Transcript Hail Frequencies and Patterns In Kansas and Oklahoma

Hail Frequencies, patterns, and
changes in Kansas and Oklahoma
Benjamin F. Grover
and
Dr. John F. Heinrichs
Introduction:
• Past studies have been done on hail trends in the
U.S. on the international scale, but have only
included data recorded from four different
stations in the state of Kansas and one in
Oklahoma. Results from this study for Kansas and
Oklahoma alone, found two different trends for
the region(Changnon, 1999).
• This study targets a smaller area utilizing more
detailed data.
Objective:
• The objective of this project is to determine
whether or not there is a recent trend or
pattern in hail events within Kansas and
Oklahoma.
Methods:
• The objective of this project was addressed using an empirical
analysis of hail data from January of 1971 through December
of 2007 (37 years) acquired on the county level for Kansas and
Oklahoma from NOAA’s National Climatic Data Center
webpage.
•
County level data was used because it gives a more detailed
statewide analysis than the three National Weather Service
stations used in previous studies can provide.
Methods:
• The data acquired came in spreadsheet format.
• It required manipulation in Excel to organize it appropriately
for use in the GIS.
• Use of formulas to obtain values arranged in a usable
format.
• The spreadsheets were joined to existing GIS vector data of
the two states’ counties acquired from the U.S. Fish and
Wildlife Service webpage and the Data Access and Support
Center.
Methods:
• The joined data layers were then manipulated in ArcMap to create
the various maps for observation and analysis.
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Total hail events by county
Total hail events per square mile by county
Total hail events per year, by specific hail stone diameter
Slope of hail events per 6, 12 and 37 year periods
Percent of Increase in hail events per 6, 12 and 37 year periods
Results:
Total hail events per county
– The possible error of hail report numbers varying due to different county areas
was questioned.
Results:
Average number of hail events per square mile
– From these two maps, a predominant concentration of hail events was
noticed in south central Kansas.
Results:
• To better understand this concentration of hail events, Oklahoma
was included in the analysis.
• After including Oklahoma, maps were created showing the slope
of hail events over different periods of the 37 year study period.
– The next three maps show the trends over two 12 year
periods and the last remaining 13 years.
Results:
Results:
Results:
• After observing these maps, it was noticed that in addition to the
concentration of hail events in south central Kansas, there is also an
increasing trend moving to the north.
Results:
Percent of Increase = Slope of events in study period / Mean number of events in study period
• This map also indicated a greater increase in Kansas hail events than in
Oklahoma, further supporting the northward movement of increasing hail events.
Conclusions:
• Sufficient evidence was found in this short study to
suggest that there is shift in hail events moving
northward from Oklahoma into Kansas.
• This northward shift shows a recent increase in hail
events in Kansas, and a decrease in Oklahoma over
the last 37 year study period.
Future Work:
• Possible causes of these trends to be
researched later include increasing westerly
winds across the mid-west pushing more dry
air into Kansas; or encroaching moist, humid
air from the south. Both of which could be
moving the boundary between dry cool air
and warm moist air (which creates hail and
tornado alley) further to the north.
Acknowledgements:
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Data used in analysis was acquired from: The National Oceanic and Atmospheric
Administration’s (NOAA) National Climatic Data Center webpage.
•
This project was funded by: The FHSU Geosciences Dept.
References:
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Changnon, Stanley and Changnon, David. (1999). Long-Term Fluctuations in Hail Incidences in
the United States. American Meteorological Society. 13. p658-664.
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Slide background image acquired from:
FusionNMT, Kyle M. Crockett
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Title Page Image acquired from:
http://www.abc.net.au/local/stories/2007/10/18/2063206.htm
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GIS data layers acquired from:
U.S. Fish and Wildlife Service and Data Access and Support Center Web pages