intensification variability of tropical cyclones in directional shear flows vortex tilt convection coupling abstractthe coupling of vortex tilt and convection and their effects on the intensification variability of tropical cyclones tcs in directional shear flows is investigated in this study the he

hurricane formation in diabatic ekman turbulence this article investigates the emergence of hurricanes from chaotic swirling motions in a three layer model of the tropical troposphere that includes basic parametrizations of cumulus convection and air sea interaction the chaotic flow is referred to as diabatic ekman turbulence det in order to emphasize that cumulus convection and ekman pumping are critical to its behaviour the time required for hurricane formation in det is examined over a broad range of sea surface temperatures tropical latitudes and surface exchange coefficients for moist entropy and momentum the mean trends are sensible but for a given set of parameters the genesis time can vary significantly with subtle changes to the initial turbulence moreover hurricanes do not always form in the event that a tropical depression develops into a hurricane the process is highly asymmetric intensification involves a shear flow instability the production of mesovortices and contraction of the basic circulation despite the complex evolution the intensification rate is largely consistent with the expectations of a quasi linear stability analysis properties of mature hurricanes and the nature of their fluctuations are discussed in the context of the model copyright 2009 royal meteorological society

geochemical relationships of petroleum in mesozoic reservoirs to carbonate source rocks of jurassic smackover formation southwestern alabama algal carbonate mudstones of the jurassic smackover formation are the main source rocks for oil and condensate in mesozoic reservoir rocks in southwestern alabama this interpretation is based on geochemical analyses of oils condensates and organic matter in selected samples of shale norphlet formation haynesville formation trinity group tuscaloosa group and carbonate smackover formation rocks potential and probable oil source rocks are present in the tuscaloosa group and smackover formation respectively extractable organic matter from smackover carbonates has molecular and isotopic similarities to jurassic oil although the jurassic oils and condensates in southwestern alabama have genetic similarities they show significant compositional variations due to differences in thermal maturity and organic facies lithofacies organic facies reflect different depositional conditions for source rocks in the various basins the mississippi interior salt basin was characterized by more continuous marine to hypersaline conditions whereas the manila and conecuh embayments periodically had lower salinity and greater input of clastic debris and terrestrial organic matter petroleum and organic matter in jurassic rocks of southwestern alabama show a range of thermal transformations the gas content of hydrocarbons in reservoirs increases with increasing depth and temperature in some reservoirs where the temperature is above 266 f 130 c gas condensate is enriched in isotopically heavy sulfur apparently derived from thermochemical reduction of jurassic evaporite sulfate this process also results in increased h2s and co2 in the gas and depletion of saturated hydrocarbons in the condensate liquids thermochemical sulfate reduction probably depends on the mineralogic composition of the reservoir rock as well as temperature because some deep 18 000 ft or 5 5 km and hot 320 f or 160 c smackover and norphlet reservoirs contain low sulfur petroleum

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

the depositional record of the frasnian famennian boundary interval in a fore reef succession canning basin western australia abstract the effects of the global frasnian famennian f f biotic crisis on the shallow marine reef builders and associated biota in a laterally extensive late frasnian reef complex on the lennard shelf northern canning basin are recorded in the well exposed fore reef succession napier formation of the napier range the conodont defined f f boundary lies within a distinctive and mappable stratigraphic interval up to 15 m thick which separates highly fossiliferous frasnian from markedly less fossiliferous famennian carbonate and siliciclastic lithofacies marked lateral facies variation within the interval means that the actual boundary is not represented by a discrete bed or surface the interval is characterised by a range of lithofacies that record very low sedimentation rates on the slope and reworking and bioturbation of slope strata indicating a condensed interval with negligible sediment input from contemporaneous carbonate platform production siliciclastic lithofacies and abundant sponge debris are locally developed macrofossil content is generally very low but there is no evidence for anoxic or hypoxic conditions during deposition at a range of palaeowater depths allochthonous blocks of stromatoporoid bearing limestone are absent from the uppermost frasnian fore reef strata and stromatoporoid debris is significantly reduced prior to the end of the frasnian this suggests that extinction of the stromatoporoid reef margins occurred before the f f boundary with microbial communities dominating the platform margins prior to the famennian sedimentological and biostratigraphic evidence suggests that a series of sea level fluctuations in response to basin tectonism generated recurring or ongoing environmental stress in the stromatoporoid dominated reefal communities because of recurring reductions in living space influxes of siliciclastic sediment supply from the proximal highlands and quite possibly generation of toxic too saline or too nutrient rich lagoonal water these conditions were potentially superimposed on a global regime of incipient cooling climate leading to widespread glaciation in the late carboniferous

