Polar Highs Areas around the poles from which the polar easterlies originate

Polar highs areas around the poles from which the

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Polar Highs Areas around the poles from which the polar easterlies originate. This zone is cold and dry.
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Jet Streams Embedded in the westerly flow are narrow ribbons of high-speed winds that meander for thousands of miles (kilometers) . Where do jet streams occur ? They occur in the middle latitudes at the tropopause , between 25,000 and 40,000 feet. Dimensions : 60 – 300 miles wide 3000 – 7000 feet thick Wind speeds :They have wind speeds in excess of 120 miles per hour, but they rarely exceed 240 miles per hour. Airlines : Use the jet stream on eastward flights. Avoid them on westward flights.
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Why are there distinct, energetic winds (Jet Streams) within the slower, general westerly flow? Areas where there are greater pressure gradients at the surface, produce faster upper air winds. Example: Large temperature differences between Georgia and Florida in winter produce faster upper air flow. Upper air flow is fast above these regions of large temperature contrasts . Large temperature contrasts occur along linear zones called fronts . Along the polar front, and associated with it, is a jet stream called the Polar Jet Stream .
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Polar Jet Stream (Also sometimes called the Mid-Latitude Jet Stream.) Occasionally it travels at more than 310 miles/hour (500 km/hour). Average Speed Winter = 77.5 miles/hour (125 km/hour) Summer = 37.2 miles/hour (60 km/hour) The difference in seasonal speeds is caused by the fact that in the mid-latitude winter, there is a stronger temperature gradient than in the summer. Winter – The polar jet stream may extend south to 30 0 N (Houston, Texas; New Orleans, Louisiana; Jacksonville, Florida) Summer – The polar jet stream is usually about 50 0 N, but can extend to 70 0 N, especially by midsummer.
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Polar Jet Stream It often meanders and may split into two jets, or flow almost north/south. Determining changes in the location and flow pattern of the polar jet stream is an important part of modern weather forecasting . Summer – The polar jet migrates north. Winter – The polar jet migrates south. Midwinter – The polar jet may penetrate to Central Florida.
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Polar Jet Stream It strongly influences areas of thunderstorm and tornado activity . February – Tornadoes occur in states bordering the Gulf of Mexico. Midsummer – Tornadoes occur in the Northern Plains and the Great Lakes States. It is an integral part of the Westerlies . It plays a big role in the weather of the mid-latitudes . a) It supplies energy to the circulation of surface storms. (i.e. It helps drive the rotational motion.) b) It also directs the path of surface storms . (Its biggest influence on storm paths occurs in the winter .)
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A close relationship exists between the location of the polar jet stream and conditions near the surface, particularly temperatures. a) If the polar jet is south of your location : Your weather is colder and stormier than normal . b) If the polar jet is north of your location : Your weather is warmer and drier than normal .
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  • Fall '16
  • Mark Smith
  • weather, Tropical cyclone, Atmospheric dynamics

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