National Weather Service Shreveport

Working Together to Save Lives

Understanding

Severe StormsSevere Storms

TopicsTopics

• Global Circulations

•Thunderstorm Ingredients

• Lightning

• Hail

• Tornadoes and Downbursts

• Flooding

Global CirculationsGlobal Circulations

Jet StreamJet Stream

Thunderstorm Ingredients

Thunderstorm IngredientsThunderstorm Ingredients

Low level warm and moist airfrom the Gulf of

Upper level jet stream can carrypockets of cold air aloft overmoist air, increasing lift andinstability

Moisture - Preferably in the lower or mid levels of the atmosphere

Thunderstorm IngredientsThunderstorm Ingredients

Source of lift – Agent which lifts the warm, moist air starting the thunderstorm

Another Source of LiftAnother Source of Lift

Thunderstorm IngredientsThunderstorm Ingredients

Instability – Ability for air to accelerate upward/downward when started up/down

Thunderstorm Life CycleThunderstorm Life Cycle

Cumulus Stage Mature Stage Dissipating Stage

Multicell Thunderstorm Multicell Thunderstorm

motion

(Cross section)

Squall Lines Squall Lines

dow

nd

raft

N

Tornado

Supercell Thunderstorms  Supercell Thunderstorms 

Shear Rotation

Shear vs. RotationShear vs. Rotation

LightningLightning

LightningLightning

Lightning FormationLightning Formation

ThunderThunder

HailHail

Weather Related Hazards Weather Related HazardsHail

Baseball size hail can do severe

damage

Hail FormationHail Formation

Tornadoes and Downburst

Tornadoes and Downburst

Tornadoes TornadoesFujita Scale

F0-F1 Winds 60 - 115 mph

F2-F3Winds 115 - 205 mph

F4-F5Winds > 205 mph

Damaging WindDamaging Wind

•Cold air ‘bursts’ down from cloud

• Spreads on ground contact

• Accelerates on outwash

• Can reach 150 mph

• Tornado-like damage

•Cold air ‘bursts’ down from cloud

• Spreads on ground contact

• Accelerates on outwash

• Can reach 150 mph

• Tornado-like damage

Downbursts and AircraftDownbursts and Aircraft

FloodingFlooding

Weather Related Hazards Weather Related HazardsFlash Flooding Safety Tips

Do not drive across a flooded roadway or low water crossing

If your vehicle stalls in high water, leave it and seek higher ground

Be especially careful at night when it is harder to recognize the dangers of flash flooding

Acknowledgments Acknowledgments

• Jetstream website – Southern Region Headquarters , National Weather Service

www.srh.noaa.gov/srh/jetstream

The EndThe End

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