Mesolow and coincident supercell produces severe weather on 19 May 2000
(Much of this was presented by Neil Stuart, as a poster at the 25th annual meeting of the National Weather Association)



Storm Relative Velocity Map Product - 2024 UTC 5/19/00Storm Relative Velocity Map Product - 2029 UTC 5/19/00Storm Relative Velocity Map Product - 2034 UTC 5/19/00Storm Relative Velocity Map Product - Loop 2024-2034 UTC 5/19/00

Storm-Relative Velocity Map Product with Tornadic Vortex Signature Overlay, 

2024-2034 UTC 19 May 2000
 

Note the two strong low-level rotations with gate-to-gate signatures (blue and green colors toward the radar, red, orange and yellow away from the radar). The storm was not a uniform mesocyclone, but had the capability to produce wind damage or tornadoes associated with each low-level circulation. The radar placed the TVS in the weaker, southern circulation.
 

Storm Relative Velocity Map Product - 2312 UTC 5/19/00MSAS Surface Analysis - 2300 UTC 5/19/00
 

Storm-Relative Velocity Map Product, 2312 UTC 19 May 2000

Note the broad circulation offshore the southern DELMARVA (green and blue colors toward the radar, red, orange and yellow colors away from the radar). This represented the surface mesolow (30-40 kt inbound and outbound couplet), depicted too far east in the 2300 UTC surface plot.


Reflectivity Cross Section - 2014 UTC 5/19/00Reflectivity Cross Section - 2034 UTC 5/19/00Reflectivity Cross Section - 2039 UTC 5/19/00Reflectivity Cross Section - 2146 UTC 5/19/00Reflectivity Cross Section Loop - 2014-2146 UTC 5/19/00

Reflectivity Cross Sections, 2014-2146 UTC 19 May 2000
 

2014 UTC - This is a northwest/southeast-oriented cross section through the highest reflectivity core, parallel to the storm motion. Note the bounded weak echo region and tilted reflectivity core.

2034 UTC - This is a northwest/southeast-oriented cross section through the highest reflectivity core, parallel to the storm motion. Note the increase in the reflectivities within the core, and a bounded weak echo region was still well-defined.

2039 UTC - This is a northwest/southeast-oriented cross section through the highest reflectivity core, parallel to the storm motion. Note the high-reflectivity core was less tilted, and the bounded weak echo region was collapsing.

2146 UTC - This is a northwest/southeast-oriented cross section through the highest reflectivity core, parallel to the storm motion. Note the high-reflectivity core was tilted again, and the bounded weak echo region had reformed.This is typical of a cyclic supercell.


Base Reflectivity - 1928 UTC 5/19/00Base Reflectivity - 2014 UTC 5/19/00Base Reflectivity - @2100 UTC 5/19/00Base Reflectivity - 2322 UTC 5/19/00Base Reflectivity - 0019 UTC 5/20/00

Base Reflectivity, 1928 UTC 19 May 2000 through 0019 UTC 20 May 2000

1928 UTC - Note the bowing nature to the high-reflectivity core. This storm had a history of wind damage, as it tracked southeast, just right of the mean 0-6Km flow.

2014 UTC - The bowing storm was evolving into a high-precipitation supercell. Note the absence of bowing, increase in the reflectivity, and beginning of the formation of an appendage on the southern edge of the storm.

@2100 UTC - This storm became dominant as it continued to track southeast. Note the decrease in the intensity of the convection surrounding the storm. Also note the continued high reflectivity core and appendage on the southern edge of the high precipitation supercell.

2322 UTC - The storm evolved into a cluster of storms as it moved offshore the southern DELMARVA. Note the two bowing segments within the cluster of storms. Also note the distinct surface boundary trailing from the offshore convection, moving south.

0019 UTC - The convection assumed a circular appearance, which may possibly be a more definitive illustration of the presence of the mesolow. The presence and strength of the mesolow, based on radar data, is uncertain due to the radar beam height. Although, the trailing surface boundary can be seen just south of the Virginia/North Carolina border.


Vertically Integrated Liquid - 2034 UTC 5/19/00

Vertically Integrated Liquid, 2034 UTC 19 May 2000

The Vertically Integrated Liquid product depicts a maximum value of 71 g/m2, suggesting large hail was present.


MSAS Surface Analysis - 1700 UTC 5/19/00MSAS Surface Analysis - 1800 UTC 5/19/00MSAS Surface Analysis - 2000 UTC 5/19/00MSAS Surface Analysis - 2100 UTC 5/19/00MSAS Surface Analysis - 2300 UTC 5/19/00

Surface plot with MSAS mean sea level pressure overlay, 1700-2300 UTC 19 May 2000

1700 UTC - Note the 1013.6 Mb surface pressure at KCHO, and the MSAS depicted 1015 Mb surface low near KCHO. There was also a surface temperature and windshift boundary between KLKU, KEZF and KOFP.

1800 UTC - The distinct surface temperature and windshift boundary had not moved, but surface pressure were falling at KOFP and KRIC. Relatively low surface pressures over southern and southeastern Virginia are a reult of a thermal trough.

2000 UTC - The surface pressure rose rapidly in KCHO, and pressures remained relatively steady from KOFP to KRIC. Based on the area surface pressures, the center of the developing mesolow was approaching KOFP.

2200 UTC - A mesohigh built into the KOFP and KRIC area, as the convection and mesolow departed. Note the lowest surface pressure at KAKQ of 1013.7 Mb, as the mesolow tracked just north of KAKQ.

2300 UTC - The surface low had pushed offshore, but MSAS was placing the center too far offshore, based on radar data. The surface windshift and temperature boundary match up well with the radar depicted boundary.