DEPARTMENT OF GEOSCIENCES                                   Name____________________

San Francisco State University                                                Metr. 201 Spring 2010

 

Metr 201 -- Monteverdi
Quizzes #5 and #6 Key 200 pts.

 

1.     Fill in the Blank or short definition.  (CHOOSE 3:  6 points each for a total of 18 points in this section).


            (a)        Dry line -- the surface boundary between warm dry air (usually drawn northeastward from the Mexican Plateau region) and warm moist air (drawn northward from the Gulf of Mexico) generally located on the south side of wave cyclones exiting the Rockies during the Spring. Normally, the warm dry air is advancing.



            (b)       Newton’s Second Law of Motion--The acceleration experienced by an object is due to the sum of the forces acting on the object . (An object at rest will be accelerated in proportion to the forces that act on the object).


      (c)        A contour of constant wind speed (or current speed) is known as an __isotach__.

 

 

      (d)        hook echo--the pendant or hook shaped configuration a radar reflectivity echo assumes in association with a persitent rotating updraft.


 

      (e)        The development of cold air downdrafts, precipitation at ground level, the anvil and lightning appear        roughly simultaneously when a cumulus congestus cloud becomes cumulonimbus. This is apparently related to the formation of ____hail_____________ at the portion of the cloud at or near  the freezing level.

 

2. Units.  Provide the metric units used conventionally for the following (6 pts each for a total of 30 pts)

           

Example

            Acceleration                 meters per sec2 or m s-2

 

           

    Vg  (Geostrophic Wind Speed)                   ___m s-1 or knots or km h-1

 

 

∆z/∆n                                     _ dimensionless

 

   frictional acceleration                      m s-2

 

   500 mb height                                             _decameters or meters

 

    Coriolis acceleration                                    ____  m s-2

 

 

 

 

 

3.  500 mb chart (50 pts).

 

Examine the 500 mb chart given below.  Note the locations given at A, B, C and D. (5 points each answer for a total of 50 points in this section).

 

a.  The strongest winds would be found at location __C_____ . Why? (5 and 10 pts)

 

 

 

  According to the geostrophic wind relationship, the wind speed is directly proportional to the pressure or height gradient. On a weather map, this appears where the isobars or height contours are closest together. The height contours on the chart above are closest together at C.

 

 

 

 

 

 

 

 

b.  The wind direction (please use the direction designation that meteorologists use, e.g., southerly) at location A is ___________ and at location B is _______________ . (10 points)

 

c.  If the wind speed at C is 55 knots, plot the correct meteorological symbol for that wind information right on the chart. (15 pts)

 

d. Locate one trough axis and one ridge axis, by placing the correct symbols on the chart.  (10 points)

 

4. Use and Interpretation of Weather Maps  (Multiple Choice (circle best answer) and Short Answer)  (102 points in this section)

 

1.              Figure1 is the surface chart for 2100 UTC 23 April 2008.  Note the frontal lines at locations a, b and c. On Fig.      1, Line a is probably (5 pts)

      a.  an Occluded Front

      b.   a Stationary Front

      c.   a Cold Front

      d.  a Warm Front

      e.   a Dry Line

 

2. On Fig. 1, Line b is probably a (5 pts)

      a.  an Occluded Front

      b.   a Stationary Front

      c.  a Cold Front

      d.   a Warm Front

      e.  a Dry Line

 

SfcAnalysis

 

3.   Figure 2 is a chart of CAPE and CIN for 2100 UTC 23 April 2008.  Note the locations A  and B, where the CAPE values are 2500 and 3000 J/kg, respectively.   The blue areas represent areas of CIN.  Assume thunderstorms  develop at both locations. At  which location will the thunderstorm's updrafts be stronger and why? (30 pts)  (Two or three sentences)

 

 

  Thunderstorm updrafts at the Equilibrium Level are controlled by the CAPE. Since CAPE is higher at location B, then the thunderstorm updraft's potential strength will be higher there.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 4.   The blue areas on Fig. 2 represent areas of CIN.  These correspond to (5 pts)

 

      a.   Regions where the tendency for convection is encouraged.  If values are

          large,    thunderstorms will likely be severe.

      b.   Tornadoes are likely to occur.

      c.   Severe thunderstorms are likely to occur.

      d.  Regions where surface air parcels are stable, but if such parcels are force      lifted to the LFC, eventually                 they will be unstable (in other words, there is CAPE, but forced lifting is needed to get the air parcels to an        elevation at which they will we warmer than the air      surrounding them at the same elevation)

      e.   Strong straight-line winds are likely to occur.