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

appleton field case study eastern gulf coastal plain field development model for upper jurassic microbial reef reservoirs associated with paleotopographic basement structures appleton oil field located in escambia county alabama was discovered in 1983 through the use of two dimensional seismic reflection data the field structure is a northwest southeast trending paleotopographic ridge comprised of local paleohighs the field produces from microbial reef boundstones and shoal grainstones and packstones of the upper jurassic smackover formation because appleton field is approaching abandonment owing to reduced profitability an integrated geoscientific study of the field structure and reservoir was undertaken to determine whether drilling additional wells in the field would extend the productive life of the reservoir the conclusion from the integrated study which included advanced carbonate reservoir characterization three dimensional geologic visualization modeling seismic forward modeling porosity distribution analysis and field production analysis was that a sidetrack well drilled on the western paleohigh should result in improved oil recovery from the field the sidetrack well was drilled and penetrated porous smackover reservoir near the crest of the western paleohigh the well tested 136 bbl oil day begin page 1700

a theory for strong long lived squall lines abstract we study herein the mechanics of long lived line oriented precipitating cumulus convection squall lines using two and three dimensional numerical models of moist convection these models used in juxtaposition enable us to address the important theoretical issue of whether a squall line is a system of special long lived cells or whether it is a long lived system of ordinary short lived cells our review of the observational literature indicates that the latter is the most consistent paradigm for the vast majority of cases but on occasion a squall line may be composed of essentially steady supercell thunderstorms the numerical experiments presented herein show that either type of squall line may develop from an initial line like disturbance depending on the magnitude and orientation of the environmental shear with respect to the line with shallow shear oriented perpendicular to the line a long lived line evolves containing individually short lived cells our analysis of this type o

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

tropical cyclone convection the effects of ambient vertical vorticity we present idealized numerical model experiments to isolate and quantify the influence of ambient vertical vorticity on the dynamics of deep convection such as that in the inner core region of a tropical depression the vertical vorticity is represented either by a uniform horizontal shear a uniform solid body rotation or a combination of both we show that the growing convective cells amplify locally the ambient rotation at low levels by more than an order of magnitude and that this vorticity which is produced by the stretching of existing ambient vorticity persists long after the initial updraught has decayed significant amplification of vorticity occurs even for a background rotation rate typical of the undisturbed tropical atmosphere and even for clouds of only moderate vertical extent this finding has important implications for tropical cyclogenesis and provides a basis for a unified theory of tropical cyclogenesis and tropical cyclone intensification the presence of ambient vertical vorticityreduces the updraught strength slightly more when the vorticity is associated with horizontal shear than when it is associated with solid body rotation on account of enhanced entrainment the reduction of the updraught strength can be attributed to the reduction of the lateral inflow by the centrifugal and coriolis forces despite the significant amplification of vorticity the sum of the centrifugal and coriolis forces is mostly small compared with the lateral pressure gradient thus at the level of background rotation studied the rossby elasticity effects in the updraught postulated by montgomery et al are not large but may be important for higher levels of background rotation the simulations ignore several processes that are likely to be important in reality such as ambient vertical shear and surface friction but they provide important benchmark calculations for interpreting the additional complexity arising from the inclusion of these effects copyright c 2011 royal meteorological society

