Chapter 13 The Nature of Storms

Think About It… During which months do we get the most damaging thunderstorms here in the Piedmont?

Focus Question… How do the major types of thunderstorms form?

Average Number of Thunderstorm Days Annually…

Types of Thunderstorms… Air Mass - Mountain Where… Why… When…

Types of Thunderstorms… Air Mass - Sea-Breeze Where… Why… When…

Types of Thunderstorms… Frontal - Cold Where… Why… When…

Types of Thunderstorms… Frontal – Warm Where… Why… When…

Thunderstorms in the Piedmont… Which types of thunderstorms do we experience here in the Piedmont?  Frontal (warm and cold)  Local Air Mass (in the summer)

Stages of Development of a Thunderstorm…

NSSL – Q&A Thunderstorms… The National Severe Storm Laboratory is in Norman, OK. m/tst_detecting.html

Severe Thunderstorms anvil Precipitation Rain Free Base

How Lightning Forms …

Lightning… What is lightning? When does a lightning bolt form? What is a stepped leader?

Lightning… What is return stroke? What causes thunder? How hot is lightning?

Lightning Damage… The damage that lightning can do…  7500 forest fires/year  300 injuries/ 93 deaths/year  Property damage Lightning-struck trees on the Blue Ridge Parkway

Lightning Q&A and Safety… ing/lightning_faq.htm#10

Severe Weather

Think About It… Where is the safest place to be during a tornado?

Focus Question… How do tornados form and how are they classified?

The Fury of the Wind… A downburst is a violent downdraft concentrated in a local area Two types of downbursts are Microbursts are deadlier b/c they are hard to detect and plan for.

Hail… What is hail?

Floods…(The main cause of thunderstorm-related deaths) What are 3 conditions that cause floods to occur?

Tornadoes (Formation of…) A. A change in wind direction and speed creates a horizontal rotation. B. Strong updrafts tilt the rotating air to a vertical position. C. A tornado forms within the rotating winds.

Tornado Alley - The Midwest! A cP air mass from Canada meets a mT air mass from the Gulf of Mexico forming a supercell. A supercell is … Most tornadoes occur in May.

The Enhanced Fujita Scale… This scale is used to classify a tornado AFTER the tornado has passed by looking at the damage and effects of the tornado.

The Enhanced Fujita Scale…EF0 or EF1 - % of all tornados…  80 - Path…  up to 3 miles - Wind Speed…  - Duration…  1 – 10 minutes Dr. Theodore Fujita

The Enhanced Fujita Scale…EF2 or EF3 - % of all tornados…  19 - Path…  15+ miles - Wind Speed…  - Duration…  20+ minutes

The Enhanced Fujita Scale…EF4 or EF5 - % of all tornados…  1 (Thankfully!) - Path…  50+ miles - Wind Speed…  - Duration…  1+ hours

Tornado Safety… 1. Move to a pre-designated shelter – to a basement if possible. 2. Move to an interior room/hall, lowest floor, under sturdy furniture. (A bath tub is safest!) 3. Stay away from windows. 4. Get out of vehicles! 5. Don’t try to outrun a tornado. 6. If outside, lie flat in a ditch or depression. 7. Abandon a mobile home for a shelter.

Tropical Storms

Think About It… From which direction do the hurricanes which hit our east coast come?

Focus Question… How does a hurricane form?

Tropical Cyclones… A tropical cyclone can be described as a… We call these storms… Tropical cyclones derive a tremendous amount of energy from…

Tropical Cyclones… Which direction do tropical cyclones turn in the northern hemisphere?  It is a low pressure system! Fran, 1996, Cape Fear, NC Name was retired!

Tropical Cyclones… As a hurricane strengthens, what do the following components do? a. Air pressure in eyewall– b. Surface wind speeds – What are two basic conditions that tropical cyclones require to form?

Tropical Cyclones… Tropical cyclones in the N. Hemisphere move steadily towards… Which wind system moves across the USA and usually guides hurricanes out into the Atlantic Ocean? Hurricane Rita – 2005, 3 rd lowest pressure in Atlantic (897 mb), hit as cat. 3

Development of a Tropical Cyclone… Tropical Disturbance –

Development of a Tropical Cyclone… Tropical Depression – Katrina as a tropical depression

Development of a Tropical Cyclone… Tropical Storm – Tropical Storm Dalila, July

Development of a Tropical Cyclone… Hurricane – Ivan 2006 Dean 2007 Katrina 2005

Hurricane History… h/history.shtml#galveston

Anatomy of a Hurricane… apollo.lsc.vsc.edu/classes/met130/notes/chapter15/vertical_circ.html

Classifying Hurricanes… What scale is used to classify hurricanes? What are the four characteristics of a hurricane described by the scale?

Classifying Hurricanes… The Saffir-Simpson Scale… a. Categories _________ b. Category that does the most damage – c. Wind speed of a category 5?

Classifying Hurricanes… A hurricane runs out of energy a. When it moves over b. When it moves over

Hurricane Hazards… The strongest winds in a hurricane are in the…

Hurricane Hazards… What is a storm surge?

Hurricane Hazards… What hurricane hazard is caused by great amounts of rain?

Hurricane Hazards… Which agency is responsible for tracking and forecasting hurricanes?  The National Hurricane Center in Miami, FL at the FIU Campus (NOAA)

The World’s Best Hurricane Safety Tip…

Terms to Know Drought – Heat Wave – Heat Index – Cold Wave – Wind-Chill Factor –