An Updated Severe Hail and Tornado Climatology for Eastern Colorado

Abstract

A localized tornado and severe hail climatology is updated and enhanced for eastern Colorado. This region is one of the most active severe weather areas in the United States because of its location immediately east of the Rocky Mountains, intrusions of Gulf of Mexico moisture into a dry climate, and various small-scale topographically forced features such as the “Denver Cyclone.” Since the 1950s, both annual tornado and severe (≥1.0 in.; 1 in. = 25.4 mm) hail reports and days have been increasing across the area, but several nonmeteorological factors distort the record. Of note is a large population bias in the severe hail data, with reports aligned along major roadways and in cities, and several field projects contributing to an absence of (E)F0 tornado reports [on the (enhanced) Fujita scale] in the 1980s. In the more consistently observed period since 1997, tornado reports and days show a slight decreasing trend while severe hail reports and days show an increasing trend, although large variability exists on the county level. Eastern Colorado tornadoes are predominantly weak, rarely above (E)F1 intensity, and with a maximum just east of the northern urban corridor. Severe hail has a maximum along the foothills and shows a trend toward a larger ratio of significant (≥2.0 in.; ≥50.8 mm) hail to severe hail reports over time. Both tornadoes and severe hail have trended toward shorter seasons since 1997, mostly attributable to an earlier end to the season. By assessing current and historical trends from a more localized perspective, small-scale climatological features and local societal impacts are exposed—features that national climatologies can miss.

Observation and numerical simulation of a weak waterspout at Hong Kong International Airport

“…Previous studies have described waterspouts over southern China in regions neighbouring Hong Kong, such as Zhuhai, which is immediately north of Macao (Chan et al ., 2020). While the observation, analysis and numerical prediction of tornados are well documented in the literature, particularly over the United States (Doswell III and Burgess, 1988; Stensrud et al ., 2009; Childs and Schumacher, 2019; Tao and Tamura, 2020), the arguably less destructive phenomenon of waterspouts has received less study (Golden, 1977; Niino et al ., 1997; Devanas and Stefanova, 2018; Rodríguez and Bech, 2018; Miglietta et al ., 2020).…”