Tornadoes of 1999
Map of all tornadoes in the United States during 1999
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| Timespan | January–December 1999 |
|---|---|
| Maximum rated tornado |
F5 tornado
|
| Tornadoes in U.S. | 1,339 (Sixth-highest since 1952) |
| Damage (U.S.) | $2 billion |
| Fatalities (U.S.) | 94 |
| Fatalities (worldwide) | >94 |
This page documents the tornadoes and tornado outbreaks of 1999, primarily (but not entirely) in the United States. Most tornadoes form in the U.S., although some events may take place internationally, particularly in parts of neighboring southern Canada during the Northern Hemisphere's summer season. Some tornadoes also take place in Europe, e. g. in the United Kingdom or in Germany. One particular event, the Bridge Creek, Oklahoma F5 tornado, was known to produce the highest wind speed ever recorded on Earth, which was 301 ± 20 mph (484 ± 32 km/h).
During 1999, a total of 1,339 tornadoes touched down across the United States, ranking it as the fourth-most active year at the time; it has since been surpassed by two other years. The year began with the most active January on record, featuring 216 tornadoes. Culminating with the largest outbreak in the month, with over 100 tornadoes touching down on January 21 and 22 (surpassing the previous daily record of 39 on January 10, 1975), many records were broken. Due in large part to this outbreak, Arkansas saw more tornadoes in 1999 than any other year, with 107 recorded, and its most active January. The state also broke the record for most tornadoes in January of any state.
The European Severe Storms Laboratory maintains a database of all severe weather events across the continent. The vast majority of tornadoes go unrated due to a lack of surveys; however, some nations, such as France, provide detailed reports on these events. Of the 87 reported tornadoes during 1999, 45 were rated.
Exceptional tornado activity took place across the United States in January, with 216 tornadoes touching down, more than ten times the average of 20. This set the record for most tornadoes recorded in the month, and more than quadrupled the previous record of 52 set in 1975. January 21, 1999 marked the single-most active day in the month on record, with 87 tornadoes forming. The extreme activity during the month was attributed to an unusually spring-like setup, with a warm, moist air mass from the Gulf of Mexico flowing northward into an area with strong upper-level westerlies. The synoptic set up of these factors was typical of March or April rather than mid-winter.
On January 1, a strong upper-level low moved over Southeast Texas, while an accompanying surface low formed over North Texas. A cold front extended southward from this surface low into the Gulf of Mexico. Ahead of this front, a strong low level jet formed, bringing a surge of warm, moist air from the Gulf northward. The combination of these factors resulted in an unstable environment favoring the development of rotating supercell thunderstorms.
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