Characteristics of Isolated Convective Storms Morris L Weisman

Characteristics of Isolated Convective Storms Morris L. Weisman Joseph B. Klemp Presented to you by: Elizabeth Polito

Talk Overview • Introduction to paper • Observed types of convective storms – Single-cell – Multicell – Supercell • Physical Mechanisms Controlling Convective storm growth and evolution – Thermodynamic structure – Vertical wind shear • Unidirectional shear, curved shear, significance of wind shear vector

Observed Types of Convective Storms • Convective Cell – Strong updraft (10 ms-1 at least) – Horizontal cross section (10 - 100 km 2) – Vertically extend through troposphere – Each form identified on radar, with own repeatable pattern • Single-cell • Multicell • Supercell

Observed Types of Convective Storms: The Single-Cell Storm Dissipating stage Towering cumulus stage Mature stage

Observed Types of Convective Storms: The Multicell Storm

Observed Types of Convective Storms: The Multicell Storm • Cell motion vs. storm motion

Observed Types of Convective Storms: The Supercell Storm • Supercell evolution on radar Initial storm 1 hour 90 minutes

Observed Types of Convective Storms: The Supercell Storm • Radar reflectivity time series • Curved hodograph – Splitting storms • Right mover more enhanced • Left mover suppressed

Observed Types of Convective Storms: The Supercell Storm

Physical Mechanisms Controlling Convective Storm Growth and Evolution • Storm type and severity dependent on environment – Thermodynamic structure (strength) – Vertical wind shear (type) • Aid from numerical models

Physical Mechanisms Controlling Convective Storm Growth and Evolution: Aid of Numerical Modeling Observed Modeled • More complex simulation 3 April 1964 – Splitting storm • Models are simplified -- but provide foundation to analyze and understand real behavior of storms.

Physical Mechanisms Controlling Convective Storm Growth and Evolution: Thermodynamic Structure • Buoyant energy (B) measure more accurate to access instability B really just measure of CAPE • Wmax = (2 B)1/2

Physical Mechanisms Controlling Convective Storm Growth and Evolution: Thermodynamic Structure • Moisture Stratification: production of downbursts and microburst

Physical Mechanisms Controlling Convective Storm Growth and Evolution: Vertical Wind Shear

Physical Mechanisms Controlling Convective Storm Growth and Evolution: Vertical Wind Shear • Unidirectional or straight hodograph • Curved hodograph

Physical Mechanisms Controlling Convective Storm Growth and Evolution: Vertical Wind Shear • Significance of Wind Shear Vector