109 The 2 March 2012 Tornado Outbreak: Where Tornadoes Did Not Form Across the Ohio Valley

Wednesday, 7 November 2012
Symphony III and Foyer (Loews Vanderbilt Hotel)
Michael J. Paddock, NOAA/NWS, Louisville, KY; and A. Lese

The 2 March 2012 Tornado Outbreak: Where Tornadoes Did Not Form Across the Ohio Valley

Michael J. Paddock1 and Angela Lese2


1NOAA/National Weather Service, Louisville, Kentucky

2NOAA/National Weather Service, Nashville, Tennessee


On the morning of March 2, 2012 surface low pressure was centered over southern Missouri with a warm front reaching east into the Ohio Valley.  Showers and thunderstorms were scattered along the warm front, and produced hail to the size of nickels during the morning hours.  By late morning the low had deepened and moved to central Illinois, lifting the warm front north of the Louisville, Kentucky Weather Forecast Office's County Warning Area and bringing an end to the morning thunderstorms.  It also put southern Indiana and central Kentucky within the warm sector of the storm system, with the system's cold front stretched from the low in central Illinois southward through Arkansas to Texas.

Temperatures over southern Indiana and central Kentucky soared well into the 70s oF by midday, with southern Kentucky actually setting record highs in the lower 80s.  The atmosphere had become very unstable with extremely strong wind shear.  The convective available potential energy utilizing the most unstable parcel reached 2000+ J/kg, effective system-relative helicity ranged between 400-600+ m2/s2, and 0-6 km effective bulk shear values reached 60+ knots.  Storms developed in this extremely unstable atmosphere, while the wind shear promoted rotating updrafts and subsequent tornado development.  The parent low of the system continued to deepen as it quickly tracked towards southern Michigan and dragged its attendant cold front into the Ohio and Tennessee Valleys.  Storms continued to erupt throughout the region and easily attained rotating updrafts, resulting in eight tornadoes and numerous reports of large hail.  One supercell produced a tornado that was rated an EF-4 on the Enhanced Fujita scale, which stayed on the ground for 49 miles through portions of southern Indiana and into north-central Kentucky. 

As the afternoon and early evening hours progressed, additional supercell storms tracked across central and south-central Kentucky within this very unstable atmosphere.  However, tornadic development was practically nonexistent, with baseball to softball-size hail being the main hazard associated with these supercells.  Upon further investigation, there were several subtle atmospheric indicators that depicted potential tornado formation would be less likely across central and south-central Kentucky.  This presentation will delve into the scientific specifics that were likely instrumental in reducing tornado formation within this very unstable atmosphere, as well as discuss the social aspects affecting warning decision-making skills in this type of environment.

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