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The Contributions Of Dynamical And Diabatic Processes Preceding And Accompanying Major Greenland Ice-Melt Events, Scott Feldman
The Contributions Of Dynamical And Diabatic Processes Preceding And Accompanying Major Greenland Ice-Melt Events, Scott Feldman
Legacy Theses & Dissertations (2009 - 2024)
Extratropical cyclones and/or short-wave disturbances can reinforce Greenland blocking through upper-level flow amplification and can increase poleward heat and moisture transport into the Arctic. Increased poleward heat and moisture transport into the Arctic may enhance Greenland ice melt during the spring, summer, and fall months. The need to better understand the underlying dynamical and diabatic processes that may contribute to Greenland ice melt motivates this thesis. The purpose of this thesis is to investigate: 1) the role of advective warming due to poleward heat and moisture transport into the Arctic in facilitating Greenland ice melt, 2) the role of adiabatic …
The Effect Of Differential Friction On Tropical Cyclone Development Close To Land, Minghao Zhou
The Effect Of Differential Friction On Tropical Cyclone Development Close To Land, Minghao Zhou
Legacy Theses & Dissertations (2009 - 2024)
Hurricane Karl (2010) underwent unexpected rapid intensification in the Bay of Campeche while remaining in close proximity (within 150 km) to land. It is hypothesized that the frictionally-enhanced inflow contributed positively to this evolution, despite reduced surface fluxes and increased momentum loss over land. In this study, the role of differential friction in the development of a tropical cyclone (TC) tracking parallel to a coastline is examined based on this prototype.A series of high-resolution, semi-idealized numerical simulations with full physics were conducted on a β-plane with curvature effects of the Earth. After initializing a TC from a synoptic-scale thermal perturbation, …
It Takes Two To Tango : Understanding The Processes That Lead To Simultaneous Changes In Tropical Cyclone Intensity And Size And Communicating The Associated Hazards To Emergency Managers, Emily A. Paltz
Legacy Theses & Dissertations (2009 - 2024)
The severity of tropical cyclone (TC) hazards is modulated by both TC intensity and size. More intense TCs produce stronger storm surges and increase wind damage. Larger TCs potentially impact more people, increase the duration of TC hazards, produce stronger storm surges and increase the amount of rainfall and flooding. Thus, accurately forecasting both TC intensity and size and effectively communicating those forecasts are critical to properly preparing communities for TC impacts. Forecast accuracy can be improved by enhancing our understanding about the processes that cause changes in TC intensity and size. This research divides the Extended Best Track dataset …
Diagnosing High Sinuosity Regimes Associated With Anomalous Greenland Ice-Melt Events Using Self-Organizing Maps, Mansour El Riachy
Diagnosing High Sinuosity Regimes Associated With Anomalous Greenland Ice-Melt Events Using Self-Organizing Maps, Mansour El Riachy
Legacy Theses & Dissertations (2009 - 2024)
Sinuosity, a metric that describes the waviness of the circumpolar flow, is adapted to quantify modification of the tropospheric polar vortex within longitudinal sectors by localized incursions of warm, moist air from middle latitudes associated with Arctic cyclones (ACs). In this thesis, we identify four corridors of high AC track frequency, on which we center 90° longitudinal sectors comprising the following regions: Pacific, West of Greenland, Atlantic, and Asian. Sectorial sinuosity is calculated for the West of Greenland sector and is used to quantify the amplitude of the 300-hPa flow associated with anomalous Greenland ice-melt events.
An Examination Of The Arctic Environment And Arctic Cyclones During Periods Of Low And High Forecast Skill Of The Synoptic-Scale Flow, Kevin Biernat
An Examination Of The Arctic Environment And Arctic Cyclones During Periods Of Low And High Forecast Skill Of The Synoptic-Scale Flow, Kevin Biernat
Legacy Theses & Dissertations (2009 - 2024)
This dissertation compares Arctic environmental conditions and Arctic cyclones (ACs) between periods of low and high forecast skill of the synoptic-scale flow over the Arctic during summer, hereafter referred to as low-skill periods and high-skill periods, respectively. This dissertation also examines features and processes influencing the evolution and forecast skill of selected categories of ACs.
