PHSH 3033: Meteorology...

PHSH 3033: Meteorology Supercells

Figure 18.1: Severe Thunderstorm Event Frequency (2006)

Figure 18.17

Supercell development requires wind shear (among other things)

Supercell Thunderstorms

Rotating Updraft --- Mesocyclone A very large single cell storm (requires vertical wind shear) Quasi-steady in physical structure: Lifetime several hours.

Persistent updraft/downdraft couplet

Potentially the most dangerous of storms:

High winds Large and damaging hail Large and long-lived tornadoes

Figure 18.16: Supercell Favorable Environment

Figure 18.18: Multiple Supercells Erupting Along Frontal Boundary

Supercell

Supercell Hook Echo (old-school radar)

Hook Echo

Figure 18.22: Supercell Thunderstorm Reflectivity 1999 May 3

Figure 18.21: Supercell Thunderstorm Anatomy 1999 May 3

Radar Supercell

Heaviest Precipitation

(core)

4 OCT 1998 2120 UTC

KTLX

Kansas

Oklahoma Woods County, Oklahoma

Supercell Cross Section

Heaviest Precipitation

(core)

4 OCT 1998 2120 UTC

KTLX

Kansas

Oklahoma Woods County, Oklahoma

Figure 18.19: Supercell Cross section

Low Precipitation (LP) Supercell

Figure 18C: LP Supercell

Tornadic LP Supercell

Hail Core and Hook Echo

Figure 18.24: Supercell Structure

Tornadic LP Supercell

Wind Shear

• Creating rotation by vertical wind shear.

Fast Wind

Slower Wind

Rotation • Air travelling along a frontal zone will develop a

horizontal rotation.

Updraft Tilting

Supercell Downdrafts

Inflow

Forward Flank Downdraft

Rear Flank Downdraft

© 1993 Oxford University Press -- From: Bluestein, Synoptic-Dynamic Meteorology -- Volume II: Observations and Theory of Weather Systems

Formation of the RFD

• Imagine a river flowing straight in a smooth channel.

• The water down the center flows smoothly at essentially a constant speed.

• The pressure down the center of the channel is constant along the channel.

Formation of the RFD

• Let us now place a large rock in the center of the channel.

• The water must flow around the rock. • A region of high pressure forms at the front

edge of the rock -- Here the water moves slowly -- Stagnation Point

Figure 18.23

Supercells in Motion http://www.youtube.com/watch?v=551OwJKBv9A LP Supercell http://www.youtube.com/watch?v=6xmvToEMwa4 Supercell http://www.youtube.com/watch?v=RLrJADfkd1I Supercell http://www.youtube.com/watch?v=lbELuEGG5zs Wall Cloud http://www.youtube.com/watch?v=GgmZ9JEPM6w Wall Cloud http://www.youtube.com/watch?v=I9ACU8N9k3M Wall Cloud http://www.youtube.com/watch?v=yEFdT9OMeHs Funnel Cloud http://www.youtube.com/watch?v=TkavH9aZue8 Microbursts http://www.youtube.com/watch?v=wDLyssxqabc Microburst