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

reefal platform development devonian of the canning basin western australia growth of devonian reefal limestone platforms on the canning basin was nearly continuous from the late givetian to the late famennian the earliest givetian and early frasnian platforms were low relief banks later frasnian and famennian platforms were normally reef rimmed with high relief upright reef margins predominated in the frasnian with intervals of backstepping associated with widespread drowning and the development of pinnacle reefs a brief emergence occurred at the frasnian famennian boundary and the succeeding famennian platforms advanced basinward over equivalent marginal slope and basin facies platform extinction in the late famennian resulted from abrupt drowning an important initial control on platform trends was basement topography resulting from middle devonian or older faulting continued faulting during the late devonian influenced the morphology of some platforms contemporary seismicity also led to neptunian fracturing and the collapse of platform margins the hypothetical sea level curve for the canning basin devonian is believed to be a combined result of global eustatism and regional diastrophism it shows gross resemblance to the equivalent euramerican curve rates of sea level rise or subsidence are thought to have largely controlled platform evolution banks and advancing platforms were associated with slow rises in sea level upright reef scarpsmore with moderately rapid rises and backstepping pinnacle reefs and drowning with very rapid rises shoaling upward cycles in back reef limestones resulted from periodic abrupt rises of a few meters followed by longer stillstands seismic stratigraphic modeling together with observed seismic records and well data suggest that the evolutionary model for the devonian platforms deduced from outcrop studies can also be applied in the subsurface less

organization of tropical convection in low vertical wind shears the role of water vapor abstract a modeling study is conducted to gain insight into the factors that control the intensity and organization of tropical convection and in particular to examine if organization occurs in the absence of factors such as vertical wind shear or underlying sea surface temperature sst gradient the control experiment integrates a cloud resolving model for 15 days using a 3d domain exceeding 1000 km in length with no imposed winds and horizontally uniform sst and forcing for convection after 2 days of random activity the convection organizes into clusters with dimensions of approximately 200 km convective systems propagate through the clusters at speeds of 2 3 m s 1 while the clusters themselves propagate at minimal speeds of around 0 5 m s 1 examining the thermodynamic structure of the model domain it is found that the convective free bands separating the clusters are very dry throughout the troposphere and due to virtual temperature effects are correspondingly warmer in the lower tropospher

tropical cyclones in rotating radiative convective equilibrium with coupled sst abstracttropical cyclones are studied under the idealized framework of rotating radiative convective equilibrium achieved in a large doubly periodic f plane by coupling the column physics of a global atmospheric model to rotating hydrostatic dynamics unlike previous studies that prescribe uniform sea surface temperature sst over the domain ssts are now predicted by coupling the atmosphere to a simple slab ocean model with coupling ssts under the eyewall region of tropical cyclones tcs become cooler than the environment however the domain still fills up with multiple long lived tcs in all cases examined including at the limit of the very small depth of the slab the cooling of ssts under the eyewall increases as the depth of the slab ocean layer decreases but levels off at roughly 6 5 k as the depth approaches zero at the eyewall the storm interior is decoupled from the cooler surface and moist entropy is no longer well mixed along the angular momentum surface in the boundary layer tc intens

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

controls on reservoir development in a shelf carbonate upper jurassic smackover formation of alabama hydrocarbon reservoirs of the upper jurassic smackover formation in alabama are predominately oolitic and pelletal dolostone pore systems are dominated by moldic and secondary intraparticle pores intercrystalline pores or mixtures of these pore types all smackover reservoirs in alabama have been strongly affected by early cementation dissolution of calcium carbonate allochems and dolomitization marine phreatic cement occluded primary interparticle porosity in much of the smackover reservoirs in alabama dolomitization of the smackover in alabama included penecontemporaneous early burial and late deep burial episodes early burial dolomite predominates fabric selective dolomitization yielded reservoirs strongly influenced by both depositional fabric and diagene is nonselective dolomitization yielded reservoirs with intercrystalline pore systems shaped primarily by diagenesis porosity evolution was controlled regionally by level of thermal exposure mode of dolomitization and proximity to the wiggins arch thermal exposure is inversely related to porosity but the relationship is weak r2 0 5 fabric selective dolostone is slightly more porous than nonselective dolostone when averaged over the entire study area averages of 18 1 and 15 1 respectively p 0 0001 but nonselective dolostone is more porous at a given level of equivalent vitrinite reflectance smackover fields on the north flank of the wiggins arch are unusually porous given their level of thermal maturity and are unusual in other ways as well local porosity variation was controlled by depositional fabric early cementation dissolution and burial compaction and cemen ation regional permeability variation cannot be explained using existing data permeability is locally controlled by pore throat size the effects of dolomite crystal size distribution early cementation fracturing and burial compaction and cementation pore throat size exhibits the strongest overall correlation with permeability r2 0 54 permeability and porosity are strongly correlated locally but the regional correlation is weak

