1. THUNDERSTORMS AND TORNADOES by Ernest M. Agee

2. An aerial view of a classic supercell thunderstorm above southern Maryland on 29 April 2002. At the time this photograph was taken this storm was producing twin tornadoes.

3. Two mini-tornado cyclones and associated wall clouds in Fort Cobb, Oklahoma.

4. Two mini-tornado cyclones each producing a single vortex tornado near Canadian, Texas (7 May 1986).

5. Colby, Kansas, 21 July 1996

6. Multiple vortex tornado, T m, near Friendship, Oklahoma (May 1982).

7. Multiple vortex columns in the formative stages of the Jarrell, Texas tornado of 27 May 1997.

10. Left: Radar image from the Quad Cities containing two supercells with well defined hook echoes (5:00 pm; 4/30/03). Right: Radar image from Tulsa, OK containing a squall line with embedded supercells ( 6:25 pm; 5/6/03).

11. Left: Radar image from San Angelo of squall line with bow echo and embedded supercells (4:30 pm; 4/7/02). Right: Radar image from Freederick, OK containing a supercell well defined hook echo (3:00 pm: 3/17/03).

12. Left: Radar image from Dallas/Forth Worth containing three supercells all with well defined hook echoes (9:20 pm; 4/5/03). Right: Radar image from Frederick, OK containing a supercell with a well defined hook echo (5:08 pm; 4/5/03).

13. First radar tracking of a tornado’s hook echo.

14. A Doppler radar image of a supercell thunderstorm near Oklahoma City on 3 May 1999. The image on the left shows a nice example of a hook echo radar feature that sometimes accompanies the mesocyclone. The image on the right shows the indication of the TVS, identified by ▼.

20. Horizontal flow relative to moving storm at 6.4 km above ground. Lengths of arrows are proportional to relative wind speed.