Record early tornado season set to add more to its tally today

March will roar in like a lion today over the Southern U.S., with another volley of strong EF2 and EF3 tornadoes possible over portions of Louisiana, Arkansas, and Mississippi. The Storm Prediction Center has placed this region under its "Moderate Risk" target today--one level below the maximum "High Risk" threat level. The powerful low pressure system responsible for today's severe weather developed over Texas and Oklahoma on Sunday, spawning at least two tornadoes and hail up to 4.25" in diameter. The huge hail was reported in Buffalo, near the Kansas border.

The intensifying low pressure system will move through Louisiana, Arkansas, and Mississippi today, dragging a cold front through those states. This front has already spawned severe thunderstorms across eastern Texas and southern Arkansas this morning, with many reports of damaging thunderstorm winds. The tornado page is a good place to track the tornadoes as they occur today, along with our severe weather page.

2008 sets early tornado season records
The year 2008 smashed the record for most January and February tornadoes, with 368. The previous record was set in 1999, with 235 January/February tornadoes. Reliable tornado records extend back to 1950. The 232 tornadoes reported in February of 2008 was a record for the month of February. Second place goes to 1971, with a relatively paltry 83 tornadoes. Each of the past three years has seen an unusually early start to tornado season (Figure 1). One would expect to see a shift in tornado activity earlier in the year in a warming climate, along with an earlier than usual drop off in activity in late spring. We can see that in both 2005 and 2006 that tornado activity dropped off much earlier than usual, and it will be interesting to see if 2008 follows a similar pattern. Note that there is a very high natural variability in tornado numbers, and the record for fewest ever January and February tornadoes was set just six years ago in 2002, when only four twisters occurred. It will be at least ten more years before we can say with any confidence that a warming climate is leading to an earlier peak in tornado season. There does seem to be a tendency for more early season tornadoes during La Niña years--four of the five years that had January/February tornado counts 75 or above were all La Niña years (1971, 1975, 1999, and 2008). The only exception was 1998, which was an El Niño year, and had 118 January/February tornadoes.


Figure 1. Tornado reports so far this year have totaled 368 for the months of January and February, by far the greatest number of tornadoes observed so early in the year. Image credit: NOAA Storm Prediction Center.

Potential South Atlantic subtropical storm fizzles
Last Friday, I mentioned the possibility of a rare subtropical storm forming the South Atlantic off the coast of Brazil. It turned out that the candidate low pressure system wrapped a lot of dry air into its center, killing any chance it had to become a subtropical storm. There is still some vigorous tropical-looking thunderstorms firing up off the coast of Brazil this morning, and it is worth continuing to watch this region for formation of a subtropical storm. A separate low pressure system in southern Brazil has brought a wide variety of severe weather to Brazil, Argentina, and Uruguay over the past few days, as documented in the metsul.com weather blog (for those of you who read Portugese). For those of you who don't, try the web page translator at http://babelfish.altavista.com/babelfish/tr.

Jeff Masters