Episode narrative: On March 3rd, 2023, a historically strong low pressure system moved across the lower Ohio Valley, bringing heavy rainfall, severe weather, and most notably, very strong gradient winds as it moved across the region. On the synoptic scale, a shortwave upper-level trough located over the mid-Mississippi Valley became negatively tilted during the morning hours of March 3rd. A 120 knot 500 mb jet developed across central Kentucky and middle Tennessee in the presence of a very strong height gradient. The footprint of this jet core was transferred into the lower levels of the atmosphere, with a 70 knot jet at 850 mb present across the Ohio and Tennessee Valleys. The orientation of the shortwave trough aloft with respect to the low level cyclone was nearly ideal for mutual amplification, with both the surface low and the upper trough undergoing deepening during the morning and early afternoon hours on March 3rd. Ultimately, the surface low's minimum central pressure dropped to approximately 976 millibars near Vincennes, Indiana by mid-afternoon on the 3rd, creating an anomalously strong low-level pressure and height gradient across central Kentucky and southern Indiana.

Before the severe weather and strong gradient winds began, the first impact from this strong mid-latitude cyclone would come in the form of heavy rainfall, primarily across southern Indiana. With the strong low-level jet helping to advect warm and moist air northward, precipitable water values were anomalously high, ranging from 1.3 to 1.6 inches across southern Indiana and central Kentucky during the morning hours on March 3rd. Coupled with an intensifying low level warm frontal boundary which provided a large-scale lifting mechanism, this axis of high moisture content contributed to a broad swath of precipitation, which lasted through much of the morning and early afternoon hours across southern Indiana. Ultimately, many locations would receive between 3 and 6 inches of rain over the span of about 12 hours, causing isolated to scattered reports of flooding.

After the initial wave of precipitation associated with the warm front lifted into central Indiana, southern Indiana and central Kentucky would briefly be located in the warm sector of the cyclone during the late morning and early afternoon hours, providing an opportunity for severe weather. Due to the proximity of the surface low and the relatively limited period for destabilization, instability was very limited for this event, with between 250-750 J/kg MLCAPE present across central Kentucky and southern Indiana. However, with the extremely strong dynamics in place, wind shear parameters were incredibly high. Effective bulk shear generally ranged from 70-100 kt, while effective Storm Relative Helicity ranged from 300-600 m2/s2. In addition, low-level Storm Relative Helicity was maximized (300-400 m2/s2) just ahead of a broken line of low-topped supercells which went on to produce three EF-1 tornadoes across southern Indiana. Across central Kentucky, the main severe impacts would come from damaging straight-line winds within a broken quasi-linear convective system. While limited instability clearly reduced the overall strength of the QLCS, some convective cores were deep enough to pull higher momentum air from aloft down to the surface, causing scattered damage and wind gusts above 58 mph. A few additional severe wind gusts would also be produced by the aforementioned line of low-topped supercells as they moved across southern Indiana and northern Kentucky.

While the heavy rainfall and severe weather were important aspects of this system, the most widespread impacts from this historic system would come from extremely strong gradient winds immediately following the passage of showers and storms along the surface cold front. As was previously mentioned, the rapid cyclogenesis as the surface low moved into western Kentucky and southwestern Indiana created an unusually strong pressure gradient across the region, even for cool season mid-latitude cyclones. This strong pressure gradient, combined with a brief period of steeper low-level lapse rates across central Kentucky thanks to temporary clearing in the wake of the cold front, helped to bring extremely strong winds and wind gusts to all of central Kentucky and most of southern Indiana. Widespread sustained winds of 30-40 mph and wind gusts of 60-80 mph were observed across the area, causing widespread tree and power line damage, as well as more scattered occurrences of structural damage. At one point, around half a million customers were without power across the state of Kentucky, with several counties seeing a temporary near-total loss in electrical service. As the mid-level cyclone moved overhead during the early evening hours, cloud cover would return, helping to reduce wind speeds and gusts somewhat, with conditions continuing to calm through the overnight hours into the morning of March 4th.

Tornado event in DUBOIS County, INDIANA
Start: 03-MAR-23 14:11:00
End: 03-MAR-23 14:18:00
Direct deaths: 0
Event narrative: An EF-1 tornado formed on the west side of Dubois County, embedded within a line of severe thunderstorms. It first touched down near a barn in the city of Duff, leaving only one wall and the area`s tornado siren standing. The tornado then crossed flat farmland, not causing noticeable damage again until it reached the corner of 450 W and 100S, where a barn had significant roof damage and a home had shingle and siding damage. A private citizen had video footage of a narrow condensation funnel looking in the direction of this damage.

From here a continuous path of damage was noted by the Emergency Manager, going through neighborhoods along Skyview Dr and Schuetter Dr west of Jasper. The tornado last caused damage in the Grassland Hills subdivision, causing multiple trees to snap near W 31st St. At this point some tree top snapping was noted as the tornado lifted.

Tornado event in JEFFERSON County, INDIANA
Start: 03-MAR-23 15:29:00
End: 03-MAR-23 15:31:00
Direct deaths: 0
Event narrative: The National Weather Service in Louisville conducted a storm damage assessment summary for the March 3rd tornado that hit halfway between Hanover and Lexington, IN. The tornado initially touched down near Ford Road, which is just south of SR-56. Drone video showed trees snapped, twisted, and uprooted and laying in multiple directions. The tornado did the most damage between 9011 to 8904 SR 56. Six outbuildings and older barns were severely damaged or destroyed. A brick home sustained significant roof damage, had windows busted, and TV antenna snapped facing a westerly direction. Most of the damaged trees on the south side of SR 56 were facing from the west northwest to the north. Winds were estimated to be 90-95 mph with a width of 100 yards. 

On the north side of SR 56, a well-built wooden home had several windows blown out, and the house foundation shifted several inches. A SUV had all its windows blown out, and looked like it had been shelled with debris. Several outbuildings were destroyed, throwing debris to the northwest and northerly directions. There was metal sheeting in the trees wrapped around branches and trees. 

A well-built 40 by 60 barn had a large portion of its roof lifted, but its foundation did not move. This caused a plethora of insulation to be thrown in every direction into the wooded area. Several cars were moved by a few feet and mud and insulation were on three sides of the barn. Pieces of this barn were thrown up to 275 yards downwind. A sturdy single wide moved several feet off its foundation, but not a single shingle was missing. Winds were strongest in this area with 100 mph max wind and a width of 100 yards.