facies heterogeneity and depositional models of a ladinian middle triassic microbial dominated carbonate ramp system catalan coastal ranges ne spain abstract the ladinian sedimentary successions record a major transgressive pulse of northeastern iberia during the middle triassic this record is arranged in two transgressive regressive t r sequences formed by two fault block microbial and shoal dominated carbonate ramps the main factor controlling the creation of accommodation space is the differential rapid syn rift subsidence which induces the generation of palaeogeographical barriers that played a key role in the sedimentary architecture and microbial development the facies architecture of these ramps was reconstructed by means of facies analysis and sequence stratigraphy t r sequence 1 corresponds to a fault block carbonate ramp system dominated by microbialites and oolitic shoals t r sequence 2 represents a fault block carbonate ramp system mainly characterised by lagoons and shoals the diverse types of microbialites stromatolites and thrombolites are widely represented in the inner and middle ramp settings reaching a width of 45 km and an average thickness of 40 m t r sequence 1 contains the most noticeable microbial deposits stromatolites in the inner ramp up to 7 m thick and thrombolites in the middle ramp up to 40 m thick t r sequence 2 is mainly characterised by the occurrence of oolitic stromatolites in the inner ramp and internal shoals and sheltered lagoons in the middle ramp microbialites exhibit a fabric selective ancient porosity which is currently occluded by coarse calcite and quartz cements the most common types of ancient porosity are interlaminar vuggy and mouldic grain dissolution and evaporite replacement the studied carbonate ramps can be used as an analogue for ancient microbialite reservoirs in rapidly subsiding depositional areas with a high diversity of microbial deposits formed in restricted to open marine conditions with a wide array of ancient porosity and a well known sequence stratigraphic context

regional jurassic geologic framework of alabama coastal waters area and adjacent federal waters area abstract to date numerous jurassic hydrocarbon fields and pools have been discovered in the cotton valley group haynesville formation smackover formation and norphlet formation in the tri state area of mississippi alabama and florida and in alabama state coastal waters and adjacent federal waters area petroleum traps are basement highs salt anticlines faulted salt anticlines and extensional faults associated with salt movement reservoirs include continental and marine sandstones limestones and dolostones hydrocarbon types are oil condensate and natural gas the onshore stratigraphic and structural information can be used to establish a regional geologic framework for the jurassic for the state coastal waters and adjacent federal waters areas evaluation of the geologic information along with the hydrocarbon data from the tri state area indicates that at least three jurassic hydrocarbon trends oil oil and gas condensate and deep natural gas can be identified onshore these onshore hydrocarbon trends can be projected into the mobile area in the central gulf of mexico and into the pensacola destin dome and apalachicola areas in the eastern gulf of mexico substantial reserves of natural gas are expected to be present in alabama state waters and the northern portion of the mobile area significant accumulations of oil and gas condensate may be encountered in the pensacola destin dome and apalachicola areas

on the creation and evolution of small scale low level vorticity anomalies during tropical cyclogenesis abstractrecent numerical modeling and observational studies indicate the importance of vortical hot towers vhts in the transformation of a tropical disturbance to a tropical depression it has re

