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The 2018 Super Outbreak is the most prolific outbreak on record in the United States, with 552 confirmed tornadoes over three days. May 1st saw 92 tornadoes, May 2nd saw 241, and May 3rd saw 219. Of these 552 tornadoes, 69 were violent, 36 EF4 and 33 EF5, making this outbreak by far the most violent on record, crushing the previous record of 30 Violent Tornadoes during the 1974 Super Outbreak. With a total of 7,051 fatalities, the 2018 Super Outbreak is the deadliest outbreak of tornadoes in World History, vastly overtaking both the Tri-State tornado and the 1989 Bangladesh F5. Of these fatalities, 5,797 came from the Houston Tornado, a violent EF5 that tore a 100+ mile path through Southeast TX from Brenham to Seabrook, straight through the heart of the city of Houston. This tornado also incurred nearly $70 Billion USD in damages, making it the costliest single tornado in history. The Houston EF5 was also found to have 321 MPH winds at peak strength thanks to RaxPol radar, making it the most intense tornado ever recorded on top of being the widest at nearly 3 miles wide. Along side the Houston EF5 were many other record setters, including an EF5 that travel 247 miles through Texas, Louisiana, and Mississippi, destructive twins that ravaged Alabama, and many others.

Meteorological Synopsis

Confirmed
Total
Confirmed
EF0
Confirmed
EF1
Confirmed
EF2
Confirmed
EF3
Confirmed
EF4
Confirmed
EF5
552 201 107 82 93 36 33



The beginning of 2018 was marked by an unprecedentedly quiet first quarter. Both January and February had no confirmed tornadoes. This was due to a powerful La Nina that brought cold air across much of the US, supressing activity. This is in spite of the multitude of severe weather that occurred in Florida and other Southern states, with the one reported tornado the entire first two months that was found to have been a powerful waterspout. Things didn't really change much for most of March. The first three weeks were plagued by blocking High Pressure, trapping cold temperatures over the US for most of the month. However, late in the final week of March was a small outbreak in the Carolinas. This signalled the change in pattern that soon followed. April was almost immediately active, with the first week seeing a moderate outbreak of tornadoes in the deep south. Following shortly after was another moderate outbreak, after which followed a sizable outbreak with multiple violent storms. The month was then book ended with sporadic activity, with the final week seeing widespread instability with a consistent, moderate shear. This would be the same system that would eventually creep its way into the plain and then to the south starting on May 1st.

May 1st

Total EF0 EF1 EF2 EF3 EF4 EF5 Total
92 31 25 22 10 3 1 92


Main article: Kingsfisher-Perry EF5

On April 30, a Moderate Risk for severe weather was issued for much of central Oklahoma and North Central Texas for an approching trough and associated Low. A Prominent dryline was expected to emerge from the Rockies to the west and be the main driver of the severe weather, providing substantial lift well ahead of the Dryline to generate a very widespread outbreak. At 12Z, soundings were released to better narrow down the forecast. Through this they found that a strong capping inversion had settled over much of the risk area. Current forecasts at the time only showed 3500 J/kg to 4000 J/kg of instability for the afternoon, so the risk was lowered to Enhanced. Despite this, a "Loaded Gun" warning was issued for Oklahoma City in the instance a violent tornado may appear.

By 17Z it became clear that the forecast models were far off. At 15Z, CAPE of 4000 J/kg had already developed throughout the area, and the cap was quickly loosing strength. By noon, the cap was still decent, but CAPE had begun to exceed 4500 J/kg. Then, finally, at 1900Z, the cap broke as daytime heating and moisture advection made CAPE values swell into the 6000 J/kg range. Horizontal Convection Rolls(HRCs) well ahead of the Dryline exploded into clusters of supercells, of which soon became tornadic. Of these was the Kingsfisher EF5, a monsterously intense storm that engulfed the town and trekked dozens of miles NNE before dissipating just north of Perry, Oklahoma. Numerous violent tornadoes sooned followed as storms erupted along HCRs and the Dryline before ejecting Northeast as a nebulous cluster of tornadic cells, continuing to produce many tornadoes into the next morning before finally dying out. In all 92 tornadoes touched down within the 10 period of 19Z to 05Z, an astonishing 9.2 tornadoes per hour, with 4 violent tornadoes terrorizing north central Oklahoma. During the chaos, at 20Z central Oklahoma was upgraded to a High Risk, the second of the 2018 season.

