2017 Central Florida tornado outbreak

The 2017 Central Florida tornado outbreak was a very unusual tornado outbreak across the state of Florida that occurred on May 23, 2017. This outbreak was the largest not in relation to a tropical cyclone to ever affect the state of Florida—producing 18 tornadoes, including multiple in the vicinity of Orlando. This outbreak was also the deadliest in the state's history, with most of the deaths attributed to a particularly destructive EF5 tornado that struck the Orlando suburb of Mount Dora, which caused 245 deaths.

The Mount Dora tornado was 3/4 of a mile (1.2 km) wide at its peak and tracked across the ground for 7.2 miles (11.6 km), inflicting some of the most violent damage ever produced from a tornado; killing 245 out of 12,534 residents in the process. The Wolf Branch subdivision of the city was literally wiped off the face of the earth, with all 518 homes in the neighborhood reduced to concrete slabs and leaving the remaining pieces of the structures either wind-rowed or finely granulated. Trees in the area were completely shredded and debarked, and grassy fields around the area were scoured to a depth of 20 inches. This was the first tornado of such intensity in the state - as well as the deadliest; and stands as one of the deadliest on record in the US.

In addition to the Mount Dora tornado, the outbreak spawned several other significant tornadoes: one EF4 tornado and three EF3 tornadoes.

Meteorological synopsis
In the late evening hours of May 22, a mesoscale convective complex had developed in Georgia and the southern portion of South Carolina. The MCS moved slowly eastward, generating gravity waves (outflow boundary) oriented from the northeast to the southwest that radiated away from the system as it eventually moved off of land and into the Atlantic. One of these gravity waves appears to have played a role in the initiation of the thunderstorm complex that eventually produced the tornado activity when it intersected the cold front in the vicinity of St. Augustine, causing the movement of the supercells and tornadoes later on to be in the southwest. However, this gravity wave moved south of the storm complex before the beginning of the tornado activity.



During the mid-afternoon and early evening of May 23, 2017, a severe weather outbreak produced numerous severe thunderstorms and multiple tornadoes across central Florida. The synoptic weather situation that occurred was an extremely atypical pattern for springtime Florida tornadoes. Most Florida tornadoes are usually associated with a “weak” meteorological pattern of typical thunderstorms that produce short-lived and often weak waterspouts. On this day, the 500 mb low center was located well to the northeast in the Atlantic, and the upper level jet stream axis was over northern Oklahoma. There was not a well defined low-level jet. A weak cold front extended from northeastern Florida in the St. Augustine area southwestward to near Bradenton. The numerous severe thunderstorms that occurred throughout central Florida developed in a situation of weak wind shear and high thermodynamic instability, along the surface boundary, where the greatest threat is typically strong winds and large hail. On this day in central Florida, there were 60 reports of severe weather—12 for large hail and 48 for tornadoes.

EF5 Mount Dora tornado
Initially a weak, pencil-like tornado upon touchdown in Eustis, the tornado tracked to the southwest for two miles, striking several homes and businesses and crossed over Lake Seneca, producing EF2 damage prior to entering the extreme northern city limits of Mount Dora, where it rapidly intensified into a violent 3/4-mile-wide multi-vortex storm at around 3:37 PM EDT. The first intense damage occurred three minutes later as a line of 13 homes on Britt road were swept away, and an orchid nursery was demolished as well. The tornado reached its peak width as it struck the Wolf Branch subdivision of Mt. Dora as a slow-moving wedge tornado, completely destroying the neighborhood. Exiting the subdivision, the tornado crossed over US-441, approaching the main part of town; destroying a hotel and several apartments along the highway. The tornado began to take a more westerly path at this point, largely sparing the center of town. An undeveloped area along Limit Ave. took the brunt of the damage, though dozens of homes, as well as the Mount Dora Water Treatment plant; the Public Library; a funeral home; and the Pine Hill Cemetery were affected in this part of the path. Graves at the cemetery were undisturbed, but most of the headstones were either tossed or shattered, and the grass was scoured away. Beginning to narrow, the still-violent tornado became rain-wrapped, destroying a running track before tearing through a subdivision of homes along Lake Gertrude. The catastrophic damage that had been observed in the Wolf Branch area of town had largely been repeated here as well. However, many of the residents fled in advance of the slow-moving tornado, resulting in less fatalities in the affected area. After producing this last bout of damage, the tornado finally crossed out over the lake and dissipated at 4:10 PM EDT.

