Tornadoes of April 8-9, 1999
Posted: Wed Apr 09, 2003 2:46 am
On April 8thand 9th, 1999, an outbreak of severe thunderstorms and tornadoes occured across the Lower Missouri, Mid Mississippi and Lower Ohio Valleys. The outbreak itself was well forecast, with a HIGH risk of severe thunderstorms placed over parts of the Lower Missouri and Mid Mississippi Valleys during the afternoon and evening of April 8th. Within the area of Iowa, northern Missouri and west-central Illinois, several supercell thunderstorms developed, with a few long track tornadoes. Other weaker tornadoes developed undeneath the mid/upper level low over eastern Nebraska. During the entire event, there was 54 tornadoes, around 65 reports of severe thunderstorm hail and around 110 reports of severe thunderstorm wind gusts.
There was three F4 rated tornadoes (two long track tornadoes in southwest and central Iowa with another just northeast of Cincinnati, OH), five F3, eight F2, twenty-four F1 and thirteen F0 tornadoes. All severe reports here exclude a minor hail event over central California and severe weather produced by a supercell along the Georgia/South Carolina border.
There was 6 fatalities and 115 injuries related to the outbreak, with 4 tornado related fatalities in the Cincinnati, Ohio area.
The most notable and studied part of this outbreak takes place over the Lower Ohio Valley. Severe supercells that moved across Missouri and Illinois on the evening of April 8th consolidated into a broken squalline of thunderstorms. These storms would progress eastward through Indiana and Kentucky overnight with occasional wind, hail and tornado reports. Many tornado watches were issued over the Lower Missouri and Mid Mississippi Valley earlier in the evening (with a few PDS tornado watches). Tornado watch number 140 was issued for a large part of Indiana and northwest Kentucky, with Tornado watch number 141 following just before 3 AM EDT April 9th, that covered much of west and central Ohio, north Kentucky and a small part of western West Virginia. The broken squalline of thunderstorms over Indiana began to break down into individual cells over central and southern Indiana by around 3 AM EDT on April 9th. Once cell is particular over south-central Indiana would produce several tornadoes across southeast Indiana and southwest Ohio between 4 and 5:30 AM. Another cell would produce a few tornadoes across west-central Ohio.
The first tornado in southeast Indiana occured at 4:05 AM EDT and stretched from 6 miles southwest of Rexville to Olean (4:22 AM EDT, Ripley County). This tornado moved into Jefferson Proving Grounds from Jennings County. Trees were knocked town, garages destroyed, a barn blown over, a truck thrown 30 yard and a mobile home destroyed. This tornado was rated F3 with $700,000 of damage. There was no fatalities or injuries.
A second tornado, rated F0, moved from 2 miles West of Aurora (4:44 AM EDT) to 1 mile west of Aurora, Indiana (4:47 AM EDT Dearborn County), A small barn was totally destroyed, a 40 foot silo was damaged and several trees were downed. Several homes were heavily damaged in rural Dillsboro. $250,000 of damage resulted, with no fatalities or injuries.
A third tornado, rated F1, moved from 1 mile West of Addyston (4:55 AM EDT) to Addyston, Ohio (5:00 AM EDT, Hamilton County). After touching down on the north shore of the Ohio River, this tornado destroyed a house, pulled metal roofing from a garage, and downed several trees. There was $200,000 of damage.
A forth tornado, rated F4, moved from Blue Ash (5:12 AM EDT, Hamilton County, Ohio) to 1 mile southwest of Maineville(5:25 AM EDT, Warren County, Ohio). The tornado began with F2 intensity in the Blue Ash area. The tornado moved through Montgomery, Symmes Township, and Loveland before entering Warren County. From here, it moved through southeast Deerfield Township and across the Little Miami River. The intensity was F2 to F3 along many points of its track, intensifying to a low F4 while in Montgomery. The width ranged from 100 yeards to 1/4 mile. Four fatalities occurred, with twi in a home and another two in vehicles. About 91 homes and apartments were destroyed along with 37 businesses. Additionally, 197 homes and apartments suffered major damage with 477 others also incurring damage. Twenty six businesses had major damage with 18 others alos incurring damage. In Warren County, the tornado damaged several houses, hundreds of mature trees along with garages and barns. There was a total of $85 million of damage resulting from this tornado.
