Name: _ MEA 214 Midterm Exam, Spring 2011 Feel free to ask me if you are confused about the meaning of any question. Good luck, and have a great spring break! 1.) For each of the characteristics listed below, indicate the type of front to which the statement best applies. Options include warm, cold, occluded, and stationary fronts. a.) Fastest-moving front b.) Slowest-moving front c.) Generally accompanied by weakest temperature contrast d.) Accompanied by steady precipitation over a large area e.) Signifies mature stage of parent cyclone 2.) Which of the following best explains why developing cyclones (low-pressure systems) are generally found east of the axis of upper level troughs? a.) The strong southwesterly flow found east of upper troughs tends to push the surface low towards the northeast; the low forms directly beneath the upper trough and is then pushed to the east of the trough axis by the strong jet. b.) Developing cyclones require divergence aloft, which, due to gradient wind balance, is found between the strong flow in the downstream ridge and weak flow in the upstream trough. c.) Cyclones typically form in the lee of the Rockies and along the East Coast of the U.S.; these locations are typically east of upper-level ridges, which are most often centered over the Rockies and Appalachian mountain chains. d.) Cyclones form directly beneath the upper-level trough due to the downward extension of the low pressure from above. 3.) Consider the vertical sounding shown above. Which of the following would most likely correspond to surface weather conditions at this location? a.) Overcast with snow and fog b.) Overcast with freezing drizzle c.) Overcast with freezing rain d.) Partly cloudy Briefly justify your answer in terms of precipitation mechanisms in the space below. 4.) Consider the 500-mb map pictured below. At which location would you most expect to observe:
a.) Rising air motion, clouds, and precipitation b.) Surface anticyclone (high-pressure system) c.) Coldest air column d.) Strongest horizontal pressure-gradient force D B A C E 5.) Cold-Air Damming (CAD) True/False a.) CAD features a low-pressure system, which provides the cold air that gets dammed up against the Appalachians. b.) CAD has a strong influence on the climatology of sleet and freezing rain in the Carolinas and Virginia. c.) The Coriolis force banks up a cold, northerly flow of air against the Appalachians, but the cold air is shallow, only as deep as the terrain to the west. 6.) Which of the following is/are important sources of error in numerical weather prediction models? Check all that apply: a.) Incomplete coverage of input data for the models b.) Errors in surface ASOS measurements c.) Inadequate knowledge of the governing equations for the atmosphere d.) Errors in model physics, such as representing convective storms. 7.) Match the observations to the most likely location on the idealized cyclone pictured below by writing the corresponding letter to the blank on the map at left:
A: B: C: D: E: F: G: 8.) Match the following short-term forecasts below to the best location on the diagram above. Assume that the map above corresponds to a morning analysis. i.) Thunderstorms, ending with clearing and colder weather by evening. ii.) Warm and breezy, with an increasing chance of showers and thunderstorms late in the day. iii.) Cloudy with rain changing to drizzle, followed by afternoon clearing, warmer temperatures, and southwesterly winds. iv.) Snow, with steady northeasterly winds this morning. Snow possibly changing to rain before tapering to flurries with clearing from the west. 9.) Which of the following best explains why the wind speed increases with increasing height up to the jet stream level in the midlatitude troposphere? a.) The wind in the upper troposphere is generally in gradient balance, meaning that in order for the centrifugal force to become important, winds speed must increase with height. b.) The effects of surface friction are reduced as one moves aloft. Above the troposphere, friction again increases due to the close proximity to the top of the atmosphere. c.) erature gradients lead to pressure gradients above. Over a deep layer of consistent temperature contrasts, the overall pressure gradient continually increases with height. d.) The horizontal temperature gradient generally increases with height up to the tropopause, then levels out again. Wind speed is directly related to the strength of the temperature gradient.