Over 1000 structures were completely destroyed by the tornado and hundreds of vehicles were rendered unrecognizable after being thrown great distances, some more than half a mile. Some of the vehicles were pulverized into many pieces and strewn across fields or the town, and others were simply never found. The vehicles that remained relatively intact were sandblasted and completely caked with mud and grass. The tornado produced extreme ground scouring, as the earth at and around the Wolf Branch subdivision was scoured out to a depth of 20 in (50.8 cm), reducing lush fields of grass and trees to wide expanses of mud. Extensive amounts of asphalt was torn from the roads and ripped down to the subgrade in the damage path. More asphalt was removed in Lake County than any other tornado in history. Telephone poles in the area were snapped off at the base and splintered, and trees were completely shredded and debarked. Many of the homes in the tornado's path were fairly new and well-constructed and bolted to their foundations, but the tornado left only the concrete slabs, and there was virtually no debris left throughout most of the damage path. The debris from the destroyed homes was finely granulated into small fragments, and scattered for long distances across the area. The tornado also picked up large amounts of loose soil as it deeply scoured the ground, producing a sandblasting effect on the houses and their occupants. The tornado's slow forward movement combined with its extreme intensity were likely the main factors as to why the damage it produced was so remarkably intense. Overall, were 245 human fatalities and over 400 injuries from this tornado.

EF3 Clermont tornado
Around the same time as the Mt. Dora EF5 tornado, another strong tornado formed about 20 miles to the south-southwest. Touching down in the Ferndale Preserve, the tornado initially caused widespread EF0 to EF1 damage limited to trees. The tornado grazed the westernmost parts of Montverde before hitting the La Finca Stables, killing several horses and crossing the Florida Turnpike, striking the southeast portions of Minneola, causing sporadic EF2 damage. The tornado then crossed into Clermont, striking many well-built homes, causing high-end EF2 damage in a few instances. Three were killed in this area. The funnel exited the residential area and damaged a small addition across Citrus Tower Blvd before striking the Clermont Pediatrics, Superior Residences of Clermont, and the Clermont Town Center plaza in succession, causing more high-end EF2 damage. It then crossed FL-50 and struck another plaza, ripping the roof off of the AT&T store that was directly in the core of the tornado's path, indicating EF3 damage. The tornado also caused minimal EF1 damage to the Lowe's right next to the plaza. The tornado passed over Wilma Lake before directly striking the Epic Theatres of Clermont, causing EF3 damage to the plaza, with the collapse of several external walls and severe damage to the roof of the theater being noted. Eight people were killed in the theater. The tornado pressed south-southwest, causing EF1 damage to a BJ's as it moved across the Clermont Crossings parking lot, mangling and throwing many vehicles considerable distances. It then moved into the South Lake subdivision, causing widespread damage, with some instances of EF3 damage visible; one person was killed in this area. The tornado continued on into the Orange Mountain addition, causing EF1-EF0 damage as it began to weaken. The tornado eventually moved out over Lake Louisa and dissipated after traveling over the lake for nearly half a mile. In total, the tornado killed 12 people, injured over 200, caused over $1 billion in damages, and traveled for 9.5 miles.

