Refers to the state of the atmosphere at a specific time and place. Refers to the state of the atmosphere at a specific time and place. The one thing that you can talk to anybody about The one thing that you can talk to anybody about If you don’t like the weather just wait around it will change in NC If you don’t like the weather just wait around it will change in NC What are some of the factors that affect the weather? What are some of the factors that affect the weather?

Temperature is the measure of the average amount of motion in particles.

a natural movement of air of any velocity; especially : the earth's air or the gas surrounding a planet in natural motion horizontally a natural movement of air of any velocity; especially : the earth's air or the gas surrounding a planet in natural motion horizontally

Humidity The amount of water vapor present in the air Relative Humidity -is a measure of the amount of water vapor present in the air compared to the amount needed for saturation at a specific temperature

 Made of small water droplets or tiny ice  crystals in the air and stick to aerosol. –Form from warm air and cool air  Three main types are cirrus, cumulus, and stratus.  Other clouds are a mixture of these three main types.

Other Cloud Types CirrocumulusCirrostratus StratocumulusCumulonimbus

More Cloud Types Altocumulus Altostratus Nimbostratus

Precipitation  Water that falls from the clouds  Air temperature determines the form of precipitation that falls  4 main types of Precipitation: Rain, Sleet, Snow and Hail

Types ofPrecipitation Types of Precipitation

Air Masses  A large body of air that has properties similar to the part of the Earth’s surface over which it develops.

Air Mass Map

Fronts  A boundary between two air masses of different density, moisture, or temperature.  Creates a change in weather, often with rainstorms, thunder, lightening, tornadoes, hail etc

Cold Front

Warm Front

Occluded Front

Stationary Front

Fronts  Warm Front –separates warm air from the cooler air it moves into (6 mph, NE) –rises over cool air masses –develops clouds and light precipitation  Cold Front –cold air advancing into warm (9 to 30 mph, SE) –pushes under warm air – rising air just ahead of front –vertical movement strong and thunderstorms or blizzard

Fronts  Stationary Front –boundary of fronts does not move –generally due to winds running parallel to each other in two areas  Occluded –where cold front overtakes warm front

Isobars  Isobars-connect points of the “same”- shows air pressure  Examples: temperature (isotherms) and wind speed  The further away the lines the lower the wind speed

Seasonal Changes  Occur because the earth’s axis is tilted  Creates opposite seasons in the northern and southern hemisphere  Factor that determines global air circulation patterns

Air Temperature  As solar energy reaches the Earth, equatorial regions heat up more than the poles.  Warm air and water at the equator travel poleward while cold air and water at the poles travel equatorward in an attempt to equalize this temperature contrast.  It is the atmosphere's continual struggle for temperature balance that brings us our changing weather.

Coriolis Effect Coriolis Effect  The Earth is a spinning globe where a point at the equator is traveling at around 1100 km/hour, but a point at the poles is not moved by the rotation.  This fact means that projectiles moving across the Earth's surface are subject to Coriolis forces that cause apparent deflection of the motion.

Air Pressure  air pressure is caused by the weight of the air pressing down on the Earth, the ocean and on the air below  the pressure depends on the amount of air above the measuring point and falls as you go higher  air pressure changes with weather

… and Weather  air in a high pressure area compresses and warms as it descends  the warming inhibits the formation of clouds, meaning the sky is normally sunny in high- pressure areas  haze and fog might form  the opposite occurs in an area of low pressure

Intertropical Convergence Zone The ITCZ is an area of low pressure located roughly 5 degrees North and South of the Equator. It is a place where air converges, rises, and condenses (forming clouds). It is the rainiest place on Earth!

So What Does a Hurricane Need in Order to Develop? So a hurricane needs warm water, time to grow, and favorable upper level winds in the troposphere. If the winds are too strong, they will blow the hurricane apart – we call that wind shear!

Hurricane

Evolution of Hurricane Development -- Stages Stage 1 – Tropical Wave (Depression) Usually has begun its life off of the west coast of Africa in the ITCZ. Tropical depressions have winds of less than 39mph, and are not given a name. Lacks structure – no well developed feeder bands or eye

Evolution of Hurricane Development -- Stages Stage 2 – Tropical Storm At this point, the tropical storm is beginning to develop some serious structure. Winds range from mph. In the Atlantic, storms are given a name when they reach this stage. Feeder bands are beginning to develop – you can see the center of the low pressure system more easily. Eye and eye wall still not well formed.

