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) Potential Instability --

A characterization of a sounding in which the surface-based CAPE exceeds the surface-based CIN and the potential energy associated with the potential buoyancy acceleration exceeds the work needed to raise the surface parcel to the Level of Free Convection.

(d) A contour of constant dew point temperature is known as an __isodrosotherm____

(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. Units. Provide the units used conventionally for the following (5 pts each for a total of 15 pts)

Example

Acceleration meters per sec2 or m s-2

Pressure gradient _______mb km-1_mb mile-1___

mixing ratio ______ g kg-1_____________________

lapse rate _______ deg km-1 or _ deg ft-1___

∆p/∆y ____ mb km-1___or ___mb mile-1__________________

3. Severe Weather Outbreak, April 29, 2010 (29 pts).

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

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.