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Comparison Of 2018-2021 Tropical Cyclone Track Forecasts Before And After Noaa G-Iv Missions, Melissa Piper
Comparison Of 2018-2021 Tropical Cyclone Track Forecasts Before And After Noaa G-Iv Missions, Melissa Piper
Legacy Theses & Dissertations (2009 - 2024)
Tropical cyclone (TC) hazards are primarily dictated by the TC position; thus, it is important to produce accurate TC track forecasts. Many different features can influence a TC’s motion, yet these features are not always well sampled by in-situ observations over the open ocean, creating a need for supplemental observation collected via aircraft, including the deployment of dropsondes. In 1997, the National Hurricane Center (NHC) began operational synoptic surveillance missions in the near-storm environments of TCs using the Gulfstream IV-SP jet aircraft (G-IV), with the goal of reducing track forecast errors. In the first 10 years of operational missions, the …
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 …
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 Impact Of North Pacific And North Atlantic Baroclinic Cyclones On Downstream Predictability, Adam Wayne Sisco
The Impact Of North Pacific And North Atlantic Baroclinic Cyclones On Downstream Predictability, Adam Wayne Sisco
Legacy Theses & Dissertations (2009 - 2024)
Baroclinic cyclogenesis can act as an impulsive disturbance along the midlatitude waveguide and promote the dispersion of Rossby waves, potentially impacting the predictability of the downstream midlatitude flow. Indeed, several studies have traced medium-range forecast errors and uncertainties to upstream cyclone development, especially when diabatic processes are involved in modifying the upper-tropospheric potential vorticity (PV) distribution. However, it remains unclear why some forecasts downstream of cyclogenesis are particularly uncertain while others are not. This study uses a 30-yr (1985–2014) sample of cool-season North Pacific and North Atlantic baroclinic cyclones and forecasts from the second-generation Global Ensemble Forecast System (GEFS) reforecast …
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.
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 …
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 …
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.
On The Mjo And Anticyclonic Wavebreaking, Kyle Macritchie
On The Mjo And Anticyclonic Wavebreaking, Kyle Macritchie
Legacy Theses & Dissertations (2009 - 2024)
The Madden Julian oscillation (MJO) is the primary mode of intraseasonal variability in the tropics. The MJO often couples with convection as it moves over the Indian Ocean and decouples as it leaves the west Pacific Ocean. The association between convection coupled to the MJO and the midlatitude flow pattern has been the primary focus of numerous studies. In particular, it has been shown that there is a statistical relationship between the position and strength of the MJO and anticyclonic wavebreaking (AWB). This study expands on this statistical relationship by examining, in detail, the two-way relationship between the MJO and …
Large-Scale Influences On The Pre-Genesis Of Tropical Cyclone Karl (2010), Kyle S. Griffin
Large-Scale Influences On The Pre-Genesis Of Tropical Cyclone Karl (2010), Kyle S. Griffin
Legacy Theses & Dissertations (2009 - 2024)
The genesis of Tropical Cyclone (TC) Karl (2010) in September 2010 provided a unique opportunity to examine the continuing problem of understanding tropical cyclogenesis. The precursor disturbance to Karl originated from a cluster of showers east of the Windward Islands and was well sampled by ongoing field campaigns, particularly the PRE-Depression Investigation of Cloud-systems in the Tropics (PREDICT), as the targeted disturbance progressed westward. While traditional genesis theories focusing on moisture and mass fields (e.g. top-down showerhead method) can explain the initial spin-up of the disturbance several days prior to its official genesis, additional perspectives are examined in concert with …