Mesoscale Convective Vortices (MCVs)

Chris Davis (NCAR ESSL/MMM and RAL) Stan Trier (NCAR ESSL/MMM)

Boulder, Colorado

60-h Radar Composite Animation (00 UTC 11 June – 12 UTC 13 June, 2003)

500 km

Acknowledgements: Morris Weisman, EOL staff

Long-time Behavior of MCSs

• Convection develops (often in response to synoptic-scale of mesoscale features)

• Convection organizes (internally or externally)• Convection leads to modified or new balanced

features (vortices)• Balanced features produce new convection

Long-time Behavior of MCSs

(twice)

ˆ ( )g

dvfk u u

dt

L

H

HWarm

Cool

Cool

Diabatic Heating• Deep convection (heating)• Mesoscale updraft (heating)• Melting and evaporation (cooling)• Radiation (cooling)• Gradient along vorticity vector determines PV

generation rate

• Dependencies in models– Cumulus parameterization– Cloud physics (and radiative interaction)– Surface-atmosphere coupling (heating versus

moistening)

MCV Induced Lifting and Destabilization

Fritcsh et al. 1994, MWR

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

Mature MCVs from the Bow Echo and MCV Experiment (BAMEX)

20 May – 6 July 2003

• May 24: remnant of severe bow echo• June 2: hybrid with cyclone wave• June 5: remnant of large MCS• June 11: Multi-day MCS/MCV system, late

became frontal cyclone• June 24: MCV from multi-MCS complex

• Data: dropsondes, MGLASS, profilers (storm relative and time-space corrected)

Precursor Conditions

500 hPa 850 hPa wind

IOP 1: 00 UTC 24 May

IOP 4: 00 UTC 2 June IOP 5: 00 UTC 5 June

IOP 8: 00 UTC 11 June

IOP 15: 00 UTC 29 June

MCS MCV

MCS Precursors to MCVs

IOP 1, 24 May

IOP 4, 2 June IOP 15, 29 June

1500 UTC

0600 UTC

IOP 5, 5 June1100 UTC

IOP 8, 11 June0600 UTC

0500 UTC

150 km

= Primary Vortex

IOP 1

IOP 5

IOP 8

IOP 15

Reflectivity, Temperature, and System-relative

Winds

IOP 4

= new convection triggered

No CAPE

No CAPE Localized CAPE Widespread CAPE

Widespread CAPE

Analysis Method• Dropsonde, profiler and MGLASS

• Composited to common reference time (const MCV motion assumed)

• Divergence and vorticity analyzed assuming linear variation along sides

• Restrictions on minimum angle, area; maximum side length and area

• Overlapping triangles used to assess “confidence” ()

•25-km analysis grid

MCV Vertical Structure

Shading=low confidence

Red line=vortex axis

Contour: 5x10-5 s-1

MCV Vertical Structure

v’

v’

Wind Profiles (averages of quadrant means)

Balance within MCVs

Procedure:

via nonlinear balance

Tv (hydrostatic)

Tv profile at sounding locations

Quadrant averages (r<Rmax; r≥Rmax)

Subtract mean outer profile from inner profile: T'v

Pre

ssu

re (

hP

a)

T'v (K)

Obs

Bal

IOPs 1 and 8 have best data coverage

00 UTC 6 July

12 UTC 6 JulyEta 500 mb , wind analysis

Airborne Doppler Domain

06 UTC 6 July

Radar Composite

Evolution of Mid-tropospheric Vortex

12 UTC 6 July

00 UTC 7 July

18 UTC 6 July

Diabatic Rossby Vortices

Conzemius et al (2007, JAS) – idealized MM5 simulations in weakly sheared flow: shown are relative vorticity and potential temperature

T=120 h (just prior to deep convection) T=173.6 h (after 2 days of convection)

Observed MCV centers

Summary4-8 km deep, centered between 500 and 600 mb

V~10 m/s

Nearly in gradient balance (Ro~1)

Tilts of vortices consistent with vertical shear

Temperature anomalies weak, even below MCV center

Deep vortices may require cyclonic precursor

Implications for rainfall organization, see S. Trier’s talk on Friday