Storm Chase // 16 April 2024 // Southeast Iowa Tornadic Supercell

 I chased southern Iowa on April 16th and was rewarded with an intense EF2 producing tornadic supercell west of Burlington, IA. I departed Fort Wayne at around 1AM, took a brief nap near the Illinois border, and then reached my target of Albia, IA by late morning. Storms developed near Kansas City and advanced northeast across my region during the next few hours. Other convection was ongoing north and east as well, all due to the early arrival of an upper jet streak spreading across the area. I moved east with the storms coming up from the south, and they took on a QLCS structure. This didn't bode well for tornadoes, but there was a quasi-discrete cell along the southern end of the line, which I decided to target as it approached far southeast Iowa. This storm quickly matured into a supercell as it reached my location, with classic wall cloud structure, strongly rotating rain currents, and a well exposed updraft that showed clear signs of midlevel rotation. I moved north with the storm as the wall cloud lowered to the ground and displayed increasing rotation. And then just as it went tornadic, rain wrapped around the low-level meso and my view of the tornado was cut off. The road network was also becoming complex as I approached the MS river, so I let the rain-wrapped tornadic storm go as it drifted north, and then intercepted several cells to my south. They displayed some interesting structure, but also seemed to ingest cooler more stable air from the storm to the north, and thus failed to produce tornadoes. All in all a good chase day...images and weather data posted below, including a NAMNEST sounding/hodograph that yielded a predicted tornado pathlength of 78 km and tornado longevity of 61 minutes, which were slightly larger than the observed pathlength of 44 km and duration of 39 minutes associated with the EF2 tornado. Storm chase video that I captured can be found here.

Strong updraft rotation and swirling rain curtains adjacent to a rain free base viewed from highway 218 southwest of Burlington, IA.

Developing wall cloud and rotating rain curtains.

Low-level rotation becoming intense as the wall cloud lowers toward the ground.

Another view of a strongly rotating wall cloud.

Storm is going tornadic at this point with a rain filled RFD just about to wrap around the low-level mesocyclone.

Another cell coming up from the south. It possessed a large rain free base.

Strongly diffluent flow at 250 mb located within the left exit region of a 100+ kt jet streak arrived early across the region and led to widespread convection that may have precluded a more significant tornado outbreak.

A cold core 500 mb low centered over SD/NE/IA/MN border region focused low-topped tornadic storms near the bent-back occluded surface low.

700 mb objective analysis valid 00Z 17 April 2024.

850 mb objective analysis valid 00Z 17 April 2024.

Subjectively analyzed surface map valid 21Z 16 April 2024.

KDVN base reflectivity valid during the time of significant tornado activity in southeast Iowa.

KDVN 0.5 degree SRV valid during the time of sigtor activity in southeast Iowa. The velocity signature seems to be consistent with an EF2 strength tornado.

A NAMNEST sounding valid 21Z 16 April 2024 at Burlington, IA. The sounding may be located within the cool side of a subtle warm-frontal zone which might explain the slightly stable boundary layer profile. Otherwise, strong shear and sufficient CAPE were present for rotating storms and possible tornadoes.

A NAMNEST hodograph derived from the sounding above. Predicted tornado pathlength and longevity are displayed within the inset. Those values were slightly larger than what was observed with the EF2 tornado that occurred west of Burlington, IA.

4/2/2024 Storm Chase: Southeastern Indiana/Far Northern Kentucky

 I drove from Fort Wayne, Indiana south to southeastern Indiana on 4/2/2024 and managed to position myself east of a cluster of messy pseudo-cellular supercellular activity. I targeted a storm that appeared to be anchored to a theta-e gradient that materialized as a result of morning thunderstorm activity. That morning activity really worked over the thermodynamic environment, and probably aided in storm under-performance, as the shear profiles were very supportive of updraft rotation and possible tornadoes. The people of Indiana, Kentucky, and Ohio were undoubtedly grateful for the low tornado count that occurred during this event. Otherwise, I followed several supercells east to the Cincinnati airport, and then dropped south along an interstate in order to position for the passage of a strongly rotating storm. That cell yielded rotating rain currents as the RFD blasted across the interstate, but I didn't observe a tornado. It then moved east into unchaseable terrain, with other nearby cells going on to produce several tornadoes just east of my location, including an EF-1 with a 12.8 km pathlength and duration of 11 minutes. I'm continuing to test a tornado pathlength/duration algorithm, and output using a 22Z RAP sounding from the Cincinnati airport yielded a predicted pathlength of 27.6 km and duration of 22.9 minutes. Perhaps the worked over airmass reduced the potential for longer pathlengths?

0.5-deg reflectivity from the KILN radar showing messy supercells advancing east-northeast across northern Kentucky into southern Ohio.

250 mb valid 00 UTC on 03 April 2024. The left exit region of a diffluent 140+ kt jet streak overspread the region of tornadic activity during the afternoon and evening hours.

500 mb valid 00 UTC 03 April 2024. A midlevel shortwave trough with 70+ kt midlevel southwesterly flow spread east/northeast across the Ohio Valley region during the tornado event.

850 mb valid 00 UTC 03 April 2024. A deep low-level cyclone was present centered over lake Michigan, with fairly robust 40-50 kt south-southwesterlies at 850 mb aiding in moist advection and enhanced low-level vertical wind shear across the Ohio Valley region.

WPC surface analysis valid 00 UTC 03 April 2024. Storms initiated off of a cold front, and it was the activity that occurred along and south of a strong east-west gradient in theta-e that posed the greatest tornado threat from roughly the Ohio river southward.

RAP sounding valid 22 UTC 02 April 2024 near the Cincinnati airport. Thermodynamics were characterized by generally weak to moderate CAPE as well as generally low CIN and minimal near-surface stable layers.

RAP hodograph valid 22 UTC 02 April 2024 near the Cincinnati airport. A favorable wind profile was in place for supercells and short to medium pathlength tornadoes, though the veer-back characteristics of the shear vectors going from 0-5 km AGL and then 5-10 km AGL might have led to messy storm interactions.