Hail - A Form of Solid Precipitation

Abstract

Hail is a form of rain or precipitation occurring during severe thunderstorms in warm weather conditions. Climatologists are very interested in predicting the size of hail, understanding that larger size hail is indicative of stronger storms. The best method for predicting the size of the hail is debatable. Three of these procedures will be discussed. They are very sophisticated methods with justifiable arguments for the validity of each method. All of the methods have gone through years of rigorous study and refining and nearly equally effective. The increased frequency of thunderstorms and severe thunderstorms over the last 10 to 15 years will be discussed and how they have resulted in damages caused by large falling hail in storms. The cost has risen into billions of dollars. Global warming is indicated as a reason for increased thunderstorm activity and so has the significant growth in America’s population. This has resulted in a worldwide critical interest in hail formation and the predictability of its causes

Hail - A Form of Solid Precipitation

Hail is a form of rain or precipitation. It usually occurs during a thunderstorm in warmer weather conditions. The winds going upward in a thunderstorm will move rain towards the freezing atmosphere. This causes the rain to freeze into ice and fall to the ground. Hail storms occur during severe thunderstorms. Since hail can cause a significant amount of damage to crops, houses and other property, the importance of predicting hail fall and its size is very important to meteorologists and climatologists. The severity and number of thunderstorms creating hail have increased in the last few years. There are several predictors of hailstorms and their varying sizes. These have been facilitated by weather monitoring services in the United States and the world.Hailstorms can be potentially very dangerous and are very damaging in the U.S. and the world. In 1995, in north Texas at an outdoor festival over 100 people were injured during a hailstorm. Hail storms have caused upwards of 2.6 billion dollars in crop and property damages each year (Jewell 2009). According to the State Farm Insurance Company in 2012 the number of damages rose to 3.9 billion. The states of Texas and Illinois had the heaviest amounts of damages (Association 2014). Hail sizes vary based on the size of the thunderstorms, therefore if the storm is severe enough the expected size of hail can be very damaging (University 2014). Although deaths caused by other severe weather conditions are higher, fatalities, though rare, have occurred as a result of hailstorms. The enormous amounts of damage and threats to life have produced open dialogues on how best to predict hailstorms and their potential danger to people.

One determinate of the severity of a hailstorm is based on the size of the hail itself. This appears to be the topic of several studies. Jewell and Brimelow prepared a study on a model to predict hail size called HAILCAST. This prediction model was successfully tested for six years at the Storm Prediction Center (Jewell 2009). The ability to predict the size of hail prior to convection is an understudied phenomenon. “Convective available potential energy (CAPE)” as stated in Jewel and Brimelow’s (2009: p.1592) journal article and “temperature levels aloft” (Winds and Temperatures Aloft Forecast) were used to unsuccessfully predict correct hail sizes. HAILCAST measures the diameter of a hail pellet. It utilizes sounds in the air for input, and the model creates companies of updrafts derived from a pattern of disturbances for a predefined location surface temperature and dew point (Jewell 2009). This is considered an authoritative method of predicting hail size.

HAILCAST is one method for predicting hail size; however, there are other scientific studies and observations. Cintineo, Smith, Brooks, and Ortega (2012: p.1236) argues that hail prediction based off of the “National Oceanic and Atmospheric Administration/National Climatic Data Center’s Storm Data publication” is somewhat inaccurate because there are no preselected reporting locations and the reports target low impact hail storms and does not report significantly on the severe hail storms. Also, the data is often based on the size of populations and other issues which are not meteorologically sound. Instead, Cintineo (2012: p.2235) notes to realize accurate calculation of hail size, dual radar technology should be utilized using “multi-radar multisensory algorithms (MRMS)” based on historical hail fall data collected over the years in the United States to determine the “maximum expected size of hail (MESH).” The MRMS-MESH system of defining hail size is considered to be a more exact approach.

The discussions over the best technique for hail size prediction are quite lengthy. Heinselman and Ryzhkov (2006) introduce what they say is a straightforward method, which is the polarimetric hydrometeor classification algorithm (HCA). Heinselman and Ryzhkov (2006: p.839) using a combination of “four radar variables: reflectivity, differential reflectivity, cross-correlation coefficient, and “reflectivity texture”’ to determine how rain and hail sound together in concert with other natural things going on at ground level. This is more accurate by 5% than the MRMS-MESH method which uses dual radar technology.