A Comparison Of The Upscale Influence Of Various Planetary Boundary Layer Turbulence Parameterizations On The Evolution Of Extratropical Cyclones, Matthew Vaughan
A Comparison Of The Upscale Influence Of Various Planetary Boundary Layer Turbulence Parameterizations On The Evolution Of Extratropical Cyclones, Matthew Vaughan
Legacy Theses & Dissertations (2009 - 2024)
Subgrid-scale turbulence in numerical weather prediction models is typically handled by a PBL parameterization. These schemes attempt to represent turbulent mixing processes occurring below the resolvable scale of the model grid in the vertical direction, and they act upon temperature, moisture, and momentum within the boundary layer. This dissertation utilizes idealized and full-physics numerical model simulations to understand how variations in turbulent mixing parameterizations may influence sensible weather forecasts of baroclinic cyclones across a variety of spatial and temporal scales. Furthermore, a primary pathway through which PBL turbulence projects upscale during baroclinic cyclone events is identified using a combination of …
The Sensitivity Of Convection To Boundary Layer Parameterization In Hurricanes Harvey And Irma 2017, Dylan Card
The Sensitivity Of Convection To Boundary Layer Parameterization In Hurricanes Harvey And Irma 2017, Dylan Card
Legacy Theses & Dissertations (2009 - 2024)
Tropical cyclones (TCs) pose a significant threat to life and property, and exhibit many severe weather hazards as they make landfall, such as storm surge, strong winds, flooding rains, and tornadoes. TC convection is associated with nearly all of these hazards, which can extend hundreds of kilometers inland; thus, understanding the characteristics and organization of convective cells is important to mitigating risk. Observational studies have noted that TC convection tends to organize downshear and that rotating thunderstorms tend to occur in the downshear-right quadrant of the TC. Modeling studies have also shown that convective cells tend to form upshear right …
Evaluating Large-Scale And Storm-Scale Characteristics Of Rapidly Intensifying And Slowly Intensifying Tropical Cyclones Using An Analog Approach, Jannetta C. Richardson
Evaluating Large-Scale And Storm-Scale Characteristics Of Rapidly Intensifying And Slowly Intensifying Tropical Cyclones Using An Analog Approach, Jannetta C. Richardson
Legacy Theses & Dissertations (2009 - 2024)
Tropical cyclone (TC) intensity change is modulated by a combination of large-scale and storm-scale processes. On the large-scale, several factors exhibit strong controls on TC rapid intensification (RI): the initial TC intensity, the environmental vertical wind shear (VWS), and the background thermodynamic environment, which determines the TC’s maximum potential intensity (MPI). Previous statistical studies comparing RI and non-RI TCs have shown that TCs undergoing RI tend to be embedded in environments of lower VWS, and have initial intensities that are farther from their MPIs. Although numerous statistical studies have compared the large-scale and storm-scale conditions of RI and non-RI TCs, …
The Impact Of Warm Conveyor Belt Forecast Uncertainty On Downstream Predictability, Jeremy Berman
The Impact Of Warm Conveyor Belt Forecast Uncertainty On Downstream Predictability, Jeremy Berman
Legacy Theses & Dissertations (2009 - 2024)
Perturbations to the potential vorticity (PV) waveguide can lead to the downstream radiation of Rossby waves, and in turn high-impact weather events. The PV waveguide is often perturbed in association with cyclogenesis, largely due to the latent heat release within the cyclone’s warm conveyor belt (WCB). Previous studies have hypothesized that forecast uncertainty associated with diabatic heating in WCBs can result in large downstream forecast variability; however these studies have not established a direct connection between the two. This hypothesis is evaluated for six cyclogenesis events characterized by highly amplified flow over the North Atlantic using ensemble model simulations.
