Tornado Outbreaks in Hurricanes

[blp]

One of the unexpected outcomes of Milton was the significant amount and strength of the tornados that formed and how many were removed from the center. I wanted to start this thread and learn a little about how many other storms this may have happened and if anyone has any guesses what was the setup that led to this outbreak.

 https://x.com/NWSMiami/status/1844134821163041058

[tropicwatch]

Hurricane Ivan

Overall, it produced 120 tornadoes, surpassing the record of 117 that was previously held by Hurricane Beulah during the 1967 Atlantic hurricane season. Ivan also produced 16 more tornadoes than Hurricane Frances, whose associated tornado outbreak struck many of the same regions about ten days earlier. The tornado outbreak was also the largest in Virginia history.

Source:wikiwand.com

[Pasmorade]

Hurricane Ivan

Overall, it produced 120 tornadoes, surpassing the record of 117 that was previously held by Hurricane Beulah during the 1967 Atlantic hurricane season. Ivan also produced 16 more tornadoes than Hurricane Frances, whose associated tornado outbreak struck many of the same regions about ten days earlier. The tornado outbreak was also the largest in Virginia history.

Source:wikiwand.com

Why are you sourcing Wikiwand? That's just a visual enhancement to Wikipedia... Nevertheless, it is interesting info.

[Blown Away]

Incredible stat, on the Treasure Coast my little town had 6 Tornado Warnings. Hurricanes always have their own calling card!

[FireRat]

Yeah, Milton certainly had some insane tornadoes over FL. I was reading about past tornado outbreaks, and the deadliest hurricane spawned hurricane on record was a F4 in Louisiana resulting from Hurricane Hilda in 1964 which killed 22 people. That same year brought a significant tornado outbreak to the Miami area with Hurricane Isbell. 2004's Ivan was a huge tornado producer as well. 2024 Milton now joins the list of significant 'tornadic hurricanes'.

[HurricaneRyan]

2004 and 2005 both had some pretty gnarly outbreaks from landfalling cyclones. Frances and Ivan really cleaned up September 2004. Bonnie '04, Cindy '05, Katrina and Rita all had outbreaks as well.

After that, the other tornadoes that stood out to me were the ones spawned by Ida in 2021 (especially that New Jersey wedge) and all the ones this year. Beryl, Debby, Helene and Milton really impacted with tornadoes tbh - all of them spawned killer tornadoes but especially Milton.

[wxman57]

One of the unexpected outcomes of Milton was the significant amount and strength of the tornadoes that formed and how many were removed from the center. I wanted to start this thread and learn a little about how many other storms this may have happened and if anyone has any guesses what was the setup that led to this outbreak.

Tornadoes in hurricanes are generally found in the outer bands, far removed from the center, so it's not unusual that Milton's tornadoes were removed from the center. I remember tracking Beulah in 1967. It held the record for the number of tornadoes. Back then, there was no Doppler radar. Tornadoes, particularly short-lived and smaller ones, were not easily seen on radar. I'm sure there were quite a few that were not identified. And in the aftermath of a strong hurricane, it's hard to distinguish between the hurricane's wind damage and an F0 or F1 tornado.

[TheFort2018]

Incredible stat, on the Treasure Coast my little town had 6 Tornado Warnings. Hurricanes always have their own calling card!

Yeah, that was an insane four or so hour period here on the Treasure Coast. Many thanks to WPBF and their crew for the up to the minute coverage and field reporting.

[USTropics]

There were 5 main factors that provided the necessary 'ingredients' to cause the tornado outbreak associated with Milton. I'll go over those using the GFS analysis of the event at 2PM ET (18z).

(1) Daytime Heating/Surface Warming
This is very critical, as it provides the necessary cap before the outer bands of Milton started moving onshore (for discrete super cells, like we saw with Milton, this is necessary). During the morning, the sun heats the Earth's surface, causing air near the ground to warm. This heating helps to create a sharp temperature gradient between the surface and the upper atmosphere, which increases the potential for instability. This gradient was further enhanced by the stalled out frontal boundary (and being reinforced by a secondary front to the north). We can see temperatures, particularly along the eastern coast towards SFL (where we saw the bulk of the tornadoes), the daytime temperatures were able to get up into the mid 80s:


(2) Increased Instability
As the surface warms, air near the ground becomes less dense and begins to rise. This process, combined with cooler temperatures aloft, leads to a situation called convective available potential energy (CAPE). Higher CAPE values mean the atmosphere is more unstable and conducive to the development of strong updrafts, which are essential for the formation of thunderstorms and supercells (the primary thunderstorm type that produces tornadoes). We can see below, parts of SFL were able to reach ~2000 CAPE (something we typically don't see in Florida and more akin to tornado outbreaks in the Plains):


(3) Lifting Mechanism
Tornadoes typically form in association with supercells or discrete cells, which require strong lifting mechanisms to form. Morning heating enhances the rising motion of warm air, which helps trigger thunderstorm development. If there are additional atmospheric triggers like fronts (we had a stalled frontal zone), drylines, low-pressure systems (check), rotating feeder bands (also check) the chances of severe storm development increase even more. We can see our surface-based lifting index was quite high for this tornadic outbreak:


(4) Moisture and Dew Points
Heating in the morning, combined with sufficient moisture at the surface (high dew points), promotes the development of towering cumulus clouds that can evolve into thunderstorms. When warm, moist air is lifted rapidly, condensation occurs, releasing latent heat and further fueling storm intensification. Again, RH values were close to 100% for the entirety of the event:


(5) Wind Shear
Tornado outbreaks often occur when there is strong wind shear (changes in wind speed and direction with height) in the atmosphere. Morning heating helps create the unstable environment that interacts with wind shear to organize thunderstorms into rotating supercells, which are more likely to spawn tornadoes. We had a sharp shear axis associated with Milton in addition to vector motion of the rotating outer bands:


While it only takes one of these ingredients (shear or instability) to produce tornadoes, when we get a combination of instability/CAPE and high shear, this is a recipe for intense tornadoes and possible tornado outbreaks (as we saw here). One last graphic, this is an overlay of hodographs with CAPE values. I won't get too much into the weeds on hodographs (they're critical for severe weather/tornadoes), but when we get this curved/bell look to them, it means we have the necessary shear environment to produce tornadoes:

[blp]

There were 5 main factors that provided the necessary 'ingredients' to cause the tornado outbreak associated with Milton. I'll go over those using the GFS analysis of the event at 2PM ET (18z).

