Thunderstorms

A thunderstorm is a form of weather with lightning and thunder

Zac Emmers

Forecasting Thunderstorms

Three times daily, a severe weather outlook is issued

Surface and upper air observations to find low level moisture and instability. It determines how winds aloft might storm development. 

Satellite imagery is used to track the movement of weather systems

Computer model data determines where favorable thunderstorm formation might be

Conditions Needed for StormsIngredients needed the most are moisture from the Gulf of Mexico or crops and instability.

Warm fronts as well form storms but not as strong

A lifting mechanism like a cold front coming out of the Rockies or winds off the ocean or mountain

Daytime heating

Life CycleFeet

40,000

10,000

20,000

30,000

Cumulus stage Mature stage Dissipating stage

Masses of moisture are lifted upwards

Two winds converge forcing air upwards

The moisture rapidly cools into liquid drops of water because of the cold.

The air is forced to spread out because it can’t rise any farther

A storm may dissipate because of a downburst causing the inflow to be cut off and cause an outflow boundary

ClassificationSupercellMulticell

Thunderstorm that are generally weak and usually not severe

Air-mass

Lifting source is uneven heating of the surface

The most common type  Strong cold fronts

Moderate-sized hail, flash flooding, and weak tornadoes

Very large, severe storm strong, rotating updraftAt least 90 percent of the time severeDestructive tornadoesThe most powerful thunderstorm

Squall lineSevere thunderstorms along or ahead of a cold front

Hail, frequent lightning, strong straight-line winds

Possibly tornadoes

Shelf Cloud in front of the winds

A Derecho is a widespread and long-lived line of storms

Bow echo

Weather Underground

Lightning

140,000 mph54,000 °F

Charges are separated when ice crystals rebound off graupel

Positive charge transferred to the ice crystals and negative charge to the graupel.

Air become a conductive discharge channel

Cloud-to-ground

Types

The best known and second most common type of lightning

Discharge between cloud and the ground.

Ground-to-cloudNegatively charged ions rise up from the ground to positively charged ions

Cloud-to-cloud lightning

Discharges occur between areas of cloud 

HailPea 0.25 inches

0.705 inches Dime

Quarter

1.00 inch1.50 inches

Ping-pong ball

1.75 inches

Golf ballTennis ball2.50 inches2.75

inches 

Baseball

Softball4.50 inches

Volleyball 8.00 inches 

The largest recorded hailstone in the United States

1.93 pounds 

Hail formation requires strong upward motion of air (updraft) and a low freezing level

As hail is pushed upward it grows as droplets of water hit it. This happens until the updraft can’t support the hail. Then it falls to the ground.

Vertical draft

Updraft  Downdraft

Warm air will rise until it reaches air warmer or less dense than itself

Low pressure area will attract air from the surrounding area. It will move to the center and then rise

High pressure region will attract air from the surrounding area. It will move towards the center and sink

Both can cause airplane crashes

DownburstMicroburst /

Column of sinking air producing damaging straight-line winds

High winds that can knock over fully grown trees.A couple of seconds to several minutes.

Is capable of producing damaging straight-line winds of over 150 mph 

Heat burst

Gusty winds, rapid increase in temperature, and decrease in dew point

Typically occur during night-time

Associated with dying thunderstorms

Caused when rain evaporates into a parcel of cold dry air high in the atmosphere. They descends rapidly, warming due to compression.

Very rare

Temperatures reach 90 °F Reports up to 120 °F

TornadoA tornado is a violent, dangerous, rotating column of air

May 1999

Come in many shapes and sizes

Warm and moist inflow to power it.

May 1999

The strongest ever. 318 MPH winds

Most have wind speeds less than110 mph 

Tornadoes are usually located on a hook echo at the southwest part of the storm.

Doppler reflecting off debris swept up in the tornado.

Wedge Tornado

August 24, 2006

Multi-vortex TornadoA Tornado that contains two or more small vortexes as part of the main vortex

The only times they are visible are when the tornado is first forming.

WatchesTornado watch

Issued when conditions are right for a tornado to form

Particularly dangerous situationAn enhanced risk of very severe and life-threatening weather. Usually a major tornado outbreak and extreme derecho event

Map of weather advisories

Issued when weather conditions are favorable for the development of severe thunderstorms. Tornadoes can still form.

Severe thunderstorm watch

(NWS website)

Warnings Tornado warning

Issued after a tornado or funnel cloud has been spotted or if radar indications of tornado formation. (Red box)

Tornado emergencyA large violent tornado expecting to cause significant damage and a high likelihood of numerous fatalities.

Is issued when trained storm spotters or a radar indicate a strong thunderstorm. (Yellow Box)

58 mph wind and 1 inch hail

Severe thunderstorm warning

Where I got my information fromNational Weather Service (NWS) and National Oceanic and Atmospheric Administration(NOAA) Websites

Wikipedia

Weather Underground Weather.com

Weather.org

Questions