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June 10 2003 St. Louis Bow Echo Event
Nolan Atkins, Chris Buschard, Ron Przybylinski, Jeff Trapp and Gary Schmocker Lyndon State College Lyndonville VT. NOAA / National Weather Service St. Louis Purdue University West Lafayette Indiana Updated July 2008 |
During the mid afternoon of 10 June, 2003 two clusters of thunderstorms over central Missouri moved east and merged just west of the Mississippi River (including the St. Louis metro area and south) between 2230 and 2300 UTC and became an organized quasi-linear convective system (QLCS). During and after system organization, several moderate to strong mesovotices formed along the leading edge of the system, just over and east of the St. Louis metro area and produced nearly continuous swaths of damaging winds and several weak tornadoes (F0 - F1 damage). This page will provide an overview of the June 10, 2003 QLCS including detailed damage map, mesoscale environment, storm reflectivity , Doppler velocity structure and mesovortex evolution. A detailed aerial and ground survey was performed after the event to map out the tornadic and downburst wind swaths produced by the system. Rotational velocities (Vr) time-height traces were used to show the structural differences between tornadic and non-tornadic mesovortices. Forecasting convection on this day was quite challenging with the potential for MCS development over the Mississippi Valley region during the early morning hours and again possibly during the late afternoon and early evening. On June 9th, BAMEX forecasters and the PI's were challenged as to which period they would consider to begin mission operations. They flew the late night - early morning MCS event which evolved from southeast Nebraska through northern and eastern Missouri. Little did they know that one of the most pronouced bow echo events during the project would occurred during the late afternoon and early evening of 10 June over the Mid-Mississippi Valley region.
The following is a summary of graphical images showing mesoscale environment, detailed radar reflectivitiy/Base Doppler velocity images, Rotational Velocity (Vr) time-height traces, and detailed mapping of the tornadic and damaging wind swaths.
Fig. 1. Radar reflectivity data at 0.5° slice from KLSX radar. Solid and short-dashed lines indicate positions
of tornadic and non-tornadic mesovortices, respectively. Tornado times are shown with thick lines. The long
dashed line seperates the 2059 and 2159 UTC radar data.
Figure 1 shows the storm and mesovortex evolution of the 10 June 2003 St. Louis bow echo event. The first bow echo (BE #1) formed from a cluster of storms over south-central Missouri and moved eastward across northern Crawford and Washington counties in east-central Missouri. BE #1 merged with a cluster of strong storms around 2200 UTC which originally formed over central Missouri (30 to 70 km southeast of Columbia MO (COU). Overall QLCS organization occurred between 2230 and 2300 UTC over and south of the St. Louis metro area. Several weak non-tornadic mesovortices occurred with the northern cluster of storms and the southern bow echo between 2200 and 2230 UTC. Just after system organization several tornadic mesovortices formed over the St. Louis metro area and moved eastward into the metro-east and parts of southwest Illinois.
Fig. 2. Skew-t Log-P diagram from KSGF 1800 UTC, 10 June 2003. Half wind barb represents
5 m s-1 while full wind barb signifies 10 m s-1.
Fig 3. Visible satellite imagery at 2115 UTC, 10 June 2003 with surface observations. The white
dashed line represents the approximate location of the surface outflow from the morning MCS.
The 2100 UTC surface analysis showed an old surface outflow extending from western Tennessee to near the St. Louis metro east region. South-southwest winds over south-central Missouri were advecting lower to middle 70 degree dewpoints north and northeastward into east-central Missouri west of the surface outflow. Dewpoints east of the outflow ranged from the upper 60s to around 70.
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Fig. 4a. Objective Mesoscale Analysis Products from the Storm Prediction Center (SPC) for 2100 UTC 10 June 2003: a) far left: is Surface-based Convective Available Potential Energy - Convective Inhibition (SB CAPE) / SBCIN, b) near left: Surface to 1 km Storm-relative helicity (m2 s-2), near right: Surface to 3 km Storm-relative helicity (m2 s-2). d) far right: 100 mb Mean Parcel LCL Height (m AGL). (click on image for a larger image).