Synergistic Effects Of Midlevel Dry Air And Vertical Wind Shear On Tropical Cyclone Development, Joshua James Alland
Synergistic Effects Of Midlevel Dry Air And Vertical Wind Shear On Tropical Cyclone Development, Joshua James Alland
Legacy Theses & Dissertations (2009 - 2024)
This dissertation seeks to better understand how midlevel moisture and vertical wind shear (VWS) modulate tropical cyclone (TC) development. The first component of this dissertation simplifies the objective by focusing solely on how midlevel moisture modulates TC development, utilizing an axisymmetric modeling framework. Results show that low-entropy midlevel air affects the upward vertical mass flux in these experiments through subsidence into the subcloud layer, which results in a longer recovery time before deep convection develops. This process, as well as descending motion closer to the inner core, limits the radial width of deep convection, reduces the area of upward motions, …
Applying Forecast Track And Intensity Diagnostics To High-Impact Northeast Winter Storms, Tomer Burg
Applying Forecast Track And Intensity Diagnostics To High-Impact Northeast Winter Storms, Tomer Burg
Legacy Theses & Dissertations (2009 - 2024)
A conventional forecasting notion is that as lead time decreases, numerical weather prediction models exhibit a leftward (i.e., west) trend in the forecast position of low-pressure systems along the East Coast of the U.S. This left trend, which may turn seemingly weak ocean cyclones into high-impact weather events for the Northeast U.S., is attributed to various potential causes, such as variability in upstream shortwave troughs, or the representation of latent heat release in the NWP models downstream of the trough associated with the incipient cyclone. This study seeks to address whether this rule of thumb holds any significant merit, and …
On The Frequency, Structure, And Characteristics Of Tropical Cyclone Diurnal Pulses, Sarah Dunn Ditchek
On The Frequency, Structure, And Characteristics Of Tropical Cyclone Diurnal Pulses, Sarah Dunn Ditchek
Legacy Theses & Dissertations (2009 - 2024)
Taking 6-h IR brightness temperature differences, Dunion et al. (2014) found that in major hurricanes, an area of cold cloud tops routinely propagated radially outward from the storm core at around 5–10 m/s over the course of each day. They defined this feature as a “diurnal pulse” and created a 24-h conceptual clock that identified at which radius the coldest cloud tops would be located based on local time (LT). Due to the inherent predictability of these pulses, this dissertation was undertaken to gain a deeper understanding of their frequency, structure, and characteristics.
Extratropical Precursors To The Onset Of Madden-Julian Oscillation Deep Convection Over The Western Indian Ocean, Jennifer Anne Gahtan
Extratropical Precursors To The Onset Of Madden-Julian Oscillation Deep Convection Over The Western Indian Ocean, Jennifer Anne Gahtan
Legacy Theses & Dissertations (2009 - 2024)
Madden-Julian Oscillation (MJO) deep convection often initially forms over the western Indian Ocean and is frequently preceded by upper tropospheric circulation precursors. These precursors include subtropical cyclonic Rossby gyres near eastern Africa and Southwest Asia, coherent extratropically circumnavigating Rossby wave trains extending back across the Atlantic, and tropically circumnavigating easterlies. Easterly acceleration associated with the circulation precursors may help to reduce large-scale subsidence over the tropical Indian Ocean prior to convective onset; when intraseasonal easterly acceleration reaches the western extent of a region of intraseasonal upper level westerlies, it produces upper-tropospheric divergence, providing a forcing for upward motion.
