I have seen and heard about El Nino making a comeback this year. It supposeddly should persist into spring 2007. Does anyone have any thoughts on how it could effect the 2007 storm chase season, if it even will at all?
However, preliminary research indicates a relationship between El Nino and the occurrence of strong to violent tornado outbreaks over the Southeast United States. In the case of F2 and greater tornadoes, more appear to occur during La Nina months. La Nina seasons are normally associated with warmer than average temperatures in the South, producing a sharper frontal zone between warmer air and the normally cold arctic air to the north. During this time, Deep South weather is more unstable and colliding air masses set the stage for more tornadoes. A study of the top 15 tornadic outbreaks (at least 40 tornadoes) showed that only one outbreak occurred during an El Nino event. Six occurred during a La Nina event, while the remaining eight occurred during neutral ENSO years.
El Nino years taken regardless of strength are characterized by lower
than average total tornadoes, fewer than average violent tornadoes, and lower than average
chance of a tornado outbreak with 40 tornadoes or more.
Texas and Oklahoma often have more severe weather events during an El Nino because the upper air storm tracks more favor severe weather in that area. In the Texas South Plains and Panhandle, that has been what has happened in the past.
There are several sure-fire things to look for during an El Nino, especially a strong one.
1). Storm tracks are farther south, since the subtropical jet stream branch is more active. Tornadoes over the deep south, even Florida, were rampant during the 1997-98 El Nino.
2). Hurricane activity in the Atlantic basin is supressed. If storms do form, they recurve back out to sea or weaken altogether. This is because of the stronger westerly winds associated with the stronger subtropical jet as well as drier conditions over Africa.
3). Hurricane activity in the Pacific may increase, and storms recurve more frequently, threatening Mexico's mainland more.
4). If you surf, or like extratropical ocean storms, go to California during an El Nino winter and awe at 50 foot waves slamming a place called "Mavericks" near Half Moon Bay about 25 miles south of SFO.
5). The "pineapple connection" sets up during an El Nino, where a conveyor of warm, moist air rides the stronger subtropical jet stream from near Hawaii into S California (wetter than normal).
6). Typhoon activity in the western pacific is supressed, since the water there is cooler than normal. Australia and Asian mainlands are drier. South America is wetter and water is warmer in the Pacific off there.
El Nino is a GLOBAL weather pattern, even though it is just a warming of the eastern equilateral Pacific off South America. The ENSO is a cyclic strengthening (during La Nina) of the easterly trades, or weakening of them (during El Nino), and occurs every 2-5 years.