(1) Daytime Heating/Surface Warming
This is very critical, as it provides the necessary cap before the outer bands of Milton started moving onshore (for discrete super cells, like we saw with Milton, this is necessary). During the morning, the sun heats the Earth's surface, causing air near the ground to warm. This heating helps to create a sharp temperature gradient between the surface and the upper atmosphere, which increases the potential for instability. This gradient was further enhanced by the stalled out frontal boundary (and being reinforced by a secondary front to the north). We can see temperatures, particularly along the eastern coast towards SFL (where we saw the bulk of the tornadoes), the daytime temperatures were able to get up into the mid 80s:
https://i.imgur.com/sEwp6UB.png

(2) Increased Instability
As the surface warms, air near the ground becomes less dense and begins to rise. This process, combined with cooler temperatures aloft, leads to a situation called convective available potential energy (CAPE). Higher CAPE values mean the atmosphere is more unstable and conducive to the development of strong updrafts, which are essential for the formation of thunderstorms and supercells (the primary thunderstorm type that produces tornadoes). We can see below, parts of SFL were able to reach ~2000 CAPE (something we typically don't see in Florida and more akin to tornado outbreaks in the Plains):
https://i.imgur.com/ECiv4Wp.png

(3) Lifting Mechanism
Tornadoes typically form in association with supercells or discrete cells, which require strong lifting mechanisms to form. Morning heating enhances the rising motion of warm air, which helps trigger thunderstorm development. If there are additional atmospheric triggers like fronts (we had a stalled frontal zone), drylines, low-pressure systems (check), rotating feeder bands (also check) the chances of severe storm development increase even more. We can see our surface-based lifting index was quite high for this tornadic outbreak:
https://i.imgur.com/FBW5MtW.png

(4) Moisture and Dew Points
Heating in the morning, combined with sufficient moisture at the surface (high dew points), promotes the development of towering cumulus clouds that can evolve into thunderstorms. When warm, moist air is lifted rapidly, condensation occurs, releasing latent heat and further fueling storm intensification. Again, RH values were close to 100% for the entirety of the event:
https://i.imgur.com/SUjx1s5.png

(5) Wind Shear
Tornado outbreaks often occur when there is strong wind shear (changes in wind speed and direction with height) in the atmosphere. Morning heating helps create the unstable environment that interacts with wind shear to organize thunderstorms into rotating supercells, which are more likely to spawn tornadoes. We had a sharp shear axis associated with Milton in addition to vector motion of the rotating outer bands:
https://i.imgur.com/j119nYx.png

While it only takes one of these ingredients (shear or instability) to produce tornadoes, when we get a combination of instability/CAPE and high shear, this is a recipe for intense tornadoes and possible tornado outbreaks (as we saw here). One last graphic, this is an overlay of hodographs with CAPE values. I won't get too much into the weeds on hodographs (they're critical for severe weather/tornadoes), but when we get this curved/bell look to them, it means we have the necessary shear environment to produce tornadoes:
https://i.imgur.com/GflS9gn.png

Thank you for the very detailed explanation. I appreciate your time and I learned a lot. After this event, I will always take away a higher respect for those outer bands.

[blp]

Wellington Tornado was classified as EF3 and traveled 21 miles with 140mph winds.

https://www.wptv.com/weather/weather-news/ef3-tornado-cut-21-mile-path-through-palm-beach-county-with-140-mph-winds-nws-says

[wzrgirl1]

Wellington Tornado was classified as EF3 and traveled 21 miles with 140mph winds.

https://www.wptv.com/weather/weather-news/ef3-tornado-cut-21-mile-path-through-palm-beach-county-with-140-mph-winds-nws-says

That's mind-boggling to me.

[chaser1]

Nice explanation and graphic visuals! I thought I had also heard that yet another tornado track was supposedly recorded to be 50 miles long?? Anyone know whether there was any validity to that? The 30-mile-long Wellington track is already bizarre to wrap my brain around (for Florida). Was there in fact an uninterrupted track of ground damage surveyed for that claim to be made, or was the tornado often aloft with a verified radar detected track which post event surveys verified multiple touch downs impact? I am assuming the latter but really do not know.

A family member of mine lives on a lake in Lakewood Park Ft. Pierce (off Ft. Pierce Blvd and Seminole Rd) and described hearing a weird low pitch howl and had some back yard chairs lifted and moved a significant number of feet and several palm treetops seemingly braided/twisted. I don't know the exact path of the tornado that hit and destroyed a number of homes and trailer homes but that was supposedly fairly close by.

[FireRat]

It really is mind boggling, the strength and long tracks of these Florida tornadoes... not far from Broward & Miami-Dade either, imagine if these tornadoes had started some 40 miles south and slightly more east, they got extremely lucky in Metro Broward, Miami-Dade and even coastal Palm Beach counties.

I lived through a strong EF-2 that destroyed several homes in Plantation back in Oct 2011, and that one's track was only a mile or two. Imagine 50+ miles! Absolute NUTS