(OAR National Severe Storms Laboratory and Cooperative Institute for Mesoscale Meteorological Studies) Tornado path length forecasts from 2010 – 2011 using ensemble updraft helicity

Journal:  Weather and Forecasting (Early online release 1/14/13)

Authors:  Adam J. Clark, (CIMMS/NSSL) Jidong Gao,(NSSL) Patrick T. Marsh, (CIMMS/NSSL) Travis Smith, (CIMMS/NSSL) John S. Kain,(NSSL) James Correia, Jr., Ming Xue, and Fanyou Kong

Summary
This paper adds new data to previous research that diagnosed a strong relationship between the cumulative path lengths of simulated rotating storms (measured using a 3-dimensional object identification algorithm applied to forecast updraft helicity) and the cumulative path lengths of tornadoes. The new forecast examples are from three major 2011 tornado outbreaks – 16 and 27 April, and 24 May, as well as two forecast failure cases from June 2010. Finally, analysis updraft helicity from 27 April 2011 is computed using a three-dimensional variational data assimilation system to obtain 1.25 km grid-spacing analyses at 5-minute intervals and compared to forecast UH from individual SSEF members.

Important conclusions:   Forecast updraft helicity pathlengths during the spring could be a very skillfull predictor for the severity of tornado outbreaks as measured by total pathlengths.

Significance:  Efforts continue to find better ways to predict tornadoes and tornado outbreaks  Weather and Forecasting (Early online release 1/14/13)

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(OAR-National Severe Storms Laboratory) A Unified Flash Flood Database over the US

Journal:  Bulletin of the American Meteorological Society (early online release 1/25/13)

Authors:  Jonathan J. Gourley (NSSL), Yang Hong, Zachary L. Flamig (NSSL), Ami Arthur (NSSL/CIMMS), Robert Clark (NSSL/CIMMS), Martin Calianno, Isabelle Ruin, Terry Ortel, Michael E. Wieczorek, Pierre-Emmanuel Kirstetter (NSSL), Edward Clark, Witold F. Krajewski

Summary:  This study is the first of its kind to assemble, reprocess, describe, and disseminate a georeferenced US database providing a long-term, detailed characterization of flash flooding in terms of spatiotemporal behavior and specificity of impacts. The database is comprised of three primary sources: 1) the entire archive of automated discharge observations from the US Geological Survey that has been reprocessed to describe individual flooding events, 2) flash flooding reports collected by the National Weather Service from 2006-present, and 3) witness reports obtained directly from the public in the Severe Hazards Analysis and Verification Experiment during the summers 2008–2010.

Important conclusions:  A major asset of the unified flash flood database is its collation of relevant information from a variety of sources that is now readily available to the community in common formats.

Significance:  It is anticipated that this database will be used for many diverse purposes such as evaluating tools to predict flash flooding, characterizing seasonal and regional trends, and improving understanding of dominant flood-producing processes.   Bulletin of the American Meteorological Society (early online release 1/25/13)

Authors:  Jonathan J. Gourley (NSSL), Yang Hong, Zachary L. Flamig (NSSL), Ami Arthur (NSSL/CIMMS), Robert Clark (NSSL/CIMMS), Martin Calianno, Isabelle Ruin, Terry Ortel, Michael E. Wieczorek, Pierre-Emmanuel Kirstetter (NSSL), Edward Clark, Witold F. Krajewski

Summary:  This study is the first of its kind to assemble, reprocess, describe, and disseminate a georeferenced US database providing a long-term, detailed characterization of flash flooding in terms of spatiotemporal behavior and specificity of impacts. The database is comprised of three primary sources: 1) the entire archive of automated discharge observations from the US Geological Survey that has been reprocessed to describe individual flooding events, 2) flash flooding reports collected by the National Weather Service from 2006-present, and 3) witness reports obtained directly from the public in the Severe Hazards Analysis and Verification Experiment during the summers 2008–2010.

Important conclusions:  A major asset of the unified flash flood database is its collation of relevant information from a variety of sources that is now readily available to the community in common formats.

Significance:  It is anticipated that this database will be used for many diverse purposes such as evaluating tools to predict flash flooding, characterizing seasonal and regional trends, and improving understanding of dominant flood-producing processes.