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Ice Here, Ice There, But There Wasn't Ice Everywhere |
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News release
issued January 24, 2001, effective immediately. Ice Here, Ice There, But There Wasn’t Ice Everywhere ARDMORE, Okla. — Residents in many parts of South Central Oklahoma are continuing to cope with broken limbs and debris from the devastating Dec. 25-26 ice storm that coated trees, fences and power lines with up to an inch and a half of solid, heavy ice. Meanwhile, residents in other parts of the region escaped with no ice problems whatsoever. Was it sheer luck, or did meteorological and geographic factors play the determining roles? At least a partial answer can be found in the temperature and rainfall data recorded by the Oklahoma Mesonet, a network of automated weather stations spread across the Sooner State from the Panhandle to Broken Bow. The Mesonet data indicated that areas closest to the Red River remained slightly above freezing during all or part of the rainfall event, while areas north of the Arbuckle Mountains hovered below the 32-degree mark during the same period. Temperatures in the intervening areas — including Ardmore and Madill — flirted with the freezing mark on Christmas Day and the following Tuesday. Local geography — such as elevation, proximity to large lakes and urban heat generation — also seemed to play a role in the intensity and duration of ice accumulation by influencing temperatures, even if by only a fraction of a degree. "When the air temperature is within half a degree or so of the freezing mark, it doesn’t take much to cause or prevent ice from forming on trees and power lines," explained Joe Lobell, communications manager for the Ardmore-based Noble Foundation. "Our horticultural and pecan specialists noticed a wide variation in tree damage over distances of only a mile or two. The Mesonet information shows us just how close to 32 degrees the surface temperatures were in many areas during the storm, and it was in those areas where the widest variations in ice damage occurred." "In the Ardmore area, most of the ice damage to pecan trees was to trees at a higher elevation. Where most of the trees are located in creek or river bottoms, there was little to no significant damage," said Scott Landgraf, a Noble Foundation pecan specialist. In Ada, for example, the temperature remained at or below 31 degrees for the entire two-day period. The lower temperatures aided in the accumulation of substantial quantities of ice in that area. At Burneyville — located along the Red River in southwestern Love County — the temperature averaged 33 degrees during the rainfall event, allowing almost all the rain to reach the ground in liquid form. In that area, according to Landgraf, the pecan trees came through with no ice damage. Complicating the problem was the quantity of rain that fell. Mesonet and other rainfall reporting sites logged between two and five inches of liquid equivalent precipitation — an extremely large amount for an ice storm event. The storm occurred when warm and extremely moist air streaming northward from the Gulf of Mexico at elevations between 3,000 and 10,000 feet overran near- or below-freezing air near the surface. Frozen precipitation falling through the relatively warm air quickly turned to liquid form. The layer of cold air at the surface was too shallow to change the rain to sleet before it reached the ground. To the south, where surface temperatures were just above freezing, the event proved to be nothing more than a persistent, cold rain. To the north, where cold air near the surface was deeper and colder, the precipitation fell mostly as sleet. Still further north, where the atmosphere was even colder, the precipitation reached the ground as snow. "The storm of Christmas 2000 was predicted several days in advance, but forecasters were unsure what type of precipitation would fall where," said Lobell, who spent two years as a weathercaster in Texas. "Obviously, three inches of rain would have been an inconvenience, but not a major problem. Three inches of sleet would have made driving a nightmare but probably would have spared the trees. "But had the temperatures been just a little lower and all that moisture fallen as sleet or snow, we might have had a very different problem on our hands," Lobell added. "Three inches of liquid moisture equals about 30 inches of snow. Had all of that precipitation come down in frozen form, we might be looking at collapsed roofs instead of broken limbs, especially on flat-roofed structures." Especially critical to the degree of ice accumulation were the temperatures from early afternoon on Christmas Day through late afternoon on Dec. 26 when the heaviest rains fell. Areas west of Interstate 35 tended to be colder on Dec. 26th while areas to the east of I-35 recorded colder temperatures during the Christmas Day rain. Graphs of temperature data from Mesonet sites in Ada, Ardmore, Burneyville, Centrahoma, Durant, Duncan, Madill, Pauls Valley, Ringling, Sulphur and Waurika can be accessed at http://www.noble.org under the Press Releases section. (Temperatures from the Mesonet site at Tishomingo were unavailable due to an equipment malfunction.) ### Graphical Temperature Data: Ada | Ardmore | Burneyville | Centrahoma | Duncan | Durant | Madill | Pauls Valley | Ringling | Sulphur | Waurika The Samuel Roberts Noble Foundation, headquartered in Ardmore, Okla., is a non-profit organization conducting agricultural, forage biotechnological, and plant biology research; providing grants to numerous non-profit charitable, educational and health organizations; and assisting farmers and ranchers through educational and consultative agricultural programs. To learn more, check out the Noble Foundation Web site at http://www.noble.org. More news releases available at www.noble.org/Press_Release |
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