- climate change,
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- The Outside Story,
Today and yesterday mark the anniversary of one of the deadliest outbreaks of tornado activity in the history of the United States. In just an 18 hour period from April 3rd and 4th of 1974, a deadly outbreak of severe weather spawn across 13 states including Alabama, Georgia, Illinois, Indiana, Kentucky, Michigan, Mississippi, North Carolina, Ohio, South Carolina, Tennessee, Virginia and West Virginia producing tornado damage of about 900 square miles (Fig 1 & 2).
Fig: 1 ( Courtesy: TornadoHistoryProject)
Fig. 2 (Courtesy of NOAA)
The US experienced around 148* tornadoes with half being a F2 on the Fujita scale, and monster tornadoes, 24* F4’s and 6* F5’s (fig. 3) or higher, to have a combined path of 2598 miles and 1881 of those tornadoes had paths over 1 mile long. By the end, ten out of the thirteen states hit were declared disaster areas killing 335* people and injuring over 6000.
Fig. 3rd (below shows the Fujita Scale which was incorporated in 1971 and later validated by its importance by Ted Fujita and his colleagues after the 1974 Super Outbreak--the scale was later revised February 1st, 2007).
- About 1,200 tornadoes hit the US each year and tornadoes kill on average about 60 people per year, mostly from flying/falling debris. From this particular event, over 15,000 homes, farms and business were destroyed and another 17,000 building were damaged. Of those that died, 74% were killed while in houses or buildings, 17% in mobile homes, 6% in automobiles and 3% while seeking shelter.
(Destruction in Northfield, Kentucky. Courtesy of Russ Conger/NWS)
It all began on the afternoon of April 1st when in the upper levels off the coast of northern California and Oregon, a strong baroclinic wave was detected. This with an associated cold front moving through Nevada and Idaho would later produce extremely severe weather over the eastern US.
It seemed the days leading up to the Super Outbreak of April 1974, the ingredients were just right and falling into place for a major weather event across the south and eastern portions of the United States. As the wave was moving inland from the Pacific, low level cyclogenesis was occurring over the Great Basin and Southern Rockies. This wave moved to the east-southeast and along with a strong polar jet this wave amplified. On the evening of April 2nd, the surface low strengthened east of the Rocky Mountains and continued its eastward movement across the United States picking up moist and warm air from the Gulf of Mexico clashing with an upper level layer of warm dry air from the southwestern states. The central pressure of this low was 983 mb (Hurricane Sandy central pressure was 946 mb at landfall along the coast of Southern New Jersey and Hurricane Katrina was at 902 mb at its most intense-920 mb at its second landfall in Buras-Triumph, Louisana) and the circulation of this low was approximately 1200 miles in diameter. The moist air continued to stream from the low toward the OH Valley and the lower Midwest states. So with a strong upper level jet, the moist air at the surface and the dry air in the upper levels, a large region of subsidence formed (where the dry air was sinking onto the lower moist air which acts like a lid, keeping the moist air from rising and dissipating energy) meaning that conditions were quickly becoming unstable and favorable for a severe weather event. This increased even more the morning of April 3rd as the sun began to continue to add energy to an already extremely dangerous atmospheric situation. So with the area of low pressure marching eastward across the US, the Gulf providing warm moist surface air, dry air in the upper level, subsidence occurring because of this and then solar heating?-->Large severe weather outbreak stretching over thirteen states and a portion of Canada.
(Below: April 3rd 1974 3:11PM EST)
- (Below: April 3rd, 5:54 PM EST)
- (Below: April 3rd, 9:00 PM EST)
However, a advance in technology that was desperately needed came with this outbreak. At the time, forecasters at the National weather service had to wait for visual confirmation of tornadoes before issuing any sort of warning which were all made my hand and sent over by a teletype machine (Fig. 4 & 5)
Fig. 4- a gentleman by the name of Pat Iannelli prepares to transmit a forecast through the teletype machine in Parkersburg, WV. During the outbreak of 1974, weather offices continued to experience slow reaction time with these machines due to the high volume of traffic during the event)
- Below Fig. 5 - Teletype machines lined up in the Fort Wayne NWS office at Baer Field, June 1967. They were installed April 18, 1961. Facsimile machines to receive weather maps were installed April 1, 1960.
Fig 6: Main workstation at NWS Fort Wayne in July 1968.
Radar was only adept to pick up green blobs that was better suited to picking up solid objects as opposed to clouds and rain and very few television stations had radar-and most that did were in black and white (Fig 6).
Fig. 6 shows a hook pattern in the radar which is synonymous with severe weather, possibly a tornado.
With the historical events of April 3rd and 4th of 1974, advances in radar were made with NEXRAD and Doppler Radar-the same technology that we use today, with improvements every year. The current average lead-time for tornadoes has now been increased to 13 minutes.
*In my research, I have seen differing information on the number of recorded tornadoes (give or take 1 or 2) as well as the number of fatalities. This is evident in my numbers and graphics. Nonetheless, even with these varying factors, this outbreak without a doubt continues to be recorded as one of the deadliest outbreaks in American History.