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.
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Strong updraft rotation and swirling rain curtains adjacent to a rain free base viewed from highway 218 southwest of Burlington, IA.
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Developing wall cloud and rotating rain curtains.
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Low-level rotation becoming intense as the wall cloud lowers toward the ground.
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Another view of a strongly rotating wall cloud.
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Storm is going tornadic at this point with a rain filled RFD just about to wrap around the low-level mesocyclone.
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Another cell coming up from the south. It possessed a large rain free base.
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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.
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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.
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700 mb objective analysis valid 00Z 17 April 2024.
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850 mb objective analysis valid 00Z 17 April 2024.
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Subjectively analyzed surface map valid 21Z 16 April 2024.
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KDVN base reflectivity valid during the time of significant tornado activity in southeast Iowa.
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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.
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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.
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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.
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