The fifth and final tornado rated F2, moved from 3 miles northeast of Maineville (5:33 AM EDT) to 3 miles southwest of Morrow, Ohio (5:40 AM EDT, Warren County). This tornado touched down in eastern Hamilton Township causing heavy damage to a farmestead. The roof of the house and an extension to a barn were destroyed. Further down the path, a house was skewed from its foundation. There was $2.5 million of damage resulting from this tornado.
It should be noted that the intensity of the thunderstorms over southeast Indiana and southwest Ohio were somewhat unanticipated early on April 9th. A great deal of study was made of this event, and findings can be found at this link: http://205.156.54.206/er/iln/sls4999gt.html
I personally still remember this event very well. I had been looking over the 72 hour Aviation model output on April 6th and even then thought that severe weather was quite possible across the Mid MS Valley. The area and threats weren't defined til later on the 7th and early on the 8th. There was some doubt early in the day as to how far south thunderstorms would develop along a dryline (storms did in fact form southward to the Arklatex region). This storm had plenty of low level moisture to work with, along with very strong low level shear. The storms closest to the upper low moved north-northeast over northern Missouri and Iowa, while storms farther east moved east-northeast. The storm that produced the Cincinnati tornadoes actually developed in southeast Missouri, tracked east-northeast with little to no severe weather til it entered southeast Indiana. Evening soundings from Lincoln, IL and Wilmington, OH pointed out the potential for severe weather in the Cincinnati area later that night, but with the storms arriving late (after 3 AM), I wasn't expecting a great tornado threat. Typically, you see decreasing low level instability (something you need for upward moving air parcels and storms) that late at night. I recall tracking the Indiana and Illinois storms all night. One cell over south-central Indiana took my attention around 3 AM as it showed some storm-scale rotation on the Indianapolis WSR-88D radar. A tornado warning was soon issued for Jennings County as the rotation strengthened, then producing the tornado in Ripley County. The base reflectivity signatures that the Indianpolis and Wilmington radars displayed didn't show the usual signatures for tornadic activity. It wasn't til the storm entered Hamilton County and began to "spin-up" that supercell characteristics began to show. By this time I was ready to head for the basement with the low level circulation only passing a few miles to the south. I never heard any reports of tornadoes, except what was in the tornado warnings. I did watch some pictures of damage in northeast Hamilton County on the early morning news before going to bed (6:30 AM).
There was three F4 rated tornadoes (two long track tornadoes in southwest and central Iowa with another just northeast of Cincinnati, OH), five F3, eight F2, twenty-four F1 and thirteen F0 tornadoes. All severe reports here exclude a minor hail event over central California and severe weather produced by a supercell along the Georgia/South Carolina border.
There was 6 fatalities and 115 injuries related to the outbreak, with 4 tornado related fatalities in the Cincinnati, Ohio area.
The most notable and studied part of this outbreak takes place over the Lower Ohio Valley. Severe supercells that moved across Missouri and Illinois on the evening of April 8th consolidated into a broken squalline of thunderstorms. These storms would progress eastward through Indiana and Kentucky overnight with occasional wind, hail and tornado reports. Many tornado watches were issued over the Lower Missouri and Mid Mississippi Valley earlier in the evening (with a few PDS tornado watches). Tornado watch number 140 was issued for a large part of Indiana and northwest Kentucky, with Tornado watch number 141 following just before 3 AM EDT April 9th, that covered much of west and central Ohio, north Kentucky and a small part of western West Virginia. The broken squalline of thunderstorms over Indiana began to break down into individual cells over central and southern Indiana by around 3 AM EDT on April 9th. Once cell is particular over south-central Indiana would produce several tornadoes across southeast Indiana and southwest Ohio between 4 and 5:30 AM. Another cell would produce a few tornadoes across west-central Ohio.
The first tornado in southeast Indiana occured at 4:05 AM EDT and stretched from 6 miles southwest of Rexville to Olean (4:22 AM EDT, Ripley County). This tornado moved into Jefferson Proving Grounds from Jennings County. Trees were knocked town, garages destroyed, a barn blown over, a truck thrown 30 yard and a mobile home destroyed. This tornado was rated F3 with $700,000 of damage. There was no fatalities or injuries.
