Convectively enhanced vorticity max lead to initiation of storms overnight Sunday across southern South Dakota. These initial storms grew upscale given concurrent downstream destabilization through northeast Nebraska and northwest Iowa.
Every event with a place to put it. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS IWX wrote it up.
Convectively enhanced vorticity max lead to initiation of storms overnight Sunday across southern South Dakota. These initial storms grew upscale given concurrent downstream destabilization through northeast Nebraska and northwest Iowa. Widespread 80-100 mph winds developed through central/eastern Iowa as this derecho matured. Northern bookend and advection wing forcing led to some supercell structures across northern Illinois/southwest Wisconsin. Northern bookend turned northeast as it moved across Lake Michigan and tracked into western Michigan. As this occurred, attendant post convective wake low weakened as it crossed the lake. Thus the local area did not experience the 80 to 100 mph winds that N IL/E IA experienced. However the resultant slowing and breakup of the line as it moved across northwest Indiana/SW Michigan, yielded a LEWP and subsequent multiple small scale circulations developing along the line. These meso-vortices were associated with pockets of enhanced wind damage and brief tornado occurrences.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Northern Indiana wrote its last area forecast discussion before the first event at Aug 10, 1:19 AM EST, 24 minutes earlier.
Area Forecast Discussion National Weather Service Northern Indiana 219 AM EDT Mon Aug 10 2020 .SYNOPSIS... Issued at 751 PM EDT Sun Aug 9 2020 An isolated shower or storm is possible toward daybreak Monday in the west. Otherwise, it will be warm and humid tonight with lows 65 to 70. Warm and humid conditions are expected for the rest of Monday, with a chance of late afternoon and overnight storms. Highs 85 to 90. Mainly dry conditions and seasonable temperatures Tuesday through Thursday followed by some chance for showers and thunderstorms Friday and Saturday. && .SHORT TERM...(Tonight through Monday Night) Issued at 144 PM EDT Sun Aug 9 2020 Complicated and bust worthy period for certain given upstream plethora of convective disturbances and potential influences going forward. Near term wrn MN MCV in combination with srn IA MCV likely to spark new storms by evening from srn WI swwd into wrn IL/se IA but these are mainly expected to dive sewd within upstream positioned low level theta-e ridge. Some bleed over into nw zones possible before daybreak yet with diminishing LLJ support and rapid ewd dropoff of said H85 based theta-e do not believe it will push far into IWX CWA Monday morning. That said, Mon fcst hinges on associated convective debris/leftovers clearing out by aftn. Substantial destabilization inferred tied to both fold over of H85 theta-e ridge and arrival of srn plains based EML. Leading edge of height falls aloft timed with rapid LLJ blossom late aftn and significant mass flux into potential peaking sfc based theta-e reservoir point to rapid storm development from srn MI late aftn and quickly backbuilding swwd through ne IL by evening per NAM solution and mentioned here given failure of 00Z models to capture aforementioned convection this morning out west. However should convective debris/leftovers lag through morning which looks more likely, muted destabilization follows in the aftn and results in convective failure with cap holding through evening before storms follow overnight and must be mentioned given this scenario reflects the cams consensus. Thus the inherent complexity and will mostly sit tight with prior inherited pops. && .LONG TERM...(Tuesday through Saturday) Issued at 144 PM EDT Sun Aug 9 2020 Low confidence/uncertain start to this period owing to complexity of short term convective evolution. That said still some shower potential exists far south/se within lagging H85 theta-e ridge but glaring 12Z consensus indicated composite outflow/sfc boundary pushes well south of the OH river. Thereafter trend has been for more sfc ridging to build across the lakes and a long running persistence indicator over this summer. Given the trend and the gamut of med range guidance shifting active frontal zone south see little reason to hold with extended running low chc pops until perhaps Friday timed with yet another stout srn Canadian wave wrapping ewd into wrn ON by late Sat. Slow moving convective complexes and a lingering instability gradient will impact the Mid MS/OH Valleys mid-late week, while ridging aloft and at the sfc builds over the Great Lakes and SE Canada. This regime should be enough to keep the bulk of shower/storm activity ssw of the area Tuesday into Wednesday, though some lower PoPs remain over southern zones given close proximity to the lingering boundary. Retained broadbrush low-mid chance PoPs area-wide (highest PM) thereafter as confidence wanes regarding positioning of the boundary and track/timing of a slow moving Mid MS trough. Seasonal temps otherwise with highs generally low-mid 80s. && .AVIATION...