Thesis (Ph. D.)--University of Hong Kong, 1984.

The Atlantic hurricane of May 1951 had several interesting characteristics. Chief among these were the high latitude and early season of its origin, the type of air mass in which it formed, its formation in a cold core low that extended high than the 200-mb level, and the loop in its path. There was not available enough observational data within and near the storm in order to make a detailed study sufficient to completely explain these phenomena. Some of the meteorological conditions observed shortly proceeding and during the existence of this storm were studied and are described here. Its formation and movement is analyzed and discussed in relation to various theories on the origin and movement of hurricanes. / Typescript. / "Submitted to the Graduate Council of Florida State University in partial fulfillment of the requirements for the degree of Master of Science." / "August, 1952." / Includes bibliographical references (leaves 15-16).

Evolutionary periods of precipitation distribution in tropical cyclones (TCs) are sometimes misrepresented in numerical weather prediction models due to the rapid nature of TC structure changes that accompany intensity change. To better understand quantitative changes in TC rainband structure around landfall, I quantify the spatial distribution of precipitation in 62 landfalling TCs along the Gulf of Mexico and Atlantic coasts of the U.S. between 1998 and 2014. The Tropical Rainfall Measuring Mission (TRMM) 3B42 product is utilized to assess three spatial measures of precipitation: 1) area, 2) closure, and 3) dispersion. Calculations are made using two rain rate thresholds, 0.254mm/hr and 5mm/hr, to capture and compare changes in light and heavy precipitation, respectively. Changes in TC precipitation are statistically different based on landfall location along the Atlantic vs. Gulf. Overall, dispersion (measure of centrality) is the most dissimilar metric due to variability between 0.254mm/hr and 5mm/hr results. Lighter precipitation decreases in area and expands away from the TC center, while heavier precipitation contracts rather than disperses in Gulf landfalling storms. A k-means clustering produces six landfall regions and reinforces the result of heavier precipitation becoming more central along the Gulf, while Atlantic landfalling storms exhibit decreased centrality. Significant differences were not found in storms that undergo extratropical transition or dissipate later in lifecycle. The holistic approach exhibited by this study reveals wide variability among a large dataset of storms making landfall; therefore, sub-setting techniques are helpful to hurricane forecasters in understanding the role of landfall location. / MS / As our coastal communities become progressively vulnerable due to increased urbanization and settlement along United States coastlines, natural disasters, such as flooding caused by hurricanes and nor’easters, will continue to cripple coastal populations. Strong winds, storm surge, and heavy rains upon landfall during tropical cyclones produce billions of dollars’ worth of damage to infrastructure and natural resources. By understanding structural changes of hurricanes in terms of the spatial coverage of rainbands before, during, and just after landfall, operational meteorologists will be better equipped to aid in public preparedness and provide improved rainfall forecasts to emergency management personnel. This research examines the structural changes in precipitation as hurricanes make landfall along the Gulf of Mexico and Atlantic coasts of the U.S. using three shape metrics; 1) area (2-D coverage), 2) closure (proportion around storm center), and 3) dispersion (spread away from storm center). Precipitation is subset into light (0.254 mmhr⁻¹ ) and heavy (5 mmhr⁻¹ ) rain rates in order to capture and compare the structural changes of 62 landfalling hurricanes between 1998 and 2014. I find that the average precipitation distributions of Gulf and Atlantic landfalling hurricanes at the time of landfall are similar; however, there are important changes in these distribution based on landfall location. Specifically, Gulf storms become larger and heavy rain contracts around the TC center, while Atlantic storms become asymmetric and spread out through landfall. These results demonstrate the importance of landfall location and the role that environmental factors may play in determining how hazards related to flooding can evolve along the U.S. coastline.

Thesis (M.S.)--Naval Postgraduate School, 2002. / Thesis advisor(s): Russell L. Elsberry, Patrick A. Harr. Includes bibliographical references (p. 69). Also available online.

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Russell L. Elsberry. Includes bibliographical references (p. 103-105). Also available online.

