Published on October 5, 2007
Topographic Influences on Storm Motion: Topographic Influences on Storm Motion Baylee Balschmiter Dr. Steve Weinbeck Background: Background Channeling Suggested that topography has an effect on intensifying storms through channeling of winds (Wasula, Bosart, and Lapenta 2002; Riley and Bosart 1983; and Bracken et al. 1998). Background: Background Area of interest Arkansas Mountains Numerous Valleys Concentrated on the larger valleys in the Boston Mountains Background: Background 30R75 Approach Storms move thirty degrees right of the mean wind at seventy-five percent of the speed (Maddox, 1976). Bunkers Method (Bunkers et al. 2000) VRM = Vmean + D[(Vshear × k)/|Vshear| VLM = Vmean - D[(Vshear × k)/|Vshear| D is the magnitude of the deviation of the supercell motion from the mean wind Methodology: Methodology Severe Plot Looked for concentrated tornado paths 10 year period: 1995-2004 What kind of topography in area? Tornado paths How are the paths oriented to the mountain ranges? Methodology: Methodology Imagery from KSRX, KSHV, and KLZK radars Gibson Ridge Level 2 software Storm Motion Storm speed Storm Speed : Storm Speed Multiple step process Located two cities that storms moved over. Determined the time length for storm to travel from starting point to ending point. Used a 2006 road atlas to determine the distance between the two reference points. Methodology: Methodology RAOB version 5.2 software Calculated the storm motion and speed using the sounding data at Little Rock. Bunker’s method 30R75 approach Modified sounding to compensate for channeling Compared both “actual” data and modified data with radar observed storm motion and speed Methodology : Methodology Channeling of low level winds by valleys Using the major valleys of interest, determined the overall direction of the each valley. Took the average for one general channeling motion Assumed that this was the direction the wind would be channeled from. Also assumed that the speed would not change Results: Results Results: Results No difference between the “channeling” motion and the Bunker’s Method and 30R75 approach. Estimating for 0-6 km Conclusion: Conclusion Adjusting the data for channeling of winds did not change the storm motion and speed. Results: Results Conclusion: Conclusion Both methods did a relatively good at estimating the storm motion and speed. Bunkers method was good with estimating the direction of the storm on January 21-22, 1999. March 5-6, 1999 Both methods estimated motion 30R75 approach also represented the speed of the storm Results: Results Future: Future Examine more closely the January 21-22, 1999 storm to determine what other processes are involved in causing cells to veer from the overall storm path. Examine other topographic regions to determine if channeling has any effect on their storms. References: References Bracken, W.E., et al., 1998: Supercells and tornadogenesis over complex terrain: the great Barrington (MA) Memorial Day (1995) tornado. Preprints, 19th Conf. on Severe Local Storms, Minneapolis, MN, Amer. Meteor. Soc., 18-21. Bunkers, M.J., et al., 2000:Predicting supercell motion using a new hodograph technique. Wea. Forecasting, 15, 61-79. Maddox, R.A., 1976: An evaluation of tornado proximity wind and stability data. Mon. Wea. Rev., 104, 133-142. Riley, G.T., and L.F. Bosart, 1983: The Windsor Locks, Connecticut tornado of 3 October 1979: An analysis of an intermittent severe weather event. Mon. Wea. Rev., 115, 1655-1677 Wasula, A.C., L.F. Bosart, and K.D. Lapenta, 2002: The influence of terrain on the severe weather distribution across interior eastern New York and western New England. Wea. Forecasting, 17, 1277-1289.