Mesoscale Convective Vortices (MCVs) Observed During the Bow-Echo and MCV Experiment (BAMEX) 2003

transcript

Part I: Kinematic and Thermodynamic Structure (Davis and Trier 2007, Mon. Wea. Rev.)

Part II: Influences on Secondary Deep Convection (Trier and Davis 2007, Mon. Wea. Rev.)

Related Papers:

Stanley B. Trier and Christopher A. Davis

NCAR, Boulder, Colorado USA

Raymond and Jiang (JAS 1990) Conceptual Model of Isentropic Lifting within a Steady Balanced Vortex (e.g., MCV)

1) Brief Overview of Methodology

2) Mesoscale Vertical Motions within the MCV Environment

3) MCV Influences on Secondary Convection

(a) Thermodynamic Influences

(b) Vertical Shear Influences

4) Conclusions

(a) Kinematic

(b) Steady, Isentropic

Contents:

Analysis Method

• Dropsonde, profiler and MGLASS data composited to common reference time (constant MCV motion assumed)

• Kinematic (full) calculated from upward integrated divergence along triangles• Steady, isentropic also calculated using triangles (requires thermodynamic data)

• Restrictions on minimum angle, triangle area

• Overlapping triangles used to assess “confidence” ()

•25-km analysis grid

Average Kinematic Profiles by Sector (Downshear, Upshear)

IOP 5 Omega Vertical Velocity (b/s)

800-hPa Kinematic / 600-hPa Relative Winds 800-hPa Isentropic / 600-hPa Relative Winds

Localized CAPE, Moderate Vortex, Strong Shear (Strong Vortex Tilt)

Widespread CAPE, Weak Vortex, Moderate Shear

No CAPE, Moderate Vortex, Strong Shear

No CAPE, Moderate Vortex, Strong Shear (Large-scale Influence)

Widespread CAPE (E-SE), Strong Vortex, Weak Shear

PBL Equivalent Potential Temperature (High, Low), Ground Relative Winds, and 600-mb MCV Center (x)

IOP 15

Variability of Thermodynamic Vertical Profiles Across MCV in Secondary Convection Cases

IOP 5 IOP 15Moderate vortex instrong vertical shear

Weak vortex inmoderate

vertical shear

Average Surface to 3.5-km AGL Vertical Shear in Different MCV Sectors

Sectors to the Right (Solid) and Left (Hollow) of Downshear Downshear (Solid) and Upshear (Hollow) Sectors

Conclusions

• Heaviest precipitation downshear, upshear typically precipitation free

Significant secondary convection in 3 of 5 cases

Conclusions

• Vertical motion influenced by environmental vertical shear and MCV strength

U/VT >= 1 (IOPs 5 and 15) Mesoscale vertical motion dipole

U/VT < 1 (IOP 8) Far more complicated vertical motion pattern

Conclusions

• Large variations in thermodynamic vertical structure across the MCVs

MCV-induced vertical motions and horizontal advection influence conditional instability

Downshear destabilization

Upshear stabilization

Conclusions

• MCVs can significantly modify vertical shear

Shear typically enhanced over that of environment (most dramatic SE of MCV center)

Conclusions

• MCVs can significantly modify vertical shear

Shear typically enhanced over that of environment (most dramatic SE of MCV center)

• Limitations of this analysis

Unable to follow evolution (inferences consistent with previous modeling studies)

Only daytime MCV cases sampled (secondary convection results may lack generality)

Average ’Profiles by Sector (Downshear, Upshear)

Mesoscale Convective Vortices (MCVs) Observed During the Bow-Echo and MCV Experiment (BAMEX) 2003

Documents