Select flelds from the Storm Prediction Center (SPC) mesoscale analysis for 2100 UTC is shown in Figure 4. Surface-Based CAPE - CIN field (far left) showed an axis of highest instability extending fom east-central through south-central Missouri then into west-central parts of the state. Values of SB CIN of 100 J/Kg were noted over parts od central and west central Missouri reflecting the current multicell convection over this area. However, much higher values of SB CIN covered much of the southern third of Illinois through southeast Missouri and into western Kentucky in response to the passing of the first MCS across the Mid-Missippi Valley region. Note that magnitudes of SB CIN ranged from 100 - 400 J/Kg over parts of southwest through south-central Illinois. Currently, Dr. Nolan Atkins from Lyndon State College along with Dr. Matt Parker from North Carolina State University are studying the effects of low-level stable layers on cold pools associated with QLCSs. Papers on this topic are located in the 23rd Conf. of Severe Local Storms.
In viewing 0-1 km SRH field for 2100 UTC, the highest values were revealed over far southern Illinois (350 m2 s-2) while values of 250 m2 s-2 extended well into parts of east-central Missouri and southwest Illinois. Magnitudes of 0-3 km SRH revealed a similar pattern to that of the 0-1 km SRH field showing the highest values SRH over far southern Illinois and western Kentucky. Again the axis greatest 0-3 km SRH extended northwest into parts of east-central Missouri and southwest Illinois. Tornadic activity occurred over the western part of this area - over parts of southwest Illinois. The LCL height field (far right) showed the heights of the lowest LCLs over parts of central through northeast and parts of east-central Missouri where heights were at or below 1000 meters.
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Fig 4b. Same as Fig. 4a except for 2300 UTC (Click on a image for a larger image).
Surface-based CAPE / CIN for 2300 UTC showed the axis of greatest instability was shunned to southwest through south-central Missouri with magnitudes exceeding 3500 J/Kg. In contrast where convection was occurring surface-based CAPE values from central through east-central Missouri were less than 2000 J/kg. Surface-based CIN values of 100 J/Kg and greater were common across central through east-central Missouri and merged with the larger area if SBCIN to the east. This increased area of CIN reflected the passage of northern bow echo across the Greater St. Louis Metro area. The area of stronger Surface-Based CIN noted earlier noted continued to persist from south-central through southeast Illinois with magniudes greater than 200 J/Kg. We will discovered that wind damage ceased with the bow when magnitudes of SBCIN were 200 J/kg and greater.
A similar to the 2100 UTC 0-1 km SRH field pattern, the 2300 UTC 0-1 km SRH showed values of 200 m2 s-2 or greater over parts of extreme east-central through southeast Missouri and over the southern third of Illinois. The 0-3 km SRH field for 2300 UTC showed a similar pattern to the 0-1 km however, values of 200 m2 s-1 did expand a little west and southwest across eastern Missouri. Both fields showed that magnitudes did retreat to the southeast at 2300 UTC compared to 2100 UTC fields of SRH. However, back ground SRH within both layers were still prevelant across much of southwest through south-central Illinois and may have aided in enhancing the probability of tornadogenesis over southwest sections of the state. .
The following is a sequence of radar reflectivity/Doppler velocity images from KLSX for the period of 2300 - 2340 UTC. The NCAR SOLO's program is used to display the base reflectivity/Doppler velocity images.
Fig. 5. Reflectivity (left), Base velocity (right) from KLSX at 2300 UTC. Outbound velocities greater than 25 m s-1 are represented by
the red area. Thin solid black lines signifies tracks of the mesovortices. Light blue line near the mesovortex track represents tornadic
damage. The light gray shading indicates region of intense wind damage (F1). The light green contour outlines the region of the
mesoscale Rear Inflow Jet (RIJ) with the heavy dashed arrow showing the primary axis of the RIJ. MAA is the location of the Mid-America Airport.
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2245 UTC
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2250 UTC
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2255 UTC
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2300 UTC
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Fig 6. Sequence of reflectivity / storm-relative velocity cross-sections and corresponding reflectivity planviews for the period of 2245
through 2300 UTC. (Click on each image for a larger image).
