Sever Weather Week 3 Lesson 3 & 4

Landspout / waterspout

over land / over water

What is the #1 cause of tornado killing?

Debris

Joplin, MO 2011

EF-% tornado = 162 deaths

Hail Fog

Fog that forms after a significant hail storm. Hail falls, then melts, releasing moisture into the atmosphere

tornado classification

Fujita Damage Scale (EF0- EF5) EF0: light damage done EF1: moderate damage done EF2: considerable damage done EF3: severe damage done EF4: devastating damage done EF5: incredible damage done

-Hail embryo is small ice particle suspended in updraft -Supercooledwater within updraft freezes to hail embryo and particle grows• -A stronger updraft can suspend a heavier and thus larger hailstone• -Hailstone falls back to earth when it is ejected from the updraft• Largest hail falls fastest and thus closest to updraft

HAIL FORMATION

_________ is frozen precipitation that falls from thunderstorms- _________is generally larger than 3 mm and can be up to grapefruit sized (or even larger)- - Most ________is small (pea sized) -Small hail can accumulate much like snow and sleet -Severe hail = 1 inch diameter Giant hail = 4 inch diameterr •Hardness of hailstones varies - Can be as soft as a snowball or rock hard!• How to get big hail? - Large instability (strong updrafts) -Strong wind shear, enabling supercell formation (stronger updrafts) -Cooler temperatures/drier air (less melting on the way down)

Hail

____________________are NOT the result of hailstones making several trips up and down within a thunderstorm• Wet growth = CLEAR ICE• Drygrowth = CLOUDY ICE

Hail Layers

If outdoors, get indoors• If in a car, pull over to a safe place and cover your eyes/face if glass is breaking• Do NOT block roadways/hide under overpasses to seek shelter from hail•Indoors, stay away from window

Hail Safety

Within which state had deadliest tornado happen? a. Texas b. California c. Oklahoma d. New York e. Illinois

Illinois 1925 - 700 people died

supercell structure

Know this cross section image!!!

If in a mobile home during Tornado

Leave and seek shelter

types supercells - Classic

Little rain near updraft, significant precipitation within forward flank•Stunning storm structure often visible from south•Most prolific tornado producers

The largest T-storm type is

Mesoscale convective system MCS

NEXRAD radar

NEXRAD or Nexrad (Next-Generation Radar) is a network of 160 high-resolution S-band Doppler weather radars operated by the National Weather Service (NWS).

Is it safe in a gym or auditorium during a tornado?

NO

Is it safe under a bridge during a tornado

NO

How does the tornadic circulation originate?

Need a downdraft to bring rotation from aloft to the ground rear flank downdraft

Name that Thunderstorm: -most common type of t-storm -usually not severe -lasts about an hour from formation to dissipation -usually develop in systems of weak vertical wind shear(most common in summer, away from fronts

Ordinary thunderstorm

Heavy-precipitation (HP) Supercells

Significant precipitation near updraft often obscures storm structure and/or tornadoes•Prolific strong hail-wind producers

Wall cloud

Sometimes rotatesDefined as a lowered cloud base beneath the updraftTornadoes can develop from rotating wall clouds - Wall cloud forms as a storm ingests humid, rotating air from forward-flank downdraft

States with most tornadoes?

#1 Missisippi #2 Arkansas #3 Alabama Large number of mobile homes in these states #4 Illinois #5 Indiana

Tornadoes are ranked #______ in fatalities

#3

Peak Tornado time

(Season: April-July) Peak= May-June, 4, 5, 6pm - we need the heat by later day to increase moisture and instability

Average Tornado

- 10m to 2+km in diameter ( 100 m wide typically = football field) - 10 mins - track length 4 miles - about 110mph - EF - rank = EF-0, EF-1 -SW NE @ 20-40 mph

Ingredient #1 - Thunderstorm An Unstable Atmosphere

- An Unstable Atmosphere -(you need to compare the temperature of the parcel to the temperature of the environment)

Forward Flank Downdraft (FFD) contains what?

- feeds / contributes to the wall cloud formation -heavy rain, strong winds, and large hail. Visibility limited.

Weak Tornadoes

- few mins. - <120mph - 5% deaths - 85% totals # of tornadoes

tornado safety

- get to a basement or lowest floor -Put as many walls between you an d tornando -Stay away from windows - Protect yourself from flying debris---> use mattress, Bike helmets, Wear Shoes - have a flashlight ready - Take cover when you hear the warning

Violent Tornadoes

- several mins to 1 hour+. - >200 mph - 70% deaths - 2% totals # of tornadoes

Strong Tornadoes

- several mins to 1 hour. - 120-200 mph - 25% deaths - 13% totals # of tornadoes

Gustnado

-Shallow Circulation along a Gust Front. Not a Tornado (Not Attached to Cloud Base)

t-storm cumulus stage

1. warm air rises, expands & cools 2.when air reaches LCL, water vapor condenses and forms a cloud 3. rising air reaches LFC and continues due to buoyancy 4. current of rising air = UPDRAFT (no updraft / no t-storm) 5.updrafts forms large cumulus clouds - "towering cumulus clouds" 6

RFD - rear flank downdraft

1.Rear-flank downdraft descends and creates another horizontal vortex along the surface/ground. 2. The updraft tilts this vortex tube upward, forming an arch. 3. Cyclonic vortex is stretched vertically as it enters the updraft and it is forced to spin faster by conservation of angular momentum.

Average Warning Time for Tornado

13 minutes

Where do most of the fatalities from toranados happen?

43.94% mobile homes

What % of the Worlds tornadoes occur in USA?