(For the 06Z TAFS through 06Z Monday Night) Issued at 213 AM EDT Mon Aug 10 2020 Shortwave and associated convection over southern Lake Michigan to bring potential showers/storms to KSBN over next few hours. Downstream stability to preclude mention at KFWA with anticipatory decay. Otherwise, period of MVFR ceilings possible this morning with moistened boundary layer at KSBN. Thereafter, evolution/timing of next round of convection varies greatly per CAMS output. Side with VCTS later in evening as convection most likely tied to upstream cold front/next shortwave, currently over Northern Plains/Upper Midwest. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && SYNOPSIS...T SHORT TERM...T LONG TERM...T AVIATION...Murphy Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana
Hazardous Weather Outlook National Weather Service Northern Indiana 351 AM EDT Sun Aug 9 2020 INZ003>009-012-014-016>018-LMZ043-046-MIZ077>081-OHZ001-002-004-005- 015-100800- La Porte-St. Joseph IN-Elkhart-Lagrange-Steuben-Noble-De Kalb-Starke- Marshall-Kosciusko-Whitley-Allen IN-New Buffalo MI to St Joseph MI- Michigan City IN to New Buffalo MI-Berrien-Cass MI-St. Joseph MI- Branch-Hillsdale-Williams-Fulton OH-Defiance-Henry-Paulding- 351 AM EDT Sun Aug 9 2020 /251 AM CDT Sun Aug 9 2020/ This Hazardous Weather Outlook is for northern Indiana, southwest Michigan, northwest Ohio and the nearshore waters of southeastern Lake Michigan. .DAY ONE...Today and tonight. There is a chance for thunderstorms late tonight across northwest Indiana and southwest Michigan. Severe storms are not expected. .DAYS TWO THROUGH SEVEN...Monday through Saturday. There is a chance for thunderstorms Monday into Monday night, best chances Monday night as a cold front moves through. There is a low risk for an isolated strong to severe storm late Monday afternoon into Monday evening across northwest Indiana and southwest Michigan. There are additional chances for showers and thunderstorms Thursday through Saturday, mainly during the afternoon and early evening hours. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time. INZ013-015-020-022>027-032>034-OHZ016-024-025-100800- Pulaski-Fulton IN-White-Cass IN-Miami-Wabash-Huntington-Wells-Adams- Grant-Blackford-Jay-Putnam-Van Wert-Allen OH- 351 AM EDT Sun Aug 9 2020 This Hazardous Weather Outlook is for northern Indiana and northwest Ohio. .DAY ONE...Today and tonight. There is a chance for thunderstorms late tonight across northwest Indiana. Severe storms are not expected. .DAYS TWO THROUGH SEVEN...Monday through Saturday. There are periodic chances for thunderstorms Monday through Saturday, with the highest probability during the afternoon and early evening hours. .SPOTTER INFORMATION STATEMENT... Spotter activation is not expected at this time.
The Northern Indiana radar (KIWX), 67 km away, was scanning. The volume nearest the first event began at 06:43 UTC.
46 thunderstorm wind, 3 tornado. Local standard time, as filed.
Local media shared a photo of a healthy looking, partially snapped tree.
The public reported a large tree was blown down.
The public reported a roughly one foot diameter tree was blown down across Lowes Road Bridge, blocking traffic.
The public reported a power line was blown down at County Road 500 North and 700 East.
The public reported a tree was blown down across a road with a power line entangled in it.
The public reported a one to two foot diameter tree was blown down and blocking the road on East County Road 400 North, bear Raccoon Circle.
The automated weather observation system at the Starke County airport recorded a 63 mph wind gust.
Trained spotters reported several trees were blown down.
Amateur radio operators reported trees and power lines were down in the area.
The public reported numerous trees and power lines down across Plymouth.
The tornado began west of the intersection of Riley Road and Dogwood Road in southeast St. Joseph County. It then tracked along and south of Riley Road. Widespread tree and structural damage occurred through this path. Grain bins were toppled and farm outbuildings sustained damage. The tornado tracked through several cornfields that resulted in significant crop damage. The tornado lifted east of Beech Road. Maximum winds were estimated at 110 mph.
The public reported a tree as well as power line down over a local road.
Trained spotters reported several trees were blown down.
Emergency management officials reported several large trees were blown down. One of these trees fell onto a residence. No one was injured.
The public reported several large trees were blown down in Nappanee.
An off duty NWS employee reported tree damage in the Northwest woods subdivision. Three healthy, one to two foot diameter trees were blown down. Numerous small to medium limbs (three to eight inches) were also blown down.