The Role Of The Subtropical Jet In Severe Dry Season Caribbean Rainstorms, Marshall D. Pfahler
The Role Of The Subtropical Jet In Severe Dry Season Caribbean Rainstorms, Marshall D. Pfahler
Legacy Theses & Dissertations (2009 - 2024)
The Caribbean region experiences a bimodal climate with a dry season during November/December–May/June and a wet season encompassing the remainder of the year. Although significant high-impact heavy rainfall events in the Caribbean are typically associated with tropical cyclones (TCs) during the wet season, significant heavy rainfall events can also occur during the Caribbean dry season without contributions from TCs. Dry season Caribbean rainstorms (CRs) can produce infrastructure- and life-threatening conditions through flooding, mudslides, and damaging winds. The most severe dry season CRs can require international aid for vital recovery resources. Severe dry season CRs can produce rainfall totals that substantially …
Influence Of Upper-Tropospheric Troughs On Tropical Cyclone Intensity Change And Structure : Observational, Reanalysis, And Idealized Numerical Modeling Perspectives, Casey Peirano
Legacy Theses & Dissertations (2009 - 2024)
The interaction between tropical cyclones (TCs) and upper-tropospheric troughs is a
Extratropical Cyclones Leading To Extreme Weather Events Over Central And Eastern North America, Alicia Marie Bentley
Extratropical Cyclones Leading To Extreme Weather Events Over Central And Eastern North America, Alicia Marie Bentley
Legacy Theses & Dissertations (2009 - 2024)
Cool-season extreme weather events (EWEs) occurring over central and eastern North America are typically associated with strong extratropical cyclones (ECs) that are governed by varying combinations of baroclinic, diabatic, and barotropic processes. This dissertation investigates the climatology, evolution, and predictability of ECs leading to EWEs over central and eastern North America, and provides a foundation on which to compare ECs leading to EWEs to ordinary ECs forming over and traversing the same regions.
An Analysis Of The Linkages Between Large-Scale Flow Regime Transitions On The Spatiotemporal Distribution Of Clustered Extratropical Cyclone Events Over The Northern Hemisphere, Eric Merton John Bunker
An Analysis Of The Linkages Between Large-Scale Flow Regime Transitions On The Spatiotemporal Distribution Of Clustered Extratropical Cyclone Events Over The Northern Hemisphere, Eric Merton John Bunker
Legacy Theses & Dissertations (2009 - 2024)
An Analysis of the Linkages Between Large-Scale Flow Regime Transitions on the Spatiotemporal Distribution of Clustered Extratropical Cyclone Events over the Northern Hemisphere
The Upper-Level Turbulence, Static Stability And Tropopause Structure Of Tropical Cyclones, Patrick Duran
The Upper-Level Turbulence, Static Stability And Tropopause Structure Of Tropical Cyclones, Patrick Duran
Legacy Theses & Dissertations (2009 - 2024)
Upper-tropospheric thermodynamic processes can play an important role in tropical cyclone (TC) structure and evolution. Despite its importance, until recently few in-situ observations were available in the upper levels of TCs. Two recent field campaigns -- the National Aeronautics and Space Administration (NASA) Hurricane and Severe Storm Sentinel (HS3) and the Office of Naval Research Tropical Cyclone Intensity (TCI) experiment -- provided a wealth of high-altitude observations within TCs. These observations revealed that the upper-level static stability and tropopause structure of TCs can change dramatically with both space and time.
