SAN FRANCISCO STATE UNIVERSITY                                                             Meteorology 430 DEPARTMENT OF GEOSCIENCES                                                      Fall 2008

Midterm #1

250 Points

Part A.  Map Set 1 (70 pts)

1,  Attached find the WXP analyses of 200 mb and 1000 mb convergence and 500 mb vertical velocities (in x, y, p coordinates) forecast by the NAM 12Z 21 October 2010.  Note the location indicated by the square off the California coast.

2.  Briefly explain to what extent the charts given in Map Set 1 GENERALLY  illustrate the principle of Dines Compensation (at the location where the small box is drawn).  (25 pts)

Dines Compensation states that upper tropospheric divergence tends to be balanced by lower convergence and vice versa. In this case, there was upper tropospheric (e.g., at 200 mb) divergence with "compensating" lower level convergence (e.g., at 1000 mb). However, the lower level convergence appears to be larger than the upper tropospheric divergence to which is linked. This appears to be an exception of the general tendency...for which the upper tropospheric divergence and/or convergence generally exceeds the compensation in the lower troposphere.

3.  Print the following (starting at 8:30AM)  for the date, time, and region indicated on the black board: 42.5N, 130W, 48 hr forecast if you are doing a forecast chart.   Several of you will be printing charts for 12 UTC today and don't need the latitude and longitude information (10 pts)

 Vanessa 500 mb vertical velocity Alexandria 300 mb chart with observations (12 UTC 10/22/10) Denise 200 mb convergence Leo 500 mb chart with observations(12 UTC 10/22/10) Jacqueline 200 mb vertical velocity Matthew 1000 mb vertical velocity Ruisi Simple surface chart with observations (12 UTC 10/22/10) Benjamin 700 mb chart with observations(12 UTC 10/22/10) Christopher 850 mb chart with observations(12 UTC 10/22/10) Hsiao-Yuan 700 mb vertical velocity Xiu Ping 1000 mb convergence

Part B.  Map Set 2 (60 pts)

Attached find the 850 mb, 700 mb, 500 mb and 200 mb charts for12Z 22 October 2004. Also included is the Eta initialization for surface isobars and 1000-500 mb thickness.

1. Discuss why the trough over the central portions of the country "tilts" towards the west (in this case).

2. Draw advection arrows and fronts for the cyclone in the midsection of the country.
(On this eta_thick, I used yellow for warm advection area/arrows. Remember, the fronts are drawn on the equatorward (or warm air side) of the greatest concentration of advection arrows/thickness contour packing).

Part C.  Map Set 3 (80 pts)

Attached find sfcplot and a plot of unanalyzed surface observations for 12Z 22 October 2004

Analyze the surface plot inside the solid lines, using proper isobar intervals, color conventions, frontal/trough symbols etc. (no isotherms or isodrosotherms).  Use the 1000-500 mb thickness analysis from Part B to help you to complete the frontal analysis. (70 POINTS)

Part D.  Map Set 4 (40 pts)

Attached find the 12UTC soundings for Davenport, Iowa and Albuquerque, New Mexico; and the surface isobars and 1000/500 mb Thickness for 12Z 22 October 2004.

Do the following sets of questions:

1.   Note the locations of Albuquerque and Davenport labeled A and B, respectively.

(a)       Plot the 1000 mb geostrophic wind vector at each location with a solid arrow.  (You will have to qualitatively estimate the length of the vector).

(b)       Plot the thermal wind vector at the same locations with dashed arrows.  (Again, you will have to qualitatively estimate the length of the vector..make it 4 times the length of the 1000 mb geostrophic wind vector you did in (a)).

(c)        Now, on the back of this sheet, replot these vectors in a manner that will allowyou to estimate the 500 mb geostrophic wind vector.  Replot the 500 mb geostrophic wind vector on the map.

2.         Describe how the thermal structure and wind profiles evident on the sounding/wind plot for Davenport and Albuquerque is consistent with your frontal analyses.

At Albuquerque, the winds are backing with height in the layer from the ground to around 700 mb. This indicates that the station is in the cold advection area on the cold air side of a cold front. At Davenport, the winds are veering with height from the surface to around 850 mb. This indicates that station is in the warm air advection area on the cold air side of a warm front. In both cases, these estimates are consistent with the relationship of each station to the frontal analysis.

The soundings also indicate that ABQ is north of a surface cold front, and the frontal inversion is located in the sounding at about 450 mb. At Davenport, the sounding indicates that the surface warm front is south of the station and the frontal inversion is located at about 600 mb.