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.

• 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.

• 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

Methods:

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.

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.

Results:

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.

• 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.

Future Work:

Acknowledgements:• 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:• Changnon, Stanley and Changnon, David. (1999). Long-Term Fluctuations in Hail Incidences in

the United States. American Meteorological Society. 13. p658-664.

• Slide background image acquired from:FusionNMT, Kyle M. Crockett

• Title Page Image acquired from: http://www.abc.net.au/local/stories/2007/10/18/2063206.htm

• GIS data layers acquired from: U.S. Fish and Wildlife Service and Data Access and Support Center Web pages