Hurricane Irene and Tropical Storm Lee: How Unusual Were They in the Catskill Mountains?

Abstract

During the late summer and early autumn of 2011, the Catskill Mountains in south-central New York State experienced devastating flooding associated with former Hurricane Irene and former Tropical Storm Lee. Even in this particularly flood-prone region, the events of fall 2011 are perceived to be unique in the known history of the region and marked a turning point in the perceptions of residents about climate change. Here, precipitation and stream gage records are analyzed to determine just how unusual this season was. The historical precipitation gage record requires careful analysis due to the changing availability of stations. After a set of stations is developed that is appropriate for this analysis, events of lengths 1 day, 5 days, and 60 days are analyzed to identify regionally significant events (as opposed to events localized to one basin) since the early 20th century and to evaluate Irene and Lee in that historical context. Gage record results corroborate the perceptions of local residents that the period between 1996 and 2011, and in particular the events of fall 2011, were unprecedented in the last 100 years and as inferred from analyses of regional tree rings, probably in the last 500 years.

Hydrological and temperature variations between 1900 and 2016 in the Catskill Mountains, New York, USA

“…In this study, we identify a set of station‐based records suitable for examining climatic variations in the Catskill Mountains and the surrounding region of south‐central New York State. The identification of stations with temperature records of suitable length and completeness complements earlier work identifying suitable precipitation records (Frei and Kelly‐Voicu, ) which in combination with regional stream gauge records enables us to document regional variations in precipitation, streamflow, and temperature between 1900 and 2016. Both time‐domain and frequency‐domain analyses are performed.…”

“…Shown in bold are the stations that meet the 0.8 criteria for inclusion in the temperature analysis. Shown in italics are the stations that meet the 0.8 criteria for inclusion in the precipitation analysis of Frei and Kelly‐Voicu () (precision of lat/lon as appears in station meta data). The full set of stations considered for use in this analysis is provided in Supporting Information.…”

“…Large streamflow events are caused by a combination of antecedent conditions and precipitation (Lumia et al ., ; Ivancic and Shaw, ; Fang and Pomeroy, ). Antecedent conditions are associated with snowmelt and other cold season processes during spring, whereas in the fall they are associated primarily with soil saturation (Matonse and Frei, ; Frei and Kelly‐Voicu, ).…”

“…The station record, which extends back as far as the late 19th century at some stations, suggests that Catskill climatology varies from season to season and from decade to decade. For example, recent increasing trends in the frequency of extreme precipitation and streamflow have been stronger during the warm season than during the cold season (Frei et al ., ; Frei and Kelly‐Voicu, ). Average seasonal temperatures between 1895 and 2011 have increased more during winter than summer (Kunkel et al ., ).…”

“…In the Catskills, the wet period that followed the drought of the 1960s and continues into the 21st century appears to be unprecedented over the past 500 years (Pederson et al ., ). The station record indicates that the years 2003–2012 experienced the greatest frequency of warm season extreme hydrological events on record, and extreme 4‐day precipitation events during the warm season have increased in frequency by about 150% during the 2000s (Matonse and Frei, ; Frei and Kelly‐Voicu, ). The flooding events of August and September, 2011, which included Tropical Storms Irene and Lee, were the largest events on record (Frei and Kelly‐Voicu, ).…”