92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Sunday, 22 January 2012
Synoptic and Mesoscale Patterns Associated with 27 April 2011 Tornado Outbreak
Hall E (New Orleans Convention Center )
Fernanda Ramos-GarcÚs, University of Puerto Rico, San Juan, PR; and T. L. Salem Jr.

Every weather event is different; however, there are many of these events that have similarities. This is why the National Weather Service office in Memphis, Tennessee has aimed their efforts to improve severe tornado forecasting. Moreover, studies have shown that this region has the highest death rate do to tornadoes. Everything is not known about tornadogenesis, but one thing is: tornadoes tend to form within supercell thunderstorms. Hence, 27 April 2011 and 25 May 2011 were days when a Tornado Outbreak was expected to arise. Although 22 tornadoes struck the region on 27 April 2011, only 1 impacted the area on 25 May 2011. In order to understand both events, comparisons of their synoptic and mesoscale features were made. These parameters were studied using the Weather Event Simulator system and the NOAA/NWS Storm Prediction database. This research concentrated on the Surface Frontal Analysis, NAM40 700mb Dew-Points, NAM80 250mb Wind Speed and NAM20 500mb Vorticity images as well as 0-6 km Shear, MUCAPE and VGP mesoscale patterns. As result of this research a Dry-Line ahead of a Cold Front, Dew-points ░5C and higher, and Vorticity going from 15x10-5s-1 to 30x10-5s-1 were synoptic patterns that influenced to the formation on supercell tornadoes. Finally, MUCAPE and VGP favored the possibility of tornadoes occurrence on 25 May 2011, but shear was the factor that made 27 April 2011 a day for a Tornado Outbreak weather event.

 

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