Predictability Of African Easterly Waves In An Operational Ensemble Prediction System, Travis J. Elless
Predictability Of African Easterly Waves In An Operational Ensemble Prediction System, Travis J. Elless
Legacy Theses & Dissertations (2009 - 2024)
African easterly waves (AEWs) are the primary synoptic-scale weather feature found in sub-Saharan Africa during boreal summer. Many studies have used observations and idealized models to highlight processes associated with the movement and growth of AEWs, yet there have been few studies documenting the performance of operational ensemble prediction systems (EPSs) for these phenomena. Here, the predictability of AEWs in ECMWF EPS forecasts is assessed during two periods of enhanced AEW activity (July--September 2007--2009 and 2011--2013). Specifically, AEW predictability is analyzed through three main areas of focus: 1) verifying AEW position and intensity forecasts, and assessing their relation to convective …
Tropical Cyclone Rapid Intensification In Environments Of Upper-Tropospheric Troughs : Environmental Influences And Convective Characteristics, Michael Fischer
Tropical Cyclone Rapid Intensification In Environments Of Upper-Tropospheric Troughs : Environmental Influences And Convective Characteristics, Michael Fischer
Legacy Theses & Dissertations (2009 - 2024)
Intensity forecasts for tropical cyclones that undergo a period of rapid intensification are particularly susceptible to large errors. For those storms that interact with an upper-tropospheric trough, tropical cyclone intensity forecasts are complicated, as upper-tropospheric troughs can provide unique intensification mechanisms, but are often associated with unfavorable environmental conditions. Although tropical cyclones in environments with nearby upper-tropospheric troughs are associated with lesser intensification rates than tropical cyclones in environments devoid of upper-tropospheric troughs, some tropical cyclone--trough interactions are associated with a period of rapid intensification. This dissertation utilizes reanalysis output, satellite observations, and ensemble modeling simulations to understand whether rapid …
On The Role Of Western North Pacific Tropical Cyclones In Shaping The Extratropical Circulation Response To The Madden-Julian Oscillation, Lawrence Christian Gloeckler
On The Role Of Western North Pacific Tropical Cyclones In Shaping The Extratropical Circulation Response To The Madden-Julian Oscillation, Lawrence Christian Gloeckler
Legacy Theses & Dissertations (2009 - 2024)
Relationships between the Madden–Julian oscillation (MJO) and the extratropical circulation have been leveraged extensively to improve subseasonal prediction. However, in certain situations, tropical cyclones (TCs), which often coincide with enhanced MJO activity, can constructively or destructively interfere with MJO organization and common pathways through which the extratropics responds to the MJO. To examine this potential interference, the first portion of this study leverages a statistical experiment to relate West Pacific TC presence in different parts of the basin during a given MJO phase to subsequent remote extratropical circulation outcomes. The results of this experiment demonstrate that significant, high amplitude remote …
Influence Of Lightning-Producing Convection On Tropical Cyclone Intensity Change, Stephanie Stevenson
Influence Of Lightning-Producing Convection On Tropical Cyclone Intensity Change, Stephanie Stevenson
Legacy Theses & Dissertations (2009 - 2024)
Lightning observations in tropical cyclones (TCs) over the ocean are a recent advance- ment, and while many studies have noted relationships between lightning and TC intensity change, the relationships are not consistent. This dissertation aims to understand the com- plexities of the relationships between lightning and TC intensity change, and associate the relationships to storm kinematic, thermodynamic, and microphysical processes.
Tropical Cyclone Intensification Under Moderate Vertical Wind Shear, Rosimar Rios-Berrios
Tropical Cyclone Intensification Under Moderate Vertical Wind Shear, Rosimar Rios-Berrios
Legacy Theses & Dissertations (2009 - 2024)
Deep-layer (200–850 hPa) vertical wind shear is generally an inhibiting factor for tropical cyclone intensification. Multiple studies—ranging from case studies to climatological analyses—have consistently shown that the chances of tropical cyclone intensification decrease with increasing vertical wind shear magnitude. However, tropical cyclones can intensify under moderate shear—the range of shear magnitudes that are neither too weak to have negligible influence on intensity nor too strong to completely halt intensification. Intensity, track, and precipitation forecasts of tropical cyclones under moderate shear can be highly uncertain; therefore, explaining how tropical cyclones evolve under seemingly unfavorable conditions is an important step towards improved …
Variations In Potential Vorticity Streamer Activity : Development Pathways, Environmental Impacts, And Links To Tropical Cyclone Activity In The North Atlantic Basin, Philippe Pierre Papin
Variations In Potential Vorticity Streamer Activity : Development Pathways, Environmental Impacts, And Links To Tropical Cyclone Activity In The North Atlantic Basin, Philippe Pierre Papin
Legacy Theses & Dissertations (2009 - 2024)
This dissertation examines the climatological occurrence of potential vorticity streamers (PVSs) during the tropical cyclone (TC) season that occur in the upper troposphere in the North Atlantic (NATL) basin, assessing how their variations in frequency, area, and intensity impact the synoptic environment, how they are induced by different synoptic-dynamic patterns, and how they modify TC activity and genesis pathways.