reservoir characterization modeling and evaluation of upper jurassic smackover microbial carbonate and associated facies in little cedar creek field southwest alabama eastern gulf coastal plain of the united states an integrated field study of the microbial carbonate and associated reservoirs at little cedar creek field in southwest alabama eastern gulf coastal plain of the united states provides an excellent opportunity to examine the spatial distribution of the sedimentary petrophysical and productivity trends in microbial reservoirs this study includes characterizing the sedimentary petrophysical and hydrocarbon productivity characteristics of microbialites developing a three dimensional geologic reservoir model and evaluating the hydrocarbon potential of these reservoirs the lower reservoir comprises subtidal thrombolitic boundstone associated with microbial buildups oriented in a southwest to northeast direction over an area that encompasses 32 mi2 83 km2 these buildups developed in clusters in the western central and northern parts of the field and attained thicknesses of 43 ft 13 m the clusters are separated by interbuildup areas of microbialites of 7 9 ft 2 3 m in thickness that are overlain by a thick section of nonreservoir microbially influenced lime mudstone and wackestone porosity in the microbial reservoirs includes depositional constructed void intraframe and diagenetic solution enhanced void and vuggy pore types this pore system provides for high permeability and connectivity in the reservoir beds permeability ranges to as much as 7953 md and porosity to as much as 20 the microbial boundstone beds have high potential as hydrocarbon flow units however the buildup areas are separated by interbuildup areas associated with a thick section of low permeability to nonreservoir beds that serve as potential baffles or barriers to flow much of the 17 2 million bbl oil produced from the field is from the microbial lithofacies the results from the little cedar creek field study have application in the design of improved development strategies for other fields producing from microbial carbonate reservoirs

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

the formation of hurricane humberto 2001 the importance of extra tropical precursors the authors examine the formation of hurricane humberto 2001 in the atlantic basin precursor disturbances originating in the extratropics appear critical for inducing tropical cyclogenesis one precursor near the tropopause arose during the development of hurricane erin on 7 september and could be tracked continuously for 12 days until 1200 utc 19 september a fully explicit numerical simulation with the psu ncar mesoscale model produces a generally realistic evolution of the developing storm during a 4 day period beginning 0000 utc 19 september diagnostics of the simulations reveal that moderate vertical shear was crucial for organizing convection and this shear was enhanced on the periphery of an upper level vortex within a lower to mid tropospheric baroclinic zone downdraughts and evaporative cooling produced a rearward propagating bore that organized new convection in a notably moistened environment with small cape vorticity generation maximized near 1 km above mean sea level and the vortex built upward with time this evolution contrasts markedly with downward development conceptual models of tropical cyclogenesis and points to the crucial need for observations in the lower troposphere before depression formation convective scale dynamics were governed by intense convective cores which produced most of the diabatic heating and lower tropospheric vertical vorticity they were constrained by vertical shear to populate the downshear left quadrant of the vortex and therefore their collective behaviour was organized despite being quasi random within the favoured region ultimately the shear that helped organize the convection in the developing depression hampered humberto s subsequent intensification copyright 2006 royal meteorological society

observed tropical cyclone size revisited abstractthis work revisits the statistics of observed tropical cyclone outer size in the context of recent advances in our theoretical understanding of the storm wind field the authors create a new dataset of the radius of 12 m s 1 winds based on a recently updated version of the quikscat ocean wind vector database and apply an improved analytical outer wind model to estimate the outer radius of vanishing wind the dataset is then applied to analyze the statistical distributions of the two size metrics as well as their dependence on environmental parameters with a specific focus on testing recently identified parameters possessing credible theoretical relationships with tropical cyclone size the ratio of the potential intensity to the coriolis parameter is found to perform poorly in explaining variation of size with the possible exception of its upper bound the latter of which is in line with existing theory the rotating radiative convective equilibrium scaling of khairoutdinov and emanuel is also f

inertial waves in axisymmetric tropical cyclones abstractthe heat engine model of tropical cyclones describes a thermally direct overturning circulation outflowing air slowly subsides as radiative cooling to space balances adiabatic warming a p

