DEPARTMENT OF GEOSCIENCES          Name_________________________

San Francisco State University                                                        Spring 2010

 

Metr 201 Monteverdi Quiz #4

100 pts.

(25 min. Test will be collected at 10:10 AM)

 

1.     Definitions.  (5 points each for a total of 25 points in this section).

 

(a)  Convective Condensation Level --

 

The elevation at which a lofted surface parcel heated to its Convective Temperature will be saturated and above which will be warmer than the surrounding air at the same elevation.

 

(b)   Convective Temperature --

 

The surface temperature that must be met or exceeded in order to convert an absolutely stable sounding to an absolutely unstable sounding (because of elimination, usually, of the elevated inversion characteristic of the Loaded Gun Sounding).

 

(c)  Lifted Index -- the difference in temperature (in C or K) between the surroundings and the rising air parcel at 500 mb.

 

(d) wave cyclone -- a cyclone in which a frontal system is centered in a wave-like configuration, normally with a cold front on the west and a warm front on the east.

 

(f)  dry line--the boundary between warm dry and warm moist air normally found in the United States on south side, or warm sector, of wave cyclones located over the Great Plains.

 

 

 

 

 

2. Symbols.  Provide the correct symbol (3 pts each for a total of 12 pts)

        

Example

         Acceleration of gravity               g

 

        

vertical wind component                    ____w

                 

potential temperature                         ____Theta

 

horizontal wind along x-axis               ____u

 

horizontal wind along y-axis               ____v

 

 

 

 

 

 

 

3. Severe Weather Chart and Parameter Interpretation (60 points)

 

Part I.  Essay Questions. 

 

A.  You are provided with the paired (a) CAPE/CIN charts;  (b) Visible Satellite Images;  and (c) radar reflectivity images for approximately 1700 UTC and 2200 UTC on 29 April 2010.  Note the locations labeled A and B. ( 20 pts).

 

.

 


Explain the differences in the satellite and radar presentation at locations A and B given the evolution of the CAPE/CIN field you see on the top chart. [Note:  this is an essay question.  It does not need to be long.  However, it needs to be written in proper English, NEATLY, with sentences that have a subject, verb and object]  (40 points)

 

The morning CAPE and CIN field suggests that all of the soundings in the area are potentially unstable, but that large values of CIN need to disappear from these soundings before the soundings become nearly absolutely unstable.   The values of CAPE at the two locations are roughly similar, but it is clear that by the afternoon while the CIN disappeared at location A, there was still significant values of it at B.  Thus, the convective temperature was probably attained at A, and thunderstorm initiation should be observed at location A, but not at B.  The radar reflectivity and visible satellite plots substantiate this, with both showing heavy precipitation associated with a cumulonimbus cloud at A, but clear skies and no precipitation at B.


 

Part 2.  Short Answer. You are provided with the surface analysis at 01 UTC 30 April 2010.  Note the boundary indicated by the arrow.  It is the dry line.

 

 

Examine the weather information on either side of the dry line.  Now briefly describe why that weatther information is consistent with the fact that the dry line is analyzed in the location shown.  [Caution:  it is up to you to decide what weather information is consistent with the analyzed dry line.]

[Note:  this is a short answer question.  It does not need to be long.  However, it needs to be written in proper English, NEATLY, with sentences that have a subject, verb and object]  (20 points)

 

The analysis shows a dry line in the warm sector of a cyclone in the Great Plains.  According to the analysis, warm dry air should be west or southwest of the analyzed boundary, and warm moist air should be east of it.  Temperatures on either side of this boundary are in the middle and high 70s, contrasted to the 50s north of the cold and stationary fronts shown.  At the same time, dew point temperatures southwest of the dry line are in the 20s and northeast of it are in the 60s.  Thus, the boundary divides warm dry air in the west moving northeastward from warm moist air in the east moving northward.  Thus, the weather information supports the analyzed boundary.

 

 

Part 3.  Sounding Interpretation.  You are provided with the sounding for Atlanta, Georgia (KFFC) for 12 UTC 27 April, 2011. (23 points)

Your task is to transform the sounding to one that estimates conditions for afternoon heating. 

  1. Find the Convective Condensation Level, and the Convective Temperature.
  2. Draw the parcel ascent curve that would occur if the afternoon temperature. 
  3. Shade in the CAPE for the ascent curve that results.