Tornado
The United States has the most tornadoes of any country, nearly four times more than estimated in all of Europe, excluding waterspouts. This is mostly due to the unique geography of the continent. North America is a large continent that extends from the tropics north into arctic areas, and has no major east-west mountain range to block air flow between these two areas. In the middle latitudes, where most tornadoes of the world occur, the Rocky Mountains block moisture and buckle the atmospheric flow, forcing drier air at mid-levels of the troposphere due to downsloped winds, and causing the formation of a low pressure area downwind to the east of the mountains. Increased westerly flow off the Rockies force the formation of a dry line when the flow aloft is strong, while the Gulf of Mexico fuels abundant low-level moisture in the southerly flow to its east. This unique topography allows for frequent collisions of warm and cold air, the conditions that breed strong, long-lived storms throughout the year. A large portion of these tornadoes form in an area of the central United States known as Tornado Alley. This area extends into Canada, particularly Ontario and the Prairie Provinces, although southeast Quebec, the interior of British Columbia, and western New Brunswick are also tornado-prone. Tornadoes also occur across northeastern Mexico.
List of United States tornadoes from January to February 2012
In January and February 2012, the local weather forecast offices of the National Weather Service confirmed 134 tornadoes in the United States, indicating an above-average period of tornadic activity. On average, 64 tornadoes occur in the first two months of the year, with 35 occurring in January and 29 in February. However, in 2012, the count for the two months was 79 and 55, respectively. The first confirmed tornado in January (and 2012) was an EF0 tornado which struck Fort Bend County in Texas at 1445 UTC on January 9. The last tornado of February was an EF0 that affected Blount County in Tennessee at 0030 UTC on March 1, though in terms of Central Time Zone, where the tornado took place, it was still February 29. The period's strongest tornado was ranked as an EF4 and occurred on February 29 in Saline and Gallatin counties in Illinois. Total economic losses in the United States from the first two months of 2012 amounted to over $600 million.