an investigation of composite dropsonde profiles for developing and nondeveloping tropical waves during the 2010 predict field campaign abstractcomposite dropsonde profiles are analyzed for developing and nondeveloping tropical waves in an attempt to improve the understanding of tropical cyclogenesis these tropical waves were sampled by 25 reconnaissance missions during the 2010 pre depression investigation of cloud systems in the tropics predict field campaign comparisons are made between mean profiles of temperature mixing ratio relative humidity radial and tangential winds relative vorticity and virtual convective available potential energy cape for genesis and nongenesis cases genesis soundings are further analyzed in temporal progression to investigate whether significant changes in the thermodynamic or wind fields occur during the transition from tropical wave to tropical cyclone significant results include the development of positive temperature anomalies from 500 to 200 hpa 2 days prior to genesis in developing waves this is not observed in the nongenesis mean progressive mesoscale moistening of the column is observe

an explanation for intense frontal updrafts and narrow cold frontal rainbands abstract measurements with doppler radar and instrumented aircraft and towers have revealed that surface cold fronts often have cross frontal circulations organized on a scale of a kilometer or less these circulations include intense updrafts 1 to 20 m s 1 that result in a narrow band of heavy rainfall we used a nonhydrostatic model to investigate the mechanism for these updrafts and to isolate those characteristics of the prefrontal environment that result in intense updrafts and narrow bands of heavy rainfall our simulations were initialized with a cold reservoir in a manner analogous to that used to produce a gravity current the similarity between the observations and our simulated frontal flows supports the hypothesis that the flow at the leading edge of surface cold fronts can sometimes be represented by gravity current dynamics we also found that the differences between frontal circulations and classical dry gravity currents can be explained by the effects of precipitation and vertical shea

a numerical study of deep convection in tropical cyclones 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

in situ initiation of east pacific easterly waves in a regional model abstractthe in situ generation of easterly waves ews in the east pacific epac is investigated using the weather research and forecasting wrf model the sensitivity of the model to the suppression of ew forcing by locally generated convective disturbances is examined specifically local forcing of ews is removed by reducing the terrain height in portions of central and south america to suppress robust sources of diurnal convective variability most notably in the panama bight high terrain contributes to the initiation of mesoscale convective systems in the early morning that propagate westward into the epac warm pool when such mesoscale convective systems are suppressed in the model ew variance is significantly reduced this result suggests that epac ews can be generated locally in association with higher frequency convective disturbances and these disturbances are determined to be an important source of epac ew variability however epac ew variability is not completely eliminated in such sensi

evolution of multiscale vortices in the development of hurricane dolly 2008 abstract as a follow up to a previously published article on the initial development and genesis of hurricane dolly 2008 this study further examines the evolution of and interactions among multiscale vortices ranging from the system scale main vortex l 150 km to the intermediate scale cloud clusters 50 km l 150 km and individual vorticity rich convective cells l 50 km it is found that there are apparent self similarities among these vortices at different scales each of which may undergo several cycles of alternating accumulation and release of convective available potential energy enhanced surface fluxes below individual cyclonic vortices at each scale contribute to the sustainment and reinvigoration of moist convection that in turn contributes to the maintenance and upscale growth of these vortices spectral analysis of horizontal divergence and relative vorticity further suggests that the cloud cluster scale and system scale vortices are predominantly balanced while the individual

mesoscale convective systems 1 mesoscale convective systems mcss have regions of both convective and stratiform precipitation and they develop mesoscale circulations as they mature the upward motion takes the form of a deep layer ascent drawn into the mcs in response to the latent heating and cooling in the convective region the ascending layer overturns as it rises but overall retains a coherent layer structure a middle level layer of inflow enters the stratiform region of the mcs from a direction determined by the large scale flow and descends in response to diabatic cooling at middle to low levels a middle level mesoscale convective vortex mcv develops in the stratiform region prolongs the mcs and may contribute to tropical cyclone development the propagation of an mcs may have a discrete component but may further be influenced by waves and disturbances generated both in response to the mcs and external to the mcs waves of a larger scale may affect the propagation velocity by phase locking with the mcs in a cooperative mode the horizontal scale of an mcs may be limited either by a balance between the formation rate of convective precipitation and dissipation of stratiform precipitation or by the rossby radius of the mcv the vertical redistribution of momentum by an mcs depends on the size of the stratiform region while the net vertical profile of heating of the large scale environment depends on the amount of stratiform rain regional variability of the stratiform rain from mcss affects the large scale circulation s response to mcs heating

