UPDATE: A late report has been received. At 445 PM on 27 February, a tornado 15 miles northeast of Taft, California occurred. It was weak, lasted approximately 3 minutes, caused no damage, and was rated EF0. So, instead of no tornadoes in the calendar month, we have had one tornado reported in the US for February 2010.
There were no tornadoes reported in the United States in February 2010. Assuming that no late reports are received, it will be the first time in the National Weather Service’s database that starts in 1950 that there has been a February without a tornado. If we include Tom Grazulis’s database of F2 and stronger tornadoes, the last time it’s possible there wasn’t a February tornado was 1947. The last tornado reported in the US was on 24 January, in north-central Tennessee. The last calendar month without a tornado was January 2003.
What does this tell us about the rest of the 2010 tornado season? Somewhere between a little and nothing at all. Most years that have started out with few tornadoes have ended up average or below. However, there have been big exceptions. Most notably, in 2003, we started out with no tornadoes in the first 45 days of the year. Even as late as 29 April, it was the slowest start in the database (after adjusting for report inflation, as discussed here.) By the 11th of May, however, 2003 was well above normal following a remarkably active week. So, even though it’s been a slow start to the season, people still need to be aware of the threats that may happen later on.
What does it tell us about long-term trends? Again, essentially nothing. The large-scale atmospheric pattern that persisted over the US for the month of February was unfavorable for tornadoes. There’s nothing in the scientific literature that provides information on any changes to expect with tornadoes in the future, so the no-tornado February can’t be interpreted in that light.