Dundee Tornado April 1 2023

Tornadoes:

Tornado - Dundee, MI Monroe County Date April 1, 2023 Time (Local) 11:03 AM - 11:08 AM EDT EF Rating EF-0 Est. Peak Winds 80 mph Path Length 7.3 miles Max Width 75 yards Injuries/Deaths 0/0 Summary: The tornado touched down at the intersection of Brewer Rd and Petersburg Rd west southwest of Dundee. Damage in this area included a stand of pine trees down, damage to an outbuilding, and some significant shingle damage to a house with winds estimated at 75 mph instrength. The tornado then tracked along Brewer Rd with damage consisting of sporadic downed large limbs as Brewer Rd turned into Riley St. upon entering into the village of Dundee. Estimated wind speeds increased to a peak of 80 mph in downtown Dundee...specifically in the immediate vicinity of Memorial Park...with increased wind speeds aided by funneling effects between downtown buildings. Damage in this area consisted of a roof being partially blown off, windows blown out, downed limbs, and nearby car damage. The tornado then tracked further east northeastward until ending near the intersection of Dixon Rd and Sullivan Rd with continued sporadic downed large limbs.     Track Map

The Enhanced Fujita (EF) Scale classifies tornadoes into the following categories:

EF0 Weak 65-85 mph	EF1 Moderate 86-110 mph	EF2 Significant 111-135 mph	EF3 Severe 136-165 mph	EF4 Extreme 166-200 mph	EF5 Catastrophic 200+ mph

Photos

Debris in Downtown Dundee Credit: Leslie Hayes	Roof Damage in Downtown Dundee  Credit: Leslie Hayes	Debris in Downtown Dundee Credit: David Malmquist

Radar

Radar Imagery for Dundee EF-0 Tornado

Figure 1. TDTW 0.1 degree reflectivity between 1504 and 1518 UTC on 01 April 2023, centered on Dundee, MI. 

Figure 2. TDTW 0.1 degree storm-relative velocity between 1504 and 1518 UTC on 01 April 2023, centered on Dundee, MI. 

Environment

The severe weather observed during the late morning hours of 1 April 2023 began as a sub-severe shower/thunderstorm complex that tracked over southwest lower Michigan with minimal impact. As this convection shifted east, however, upper level features caught up to a modestly destabilized low level atmosphere and resulted in isolated severe weather and a brief EF-0 tornado over southeast Michigan. The upper-level synoptic pattern was characterized by a positively tilted upper trough that gradually gained a more neutral orientation as it tracked into the Great Lakes between roughly 13-15z (Figure 1). The disturbance aloft helped initiate surface cyclogenesis near Lake Erie, with the development of a 992mb surface low by 15z per SPC mesoanalysis (Figure 2). As this surface low deepened, a notable region of convergence extended from northern OH to roughly the I-94 corridor which served as a boundary for thunderstorms to latch onto (Figure 3). 

In terms of typical thunderstorm ingredients, this was a high shear, low instability scenario. SBCAPE at 14z was only a few hundred J/kg according to SPC mesoanalysis (Figure 4), as temperatures were only in the 50s and dewpoints in the mid 40s at their peak. Nonetheless, the thunderstorm complex was able to tap into the surface indicated by 0-3 km lapse rates of 7.5-8 C/km (Figure 5) and TDTW inbound base velocities over 60 knots below 500 feet (not shown). Shear profiles were certainly more impressive than instability, with a 50+ knot low level jet just clipping Lenawee and Monroe Counties. This resulted in a localized increase in 0-1 km bulk shear to 20-25 knots as the thunderstorm complex approached from the west (Figure 6). As this occurred, upstream surface winds had also backed to the south-southwest with KADG and KTTF ASOS sites both reporting wind directions of 160-190 degrees. Resultant hodographs were thus more favorable for rotation as the backed surface flow resulted in higher values of 0-1 km storm-relative helicity (SRH) up to 150 m2/s2. Similarly, the backed profiles allowed for more of a streamwise component to the storm-relative inflow. 

While the overall environment was not supportive of widespread severe weather, the interaction between the localized increase in low level shear and the passage of the upper level vorticity maximum did produce a brief/weak EF-0 tornado that impacted downtown Dundee. The mid-level rotation associated with this cell was transient yet persisted until the storm departed into Ontario, and the EF-0 in Dundee was the only observed tornado. Additional severe reports consisted of straight-line wind damage with this same cell, with trained spotters also reporting pea-sized to M&M sized hail as far north as Washtenaw County.

Figure 1: 500mb Analysis, valid 1400 UTC 1 Apr 2023	Figure 2: Surface Analysis, valid 1500 UTC 1 Apr 2023	Figure 3: Deep Layer Moisture Convergence, valid 1400 UTC 1 Apr 2023
Figure 4: Surface-Based Convective Available Potential Energy, valid 1400 UTC 1 Apr 2023	Figure 5: 0-3km Lapse Rates, valid 1400 UTC 1 Apr 2023	Figure 6: 0-1km Bulk Wind Shear, valid 1400 UTC 1 Apr 2023