origin of dolostone reservoir rocks smackover formation oxfordian northeastern gulf coast u s a formation of regionally extensive dolostone reservoir rocks in the smackover can be understood despite the possible effects of recrystallization geochemical and petrographic data suggest that dolomitization took place in 1 seawater seepage 2 reflux 3 near surface mixed water 4 shallow burial mixed water and 5 deeper burial environments which overlapped in time and space to form a platform scale dolostone body composed of a complex mixture of dolomites seawater seepage and reflux dolomitization occurred in the near surface penecontemporaneously with deposition of the smackover and overlying haynesville formations dolomitization by seawater seepage occurred within an oolite grainstone sill which separated an intraplatform salt basin from the open sea seawater flowed landward through the sill in response to evaporitic drawdown of brines in the isolated intraplatform basin isolation of the salt basin occurred during the oxfordian when the shoreline retreated from the conecuh embayment dolomite located at the top of the smackover enriched in 18 o suggests additional dolomitization by reflux of hypersaline brines reflux occurred as buckner coastal sabkhas prograded over smackover oolite grainstone shoreface deposits vugs lined with shallow burial calcite and dolomite cements indicate flushing of the smackover grainstone aquifer with fresh water freshwater intrusion probably occurred following sea level lowstands during the late jurassic and early cretaceous leaching in the proximal portion of the freshwater aquifer produced excellent limestone reservoir rocks in the updip smackover dolomitization in the contemporaneous downdip mixed connate freshwater zone formed dolostone reservoir rocks with depleted isotopic compositions consistent with a shallow burial mixed water origin

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

a spatial filter approach to evaluating the role of convection on the evolution of a mesoscale vortex abstracta new spatial filter is proposed that exploits a spectral gap in power between the convective scale and the system vortex scale during tropical cyclone tc genesis simulations using this spatial separation this study analyzes idealized three dimensional numerical simulations of deep moist convection in the presence of a symmetric midlevel vortex to quantify and understand the energy cascade between the objectively defined convective scale and system scale during the early stages of tropical cyclogenesis the simulations neglect surface momentum heat and moisture fluxes to focus on generation and enhancement of vorticity within the interior to more completely close off the energy budget and to be consistent for comparison with prior benchmark studies of modeled tc genesis the primary contribution to system scale intensification comes from the convergence of convective scale vorticity that is supplied by vortical hot towers vhts they contribute more than the convergence of system scale v

improving recovery from mature oil fields producing from carbonate reservoirs upper jurassic smackover formation womack hill field eastern gulf coast u s a reservoir characterization modeling and simulation were undertaken to improve production from womack hill field eastern gulf coast united states this field produces oil from upper jurassic smackover carbonate shoal reservoirs these reservoirs occur in vertically stacked heterogeneous depositional and porosity cycles the cycles consist of lime mudstone and wackestone at the base and ooid grainstone at the top porosity has been enhanced through dissolution and dolomitization porosity is chiefly interparticle solution enlarged interparticle grain moldic intercrystalline dolomite and vuggy pores dolostone pore systems and flow units have the highest reservoir potential petroleum trapping mechanisms include a fault trap footwall uplift with closure to the south against a major west southeast trending normal fault in the western area a footwall uplift trap associated with a possible southwest northeast trending normal fault in the south central area and a salt cored anticline with four way dip closure in the eastern area potential barriers to flow are present as a result of petrophysical differences among and within the cycles as well as the presence of normal faulting reservoir performance analysis and simulation indicate that the unitized western area has less than 1 mmstb of oil remaining to be recovered and that the eastern area has 2 3 mmstb of oil to be recovered a field scale reservoir management strategy that includes the drilling of infill wells in the eastern area of the field and perforating existing wells in stratigraphically higher porosity zones in the unitized western area is recommended for sustaining production from the womack hill field