75%

Tornado

A violently rotating column of air in contact with the ground and pendant from a cumuliform cloud. -Rotation, not visible funnel defines tornado- -Not in contact with the ground = funnel cloud

Multiple Vortex Tornadoe

A. Initially, a tornado is composed of a single, rotating column with ascending air in the center B. Extremely low pressure in the center near the surface leads to the formation of a downdraft in the center of strong tornadoes C. Tornado widens as downdraft hits the groundD. The rotation associated with the tornado breaks into suction vortices (see next slide

rear flank downdraft

Brings on the tornadic circulatiom

What is the rotating updraft with a supercell thunderstorm called? a, Tornado b. Rear Flank downdraft c. Mesocyclone d. Scud Bomb

C. mesocyclone

Tornado deaths 30 year avg = _______deaths 10 year avg = 101 deaths Over 7600 deaths since 1940

69

The 3 stages of Thunderstorm Development: a. Cumulus stage b. ____________________ c. Dissipation Stage

Mature stage

Are cars and trucks safe from tornados?

NO

Ted Fujita, known as Mr. Tornado, was a professor and studied ?

Studied 70 yrs worth of tornado damage (over 30,000 tornadoes) - Tornados rated by maximum damage

-lived rotating thunderstorms •Can last for hours •Often isolated -Most intense thunderstorms on the planet •Most rare type of thunderstorm -Always rotate -Typically single celled and small (county or smaller) -Produce majority of tornadoes •Nearly all EF-2+ tornadoes •Produce nearly all hail golfball sized or larger -Severe aspects: Tornadoes, hail, straight line winds

Supercell Thunderstorm

1.Development of the mesocyclone (rotating updraft) at mid-levels within a supercell thunderstorm 2.Development of a mesocyclone at low levels (cloud base) and a wall cloud 3.Transport of horizontal and vertical rotation to the surface by a downdraft 4.Ingestion of this air by the updraft and amplification of this rotation into a tornado-strength circulation

Supercell Tornadogenesis A four-step process

Do you need strong or weak wind shear for a supercell to develop?

Supercells need STRONG wind shear

US Tornado Tarcks

Tornado Alley and Dixie Alley: Where all 4 ingredients come together most frequently ----Trigger mechanism ----Gulf moisture ----Unstable atmosphere ----Wind shear

Tornadoes typically develop from: a. Shelf clouds b. Wall clouds c. Tail clouds d. Mamatus clouds

b. Wall Clouds

Which type of supercell typically produces the most tornadoes. a. low- precipitation LP supercell b. classic supercell c. heavy precipitation HP supercell d. all types of supercells produce tornadoes equally often

b. classic supercell

funnel cloud

a rotating funnel-shaped that cloud form the core of a tornado - wide at the top / narrow at the bottom

supercell

a system producing severe thunderstorms and featuring rotating winds sustained by a prolonged updraft that may result in hail or tornadoes. (see slide #7)

supercell updrafts typically appear as.... a. rain free cloud bases b. opaque regions of hail & rain c. clear slots near the cloud base d. violent rotation in contact with the ground

a. Rain-free cloud basis

Strong shear (strong winds aloft) in supercell environments often yields long.

asymmetric anvils

Which of the following is most closely tied to tornadogenesis? a. Forward flank downdraft b. Rear Flank downdraft c. Shelf Clouds d. Mamatus cloud

b. Rear

the rotation in tornadoes forms through what 2 processes? a. Freezing and melting b. tossing and turning c. tilting and stretching d. rocking and rolling

c. Tilting & Stretching

What is the formal name of the cloud that produces a thunderstorm? a. stratus b. altocumulus c. cumulonimbus d. cirruse. lenticular

cumulonimbus

Mamatus clouds

cumulonimbus clouds with downward motions that make them appear like hanging sacks. - beautiful but not threatening.

Mamatus clouds are typically associated with a. large hail b. damaging winds c. tornadoes d. none of the above

d. none of the above - (underside of anvils and they are nice to look at but pose no danger)

Wedge Tornado

largest and most violent

Low-precipitation (LP) Supercells

little to No rain

over 60 dBZ

look out for Hail!!

During which of the three stages of development of an ordinary thunderstorm does the downdraft develop? a. cumulus stage b. mature stage c. dissipation staged. the downdraft is present in all three stages.

mature stage

Name that Thunderstorm: - thunderstorm complexes - forms in environments with moderate to strong vertical winds

multicellular (MCSs)

Should the RFD of tornando genesis be most likely warm or cold

relatively warm - warm air is more likely to be ingested by the updraft

TORNADO DISSIPATION: Lifetime ranges from _____ _____ ______ ______ -----Not completely sure why some tornadoes last for a long time while other do not •Funnel becomes deformed -----Winds inside of storm blow in different directions aloft and near ground -----Circulation forms an elongated rope shape ("roping out")• Cold outflow air wraps around tornado ----Cold air not buoyant, does not rise

seconds to an hour

Cone Tornado

shaped like a cone

Visually, the RFD appears as a clear slot near the updraft base. Why??

sinking air within the RFD suppresses cloud formation - resulting in a clear slot - contributes to the tornado formation

Tornado genesis Failure

stops forming

Name that Thunderstorm: -severe- produce intense tornados and hail (larger than a ball) - form in environments with strong vertical wind shear

supercell

A hook echo on a radar screen often indicates:

the possible presence of a tornado-producing thunderstorm - shape is called a debris ball

Mesocyclone of a supercell thunderstorm

the rotating updraft of a supercell thunderstorm

velocity couplet

Two winds of opposing directions adjacent to each other

World-record hailstone fell in ______.

Vivian, SD, July 23, 2010

Supercell updraft

When storms rain into their updrafts, they quickly dissipate. Strong winds aloft in supercell environments blow precipitation out of the updrafts, allowing supercells to persist much longer than ordinary thunderstorms.

what's the most important factor when determining thunderstorm types?

vertical wind shear