Thunderstorms, Hurricanes and Tornadoes

Thunderstorm Facts

• Right now there are about 2,000 thunderstorms occurring worldwide

• There are about 45,000 thunderstorms per day!!

• U.S. gets 100,000 per year!

Severe Thunderstorms

• Torrential Downpours

• Strong winds at greater than 58 mph

• Hail ¾ inch diameter (or larger)

• Frequent lightning

Severe Thunderstorm Watch

• Issued by National Weather Service

• This means that conditions are favorable for a thunderstorm

• Length is multiple hours.

Severe Thunderstorm Warning

• Issued By Local Weather Service

• Means a severe storm has been spotted by doppler radar

• Usually only an hour

Lightning

Types of Lightning

• Cloud-to-ground (CG)

• Intra-cloud (IC)

• Ribbon lightning

• Sheet lightning

• Heat lightning

• Ball lightning

Cloud-to-ground (CG) Lightning

Intra-cloud (IC) Lightning

Ribbon Lightning

Sheet Lightning

Heat Lightning

Ball Lightning

Lightning Safety

• Stay indoors, away from doors and windows.

• Do not take baths or showers.

• Do not use phones with cords.

• Cars are pretty safe…

Thunder

How Far Away Was That Lightning?

• When you see the flash, start counting seconds.

• When you hear the thunder, stop counting.

• Every 5 seconds is equal to 1 mile.

Tornadoes

F-Scale

• F0 – Light damage

• F1 – Moderate damage

• F2 – Considerable damage

• F3 – Severe damage

• F4 – Devastating damage

• F5 – Incredible damage (Auntie Em!)

Tornado Watch

• Conditions are favorable for a tornado to form

Tornado Warning

• A tornado has formed.

Tornado Safety

• Get indoors and stay there

• Stay away from doors and windows

• Get to lowest level possible

• Don’t get near things that can fall on you

When to expect

• Hurricane season is June through November

• Peak is in September

Formation of Hurricanes

• Tropical Depression

• Tropical Storm

• Hurricane

Tropical Depression

• Cluster of organized thunderstorms

• Not very compact

• Sustained winds of at least 30 mph

• Given a number

Tropical Storm

• Winds above 39 mph

• Given a name

• More organized

• If hits land, most damage caused is by rainfall.

Hurricane

• Winds over 74 mph

• Well defined center of circulation

• Eye Wall

• Damage from includes:– Wind– Storm surge– Rain

Pressure in hurricane

• A way to tell strength of hurricane is by its pressure

• Measured in millibars (mb)

• Higher pressures are weak, lower are stronger

Naming System

• A list of names from A-W (excluding Q)

• Alternate from male to female

• 6 lists, repeated in cycle

• Big name storms replaced

Saffir-Simpson Scale

• Designed by Herbert Saffir and Bob Simpson

• Divides hurricanes into categories based on maximum sustained winds.

Category 1

• Winds- 74-95 mph

• Storm Surge- 4-5 ft.

• Pressure- 986mb

• Damage- mobile homes, trees, minor costal flooding

Category 2

• Winds- 96-110 mph

• Storm surge- 6-8 ft.

• Pressure- 965- 979 mb

• Damage- Some roof and window. Damage to piers on coast. Small crafts. vegetation

Category 3

• Winds- 111-130 mph

• Storm surge- 9-12 ft.

• Pressure- 945-964 mb

• Damage- structure damage to homes and buildings. Mobile homes destroying. Major coastal flooding with a potential for inland flooding.

Category 4

• Winds 131-155 mph

• Storm surge- 13-18 ft.

• Pressure- 920-944 mb

• Damage- Complete roof damage. Major erosion to beaches. Further inland flooding.

Category 5

• Winds- Greater than 156 mph

• Storm surge- over 19 ft.

• Pressure- less than 920 mb

• Damage- Roofs torn off, buildings collapse, major inland flooding.

Hurricane Watch

• A hurricane poses a possible threat within the next 36 hours

Hurricane Warning

• Hurricane conditions expected within 24 hours

Most Damaging Storms

• 1) Katrina (2005)- 75 billion

• 2)Andrew (1992) 34 billion

• 3)Charley (2004)- 14 billion

• 4) Ivan (2004)- 13 billion

• 5) Wilma (2005)- 12 billion

• ..9) Agnes 1972 8.6 billion

Hurricane Safety

• Best plan is to evacuate– Towns have voluntary evacuation during a

watch, and some switch to mandatory during a warning.

• Plan early in advance

IF you choose to stay

• Board all windows

• Prepare Flashlights, avoid candles

• Stay tuned to radio

• Stay indoors