10.) The cross-section diagram below is taken through the mid-latitude jet stream. a.) For typical Northern Hemisphere conditions, is the wind blowing into or out of the page? b.) For each blank on the diagram, indicate whether the temperature is warmer, colder, or similar to the other temperature at the same pressure level indicated. 100 mb 250 mb Jet Stream Core 500 mb 1000 mb 11.) For the surface observations shown below, analyze the sea-level pressure with a 4- mb contour interval, starting with the 1012-mb contour, and sketch the most likely location of a frontal boundary. North 198 180 190 204
12.) A major problem for numerical weather prediction models is the lack of data over the Earth's vast oceans. Which of the following are used to compensate for this? Place an X next to those types of observations that provide an important data source over the oceans. a.) Radiosonde measurements b.) Profilers c.) Commercial aircraft observations d.) Satellite measurements e.) Surface ship and buoy reports f.) Radar 13.) Lake-Effect snow true/false: a.) It is primarily a springtime phenomenon, when the atmosphere is least stable. b.) Snowfall totals can be highly localized due to the convective nature of the storms. c.) A similar phenomenon occurs when warm air flows over a colder ocean surface. d.) It is common during the coldest time of year, when the lakes are frozen over. 14.) The term self development describes a situation in which a positive feedback takes place between the lower-level cyclone and the upper-level wave. Which of the following facts or mechanisms are important to this feedback? Check all that apply. a.) Pressure decreases less rapidly with height in warm air, more rapidly in cold. b.) The temperature advection pattern with the surface cyclone. c.) Jet streaks feature divergence aloft in the left exit and right entrance. d.) Radiational heating of cold air behind a cyclone, and warming ahead of it can tend to amplify the upper-level wave. _ 15.) The earth system is characterized by excess radiational heating in the tropics and a deficit in the polar regions. Which of the following best describes the processes that work to equalize these differences? a.) The difference is mostly made up by ocean currents. Because water has such a large heat capacity, it is a more efficient heat transport mechanism than the atmosphere. b.) The atmosphere and oceans contribute roughly equally to the poleward heat transport in midlatitudes. c.) The atmosphere, with cyclones being a key element, are associated with greater poleward heat transport than the oceans. d.) This heat transport is largely accomplished by the atmospheric Hadley circulation. 16.) Which of the following best explains the observation that surface cyclones tend to dissipate (weaken) along the western slopes of the Rocky Mountains? a.) The temperature contrast there is generally weakest, favoring cyclone decay because cyclones rely on temperature contrasts for their energy. b.) Ridges in the upper jet stream are often located just to the west of the Rockies; these waves are responsible for cyclone dissipation. c.) The air column tends to compress vertically in that location as air ascends the winward slopes. d.) The air column tends to vertically stretch there, favoring vorticity (cyclone) decay.
_17.) In a typical negative cloud-to-ground lightning stroke, the stepped leader a) usually progresses upward from the ground towards the cloud. b) is usually invisible to the human eye. c) is followed immediately by a bright and visible dart leader. d) none of the above 18.) Supercell thunderstorms differ from air mass storms in that a.) they have a much longer life span, often existing for more than an hour b.) there is often a single main updraft core in supercell storms, while airmass storms have several strong updraft cores. c.) severe hail is much more likely with supercells. Airmass storms are much less conducive to large hail than supercell storms. d.) Both a.) and c.) 19.) Suppose that you and some of your non-meteorologist friends visit Florida for spring break. Being the only meteorologist in the group, it is your responsibility to monitor the weather while your friends party on the beach. One first morning, you download the 12Z rawinsonde data from Miami, plot it on your handy skew-t, and assess the situation. a.) Plot these data on the skew-t diagram provided (following page). Use red pencil for the temperature and blue for the dew point temperature. Pressure(mb).(C) Dew pt(c) 1000.00 20.0 17.0 925.00 19.0 14.0 900.00 18.0 11.0 850.00 15.0 3.0 700.00-1.0-10.0 650.00-3.0-24.0 500.00-20.0-37.0 300.00-41.0-58.0 250.00-42.0-62.0 200.00-44.0-66.0 b.) On the beach later that morning, ominous-looking cumulus clouds begin to develop. Your friends ask you whether a thunderstorm will develop from the cumulus cloud. Again, you whip out a skew-t and determine the LFC, and check the CIN and CAPE. You boldly make your forecast. Write the LFC pressure and your forecast below, and indicate CAPE and CIN on the skew-t that follows. LFC: mb T-storm forecast: (Select: no chance, unlikely, slight chance, likely) c.) You worry that your friends think you re a science nerd. To counter this, you decide to show them how cool you are by producing a maximum-temperature forecast. Assume that wind and solar heating will allow dry-adiabatic mixing up to the 850-mb level. List your temperature forecast below. The surface pressure is 1000 mb. High temperature: _
20.) What are the three necessary ingredients for the occurrence of convective storms? For the sounding plotted above, is there evidence for the presence of these ingredients? Very briefly, describe the evidence you see for each in the sounding. Ingredient 1: (yes or no) Evidence? Ingredient 2: (yes or no) Evidence? Ingredient 3: (yes or no) Evidence? 21.) True or False (answer T or F): a.) Heat lightning is lightning that does not produce thunder. b.) An individual lightning strike may include up to 30 return strokes. c.) Thunder is the sound generated by clashes between updrafts and downdrafts during the mature stage of a thunderstorm. d.) The visible channel (return stroke) for most negative cloud-to-ground lightning progresses upward from the ground towards the cloud.