The public reported large trees were blown down in Peru.
Local media shared a picture of a large tree branch down across State Route 15, just south of Leesburg. Some signs of rot were visible.
An off duty NWS employee reported a large tree limb, over 2 feet in diameter, was blown down onto North County Road 300 East, south of East County Road 750 North. Rot was noted on the tree where it broke off.
Local media shared pictures of several large tree branches blown down.
The public reported several large tree limbs down in the town of Leesburg.
Trees were snapped west of State Route 13 as the tornado touched down. The tornado pushed over 2 power poles as it crossed SR 13, then continued southeast, causing a notable path of snapped trees and broken limbs. The debris was scattered throughout a nearby church parking lot. The church sustained minor loss of roof covering. Additional areas of tree damage were noted farther to the east-southeast. Some homes sustained damage as a result of falling trees and branches. The tornado crossed Webster Lake, coming onshore around EMS W17 Lane, where extensive tree damage occurred. Some residence damage was noted, both from the winds and falling trees. The tornado crossed East Backwater Road/East County Road 600 North and dissipated.
Emergency management officials reported large tree limbs were blown down in North Manchester.
An off duty NWS employee reported a large tree was blown down.
Trees were reported down by trained spotters.
Emergency management officials reported trees and power lines were blown down.
Emergency management officials shared a picture of a healthy tree snapped at the base.
Emergency management officials reported an empty grain bin was toppled.
Emergency management officials reported a large portion of a tree was down per a shared picture.
The public reported a 25 foot tall tree was snapped two to three from the ground, landing onto a fence.
Emergency management officials reported mature corn was blown down in a field.
Law enforcement officials reported a large tree was blown down.
The public reported large trees down on private property.
A trained spotter reported several trees down blocking the road near County Road 900 North and 300 East. Damage was also noted to a home.
Emergency management officials reported a tree was blown down onto a home, with notable damage to the residence.
Emergency management officials reported power poles were blown down.
Emergency management officials reported numerous large tree branches down onto a home.
Emergency management officials reported a new barn that was under construction sustained significant roof and wall damage.
A trained spotter reported a tree was blown down onto a home.
The public reported a large tree was blown down and power lines down in Kendallville.
Dispatch reported trees and power lines down across mainly the northern parts of Fort Wayne.
A trained spotter measured a 69 mph wind gust.
Emergency management officials reported a power pole snapped in the Lake Arrowhead area.
The public reported the top half of a one foot diameter was snapped at the intersection of Leo Road and Arapaho Passover.
Amateur radio operators reported a semi was blown onto it side.
Local law enforcement reported multiple trees and large tree branches down across State Route 327, between County Roads 56 and 64.
A tornado touched down just west of the intersection of South County Road 700 North and South Beaver Dam Road, causing damage to trees to properties on either side of that intersection, with debris left on the roadway. A local fire chief witnessed the tornado lift over two structures and a grain bin with no noted damage. The tornado then touched down just east of the intersection in a mature corn field where it flattened a 100 to 150 foot circle in the corn, lifted briefly and then touched down again, causing the same type of damage before lifting again. The funnel attempted to touch down a third time but dissipated near a row of trees. Debris was still visible in the air. Maximum winds were estimated at 80 mph.
A mobile home rolled due to a failure of 1 or more properly secured straps from strong winds. A 74 year old woman was critically injured and later died at a nearby hospital. The woman was holding a 4 year old boy that only suffered minor injuries. The home rolled into an adjacent double wide mobile home. The initial mobile home was destroyed but all debris remained near the site. The adjacent mobile home suffered damage to the side and roof due to the home striking it. Other damage in the area was limited to some skirting of the mobile homes.
Amateur radio operators reported a semi was overturned on US 24, northeast of Fort Wayne.
As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.
| Event | Date | Age | Sex | Where | Kind |
|---|---|---|---|---|---|
| Thunderstorm Wind, Allen | 2020-08-10 | 74 | Male | Mobile/Trailer Home | Direct |
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Indiana in 2020Every state in 2020This day in weather historyThe tornado archive for Indiana, 2020Warnings in Indiana, August 2020
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 919307, 919308, 919309, 919310, 919311, 919312, 919633, 919314, 919315, 919316, 919273, 919317, 919318, 919320, 919321, 919322, 919323, 919324, 919326, 919327, 919328, 919278, 919329, 919331, 919347, 919362, 919363, 919364, 919365, 919375, 919393, 919493, 919494, 919496, 919498, 919500, 919502, 919505, 919506, 919630, and more.