STORM TRACK: January 31, 1987 (Volume 10 Issue 2)
As the spring thaw arrives, it is the dawn of another chase season. A time to check the camera batteries, order film, and make sure the car is tuned up and reliable. What will the chase season be like this year? Will your wall be decorated with wall clouds by the end of the season or dust? Is there any way to forecast how the season will behave?
The editor has sought out those who are willing to stick their necks out and forecast the spring chase season. There is a consensus of opinion and the news is not good. Many forecasters say this year will be a below average year for catching tornadoes. Blame it on El Nino, a warm pacific ocean current which causes subtle weather changes, most notably droughts. Spring jet streams over the U.S. head southward for the winter causing more storminess over the Gulf. An increase in clouds over the Gulf causes cooler ocean surface temperatures which reduces evaporation. As El Nino weakens, a warm, high pressure system builds over the western states causing a rapid seasonal change into summer. Whether or not the effects of El Nino correlates to tornado frequency is still being debated, however, since El Nino strengthened during the spring of 1983 and continued, a drop in U.S. tornado frequency has occurred. Note the following maps from STORM DATA.
TORNADO STATISTICS YEAR FO F1 F2 F3 F4 F5 TOTAL 1982 152 92 34 15 1 0 294 1983 75 64 43 29 0 0 211 1984 62 71 27 9 0 0 169 1985 94 46 17 13 10 1 181 1986 101 58 10 4 0 0 173
May, 1982, was an above average tornado season for Oklahoma and Texas. Every other day there seemed to be tornadic storms in this area. Note several tornadoes also occurred in Missouri, Iowa, Nebraska, and Colorado. May, 1983, showed a shift in tornado frequency toward the east. The Gulf Coast States had a remarkable increase in the number of tornadoes, whereas the frequency in the Northern Plains decreased substantially from the previous year.
May, 1984, revealed fewer tornadoes across the U.S. The plain states were "void" of tornadoes making this one of the worst chase seasons in recent history. However, Alabama and Tennessee saw an increase in the number of tornadoes reported. Tornadoes were also few and far between in May, 1985. The Northern Plains seemed to have an average year, but Oklahoma and West Texas had few tornadoes. Note the Ohio and Pennsylvania outbreak shows up as a large cluster. Only in May, 1986, did the tornado frequency return to near normal in Oklahoma and West Texas. Was the reduction and shifting of the tornado maximum due to El Nino or was it just a statistical perturbation? Hmm. What will be remains to be seen. It could be
