Creating a Database of All-Time Monthly Sea Level Pressure Records for the Lower 48 United States
Roth, David Mark
In recent years, extratropical storms?those associated with temperature and moisture differences within their circulation?have gained unprecedented attention. This is thanks to a record-breaking late October 2010 storm in the northern Plains and Hurricane Sandy's impact, including high winds and a high storm surge near its point of landfall as an extratropical storm on the northern mid-Atlantic states in late October 2012. The intensity of these storms?as measured in large part by record-setting low sea level pressures?and the headlines they made added pressure to scientists who were already looking to compile data from extratropical storms to answer questions about climate change.
The strongest extratropical cyclones have central sea level pressures that rival those in some Category 5 hurricanes on the Saffir-Simpson Scale. The October 2010 Northern Plains storm was provisionally declared the strongest extratropical cyclone to affect the Lower 48 United States. This could not be confirmed due to the relative dearth of information regarding sea level pressure extremes for extratropical cyclones. Later, crowd sourcing within the meteorological community determined it was the strongest extratropical storm to affect the United States between the Rockies and the Appalachians.<br>In general, the strongest extratropical cyclones occur during the winter season, when the upper disturbances that spawn them reach their peak strength. This is driven by the temperature differential between the poles and equator, which helps to strengthen the jet stream during the fall, winter, and spring months.<br>In the wake of this storm and Hurricane Sandy, and to help predict future record-breaking extratropical storms and improve forecasting and warnings, the United States Signal Corp, the United States Weather Bureau, and the National Weather Service took the necessary steps to compute sea level pressure data in real-time from 1871 to present, similar to other atmospheric quantities. However, datasets for sea level pressure and other characteristics of extratropical cyclones are neither well organized nor easily accessible, which makes analysis of the data a challenge.
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