The accuracy of these three studies is very close and all can be used to quantify the size of hail. The use of algorithms and the latest radar technology and historical severe weather data will continue to come closer in predicting the size of hail, and the probability of hail fall. This is will help warn people to prepare so that damages can be kept at a minimum. The impact of hailstorms is felt all over the world. Finland has been observing hailstorm patterns for the last fifty years (Tuovinen 2008). China also conducted a significant study for the years 1951-1960 and from 1961- 2005 (Chunxi 2008). Both understand the implications of underestimating powerful storms and the impact of strong hail fall.

Now that it is established that hailstorms are a global concern, has the increase and intensity of severe weather storms help to bring hailstorms to the forefront? Changnon’s article confirms that in the last 10-15 years increases in severe storms have been documented (Changnon 2010). Thunderstorms have reported the greatest increases followed by hurricanes. These storms have significantly raised reported damages which impacts everyone. Naturally, it has become critical to predict where and when severe storms occur.

The insurance industry describes a storm as catastrophic when the damages exceed twenty-five million dollars. Between the years of 1949 and 2008 hail ranked three in the total number of storms reported, and fourth based on reported cost damages. Hurricanes, though small in the number reported, far exceeds other storms when comparing damages. (Changnon 2010)

From 1950 to 2008, almost sixty years, it is significant to note the six of 10 most intense hailstorms happen after 1986. Two hailstorms in 2002 and 2006 had the highest amount of damages. In 2002 Kansas City and Saint Louis were areas most significantly damaged by hailstorms. Changnon (2020: p.39) said that the damages were caused by “large and long lasting supercells.” He eluded that the urbanization of these areas may have been a factor since three to four decades earlier these were mostly rural areas. This may give some indication of specific conditions that might be contributing to climatic changes resulting in increased storm activity.

In April 2006 fifteen significant hailstorms attacked states in the Midwest area of the United States within twenty-four hours. The losses reported were nearly two billion dollars. Changnon (2010: p.42) explained that “The storms included a series of three long-track supercell storms that did extensive damage in Milwaukee, Wisconsin; Peoria, Illinois; Bloomington, Illinois; and Indianapolis, Indiana.”. In 2001 Saint Louis and Illinois experienced another devastating hail storm that is worth noting. It reported hail sizes between 2.5 to 7.5 in diameter fell during a short eight-hour period. The damages caused by this hailstorm were almost 2 billion dollars (Changnon 2003). This was also a long term supercell storm. The high winds, the large hail sizes and that the fell over populous areas are why the damage was so significant. History was made in Aurora, Nebraska in June 2003 because of the enormous hailstones which fell to the ground. Scientists found the largest hailstone recorded, however, though larger in measurable size it was not as dense or heavy as some other hailstones, and this is the more important measurement. The sizes were so significant that people kept the large ones in their freezers.

The increased frequency of thunderstorms can possibly be linked to climate change and the environment. However, the increased damage caused by thunderstorms, hailstorms, tornados, and other severe weather may be due to an increased population. The population in 2009 is twice that of 1950 (Changnon 2010). Therefore, the predictability of hail size becomes an important factor in understanding the severity of a storm and the ability to provide accurate information to the public.

The varying methods of predicting hail storms should continue to be utilized and perfected. They are all valid and should be used interchangeably. Climate change and population growth should be factored to perhaps enhance hail storm study and possibly avert increased occurrences of catastrophic events.

Reference List

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Cintineo, J. L., Smith, T. M., Lakshmanan, V., Brooks, H. E., & Ortega, L., (2012) An objective high-Resolution hail climatology of the contiguous united states. Cooperative Institute for Mesoscale Meteorological Studies, 27(5), pp. 1235-1247. Available from: Academic Search Complete [Accessed 26 February 2014].

Heinselman, P., & Ryzhkov, A., (2006) Validation of polarimetric hail detection. Cooperative-Institute for Mesoscale Meteorological Studies, 21(5), pp. 839-850. Available from: Academic Search Complete [Accessed 26 February 2014].

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Rocky Mountain Insurance Information Association, (2014) Hail. [Online] Available at http://www.rmiia.org/catastrophes_and_statistics/Hail.asp

Tuovinen, J., Punkka, A., Rauhala, J., Hohti, H., & Schultz, D., (2008) Climatology of severe hail in Finland 1930-2006. Monthly Weather Review, 137(7), pp. 2238-2249. Available from: Academic Search Complete [Accessed 26 February 2014].

University, A. S. T. A. &. M., (2014) Hail Formation. [Online] Available at: http://atmo.tamu.edu/weather-and-climate/weather-whys/673-hail-formation [Accessed 27 2 2014].