Hurricanes

What needs to happen in the atmosphere for storms to form? Warm, moist air rises in the troposphere Warm air condenses and releases heat in the atmosphere

Tropical Storms Tropical storms are large, rotating, low pressure storms The strongest of these storms are known as hurricanes

Tropical Storms Tropical storms form in a low pressure system when water evaporates off of warm, tropical waters This creates a region of low pressure which attracts surrounding air They spin and move across Earth’s surface

Coriolis Effect! So Why Do They Spin? https://www.youtube.com/watch?v=i2mec3vgeaI

Coriolis Effect

How do hurricanes become hurricanes? As the rotation (caused by the Coriolis Effect) of the storm increases, the winds around the center pick up speed until they become first a tropical storm (sustained winds of 35 mph), and then a hurricane (sustained winds of 75 mph, or greater). The Coriolis effect is a deflection of a moving object when viewed in a rotating reference frame. Thus, if the student were on a merry-go-round, and they rolled a ball while rotating around the merry-go-round, the ball would appear to deflect to one side depending on the direction of rotation. In our current case, the rotating reference frame is the Earth spinning on its axis, and the moving object is a large region of rising warm moist air called a tropical wave. The result is that the storm begins to deflect to one side. Once started, the deflected air begins to rotate counterclockwise. Wikipedia has a good discussion of the Coriolis effect.

The highest winds are found in the eyewall of a hurricane. Damaging winds and heavy rain can also occur in the rainbands of a hurricane. Air in a rotating hurricane is drawn into the center of the storm, called the eye. When the air reaches the eye, it rises up through the eyewall and spreads out on top of the hurricane forming dense cirrus clouds. Inside the eye is relatively calm and 20-40 miles long 1) Rainbands are also called feederbands in a hurricane.

https://www.youtube.com/watch?v=Xtu2_ziBI_w

Energy of a Hurricane Hurricanes will last until it can no longer produce enough energy to sustain itself Usually happens when a hurricane moves over land – act as brakes to the rotation of the storm

Hurricane Damage The most extreme forms of damage from a hurricane are along coastlines. Here, only a single home remains standing along the Texas coastline after Hurricane Ike hit in 2008. Hurricane damage along a coastline is the most severe because of high winds, pounding rain, and the storm surge. What is a storm surge? The photo above was taken after Hurricane Ike hit the Texas coastline in 2008. The level of damage is almost 100%. This level of catastrophic damage only occurs when a very strong hurricane hits a coastline at high tide. Why? Because the storm surge plus the high tide brings pounding surf further inland than if the hurricane storm surge hit at low tide. This was the case in Hurricane Ike. Thus, sometimes the same strength of a hurricane might cause very different levels of damage depending on when and where each storm hits the coast. The next slide explains a storm surge.

Hazards – Storm surge Occurs when hurricane force winds drive a mound of ocean water toward coastal areas Can reach 6 meters above normal sea level 95% of the storm surge height is caused by wind pushing the ocean in front of the storm.

Hurricane Tracking How strong will they get? Where will they go? This is a satellite image from 2008. It shows one hurricane in the Gulf of Mexico and two hurricanes in the Atlantic Ocean. Try quizing the students on where Florida is located…..or Mexico….or South America…..etc.

How is a hurricane tracked? National Hurricane Center Weather satellites collect photos and other data each day during hurricane season. Images from several different types of satellites are studied to estimate the position, direction, and intensity of a storm. Then, hurricane tracking aircraft fly into the storm to confirm wind speed and direction, rainfall, and internal pressure of the hurricane eye. The National Hurricane Center is located in Miami, FL. The hurricane season starts on June 1st each year and extends until November 30th. The National Hurricane Center website is: www.nhc.noaa.gov.

Inside the Eye of a Hurricane This photograph was taken onboard a Lockheed WP-3D Orion hurricane tracking airplane when it flew inside the eye of Hurricane Katrina in 2005. The cloud bank in the distance is the eyewall of Hurricane Katrina. It is safe to fly into hurricanes because airplanes fly into the wind, and they do not try to land in a hurricane.

Hurricane Tracks 1) The above track is for tropical storm Irene in 2011. Every tropical storm and hurricane has a track similar to this one. They are posted on the National Hurricane Center’s website at: www.nhc.noaa.go. What does the track show? The little orange dot at the far right is the current location of the storm when this map was posted. The storm was only a tropical storm when this announcement was posted. The letters S & H refer to the predictions when the storm will remain a tropical storm (S), and when it is expected to develop into a hurricane (H). Latitude and longitude coordinates are given on the bottom (longitude) and left (latitude) of the map. The colors correspond to the watches and warnings that the National Hurricane Center gives out 6 times per day. The white outline and highlighted area is called a ‘prediction cone’ of where the hurricane might go. The prediction cone gets wider the longer into the future that the predictions are made. Use the information posted on the National Hurricane Center’s website to track each storm in the classroom. A blank hurricane tracking map is given at the end of the slide show.

Classifying Hurricanes The Saffir-Simpson hurricane scale classifies hurricanes based on: Wind speed Air pressure Potential for property damage

Hurricane Preparation Hurricanes can be observed from weather satellites orbiting the Earth Can improve hurricane warnings which can give people time to leave During hurricanes you should: Board up the house Stay indoors Have plenty of food and water Stay away from windows

Before and after photographs for the damage along the New Jersey coastline during Hurricane Sandy in 2012.

1) Look how BIG a hurricane can be 1) Look how BIG a hurricane can be. This one is hurricane Isabel in 2003. It stretches from South Carolina all the way north into Canada.

Hurricane Katrina New Orleans, Louisiana. Category 3 Hurricane 1,836 Deaths, mostly resulted from the levee breaking Deadliest US Hurricane since 1928