THE OROTE POINT THUNDERSTORM: LEESIDE CONVECTION OVER GUAM’S NEARSHORE WATERS DURING THE SEASONAL TRANSITION
| dc.contributor.advisor | Chen, Yi-Leng | |
| dc.contributor.author | Hitzl, David Eugene | |
| dc.contributor.department | Atmospheric Sciences | |
| dc.date.accessioned | 2025-02-20T22:36:28Z | |
| dc.date.available | 2025-02-20T22:36:28Z | |
| dc.date.issued | 2024 | |
| dc.description.degree | Ph.D. | |
| dc.identifier.uri | https://hdl.handle.net/10125/110165 | |
| dc.subject | Meteorology | |
| dc.subject | Atmospheric sciences | |
| dc.subject | convection | |
| dc.subject | Guam | |
| dc.subject | mesoscale | |
| dc.subject | Micronesia | |
| dc.subject | orographic | |
| dc.subject | thunderstorms | |
| dc.title | THE OROTE POINT THUNDERSTORM: LEESIDE CONVECTION OVER GUAM’S NEARSHORE WATERS DURING THE SEASONAL TRANSITION | |
| dc.type | Thesis | |
| dcterms.abstract | The Orote Point Thunderstorm (OPT) is a recurring, mesoscale convective system which forms over Guam’s leeside waters during the monsoon seasonal transition and poses a hazard to local aviation. Historically underpredicted, OPT forecasting can be improved by greater understanding of its mechanisms through climatological analysis and the application of high-resolution mesoscale models. The OPT shares characteristics with small heat island convection and tropical, quasi-stationary, recurring thunderstorms found globally. Like these, it is supported by a seasonal transition pattern, including light to moderate trade winds (<= 7 m s-1), moderate to high CAPE (>1000 J kg-1), and high precipitable water (>40 mm) values. Uniquely, the OPT is triggered by island induced leeside convergence, which is optimized by easterly trades coupled with yearly maximum surface temperatures preceding and following the rainy season. A radar based OPT catalogue indicates greatest OPT frequency during the dry to wet season transition. A 2015-2020 ERA5 OPT climatology identifies the coinciding synoptic features as: ENE to ESE airflow, a weak upper-level trough, moderate to high CAPE and PWAT values (> 1000 J kg-1 and 40 mm, respectively) and steep mid-tropospheric e lapse rates. WRF 36-h daily, high-resolution (500-m) model runs with the Unified Noah Land Surface Model, Coastal Change Analysis Program, (C-CAP)) ground cover, and updated soil moisture are used to construct a 5-year mesoscale, seasonal transition (JJA), climatology. An OPT case study within the climatology demonstrates WRF’s skill in simulating the timing, location, and evolution of an OPT event as verified by multi-spectral satellite imagery. The mesoscale climatology reveals the interdependence of local pressure gradients, differential heating, mesoscale airflows, sensible and latent heat fluxes, and mesoscale vertical motions as they contribute to the development and maintenance of offshore convective cells. A model sensitivity test in which the terrain is replaced with a uniform surface at sea level reveals that the tip jet mechanism leading to local convergence and convection is primarily the result of afternoon land surface heating rather than local topography. | |
| dcterms.extent | 158 pages | |
| dcterms.language | en | |
| dcterms.publisher | University of Hawai'i at Manoa | |
| dcterms.rights | All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner. | |
| dcterms.type | Text | |
| local.identifier.alturi | http://dissertations.umi.com/hawii:12449 |