The Air Force Weather Agency (AFWA) version of the Advanced Research Weather Research and Forecasting (ARW) model with a moving 4-km nested grid is examined for 10 track and intensity predictions of six western North Pacific tropical cyclones during 2005. In three of the 10 integrations, the ARW vortex tracker algorithm based on the 500-mb height minimum failed to appropriately move the nest and thus lost track of the storm vortex. For the other seven cases, the ARW track forecasts are more skillful than the AFWA MM5 forecasts and (except at 12 h) the CLIPER-type forecasts. The ARW intensity forecasts were less skillful than the MM5 and CLIPER-type forecasts at all forecast intervals, and were severely degraded by a large negative bias at the initial time. The deficiency in these intensity forecasts is shown to be related to model spin-up (lasting 12-54 h) problems caused by the lack of a bogus vortex and a cold start initialization from the interpolation of the NCEP Global Forecast System (GFS) analysis to the 12- km and 4-km grids. Thus, a more appropriate initial vortex representation will be required to improve intensity forecasts.

A mesoscale tropical channel model is constructed to study the long-standing problem of the initiation of the Madden-Julian Oscillation (MJO). Two observed cases of MJO are chosen, one in boreal spring and one in boreal winter, without a priori knowledge of their initiation mechanism. With initial and lateral boundary conditions provided by a global reanalysis, this model is able to reproduce the initiation and gross features of two observed MJO events up to two months after the start of simulations. This leads to a conjecture that these two MJO events are generated by the influences from the lateral boundaries. This conjecture is supported by a series of sensitivity tests. These sensitivity tests demonstrate that the simulated MJO initiation does not critically depend on detailed characteristics of sea surface temperature (varying vs. constant in time, mean distribution from boreal spring vs. winter), initial conditions (within a 10 day period, perturbations in the initial conditions), the latitudinal location of the lateral boundaries (21 - 45˚N and S), and even latent heating and moist processes. The only factor found critical to the reproduction of the MJO initiation is time varying lateral boundary conditions from the reanalysis. When such lateral boundary conditions are replaced by time independent conditions, the model fails to reproduce the MJO initiation. The analysis of moist static energy has revealed that the discharge-recharge mechanism is not sufficient for the MJO initiation in the model. It is found that the latitudinal transport of westerly momentum from the extratropics is crucial in generating the lower tropospheric westerlies in the reanalysis and model. The energy source for the extratropical perturbation is through extraction of kinetic energy from the mean flow. The estimation of wave activity flux has revealed that there is a major region over the southern Indian Ocean, which produces wave activity flux towards the tropical genesis region of the MJO initiation. We have also investigated the time-scale of the boundary conditions that are responsible for the MJO initiation. Additions of small perturbations in the boundary conditions, and use of 10-day interpolated boundary conditions do not affect the MJO initiation. Thus boundary conditions responsible for the MJO initiation in the model must have time scales greater than 10 days, indicating that the shorter time scale stochastic forcing through the lateral boundaries did not play any major role. The estimation of the zonal momentum budget for the MJO initiation region has revealed the importance of the advective terms, particularly by the meridional winds before the onset of the MJO. The importance of the extratropical influences in initiating the MJO in the channel model leads to a speculation that a multi-year simulation using a tropical channel model would also produce reasonable MJO statistics if forced by time varying boundary conditions. Interestingly, the MJO statistics in the multi-year simulation using a tropical channel model is found to be not better than the global models. Increase of horizontal resolution and use of a different cumulus scheme did not improve the MJO simulation. We found that the error in the mean state was the main reason for the lack of MJO statistics in the model. The model took less than five days for the error to reach its climate bias. Thus, a good simulation of the mean state is important for the successful simulation of the MJO. Implications of these results are discussed. In short, this study has shown that the extratropical influences can be an efficient mechanism for the MJO initiation and calls for further research attention to this mechanism that has been somewhat neglected by mainstream MJO research.

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2004. / Thesis advisor(s): Patrick A. Harr, Russell L. Elsberry. Includes bibliographical references (p. 117-118). Also available online.

Thesis (Ph.D.)--George Mason University, 2008. / Vita: p. 160. Thesis director: Ben P. Kirtman. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Climate Dynamics. Title from PDF t.p. (viewed July 18, 2008). Includes bibliographical references (p. 152-159). Also issued in print.

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): C.-P. Chang. Includes bibliographical references (p. 49-51). Also available online.