The time series of reflectivity cross-sections shown in Fig 6. reveals the presence of multicell evolution during the period of 2245 through 2300 UTC. The developing tall convective towers shown at 2245 merge with the mature towers by 2350 UTC. New cell growth is still noted just downshear from the mature towers at 2255 and 2300 UTC but not as pronounced.
The 2345 UTC SRM cross-section shows the very early stages of the mesoscale Rear Inflow Jet (RIJ) and Front-to-Rear (F-T-R) flow. Note the strong inbound velocity maximum at 2245 UTC signifies an intense updraft core just downshear from the mature convective towers. With time individual updraft pulses (stronger local inbound velocity maximums) appear to correspond with the developing convective towers at 2255 and 2300 UTC. Additionally, a well defined line of covergence is noted within the 3-5 kft (0.9 - 1.5 km) layer. Note how the mesoscale RIJ builds rearward with time and in concert with the mesoscale Front-To-Rear flow. The mesoscale RIJ appears to descend to the lower part of the boundary layer at 2255 and 2300 UTC. Tornadogenesis occurred with the individual mesovortices at and after 2255 UTC over parts of southwest Illinois.
Just prior to 2300 UTC, the first of several tornado touchdowns occurred in the Dupo Illinois area (approximately 7-8 miles south of downtown St. Louis). The Dupo Illinois tornado was associated with Circulation 3 (Vr trace) which formed near the apex of the developing mesoscale Rear Inflow Jet (RIJ). The Caseyville Illinois tornado occurred just after 2300 UTC within the region of reflectivity concavity and north of the RIJ axis (northern most mesovortex track (Circ 5)). Base reflectivity imagery shows rapid new cell development (multicell evolution) just downshear of the small bowing segment.
Fig 7. Same as Figure for 4 except for 2310 UTC.
Between 2300 and 2310 UTC, the Caseyville Illinois tornado (F1 damage) occurred with Circ 5 (northern most mesovortex track). Several house trailers and homes were damaged by this tornado as it moved along the southwest and south side of the town limits. Additionally several witnesses southeast of town were able to observe the tornado. This tornadic mesovortex track remained north of the primary RIJ axis. Circ 3 (Dupo Illinois mesovortex) continued to track eastward and now was north of the primary RIJ axis. Significant tree damage occurred along this mesovortex track west of Mid-America Airport (MAA) (western part of the gray shaded area). Much of the damage was along the mesovortex tracks while there was an absence of damage outside the circulation tracks during this time period. The small convective cells identified earlier downshear of the northern bowing segment merged with this bowing segment at this time. The southern-most mesovortex track (Circ 1) spawned a weak tornado (F0 damage) 2 to 4 miles southwest of Red Bud Illinois. This mesovortex was the longest and most persistent circulation of the group. Scattered wind damage was identifed from 5 miles southwest of the tornadic track to 2 miles east of the tornadic damage track (or just south of Red Bud). Circ 1 was associated with the southern bowing segment.
Fig. 8. Same as Fig 4 except for 2320 UTC.
At 2320 UTC Mesovortices #3 and #5 merged northeast of Mid America Airport (MAA) . A swath of F1 wind damage (gray shaded region) was uncovered within and east of the point of merger. Both vortices remained north of the primary mesoscale RIJ axis through 2320. Multicell evolution continued with the northern bowing segment (within the vicinity of the swath of F1 damage) and also with the southern bowing segment. During the previous 20 minutes (ending at 2320 UTC), there was an absence of wind damage with the primary RIJ axis. The southern-most mesovortex track (Circ 1 - Redbud circulation) weakened at 2325 and was no longer discernable. A microburst was identified southeast of Redbud. Note the presence of isolated cell development near Nashville Illinois. Przybylinski and DeCaire (1985) have documented this type of cell growth several ten's of kilometers downshear from organized bow echoes and segments.
Fig. 8. Same as Fig 4 except for 2330 UTC.