model for how microbial methane generation can preserve early porosity in dolomite and limestone reservoirs in some dolomite and limestone hydrocarbon reservoirs protection from cementation is a primary factor in porosity preservation we present a model in which methanogens methane producing microorganisms produce methane gas ch4 g that outgasses from solution in pore space creating a two phase system that reduces effective hydraulic conductivity k protecting pore space from cementation methanogens have been implicated in dolomite formation and can generate methane to fill pore space of a model near surface carbonate sediment 37 5 primary porosity with ch4 g in 180 to 4650 yr depending on nutrient levels gas generation results in occlusion of the aqueous phase from pore spaces and throats creating a two phase flow regime reducing the effective hydraulic conductivity of model marine carbonate sand by about 50 from 2 8 to 1 2 cm day in as little as 55 yr therefore reducing aqueous fluid flow necessary for cementation despite rapid burial and complete cessation of methanogenesis effective hydraulic conductivity could take more than 100 000 yr to return to its original value if methanogenesis continues with burial the effective hydraulic conductivity is reduced to zero after 250 yr dolomites can preserve more primary porosity with depth than other carbonates we propose that in addition to increased structural resistance a biogenic model exists for porosity preservation in dolomites that is linked to the activity of methanogens this model represents specific end member cases and illustrates the effect of methane buildup in relationship to the extent of reservoir diagenesis

diagenetic controls on reservoir development and quality smackover formation of southwest alabama abstract abstract smackover reservoirs in southwest alabama are much more complex than those encountered in the central and western portions of the gulf coast basin this heterogeneity is a product of a complex history of diagenetic modification the diagenetic history can be divided into five separate stages 1 marine stage extensive grain micritization and precipitation of minor amounts of fibrous cement 2 meteoric vadose stage extensive dissolution of aragonitic grains 3 meteoric phreatic stage precipitation of granular and blocky cements 4 brine reflux stage extensive dolomitization and sulfate emplacement associated with refluxing of buckner brines and 5 burial stage grain to grain compaction of lithologies not stabilized by early cements stylolitization precipitation of poikilotopic calcite and dolomite cements minor dissolution of calcite associated with the introduction into the formation of undersaturated fluids hydrocarbon migration and sulfate replacement and cementation the diagenetic sequence varies dramatically over short distances in southwest alabama reflecting variation in paleotopography the products of this complex diagenetic history are heterogeneous reservoirs which consist of one or some combination of primary interparticulate moldic dolomitic intercrystalline and vuggy porosity primary interparticulate porosity is less common in southwest alabama than in the central and western portions of the gulf coast basin largely because of extensive compaction or early cementation where present however interparticulate reservoirs are characterized by moderate to high porosity and good permeability moldic porosity is produced by early fabric selective dissolution of aragonitic allochems and is associated with areas of subaerial exposure moldic reservoirs commonly have high porosity but low permeability and are generally productive only when permeability is enhanced by other pore types dolomitic intercrystalline porosity is common in the smackover of southwest alabama intercrystalline porosity alone however is seldom of reservoir quality and hydrocarbon production from dolomitized lithologies is generally dependent upon the coexistence of moldic or vuggy porosity vuggy porosity is the product of late non fabric selective dissolution of calcite vuggy pores are produced by solution enlargement of earlier formed interparticulate moldic or intercrystalline pores vuggy reservoirs are by nature composite and are characterized by moderate to high porosity and good permeability

evolution of a late jurassic carbonate evaporite platform conecuh embayment northeastern gulf coast u s a successive time slice lithofacies maps of the smackover haynesville depositional sequence constrained by marker beds an interpreted maximum flooding surface and interpreted sequence boundaries show an onlapping and retrograding sequence of lithologies characteristic of a transgressive systems tract tst the tst is followed by several prograding sequences characteristic of a highstand systems tract hst and stacked shelf margin wedges smw comparison of stratigraphic cross sections lithofacies maps and a paleotopographic map of the sub smackover transgressive surface shows that the distribution of lithofacies within the tst was strongly controlled by two types of sub smackover paleotopographic highs 1 norphlet dune fields and 2 eroded basement rock as th tst became progressively buried during deposition distribution of lithofacies within the hst and the smws was controlled less by these early paleotopographic features and more by 1 differential compaction around shoal water facies in the tst 2 early louann salt movement 3 basement related faulting and 4 freshwater influx along the basin rim

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