EF4 Zephyrhills tornado
About 90 minutes after the Mount Dora and Clermont tornadoes, another strong tornado developed along the eastern banks of the Withlacoochee River. Initially the tornado was weak, twisting and uprooting many trees in the area. The intensity of the damage steadily increased as the tornado tracked to the southwest. Along Messick Road, two frame homes suffered a collapse of external walls, as well as significant roof removal; an additional four mobile homes and seven metal barns were leveled nearby. A trucking business was also hit in this vicinity, resulting in the loss of over a hundred semi trailers and several rigs were found severely deformed as far as a quarter mile from their point of origin. Crossing the U.S. Highway 98, the tornado struck the Sunshine Mobile Home Park, sweeping away virtually every home in the subdivision. Only five homes lining Trotter Lane to the north survived, but sustained major damage making them totally uninhabitable. The adjoining Sunburst Hills subdivision lost 58 homes. After tracking over an open field for half a mile, the tornado entered the eastern outskirts of the Scotland Yards Gulf Club neighborhood, and severely damaged 39 frame homes. In a cul-de-sac lining the southern end of Masters Boulevard, seven homes were completely leveled; ground scouring was also observed in a field next to this subdivision. Damage in this particular area was the basis for the tornado's EF4 rating. The tornado began to narrow and weaken as it entered an industrial area, producing widespread EF2 damage, with patches of EF3 damage also observed. Here, the damaged facilities were a concrete production and distribution plant, a recycling facility, and a automobile repair shop. Hundreds of vehicles were tossed and mangled, and the structures experienced severe roof and siding damage. The tornado crossed Gall Boulevard and dissipated in a small wooded area north of Bailey Hill Road.

During its existence, the tornado was on the ground for 5.6 miles, during which it attained EF4 intensity and killed 61 people; a fatality count reflected by the high proportion of victims being in mobile homes during the violent tornado.

Damage
On May 24, the day after the outbreak, a major disaster declaration was signed for 6 counties due to the extensive damage and loss of life that occurred. The American Red Cross opened ten shelters overnight across central Florida, housing over 2,500 people immediately following the disaster. By May 25, this number had lowered to just over 800. Throughout May 25, several post-disaster teams from FEMA were deployed to the region, including emergency response and preliminary damage assessment units. Initial surveys estimated that about 20% of the structures in Mount Dora were destroyed due to the tornado which moved through the town, as the northeastern portion of the city was virtually gone, and the tornado left little for rescue workers to sift through. One rescue worker, who arrived within minutes of the tornado from the local fire department, said that he was amazed at “how quiet it was… no one was yelling for help, no dogs were barking, there were no sounds at all except rain falling on the dirt.” The United States Department of Defense placed the U.S. Army Corps of Engineers on standby for assistance. Medical and mortuary teams were also sent by the Department of Health and Human Services.

Continuing search and rescue efforts for hundreds of people who were listed as missing through May 27 were assisted by urban search and rescue dogs from across the country. Nearly 1,000 members of the Florida National Guard were deployed throughout the affected region. On May 28, disaster recovery centers were opened in Mount Dora, Clermont and Zephyrhills for individuals recovering from the tornadoes. Within the first few days of the disaster declaration, relief funds began being sent to families who requested aid. Debris removal finally began on June 2 as seven cleanup teams were sent to the region, more were expected to join over the following days. That day, FEMA also declared that 3 counties −Volusia, Lake and Pasco− were eligible for federal financial assistance. By June 3, roughly $2.3 million in disaster funds had been approved for housing and businesses loans. This quickly rose to more than $8.6 million over the following five days.

EF5 rating debate
In the immediate days after the tornado, there was some debate among meteorologists as to whether or not the Mount Dora tornado's rating should remain at EF4 or be increased to EF5. The debate in part was sparked by the tornado's slow forward speed, which was about 8 mph at most, likely exposing some of the homes in the center of the damage track to tornadic winds for as much as three solid minutes, which may have exacerbated the destruction to some extent. Most of the homes in the Lake and Golf Reality subdivision were found to be well-constructed during later analysis. Another argument that led to the tornado's upgrade was that there had been several other slow-moving tornadoes in the years prior to this event under the Enhanced Fujita Scale, but did not cause anywhere near the damage observed in Mount Dora. Because the Enhanced Fujita Scale is a damage scale, the surveys conducted were focused more on the empty foundations and not specifically on the other damage indicators, which led surveyors to eventually award an EF5 rating a week later on May 30. This made the Mount Dora tornado the first EF5 tornado in the United States since 2013, and the first ever tornado to attain such intensity in the state of Florida.