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    Synoptic Climatological Analyses of Extreme Snowfalls in the Sierra Nevada

    Source: Weather and Forecasting:;2009:;volume( 024 ):;issue: 006::page 1610
    Author:
    O’Hara, Brian F.
    ,
    Kaplan, Michael L.
    ,
    Underwood, S. Jeffrey
    DOI: 10.1175/2009WAF2222249.1
    Publisher: American Meteorological Society
    Abstract: The Sierra Nevada of eastern California receives heavy snowfall each year. However, it is the snowstorms that deposit heavy snowfall in a relatively short period of time that can cause major inconveniences and even life-threatening situations for the residents and visitors to the region. Some of these snowstorms are so extreme as to become legendary, and with increased population in this region a synoptic climatology of these extreme snowstorms can be a useful tool for assessing snowfall potential by operational forecasters. Additionally, the hydrological and climatological implications of extreme Sierra Nevada snowfalls are important for state and local resource- and emergency-planning purposes. A climatology of these snowstorms will be presented. The period of study will include the snowfall seasons (October?May) 1949/50 through 2004/05. A total of 542 snowstorms occurred during these 56 snowfall seasons. These snowstorms were analyzed to determine any common synoptic features. The most intense snowstorms in the highest decile of snowfall totals were analyzed in more detail in order to determine the parameters associated with these strongest snowstorms. Upper-level synoptic and thermodynamic characteristics associated with each snowstorm were then diagnosed to determine what common synoptic hydrodynamic and thermodynamic parameters the snowstorms share. Synoptic patterns were studied using the National Centers for Environmental Prediction (NCEP) model reanalysis data. Wind speeds at 200 hPa, and height anomalies at 500 hPa, were analyzed for each snowstorm from 3 days prior to the start of snowfall and continuing through the end of the storm. Anomalies and the transport of precipitable water were studied in order to determine the relative amount of moisture that was available to each snowstorm. A conceptual model for forecasting the strongest snowstorms was developed. Key findings include the following: 1) the importance of a fetch of moisture from the subtropics with relatively large positive moisture anomalies, 2) the importance of the atmospheric moisture stream being normal to the Sierra, 3) the low static stability accompanying these snowstorms, and 4) the importance of relatively strong upper-level dynamics, which helped to intensify the systems as they approached the Sierra.
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      Synoptic Climatological Analyses of Extreme Snowfalls in the Sierra Nevada

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    contributor authorO’Hara, Brian F.
    contributor authorKaplan, Michael L.
    contributor authorUnderwood, S. Jeffrey
    date accessioned2017-06-09T16:32:47Z
    date available2017-06-09T16:32:47Z
    date copyright2009/12/01
    date issued2009
    identifier issn0882-8156
    identifier otherams-69745.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4211448
    description abstractThe Sierra Nevada of eastern California receives heavy snowfall each year. However, it is the snowstorms that deposit heavy snowfall in a relatively short period of time that can cause major inconveniences and even life-threatening situations for the residents and visitors to the region. Some of these snowstorms are so extreme as to become legendary, and with increased population in this region a synoptic climatology of these extreme snowstorms can be a useful tool for assessing snowfall potential by operational forecasters. Additionally, the hydrological and climatological implications of extreme Sierra Nevada snowfalls are important for state and local resource- and emergency-planning purposes. A climatology of these snowstorms will be presented. The period of study will include the snowfall seasons (October?May) 1949/50 through 2004/05. A total of 542 snowstorms occurred during these 56 snowfall seasons. These snowstorms were analyzed to determine any common synoptic features. The most intense snowstorms in the highest decile of snowfall totals were analyzed in more detail in order to determine the parameters associated with these strongest snowstorms. Upper-level synoptic and thermodynamic characteristics associated with each snowstorm were then diagnosed to determine what common synoptic hydrodynamic and thermodynamic parameters the snowstorms share. Synoptic patterns were studied using the National Centers for Environmental Prediction (NCEP) model reanalysis data. Wind speeds at 200 hPa, and height anomalies at 500 hPa, were analyzed for each snowstorm from 3 days prior to the start of snowfall and continuing through the end of the storm. Anomalies and the transport of precipitable water were studied in order to determine the relative amount of moisture that was available to each snowstorm. A conceptual model for forecasting the strongest snowstorms was developed. Key findings include the following: 1) the importance of a fetch of moisture from the subtropics with relatively large positive moisture anomalies, 2) the importance of the atmospheric moisture stream being normal to the Sierra, 3) the low static stability accompanying these snowstorms, and 4) the importance of relatively strong upper-level dynamics, which helped to intensify the systems as they approached the Sierra.
    publisherAmerican Meteorological Society
    titleSynoptic Climatological Analyses of Extreme Snowfalls in the Sierra Nevada
    typeJournal Paper
    journal volume24
    journal issue6
    journal titleWeather and Forecasting
    identifier doi10.1175/2009WAF2222249.1
    journal fristpage1610
    journal lastpage1624
    treeWeather and Forecasting:;2009:;volume( 024 ):;issue: 006
    contenttypeFulltext
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