested grid configuration that permits the representation of cloud system processes the simulation commences during the wave stage of the precursor african easterly wave disturbance here the simulated and observed developments are compared while in part ii of the study various large scale analyses physical parameterizations and initialization times are explored to document model sensitivities in this first part the authors focus on the wave vortex morphology its interaction with the adjacent intertropical convergence zone complex and the vorticity balance in the neighborhood of the developing storm analysis of the model simulation points to a bottom up development process within the wave critical layer and supports the three new hypotheses of tropical cyclone formation proposed recently by dunkerton montgome

application of the marsupial paradigm to tropical cyclone formation from northwestward propagating disturbances awave trackingalgorithmisdevelopedfornorthwestward propagatingwavesthat onoccasion playarole in tropical cyclogenesis over the western oceans to obtain the lagrangian flow structure the frame of reference is translated obliquely at the same propagation speed with the precursor disturbance trajectory analysis suggests that streamlines in the obliquely translated frame of reference can be used to approximate flow trajectories the algorithm was applied to super typhoon nakri 2008 tropical cyclone erika 2009 and a few other examples diagnoses of meteorological analyses and satellite derived moisture and precipitation fields show that the marsupial framework for tropical cyclogenesis in tropical easterly waves is relevant also for northwestward propagating disturbances as are commonly observed in the tropical western atlantic the gulf of mexico and the western north pacific finally it is suggested that analysis of the global model data and satellite observations in the marsupial framework can provide useful guidance on early tropical cyclone advisories

initial development and genesis of hurricane dolly 2008 abstract based on a successful cloud resolving simulation with the weather research and forecasting model this study examines key processes that led to the early development of hurricane dolly 2008 the initial development of dolly consisted of three stages i an initial burst of convection ii stratiform development dry intrusion and thermodynamic recovery and iii reinvigoration of moist convection and rapid intensification advanced diagnosis of the simulation including the use of vorticity budget analysis contour frequency analysis diagrams and two dimensional spectral decomposition and filtering suggests that the genesis of dolly is essentially a bottom up process the enhancement of the low level vorticity is mainly ascribed to the stretching effect which converges the ambient vorticity through stretching enhanced by moist convection in the rapid intensification stage smaller scale positive vorticity anomalies resulting from moist convection are wrapped into the storm center area u

the genesis of hurricane guillermo texmex analyses and a modeling study abstract the transformation of a mesoscale convective system into hurricane guillermo was captured by aircraft and doppler wind data during the tropical experiment in mexico the early phase of the system evolves in a way very similar to previously documented mesoscale convective systems with a midlevel mesocyclone developing in the stratiform precipitation region more unusually the cyclone extends to low altitudes a weak cyclone is discernable even in the 300 m altitude wind field after another day of evolution a small surface based warm core cyclone is observed to develop within the relatively cold air associated with the mesocyclone aloft this mesocyclone develops into a hurricane over the subsequent day a nonhydrostatic axisymmetric numerical model is used to explore the evolution of the initially cold core midlevel vortex into a tropical cyclone a mesoscale midlevel showerhead is switched on in an initially quiescent tropical atmosphere overlying a warm ocean surface evaporation of t

diabatic divergence profiles in western pacific mesoscale convective systems abstract heating in the atmosphere can be expressed as diabatic divergence d which is nearly equal to the actual horizontal divergence in tropical convection high quality profile measurements from airborne doppler radar purls in ten mesoscale convective systems mcs observed during toga coare are examined and the mean profile is compared with rawinsonde array measurements young convective features have strong near surface convergence while older cells with better developed downdrafts and stratiform precipitation areas have their peak convergence aloft in the mean then surface flow is only weakly convergent or oven divergent so that the main convergence into mcss is deep and peaked aloft with a sharp melting convergence at 0 c divergence prevails above 10 km altitude but was undersampled by the radar unusual but well sampled observations in the purl dataset include a persistent widespread profile feature in one well sampled mcs a cyclone rainband oscillatory reverberations c

scale interactions during the formation of typhoon irving the development of typhoon irving is investigated using a variety of data including special research aircraft data from the tropical cyclone motion tcm 92 experiment objective analyses satellite data and traditional surface and sounding data the development process is treated as a dry adiabatic vortex dynamics problem and it is found that environmental and mesoscale dynamics mutually enhance each other in a cooperative interaction during cyclone formation synoptic scale interactions result in the evolution of the hostile environment toward more favorable conditions for storm development mesoscale interactions with the low level large scale circulations and with other midlevel mesoscale features result in development of vorticity in the midlevels and enhancement of the low level vorticity associated with the developing surface cyclone multiple developments of mesoscale convective systems after the storm reaches tropical depression strength suggests both an increase in low level confluence and a tendency toward recurrent development of associated mesoscale convective vortices this is observed in both aircraft data and satellite imagery where subsequent interactions including mergers with the low level tropical depression vortex are observed a contour dynamics experiment suggests that the movement of mesoscale convective systems in satellite imagery corresponds well to the movement of their associated midlevel vortices results from a simple baroclinic experiment show that the midlevel vortices affect the large scale low level circulation in two ways 1 initially interactions between midlevel vortices produce a combined vortex of greater depth 2 interaction between midlevel vortices and the low level circulation produces a development downward of the midlevel vorticity this strengthens the surface vortex and develops a more cohesive vortex that extends from the surface through the midtroposphere

what is the key feature of convection leading up to tropical cyclone formation abstractinfrared brightness temperature data are used to investigate convective evolution during tropical cyclone tc formation in a quasi lagrangian framework more than 150 named atlantic storms

an air sea interaction theory for tropical cyclones part ii evolutionary study using a nonhydrostatic axisymmetric numerical model abstract in part i of this study an analytical model for a steady state tropical cyclone is constructed on the assumption that boundary layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex the reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple carnot engine acquiring heat at the high temperature ocean surface and losing heat near the low temperature tropopause although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane there is also wide acceptance of conditional instability of the second kind cisk which makes no specific reference to surface heat fluxes as the formative mechanism this ambivalence is seen in that all numerical simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere the hypothesis put forward in part i based on the steady state theory is t