1. AOSC 200 Lesson 18

2. Fig. 11-1, p. 312

3. Lifted Index A parcel of air will not rise unless it is unstable. The lifted index follows a parcel of air as it is lifted from the surface and cools at the dry adiabatic lapse rate until saturation occurs, and then cools at the wet adiabatic lapse rate. The lifted index is defined as: The environmental temperature at 500 mb minus the temperature of the parcel of air when lifted to 500 mb If the lifted index is negative then the atmosphere is unstable. Severe thunderstorms require a lifting index less than -3

4. Fig. 11.7 Life cycle of an ordinary thunderstorm cell

5. THUNDERSTORM GROWTH AND DEVELOPMENT AIR NEEDS TO BE UNSTABLE DRYLINE - LINE BETWEEN cT AND mT AIR MASSES-LEADS TO UNSTABLE AIR LIFTED INDEX - DIFFERENCE BETWEEN THE ACTUAL TEMPERATURE AT 500 MB, AND TEMPERATURE OF AIR PARCEL AFTER ADIABATIC EXPANSION TO 500 MB LIFTED INDEX IS NEGATIVE, AIR IS UNSTABLE VERTICAL WIND SHEAR CAN ‘SPIN UP’ THUNDERSTORM SEVERE THUNDERSTORMS - mT MEETS Cp. GREATEST CONTRAST - SPRING AND EARLY SUMMER CAPPING INVERSION

6. Fig. 11-3, p. 314 A climatology of the average number of thunderstorm days in a year

7. Fig. 11-4, p. 315

8. Table 11-1, p. 315

9. Fig. 11-10, p. 320 Schematic of a multicell thunderstorm. Red arrows represent the warm updraft, blue arrows the cool downdraft

10. Squall Line Is a set of individual intense thunderstorm cells arranged in a line. They occur along a boundary of unstable air – e.g. a cold front. Strong environmental wind shear causes the updraft to be tilted and separated from the downdraft. The dense cold air of the downdraft forms a ‘gust front’.

12. Fig. 11.10a Squall line associate with a cold front.

13. Fig. 11.13

14. Mesoscale Convective Complex A Mesoscale Convective Complex is composed of multiple single-cell storms in different stages of development. The individual thunderstorms must support the formation of other convective cells In order to last a long time, a good supply of moisture is required at low levels in te atmosphere.

15. Fig. 11-13, p. 322 Infrared image of a mesoscale convective complex over Kansas, July 8 1997.

16. SUPERCELL THUNDERSTORM SINGLE CELL THUNDERSTORM THAT PRODUCES DANGEROUS WEATHER REQUIRES A VERY UNSTABLE ATMOSPHERE AND STRONG VERTICAL WIND SHEAR - BOTH SPEED AND DIRECTION UNDER THE INFLUENCE OF THE STRONG WIND SHEAR THE ENTIRE THUNDERSTORM ROTATES FAVORED REGION IS THE SOUTHERN GREAT PLAINS IN THE SPRING

18. TYPE OF THUNDERSTORM SINGLE-CELL THUNDERSTORM MULTICELL THUNDERSTORM MESOSCALE CONVECTIVE C0MPLEX SUPERCELL THUNDERSTORM