DEPARTMENT OF GEOSCIENCES                                     Spring 2009

San Francisco State University                                               Metr. 201

 

Synoptic Metr Quiz #3

100 pts.

(Test will be collected at 9AM)

 

1.    Definitions.  Choose two of the terms below.  Provide a one sentence definition (if the term is an abbreviation, first “unabbreviate” it and then define it).  (5 points each for a total of 10 points in this section).

(a) Dry line -- The boundary, often located in the Great Plains in the Spring, between warm dry and warm moist air masses, along which the dry air is usually 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) CCL -- The convective condensation level (CCL) is the elevation at which a convective cloud base is found when surface air parcels are heated to the convective temperature, termed the convective temperaturre, the lowest temperature to which the surface air must be heated to make the sounding absolutely unstable.

or

 

On a thermodynamic diagram, the point of intersection of a sounding curve (representing the vertical distribution of temperature in an atmospheric column) with the saturation mixing ratio line corresponding to the average mixing ratio in the surface layer (i.e., approximately the lowest 1500 ft).

 

(e) Radar echo -- The portion of the energy emitted by the radar that is scattered or reflected back to it by precipitation particles.

 

(f)  Visible image -- A digital image of the visible portion of the electromagnetic spectrum, detected by weather satellite, that is reflected by objects in the earth-atmosphere system.

 

2.  Units.  Provide the units (metric) used conventionally for the following (8 pts)

        

         horizontal winds    meters per sec or m s-1 (or km h-1)    

 

        

         Coriolis acceleration                 _________m s-2 ________________

 

         lifted index                              __________K0 or C0_________________

 

         Ĺ                                          ___________ s-1 __________________

 

         Convective Temperature           _________F0 or C0___________________

 

 

 

Part C.  Use and Interpretation of Weather Maps  (Multiple Choice and Short Answer)

 

Figure1 is the surface chart for 2100 UTC 23 April 2008.  Note the pressure systems at A and B and the frontal linesat locations a, b and c. On Fig. 1, Line b isprobably

 

      a.          an OccludedFront

 

      b.          a Stationary Front

 

      c.          a Cold Front

 

d.           a Warm Front

 

      e.          a Dry Line

 

2. On Fig. 1, Line a is probably a

 

      a.          an OccludedFront

 

      b.          a Stationary Front

 

      c.          a Cold Front

 

 d.          a Warm Front

 

      e.          a Dry Line

 

 

 

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?

 

The thunderstorm updrafts will be the strongest at location B because the CAPE values are larger. The strength of convective updrafts is directly proportional to the CAPE.

 

 

 

 

 

 

 

 

 

4.   The blue areas on Fig. 2 represent areas of CIN.  These correspond to

 

      a.          Regions where the tendency forconvection is encouraged.  Ifvalues are large, thunderstorms will likely be severe.

 

      b.          Tornadoes are likely to occur.

 

      c.          Severe thunderstorms are likely tooccur.

 

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

 

      e.   Strong straight-line winds are likely tooccur.

 

5.       Figure 2 is a chart of CAPE and CINfor 2100 UTC 23 April 2008.  Notethe 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?

 

Thunderstorms are likely to develop at A and not at B. Despite the fact that CAPE values are larger at B, there is too much CIN at that location. There is no CIN at location A. Hence, the atmosphere there is nearly absolutely unstable with respect to surface parcel lifting, and thunderstorms are likely to develop at A.

 

 

 

 

 

 


 

6.  Figure 3 is a chart of surface dew point temperatures and isobars for 2100 UTC23 April 2008.  One can use thischart to

 

      a.   find fronts.

 

      b.   locate areas of fog formation.

 

      c.   determine the position of the jetstream.

 

      d.  find areas of high relative humidity.

 

      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 theradar signature of rotation in thunderstorm updrafts. This signature is called

 

      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 ¾” or larger will be observed within 25 miles of a given location.
  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.

 

 

 

 

 

 

 

 

map

 

 

 

Figure 1:  Surface Chart, 2100 UTC 23 April 2008  

 

 

 

ap

 

 

 

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

 

 

 

 

 

  ap

 

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 April2008

 

 

 

 

Figure 6.  Convective Outlook for 23 April 2008