CHAPTER 17 Weather and Climate - Mr. Barrow's Science Center

Topic: Hurricane TrackingVisit gpescience.com for Weblinks to information abouthurricanes and hurricane tracking.Activity Research six hurricanes.Make a table that lists how eachwas tracked as a tropical depressionand then as a hurricane.Figure 10 Texas, Oklahoma,and Kansas frequently experiencetornadoes.Fewerthanten101010Scale0 500 mi 100 1000 km10 10501002003005010010050Tornadoes and Hurricanes Two types of violent windstorms that differ greatly in their origins and effects aretornadoes and hurricanes. Tornadoes are intense, short-lived,localized storms in the mid-latitudes. They originate in cumulonimbusclouds under special conditions. Typically, tornadoesthat occur in the United States form when dry air from thedeserts of Mexico and the southwest overrides warm, moist airfrom the Gulf of Mexico. This happens frequently in the GreatPlains, the lower midwest, and parts of the south, as shown inFigure 10. In the south, they often accompany hurricanes.A twisting, funnel-shaped tornado cloud can move acrossland at a speed of around 50 km/h creating a path 150 m wideand 10 km long. Intense, circular winds in the funnel can reachspeeds up to 400 km/h. The extreme low pressure at the centercan result in more damage than that from the wind.Hurricanes are tropical storms that cover vastFewer thanten1010050505010areas and last for days. Those affecting the UnitedStates often form as tropical depressions over thewarm waters of the southern Atlantic off thecoast of Africa. When winds exceed 118 km/h, thestorms are called hurricanes. A typical hurricaneconsists of vast cloud bands that spiral inwardtoward the clear center, called the eye. Scientistsoften fly into the eye to study the storm. WesternPacific hurricanes are called typhoons.SummaryGlobal•Wind and Pressure SystemsFour major pressure systems produce threemajor wind systems in each hemisphere.•High and Low Pressure SystemsAir flows counterclockwise around lowsand clockwise around highs in the northern•hemisphere.Air rises in the center of lows and sinks in thecenter of highs.Weather Fronts and Severe Weather•Air masses interact at weather fronts.Warm fronts are associated with stratus-typeclouds and cold fronts with cumulus-type•clouds.Severe weather includes hurricanes, tornadoes,and downbursts.Self Check1. Explain how Earth’s rotation affects winds.2. Compare and contrast tornadoes and hurricanes.3. Infer the wind directions around a high in the southernhemisphere.4. Describe common differences between continental airmasses and maritime air masses.5. Compare and contrast warm fronts and cold fronts.6. Think Critically If the polar front jet stream were tomove southward over the U.S., what other weathersystems are likely to be affected?7. Use Percentage A tornado watch was issued on25 days during one year in a midwest city. Whatpercent of the year does this represent?528 CHAPTER 17 Weather and ClimateMore Section Review gpescience.com