22.) The map below shows 500-mb level winds, with latitude/longitude lines superimposed. Use this map and the indicated points to select the location that: a.) Has both u and v wind components that are strong and positive: b.) Has a negative v wind component: _ c.) Is characterized by dv/dx being positive: _ d.) Has the largest vorticity: _ E C A B D _ 23.) Thunder is the result of a) sound waves generated by colliding airmass boundaries. b) the sound of strong updrafts interacting with the Bergeron process. c) lightning bolts hitting the ground with tremendous pressure and force. d) rapid expansion of lightning-heated air. _ 24.) What environmental characteristic is the most important in determining thunderstorm type (e.g., supercell vs multicell vs air mass) a.) The presence of vertical wind shear. b.) The availability of moisture. c.) The presence of divergence aloft. d.) The presence and degree of convective instability
25.) Suppose that you are forecasting for Raleigh and vicinity in a situation when the potential for overnight thunderstorm development is uncertain. Easterly flow has developed over North Carolina, but a shallow frontal boundary is located over east central NC between the coast and Raleigh. You are provided with the following data from the Morehead City (on the NC coast) rawinsonde at 00 Z that evening: Pressure erature Dew Point Height (m) 1000.0 20.0 10.0 0.0 800.0 10.0 7.0 2000.0 a.) Plot the data listed above on the skew-t diagram below, using a red line for the temperature and a blue line for the dew point. b.) What is the lapse-rate stability of this layer? i.) absolutely stable ii.) conditionally unstable iii.) absolutely unstable c.) Suppose that the layer of air plotted above is lifted up over a shallow frontal boundary that is located between the coast and Raleigh. The entire layer of air is lifted by 200 mb. Use the skew-t diagram to lift this layer, and show your work. d.) What is the stability of the layer after lifting? i.) absolutely stable ii.) conditionally unstable iii.) absolutely unstable e.) Did the layer become more or less stable after lifting? _ What physical process was responsible for the change? 26.) Yesterday evening, a strong squall line moved through North Carolina. Which of the following best explains why a squall line was observed and not other types of storm structure (e.g., supercell or air mass storms)? a.) There wasn t enough instability for supercells, but too much for air mass storms. b.) There was strong shear, but it was mostly uni-directional (more speed shear than turning of the wind with height). c.) Because the lifting mechanism was a cold front, the storms tended to form along this linear feature. d.) Both b.) and c.)
On Sunday, 4 May 2003, a deadly tornado outbreak took place across Missouri and surrounding states. The NWS had launched special rawinsondes at 18Z in several locations in order to help pinpoint the severe threat. The Little Rock, AR sounding from 18Z 4 May is shown above. 27.) On the skew-t diagram above, determine (for an air parcel based at the surface): a.) the LCL: _ mb b.) the CIN (label on diagram) c.) the CAPE (shade and label on diagram) d.) the EL: _ mb 28.) Which characteristics of this sounding are consistent with a severe weather outbreak? a.) Strong instability b.) Potential instability c.) abundant moisture d.) A veering wind profile e.) A backing wind profile 29.) Consider the sequence of surface observations taken at RDU airport shown above. Based on this information: a.) Did a front pass RDU during this time frame? _ (yes, no, maybe)
b.) If yes, what type of front was it?