Turbulence In The Upper Levels Of Tropical Cyclones, Michaela Leigh Rosenmayer
Turbulence In The Upper Levels Of Tropical Cyclones, Michaela Leigh Rosenmayer
Legacy Theses & Dissertations (2009 - 2024)
Turbulence in the cirrus canopy of tropical cyclones (TCs) can give an indication about the physical processes that occur in this expansive cloud deck. The low stability and/or large shear that likely coincides with turbulent layers can be produced by radiative forcing, convective forcing, and sublimation of frozen precipitation from the cirrus canopy. As a result, turbulence in the cirrus canopy can give an indication about the impact of various physical processes in tropical cyclones.
The Tropical Cyclone Diurnal Cycle, Jason Paul Dunion
The Tropical Cyclone Diurnal Cycle, Jason Paul Dunion
Legacy Theses & Dissertations (2009 - 2024)
The research presented in this thesis explores a phenomenon referred to as the tropical cyclone (TC) diurnal cycle (TCDC) and presents satellite, numerical modeling, and observational perspectives pertaining to how it can be monitored, its evolution in time and space, its relevance to TC structure and intensity, and how it manifests in numerical simulations of TCs. Infrared satellite imagery was developed and used to investigate diurnal oscillations in TCs and finds a diurnal pulsing pattern that occurs with notable regularity through a relatively deep layer from the inner core to the surrounding environment. A combination of satellite, numerical model simulations, …
Evolution Of African Easterly Waves And Their Relationship To Tropical Cyclogenesis, Alan Brammer
Evolution Of African Easterly Waves And Their Relationship To Tropical Cyclogenesis, Alan Brammer
Legacy Theses & Dissertations (2009 - 2024)
The research in this thesis explores the relationship between African easterly waves (AEWs) and tropical cyclogenesis over the eastern Atlantic. This research utilises 33 years of reanalysis and satellite data to investigate the interaction between AEW troughs, the surrounding environment and the embedded vortex.
Evaluating Preferred Direction Tropical Cyclone Track Variability In An Operational Global Ensemble Prediction System, Travis Elless
Evaluating Preferred Direction Tropical Cyclone Track Variability In An Operational Global Ensemble Prediction System, Travis Elless
Legacy Theses & Dissertations (2009 - 2024)
Ensemble forecasts of Tropical Storm Debby and Hurricane Sandy (2012) highlight instances where variability in tropical cyclone (TC) position forecasts are stretched along a preferred direction. The goal of this thesis is to analyze this stretching of variability in a global ensemble prediction system, particularly the European Centre for Medium-Range Weather Forecasts (ECMWF), to determine how often and under what conditions does variability stretching occur, and ultimately what feature(s) are responsible for generating this variability.
Diagnosis Of The Source Of Medium-Range Forecast Errors For An Extratropical Cyclone, William Lamberson
Diagnosis Of The Source Of Medium-Range Forecast Errors For An Extratropical Cyclone, William Lamberson
Legacy Theses & Dissertations (2009 - 2024)
Medium-range forecasts of an extratropical cyclone set to impact Western Europe on 16 Dec 2011 consistently predicted that the cyclone would be intense, with a minimum pressure as low as 930-hPa and an expansive area of high winds. In actuality, the cyclone never deepened below 965-hPa and its impact on Western Europe was minimal.
The Intensification Of Sheared Tropical Cyclones, Leon Nguyen
The Intensification Of Sheared Tropical Cyclones, Leon Nguyen
Legacy Theses & Dissertations (2009 - 2024)
Environmental vertical wind shear has been shown to have a generally detrimental impact on tropical cyclone (TC) intensity change. However, many cases of rapidly intensifying (RI) sheared TCs have been observed, and TCs in moderate (5-10 m s-1) shear often have the largest intensity forecast errors. Thus, advancing the understanding of TC-shear interactions is vital to improving TC intensity forecasts, which have not seen much improvement over the past few decades. This dissertation employs both observational and high-resolution numerical modeling approaches to investigate how some TCs are able to resist shear and intensify.