Evolution of Hurricane Development -- Stages Stage 3 – Category 1 Hurricane Winds range from mph. Well developed feeder bands. An eye begins to form (although it is covered in clouds). Storm is tightening around center.

Evolution of Hurricane Development -- Stages Stage 4 – Category 2 Hurricane Winds range from mph. Well developed feeder bands. An eye and eye wall are usually very well formed. Storm continues to tighten around center.

Evolution of Hurricane Development -- Stages Stage 5 – Category 3 Hurricane Winds range from mph. Now considered a “Major Storm”. Intense flooding and building damage will occur to most areas on the coast. Further inland, the damage will still be substantial.

Evolution of Hurricane Development -- Stages Stage 6 – Category 4 Hurricane Winds range from mph. All shrubs, signs and trees blown down. COMPLETE DESTRUCTION of mobile homes. Extensive damage to doors and windows. Major damage to lower floors of structures near the coast.

Evolution of Hurricane Development -- Stages Stage 7 – Category 5 Hurricane Winds greater than 156 mph! Complete roof failure on many residential and industrial buildings. Some complete building failures with small utility buildings blown over or away. Massive evacuation of residential areas on low ground within 5-10 miles of the coastline maybe required.

Humidity  relative humidity is the amount of water vapor in the air compared with the potential amount at the air's current temperature –expressed as a percentage, measured by hygrometer –depends on air temperature, air pressure, and water availability  the Earth has about 326 million cubic miles of water  only about 3,100 cubic miles of this water is in the air as water vapor > clouds > precipitation

Cloud cover  moisture in the atmosphere forms clouds which cover an average of 40% of the Earth at any given time  a cloudless Earth would absorb nearly 20 percent more heat from the sun  clouds cool the planet by reflecting sunlight back into space. This is known as Albedo However  clouds reduce the amount of heat that radiates into space by absorbing the heat radiating from the surface and reradiating some of it back down  the process traps heat like a blanket  “Cloud cloudlg.htm cloudlg.htmwww.nasm.si.edu/earthtoday/ cloudlg.htm  -Dec :52:11 EST

Severe Weather - Thunderstorms  occur from equator to Alaska  may have hail, strong winds, lightning, thunder, rain & tornadoes  moist air rises due to frontal zone lifting causing loss of heat leading to cumulus clouds with updrafts  at 42,000 feet downdrafts and precipitation start  may last an hour  severe thunderstorms occur when cold front approaches warm front (which supplies moisture and energy) –winds over 60 mph –hail > 3/4 inch

Severe Weather Thunderstorms Lightning Tornadoes

More Severe Weather Hurricanes Blizzards

Severe Weather Safety WWWWatches- conditions are favorable WWWWarnings- conditions already exist EEEExamples- Tornadoes, Flooding, Thunderstorms, Blizzards, Winter Mixes and Hurricanes

Lightning

Tornadoes Tornadoes  A tornado is a violently rotating column of air in contact with the ground and out from a cumulonimbus cloud.  Tornadoes are capable of inflicting extreme damage.

Fujita Tornado Intensity Scale The Fujita scale, or F scale, categorizes tornado severity based on observed damage to man-made structures and not on recorded wind speeds. F0: Gale tornado (40-72 mph); light damage. Some damage to chimneys; break branches off trees; push over shallow-rooted trees; damage to sign boards.

F1: Moderate tornado ( mph); moderate damage. The lower limit is the beginning of hurricane wind speed; peel surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads.

F2: Significant tornado ( mph); considerable damage. roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light-object missiles generated. F2: Significant tornado ( mph); considerable damage. roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light-object missiles generated.

 F3: Severe tornado ( mph); Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off ground and thrown.

 F4: Devastating tornado ( mph); Devastating damage. Well- constructed houses leveled; structure with weak foundation blown off some distance; cars thrown and large missiles generated.

 F5: Incredible tornado ( mph); Incredible damage. Strong frame houses lifted off foundations and carried considerable distance to disintegrate; automobile sized missiles fly through the air in excess of 100 yards; trees debarked; incredible phenomena will occur.