A synoptic climatology of tornadoes in the northeast United States

Benjamin, Andrew
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University of Delaware
A tornado climatology is constructed for the northeast United States. Few studies have focused on this portion of the country due to the fact that this region reports fewer tornados than the other areas of the United States. However, this region is highly susceptible to tornado damage as it boasts dense populations and includes several major cities where the risk of tornadoes is often ignored. This study provides a general climatology of tornadoes in the northeast United States from 1950-2010 by exploring the spatial and temporal characteristics of Northeast tornadoes in addition to potential population influences on tornado reporting. Additionally, 161 days defined as significant tornado days are used to examine the synoptic patterns and thermodynamic characteristics of Northeast tornado environments. The results indicate that tornado reports have increased since 1950, however most of this increase is due to better reporting practices and enhanced monitoring technology, especially Doppler radar. Tornadoes in the Northeast were most frequently reported in the late afternoon/early evening hours, between 1300-1900 LST. July was the peak month for tornado reports, while December reported the fewest. Around 75% of all Northeast tornadoes were given an Enhanced Fujita scale intensity rating of 1 or lower. A linear regression analysis found that approximately 38% of the variance in the spatial distribution of tornadoes can be explained by population. The composite synoptic maps indicate that Northeast tornado outbreaks are commonly associated with a 500 hPa trough and surface low pressure system over the Great Lakes. A distinct cold front is found ahead of the trough, separating warm, moist air in the Northeast from cooler and drier air to the west. Analysis of 00UTC soundings of several thermodynamic environments indicates that severe weather indices generally are less intense in Northeast tornado environments than in other parts of the country. Northeast tornadoes commonly form in low-CAPE environments. The information from this research should aid forecasters in their diagnosis of atmospheric conditions when trying to identify potential Northeast tornado environments.
Tornado , Northeast , Climatology , United States