Abstract
Abstract The method of k-means cluster analysis is applied to U.S. wintertime daily 850-hPa winds across the Northeast. The resulting weather patterns are analyzed in terms of duration, station, gridded precipitation, storm tracks, and climate teleconnections. Five distinct weather patterns are identified. Weather type (WT) 1 is characterized by a ridge over the western Atlantic and positive precipitation anomalies as far north as the Great Lakes; WT2, by a trough along the eastern United States and positive precipitation anomalies into southern New England; WT3, by a trough over the western Atlantic and negative precipitation anomalies along much of the U.S. East Coast; WT4, by a trough east of Newfoundland and negative precipitation anomalies along parts of the U.S. East Coast; and WT5, by a broad, shallow trough over southeastern Canada and negative precipitation anomalies over the entire U.S. East Coast. WT5 and WT1 are the most persistent, while WT2 typically progresses quickly to WT3 and then to WT4. Based on mean station precipitation in the northeastern United States, most precipitation occurs in WT2 and WT3, with the least in WT1 and WT4. Extreme precipitation occurs most frequently in WT2. Storm tracks show that WT2 and WT3 are associated with coastal storms, while WT2 is also associated with Great Lakes storms. Teleconnections are linked with a change in WT frequency by more than a factor of 2 in several cases: for the North Atlantic Oscillation (NAO) in WT1 and WT4 and for the Pacific–North American (PNA) pattern in WT1 and WT3.
Highlights
Weather type (WT) analysis is a way to objectively and compactly describe the climatology of main weather patterns for a region
The link between the WTs and large-scale circulation regimes is explored by investigating the relationship of each WT to several important climate teleconnections: the North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Pacific–North American (PNA) pattern, and El Niño–Southern Oscillation (ENSO)
Each WT is considered in terms of mean and anomalous 850-hPa winds and gridded precipitation, and the transitioning and persistence of each WT are analyzed
Summary
Weather type (WT) analysis is a way to objectively and compactly describe the climatology of main weather patterns for a region It can be used as a basis for understanding a broad scale of relationships such as flow. The goal of this paper is to objectively determine the primary daily circulation patterns over the northeastern United States during winter, and to examine their links to known teleconnections, synoptic regimes, and precipitation. We use WTs to better understand the link between synoptic patterns in the U.S Northeast and the larger-scale circulation. The link between the WTs and large-scale circulation regimes is explored by investigating the relationship of each WT to several important climate teleconnections: the North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Pacific–North American (PNA) pattern, and El Niño–Southern Oscillation (ENSO). A brief summary of the teleconnections and their links to Northeast weather follows
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