Several Convective Addiction chasers intercepted supercells in southern Indiana on Friday, March 2, 2012 as part of the regional severe weather outbreak on that day. We’ll take a brief look at the synoptic overview and then link some of the photos and footage from that event. Our thoughts and prayers are with the victims who sustained loss of life and/or property in this rather large severe weather event this past week.
The Storm Prediction Center had place large portions of Dixie Alley in a high risk, as noted in their 1630z outlook below.
By late morning, cells were beginning to fire southeast of the surface low pressure system across parts of SE IL, E MO, NW KY and SW IN. The initial storm produced some brief tornado reports, but may have been somewhat hampered until the cells later matured and moved into a region of better instability as some clearing occurred south of the surface warm front per the early afternoon satellite imagery (see 1645z imagery below).
However, by 20z, explosive development was occurring near the US 64 corridor in S IN, as storms began to rapidly move northeast into better instability. A few radar grabs from the Louisville, KY office (KLMK) are show below as the tornado crossed I-65 and moved into Henryville and points ENE.
The early afternoon surface synopsis showed a strong low pressure system centered over central Illinois, with a warm front extending SSE into the Ohio River valley and a strong cold front approaching from the west. The vigorous surface cyclone promulgated the northward advection of seasonably rich moisture into a region of enhancing instability and very strong low-level shear behind the advancing warm front. This set the stage for explosive thunderstorm development over the next 12 hours or so across areas to the E/NE and E/SE as the outbreak commenced. It might be noted, per the purple hatched area below, that the supercell that produced the Henrysville tornado appeared to track proximal to the nose of the 60 degree dewpoint isopleth.
A look at mesoanalysis data for the upper and mid-levels of the atmosphere shows the region lies in the exit region of a strong jet core that was rounding the basal side of a trough, placing the region in the crosshairs of enhanced DPVA (positive vorticity advection) juxtaposed with the aforementioned low-level moisture and instability.
Of further note is a dry punch that was evident at 700 mb on the 19z mesoanalysis chart, which certainly enhanced lift across the region as the supercells developed and moved northeastward.
A 60 kt LLJ was maxima was approaching from the SSW at 19z (see below) and, when juxtaposed with 15kt southerly mean flow at the surface, likely enhanced shear values in the lowest 1 km and led to ambient streamwise vorticity to sustain the supercell as it tracked towards Marysville and points NE.
The supercells tracked into a very ambient environment, with 0-1 km SRH values sitting at 500 m**2/s**2 and MLCAPE values at 1,000 J/KG, each of which are more than favorable by early spring standards, especially the CAPE, which is still respectable by early March standards that far north (both graphics below are from 19z/02).
The NWS had put out a tornado warning when the cell was well to the SW of Henryville, and this was later upgraded to a tornado emergency (see the text below):
513 WWUS53 KLMK 022017 SVSLMK
SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE LOUISVILLE KY
317 PM EST FRI MAR 2 2012
SCOTT IN-WASHINGTON IN-JEFFERSON IN-CLARK IN-TRIMBLE KY-
317 PM EST FRI MAR 2 2012
…TORNADO EMERGENCY CONTINUES FOR NORTHERN CLARK COUNTY INDIANA…
…A TORNADO WARNING REMAINS IN EFFECT UNTIL 345 PM EST FOR NORTHERN
TRIMBLE…NORTHERN CLARK…JEFFERSON…EASTERN WASHINGTON AND
SOUTHEASTERN SCOTT COUNTIES…
AT 314 PM EST…MULTIPLE REPORTS OF A TORNADO CONTINUE TO BE
RECEIVED BY THE NATIONAL WEATHER SERVICE IN LOUISVILLE. THIS
TORNADO JUST CROSSED I-65 AND IS HEADING NORTHEAST AT 60 TO 65 MPH.
IF YOU ARE IN AREAS SUCH AS HENRYVILLE…MARYSVILLE AND LEXINGTON
INDIANA TAKE COVER NOW!
* THIS DANGEROUS STORM WILL ALSO IMPACT…
CHELSEA AND SALUDA…
HANOVER BEACH AND HANOVER…
MILTON AND NORTH MADISON…
TO REPORT SEVERE WEATHER…CONTACT YOUR NEAREST LAW ENFORCEMENT
AGENCY. THEY WILL RELAY YOUR REPORT TO THE NATIONAL WEATHER SERVICE
Skip Talbot’s full video
Jonathan Williamson’s video (was riding with Adam Lucio)
A few video grabs from another Convective Addiction chaser’s video:
Please check back for more updates as we add to this page.
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