Answer:
Last year in 2011, there were over 1800 tornado reports (of which about 1700 were confirmed), but the number of tornado warnings was higher as not all warnings correspond to a formal report. So the number of warnings issued in 2011 was likely well over 2000. However, 2011 was an extremely active tornado season. An average tornado season sees about 1200 tornadoes in the U.S., which would likely work out to about 1800-2000 warnings.