A second tornado, rated F0, moved from 2 miles West of Aurora (4:44 AM EDT) to 1 mile west of Aurora, Indiana (4:47 AM EDT Dearborn County), A small barn was totally destroyed, a 40 foot silo was damaged and several trees were downed. Several homes were heavily damaged in rural Dillsboro. $250,000 of damage resulted, with no fatalities or injuries.
A third tornado, rated F1, moved from 1 mile West of Addyston (4:55 AM EDT) to Addyston, Ohio (5:00 AM EDT, Hamilton County). After touching down on the north shore of the Ohio River, this tornado destroyed a house, pulled metal roofing from a garage, and downed several trees. There was $200,000 of damage.
A forth tornado, rated F4, moved from Blue Ash (5:12 AM EDT, Hamilton County, Ohio) to 1 mile southwest of Maineville(5:25 AM EDT, Warren County, Ohio). The tornado began with F2 intensity in the Blue Ash area. The tornado moved through Montgomery, Symmes Township, and Loveland before entering Warren County. From here, it moved through southeast Deerfield Township and across the Little Miami River. The intensity was F2 to F3 along many points of its track, intensifying to a low F4 while in Montgomery. The width ranged from 100 yeards to 1/4 mile. Four fatalities occurred, with twi in a home and another two in vehicles. About 91 homes and apartments were destroyed along with 37 businesses. Additionally, 197 homes and apartments suffered major damage with 477 others also incurring damage. Twenty six businesses had major damage with 18 others alos incurring damage. In Warren County, the tornado damaged several houses, hundreds of mature trees along with garages and barns. There was a total of $85 million of damage resulting from this tornado.
The fifth and final tornado rated F2, moved from 3 miles northeast of Maineville (5:33 AM EDT) to 3 miles southwest of Morrow, Ohio (5:40 AM EDT, Warren County). This tornado touched down in eastern Hamilton Township causing heavy damage to a farmestead. The roof of the house and an extension to a barn were destroyed. Further down the path, a house was skewed from its foundation. There was $2.5 million of damage resulting from this tornado.
It should be noted that the intensity of the thunderstorms over southeast Indiana and southwest Ohio were somewhat unanticipated early on April 9th. A great deal of study was made of this event, and findings can be found at this link: http://205.156.54.206/er/iln/sls4999gt.html
I personally still remember this event very well. I had been looking over the 72 hour Aviation model output on April 6th and even then thought that severe weather was quite possible across the Mid MS Valley. The area and threats weren't defined til later on the 7th and early on the 8th. There was some doubt early in the day as to how far south thunderstorms would develop along a dryline (storms did in fact form southward to the Arklatex region). This storm had plenty of low level moisture to work with, along with very strong low level shear. The storms closest to the upper low moved north-northeast over northern Missouri and Iowa, while storms farther east moved east-northeast. The storm that produced the Cincinnati tornadoes actually developed in southeast Missouri, tracked east-northeast with little to no severe weather til it entered southeast Indiana. Evening soundings from Lincoln, IL and Wilmington, OH pointed out the potential for severe weather in the Cincinnati area later that night, but with the storms arriving late (after 3 AM), I wasn't expecting a great tornado threat. Typically, you see decreasing low level instability (something you need for upward moving air parcels and storms) that late at night. I recall tracking the Indiana and Illinois storms all night. One cell over south-central Indiana took my attention around 3 AM as it showed some storm-scale rotation on the Indianapolis WSR-88D radar. A tornado warning was soon issued for Jennings County as the rotation strengthened, then producing the tornado in Ripley County. The base reflectivity signatures that the Indianpolis and Wilmington radars displayed didn't show the usual signatures for tornadic activity. It wasn't til the storm entered Hamilton County and began to "spin-up" that supercell characteristics began to show. By this time I was ready to head for the basement with the low level circulation only passing a few miles to the south. I never heard any reports of tornadoes, except what was in the tornado warnings. I did watch some pictures of damage in northeast Hamilton County on the early morning news before going to bed (6:30 AM).
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