The reflectivity patten (left) at 2330 UTC, continued to show two bowing segments within the larger convective line. A 'Rear Inflow Notch' (RIN) evolved along the trailing flank of the 50 dBZ echo with the northern bowing segment. Clusters of damaging downburst winds occurred at of just north of the apex of the northern bowing segment and mainly north of the mesoscale RIJ axis (and northern part of the RIN) just downshear of the merged mesovortices #3 and #5. The location of the RIN (green contour) coincided quite nicely with the location of the mesoscale RIJ (left reflectivity image). However, note the absence of wind damage directly with the mesoscale RIJ axis. A new mesovortex formed just south of the apex of the northern bowing segment (or approximately 15 miles west of Nashville Illinois - Washington County). This mesovortex also became tornadic and had a damage path from 12 miles west of Nashville to just 1.5 miles north of town. Several machine sheds, a few homes and trees were damaged along the path of the tornado. The tornadic damage was rated F1.
Fig 10. Same as Fig 4 except for 2340 UTC
At 2340 UTC, the northern bowing segment became the predominant bowing structure while the southern bowing segment was not discernible. The RIN expanded along the trailing flank of northern bowing segment and continued to coincide with the mesoscale RIJ (green contour). As in the previous time (2330 UTC), the greatest degree of damaging downburst winds occurred in the vicinity of the apex of the northern bowing segment and coincided north of the mesoscale RIJ axis (and northern part of the RIN). The tornadic Nashville mesovortex continued to travel eastward south of the apex of the northern bowing segment. From this time through 0005 UTC a large line-end vortex evolved near the comma-head of the bow echo. Wind damage ceased as the bow echo moved across Marion county Illinois and points eastward. A shallow stable layer of air from the morning MCS may have contributed to the absence of wind damage over south-central through southeast Illinois.
Fig 11a. Rotational Velocity trace for the later part of Circulation #1(Redbud Illinois mesovortex).
The above Vr trace shows that Circ #1 intensified and deepened after 2240 UTC. The greatest intensification occurred after 2245 UTC within the lowest 3 km. A weak tornado (F0 damage) occurred between 2300 and 2310 UTC west-southwest of Redbud Illinois.
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Fig. 11b. Rotational velocity traces of Circulations 3 (Dupo Illinois mesovortex) and Circulation 5 (Caseyville Illinois mesovortex). Both circulations were responsible for spawning tornadoes just east and southeast of the immediate St. Louis downtown area.
Circulation 3 formed over southwest St. Louis county and traveled eastward across south St. Louis city. This mesovortex spawned the first of two tornadoes over Dupo Illinois. Damage was rated F1. Circulation 3 rapidly intensified and deepened between 2234 and 2250 just prior to tornado touchdown. The strongest low-level rotation was identified at 2240 (or ten minutes preceding tornado occurrence) where magnitudes of delta-V were 30 m s-1. Note this first of two circulation peaks (greatest depths) occurred at the beginning of tornado touchdown. We have documented previous observations of this kind of tornadic mesovortex trends in earlier studies (e.g. May 27, 2000 QLCS, June 29, 1998 Derecho). Circulation 3 spawned a second tornado over the Shilo Illinois area (west of Mid America Airport MAA) between 2310 and 2315 UTC. Again damage was rated F1. Circulation 5 formed just east of the St. Louis Arch and spawned a tornado 1.5 miles west of the town of Caseyville Illinois between 2305 and 2310 UTC. The tornado occurred just after the mesovortex reached its first peak (greatest depth) while rotational velocities rapidly intensified between 2255 and 2300 within the lowest 2.5 km. At 2305 UTC we were able to observe a tornadocyclone velocity signature from the WSR-88D at KLSX. The time between the first identification of mesovortex 5 and tornado occurrence was shorter compared to the detection of mesovortex 3 and its associated tornado touchdown. However the overall trend - rapid deepening and intensification of mesovortex 5 was similar to #3.
Fig 12. Overall map of the wind and tornadic damage pattern over southwest and parts of south-central Illinois associated with the St. Louis Bow Echo on 10 June 2003.
A paper on the 10 June 2003 St. Louis Bow Echo event was published in the August 2005 issue of AMS Monthly Weather Review (MWR).
