Introduction to Meteorology

Introduction to Meterology

Severe and Hazardous Weather

ACTUALLY ON TEST 12/12/2014 LECTURE 16 What is upwelling, how does it aﬀect ocean temperature?  Vertical transport of deep ocean waters  Results in cooler surface water temps What is ENSO, El Nino, La Nina?  Trade winds blow east  west, atmospheric oscillation after El Nino  El Nino: trade winds blow east to west, create cycle, push warm water to the west  L

ATMS | 100 | Introduction to Meteorology | ACTUALLY ON TEST 12/12/2014 LE

11/7/13, 3:56 PM Take Test: Exam #2 FA2013 Page 3 of 25 https://compass2g.illinois.edu/webapps/assessment/take/launch.jsp?c…sment_id=_31531_1&course_id=_9160_1&content_id=_724152_1&step=null a. The incredible speed at which the lightning strike travels splits the air molecules and when they reform an incredible shockwave is produced. b. Large cumulonimbus clouds have updrafts that collide with downdrafts. When they strike one another, an incredibly large sound wave is produced c. Thunder is the result of dragons ﬁghting in the skies d. Lightning heats the air around the bolt which causes a rapid expansion of this air which produces a huge pressure surge that travels as sound wave. e. Thunder is caused when God claps his hands. What is the physical process that occurs in the thunderstorm that produces the sound of thunder? a. Dust particles within the cloud collide countless numbers of times allowing for the static build-up of electricity within the cloud. b. As a thunderstorm moves over land, friction with the air near the surface allows for the stripping of electrons from the ground by the lowest regions of the thunderstorm. This negatively charges the lower part of the cloud and creates the charge separation necessary for lightning to develop. c. Countless collisions between rain drops within a mature thunderstorm create a static build up within the convective region of the storm which separates into a positively charges upper portion of the cloud and negatively charged lower portion of the cloud. d. The top of most cumulonimbus clouds reach into the ionosphere where interactions with the ions in this layer of the atmosphere cause the top of the cloud to accumulate a positive net charge while the bottom of the cloud maintains a negative net charge. e. Ice crystals collide with hail stones and graupel and exchange electrons. The ice crystals are then swept to the top of the cloud with a net positive charge, while the hail and graupel remain in the lower part of the cloud with a net negative charge. Which of the following statements best describes how a cloud builds an electrical ﬁeld capable of producing lightning? Question 8 2 points Saved Saved Which of the following diagrams best shows the charge distribution prior to a cloud- to-ground lightning strike? Question 9 2 points Saved Saved 11/7/13, 3:56 PM Take Test: Exam #2 FA2013 Page 4 of 25 https://compass2g.illinois.edu/webapps/assessment/take/launch.jsp?c…sment_id=_31531_1&course_id=_9160_1&content_id=_724152_1&step=null a. A b. B c. C d. D True False True or False: In a negative polarity cloud-to-ground lightning strike, the return stroke creates the bright ﬂash. This bright ﬂash starts from the ground and travels upward into the cloud. Question 10 2 points Saved Saved a. Strong vertical wind shear b. An updraft that is separated from the downdraft c. Ice Which of the following must a thunderstorm contain to create lightning? Question 11 2 points Saved Saved

ATMS | 120 | Severe and Hazardous Weather | exam | 11/7/13  3:56 PM Take Test: Ex

atmos_study_guide.docx-Heather Jozwiak Atmos Study Guide Lecture

 Ordinary (single-celled) thunderstorms o Usually not severe o Most common o Usually in the summer o Weak vertical wind shear  Multicellular thunderstorms (MCSs) o Thunderstorm complexes o Strong vertical wind shear  Supercell thunderstorms o Almost always severe o Strong vertical wind shear 20. What is the typical life cycle of an ordinary thunderstorm?  About an hour 21. What is the updraft? Downdraft? Overshooting top? Anvil? How do they form?  updraft: warm, moist air that rises  When air is cooler than its surroundings, it sinks, sinking air is downdraft  Precipitation is required to form a downdraft  overshooting top: Top of updraft may penetrate into stratosphere  Air diverges outward when it reaches tropopause, forming anvil cloud at top of storm 22. Why do ordinary thunderstorms typically only last for about an hour?  They develop in regimes of weak vertical wind shear  Typically last about an hour, because their updraft and downdraft aren’t separated by vertical wind shear 23. What is outflow? How does it form?  When the cold downdraft reaches ground, it spreads outward, forms pool of cold air at surface beneath storm= outflow 24. What is a gust front or outflow boundary?  Boundary between cold outflow and warm inflow is called gust front or outflow boundary 25. What are the criteria used by the National Weather Service to determine if a storm is severe? How often does each type of severe weather occur in the US each year?  winds of 58 mph (50 kts) OR hailstones of 1" of greater OR tornado 26. What is the difference between a watch and warning?  Watch = conditions are favorable for severe weather  Warnings = severe weather is happening now o Tornado has been sighted by an official or trained storm spotter  Doppler radar has detected rotation within a storm or tornado debris 27. What is a shelf cloud? How does it form and what weather conditions might be expected as one passes?  Shelf cloud: large, low-hanging, typically non-precipitating  Non rotating  Causes convective clouds 28. What are downbursts and microbursts? How do they form?  Downburst = a strong downdraft that comes in contact with the ground o Form when sinking air is colder than air around it, rain falls into unsaturated air and evaporates (cooling air, cold air sinks), rain drags air downward with it  Can sink as fast as 40-50 mph  Aviation hazard  Microburst = smaller (more intense) downburst 29. What is a bow echo and what is the main weather hazard associated with them?  Section of high radar reflectivity (intense storms) that “bow” outward  Mesoscale convective system 30. Review the main components of a squall line – Gust front and shelf cloud, convective zone, and trailing stratiform region. What are the characteristics of each?  Trailing region = light to moderate rain that follows the intense leading thunderstorm o Can contain lightning  Convective zone o Line of thunderstorms just behind gust front o Heavy rain, strong gusty winds o Line of high reflectivity (yellows/red) on image  Stratiform region o Large area of light to moderate rain behind convective zone  31. What is a derecho?  a line of intense, widespread, and fast-moving windstorms and sometimes thunderstorms that moves across a great distance and is characterized by damaging winds. 32. What is a supercell?  Long-lived rotating thunderstorms that can last for hours o Often isolated  Most intense thunderstorms on the planet  Most rare type of thunderstorm  Always rotate  Typically single celled and small (county or smaller)  Produce majority of tornadoes o Nearly all EF-2+ tornadoes  Produce nearly all hail golfball-sized or larger  Straight-line winds  Strong shear (strong winds aloft) in supercell environments often yields long, asymmetric anvils

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