 

5.         Figure 2 is a chart of CAPE and CIN for 2100 UTC 23 April 2008.  Note the locations A and B, where the CAPE values are 2500 and 3000 J/kg, respectively.  The blue areas represent areas of CIN.  At which location are thunderstorms likely to develop in the short term and why? (32 points --two or three sentences)

Thunderstorms are most likely to develop at A because the CIN has been removed. This means that, relative to parcel theory, the soundings in that area are absolutely unstable, and the LFC is at the ground. Even a very small parcel lofting from the ground will result in a buoyant updraft.

 

 

 

 

 

 

 

6.  Figure 3 is a chart of surface dew point temperatures and isobars for 2100 UTC 23 April 2008.  One can use this chart to (5 pts)

 

      a.   find fronts.

      b.   locate areas of fog formation.

      c.   determine the position of the jetstream.

      d.   find areas of upward vertical velocity.

      e.   locate the Dry Line.

 

7.         Figure 4 is the Radar reflectivity, 2108 UTC 23 April 2008, Roughly Centered at      Location A from Fig 2. Two thunderstorms are shown on the diagram.  Both of        them provide examples of the radar signature of rotation in thunderstorm updrafts. This signature is called (5 pts)

 

      a.   horizontal wind shear.

      b.   vertical wind shear.

      c.   the mammatus formation.

      d.  a hook echo.

      e.   an outflow boundary.

 

8.         Figure 5 is the Probabilistic Hail Outlook for 23 April 2008.  The outlook    basically shows

                   a.   the chances that rain will also have hail mixed with it.
      b.   the probabilities that severe storms will occur.
      c.   the probabilities that hail 1” or larger will be observed within 25 miles of a given point.
      d.   the probabilities that hail will occur at a given location.
      e.   None of the above.

9.         Figure 6 is the Convective Outlook for April 23.  The outer arrow (normally colored brown or orange)        encompasses

      a.   the region that has a 10% probability that  strong and violent tornadoes will be                                                         observed within 25 miles of a given location.
      b.  the portion of the United States expected to experience general thunderstorms.
      c.   the portion of the United States expected to experience tornadoes.
      d.   the region in which severe downbursts are sure to occur.
      e.   the portion of the United States expected to have a high risk for severe      thunderstorms.

10.       The inner arrow (normally colored yellow or red) on Fig. 6 encompasses

 a.   the region that has a 10% probability that  strong and violent tornadoes will be observed within 25 miles                       of a given location.
b.   the portion of the United States expected to experience general thunderstorms.
c.   the portion of the United States expected to experience tornadoes.
d.   the region in which severe downbursts are sure to occur.
e.   the portion of the United States expected to have a moderate risk for severe       thunderstorms.

 

 

 

 

 

 

 


 

 

 

 

 

 

Figure 1:  Surface Chart, 2100 UTC 23 April 2008  

 

 

 

 

 

 

Figure 2: Chart of CAPE/CIN , 2100 UTC 23 April 2008

 

 

 

 

 

 

Figure 3: Chart of dew point temperature and surface pressure, 2100 UTC 23April 2008

 

 

 

 

 

 

 

 Figure 4: Radar reflectivity, 2108 UTC 23 April2008, Roughly Centered at Location A from Fig 2

 

 

 

 

 

 

 

Figure 5. Hail  Outlook for 23 April 2008

 

 

 

 

 

Figure 6. Convective Outlook for 23 April 2008