May 2

Total EF0 EF1 EF2 EF3 EF4 EF5 Total
241 82 55 37 23 18 17 241


Main article: Houston-Pasadena Tornado

The pre-dawn hours saw a weakening MCS from yesterday afternoon's storms eject itself northward before dying in Illinois. Throughout that time period 32 tornadoes touched down, right until the very last cell dissipated. At the same time, a High Risk was issued for a vast area stretching from Houston to Hunstville. A 60% risk for EF0 to EF1 tornadoes was highlighted within this vast region, mostly in what would be warm sector where sporadic initiation would take place. Within Ark-La-Tex, however, a hatched risk was emphasized over the 60% risk area. The SPC described the hatched area as a region "Favorable to frequent strong to violent tornadogenesis". Advection from a powerful upper level jet along with proximity to the gulf made the region a ticking time bomb, inevitably to detonate. CAPE values soared into the >7000 J/kg range as storms began to explode along a surging warm front mid-morning. Tornadic activity started off the day almost immediately, as numerous funnels tore through the deep south, racing north at 70 MPH. Alongside the extreme instability existed extreme levels of Storm Relative Helecity(SRH), with 0-1km values as high as 600m²/s², and 0-3km values soaring into the 900-1000m²/s². The extreme storm motion of the Warmfront event of the day didn't help either. Strong conversion drew instability and moisture into HCRs, and as the winds shifted into optimal position, huge clusters of supercells exploded into the region, with numerous rainwrapped and violent cell mergers taking place. EF5s and EF4s terrorized Louisiana and Arkansas, before racing into Mississippi, tearing up the marshes and deforesting the land. Town after town was wiped off the map, and by 19Z, at least 600 had lost their lives to the rampage. However, the afternoon was still young, and there was still a prominent dryline ready the unleash its wrath on Texas.

Throughout the morning, noon, and early afternoon hours, Texas had enjoyed a rather quiet day as storms ravaged the Southeast. This was soon to change, however. Strong converging winds had been building instability all day along the dryline. This, on top of the advection and heating, allowed CAPE to be explosive. Despite this, for most of the day, nothing happened. A strong cap had remained somewhat in place for most of the day due to the frequency of severe weather in the area. This obviously wasn't to last however, as supercells soon exploded over East-Central Texas around 1830Z. The swelled CAPE of 8000 J/kg had resulted in explosive updrafts, helical rotating into hot towers over 70kft high. The powerful inflow from these extreme updrafts pulled and stretched the air as it twisted and tightened. Soon, drillbits were digging into the earth all along the dryline. The sharp pressure falls and extreme vorticity on top of extreme vertical shear quickly evolved these needles of air into massive wedges as the high dewpoints condensed the air around them. By 1900z, more than Half a dozen EF5s had touched down in east Texas, ready to terrorize the populace just as their brothers and sisters had to the deep south. First in their cross hairs was Dallas-Fort Worth, as an EF5 tore through the Southeastern suburbs of the metropolis, killing dozens and doing billions in damage. Next in line was Waco, then Killeen, Austin, and last but not least, Houston. All four were of EF5 strength, laying waste to the cities they ate their way through. By the end of it, 8,141 had died, and more than ≈$85 Billion USD in damages had been done. Eastern Texas was in ruin. Storms would from then on eject Northeast, converging into a powerful MCS that would produce dozens of more storms throughout the evening and into the next morning. In all, 241 tornadoes, including 35 violent, would rip through the south for 24 hours straight. It is the largest single day outbreak in history, surpassing that of April 27, 2011. It also the most violent, being the only outbreak to overtake 1974 with 35 violent storms, 18 EF4, and 17 EF5. Despite the terror of this days storms, there was still more to come, not unlike May 2, would be a very destructive and deadly day.

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