Severe Storm Workshop Winter 2007, Saint Louis University
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Transcript of Severe Storm Workshop Winter 2007, Saint Louis University
![Page 1: Severe Storm Workshop Winter 2007, Saint Louis University](https://reader036.fdocuments.net/reader036/viewer/2022062517/56812ef2550346895d9491f3/html5/thumbnails/1.jpg)
Analysis of the 2 April 2006 Quasi-Linear Convective System (QLCS) over the Mid-Mississippi Valley Region: Storm Structure
and Evolution from WSR-88D data
Ron W. Przybylinski and James E. Sieveking NOAA/ National Weather Service St. Louis MO
Nolan T. AtkinsLyndon State College
Lyndonville VT
Severe Storm Workshop Winter 2007, Saint Louis University
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It is 10 March 1986and you are the warningforecaster. You needto issue warnings from the conventional WSR-74C at WFO IND(125 nm range).
What type of warnings would you Issue based on the conventional reflectivity data?
Any particular locations?
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2 April 2006 Outline
• Storm Damage Assessment
• Synoptic / Mesoscale Environment
• Radar Analysis- Early Stages- Northeast of St. Louis- St. Louis Area and immediate southwest Illinois(metro east)
• Summary
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Some Findings:
• 9 tornadoes occurred within the WFO LSX CWA(with many of these tornadoes occurring along theleading edge of the squall line).
• Tornadic damage ranged from F0 to F2 intensity• F2 damage intensity occurred in Fairview Heights
and east of the O’Fallon Illinois area. • The longest tornadic damage track occurred over
Montgomery County Illinois (20 miles long). • 2 fatalities (one in St. Louis County and the other in
Fairview Heights Illinois) and 20 injuries occurred with this event.
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East-Central Missouri – Southwest Illinois Damage Map
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Most of our damaging wind reports with organized convective lines occur between 4:00 PM – 8:00 PM
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Most of our squall line (non-supercell) tornadoes also occur between 4:00 PM and 8:00 PM CDT.
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Visible Satellite and Surface Analysis for 1900 UTC
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Sounding Analysis from KSGF at 1800 UTC
CAPE = 2056 J/kg
BRN = 43.7
0-5 km Bulk Shear27 m s-1 (54 kts)
0-3 km Bulk Shear16 m s-1 (32 kts)
0-3 km SR Helicity215 m2 s-2
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What was the degree of instability on this day?From SPC mesoanalysis
At 1900 UTC (2:00 PM) MLCAPE /MLCIN analysis showed the greatestinstability was located over central Missouri 1500 - 2000 J/kg.
At 2100 UTC (4:00 PM) Axis of highest instabilityextended from southeast Iowathrough east central Missouri1500 – 2000 J/kg.
www.spc.noaa.gov/exper/mesoanalysis
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Along warm or near stationary frontal boundarieswe frequently observe strong thermal gradients which supports potential fornear surface and low-level rotation.
From Markowski et al. 1998
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0-1 km Storm-relative helicity (SRH)for 2:00 PM CDT from SPC. Axis of highest values are aligned with the warm frontal boundary from northeast Missouri through south-central Illinois. Units m2 s-2
0-3 km Storm-relative helicity (SRH) (deeper layer) for 2:00 PM CDT. Axis of highest values are similar to 0-1 km SRH from northeast Missouri through south-central Illinois.
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0-1 km Storm-relative helicity (SRH)for 4:00 PM CDT. Magnitudes of SRH increased from 2:00 PM CDT. Again the axis strongest values were aligned along the warm frontal boundary – west central throughsouth-central Illinois.
0-3 km Storm-relative helicity (SRH)(deeper layer) for 4:00 PM CDT.
Similar to the 0-1 km SRH image the axis of highest magnitudes werealigned along the warm frontal boundary.
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Radar Composite including mesovortices 1 through 10 and tornado tracks (shown in red). Except for MV 1 and MV 7 the tornadic mesovortex tracks in the 2 April case revealed longer paths compared to the 10 June 2003 St. Louis bow echo case during BAMEX.
3:30 PM 4:30 PM 5:30 PM
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On this day, I was traveling southbound on I 55 headingtowards STL. With the approaching line of storms I stoppedand positioned myself just northeast of Staunton Illinois.
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Viewing southwest towards the town of Staunton IL. No Shelf Cloud Yet!!!
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Approaching Shelf Cloud from the southwest. Viewingsouthwest towards the town of Staunton IL.
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Viewing south – Shelf cloud overhead. Any possible rotation with the shelf cloud? Winds estimated 50 to 60 mphwith hail (dime size) at this time. I- 55 is just to the left.
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A Wall Cloud along the leading edge of the large bow echo near Springfield Illinois (April 2, 2006).
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Mesovortices #2, 3, 4 and 5 over southwest Illinois; 55 km NNE of KLSX over Macoupin County IL. Light blue contours represent tornadic damage path. Light blueand black contour signifies path of mesovortex.
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Rotational Velocity trace of Mesovortex #2
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KLSX planview reflectivityand cross-section at 2226 UTC (Images from WDSS-II). Multicell evolution noted along theleading edge at this time.
KLSX plan view base velocity and cross-sectionat 2226 UTC. MesoscaleRIJ appears to be descendingto near the surface at this time.
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REFLECTIVITY CROSS SECTION
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VELOCITY CROSS SECTIONDESCENDING REAR INFLOW JET (RIJ)
Mesoscale RIJ originated near 4.0 km (white – light gray area greater than 70 kts) then descends to near the surface as to line approaches western St. Charles and St. Louis counties.
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Mesovortices #5, 6, and 7 over Metro East
Fairview Heights and O’Fallon Illinois are located along the path of MV #6 (Light blue region).
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Rotational Velocity trace of Mesovortex #6
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Rotational Velocity trace of Mesovortex #7
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Summary
• 2 April 2006 Tornadic QLCS was one of the most challenging severe weather episodes in recent history.
• Widespread wind damage occurred over parts of east-central Missouri, while much of the higher intensity damage over southwest Illinois occurred along the paths of the mesovortices (circulations).
• Tornadic damage ranged from F0 – F2 intensity.
• Two fatalities and 20 injuries occurred.
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Summary Continued
• Tornado touchdown occurred at or just after the initial identification of the mesovortex. (Thus very limited lead time for warnings in this case).
• Rapid convective line motion combined very small mesovortex core diameters and weak to moderate intensity rotational velocities lead to the complexity of the April 2nd tornadic case.
• Of the 38 cases studied over the Mid-Mississippi Valley Region, this case could be placed near the far left end of the spectrum of cases.