DataStreme Activity 8B:

UPPER-AIR WEATHER MAPS

Do Now:

  1. Print this file.
  2. Print the Wednesday Image 1, Image 2 and Image 3 Files.
  3. Print (when available) the Thursday, 1 November 2001, Daily Summary File.

To Do Activity:

  1. Read Chapter 8 in STUDY GUIDE, Part A: Narrative.
  2. Go to STUDY GUIDE, Part B: Applications. Start Activity 8B.
  3. Return here (Wednesday Activity B File) when told to do so.

Go To STUDY GUIDE - Activity 8B Now


WELCOME BACK: Procedure continued from STUDY GUIDE.

  1. As noted in the Wednesday, 31 October 2001, Daily Weather Summary, with the exception of rainy areas in the Great Lakes and the western mountains, the weather was relatively tranquil across most of the lower 48 states. The Wednesday, Activity B Image 1 is the surface map (Isobars, Fronts, Radar & Data) for Tuesday evening, 00Z 31 OCT 2001. The dominant weather feature across the eastern two-thirds of the country is a warm front that divides seasonable air to the south from cooler air to the north. This warm front resulted from the western end of a cold front that crossed the area, stalled and began moving back northward. The storm system in the West is producing precipitation through the mountains. The disruption of storm circulation by mountainous terrain adds to the computer location of various Hs and Ls there.

    The orientation of the frontal systems across the country is generally [(east-west) (north-south)]. Wind speeds reported at stations across the map are generally from [(twenty to fifty) (calm to fifteen)] knots.

  2. Image 2 is the 500-mb map for Tuesday evening, 00Z 31 OCT 2001. This upper-air map depicts the atmospheric conditions found at the 500-mb pressure level over the coterminous US and southern Canada at the same time as the conditions shown on the Image 1 surface map. These mid-tropospheric conditions were associated with the fronts and storm conditions evidenced on the surface map. Weather systems extend from the surface well into the troposphere, hence the need to examine upper-air maps to describe them more fully.

    On an upper-air map the observational data from the rawinsonde reports at that pressure are plotted around each station location in an upper-air station model format, as discussed earlier in this activity and the User's Guide, linked from the Extras section of the DataStreme homepage.

    The plotted report for Bismarck, North Dakota, on the Image 2 map shows that at 500 mb over the station, the conditions were:

    temperature (°C): [(-14) (-26)]
    dewpoint (°C): [(-11) (-20)]
    wind direction: [(west) (southeast)]
    wind speed (kt)*: about [(10) (30)]
    height (m):* [(5690) (5750)]

    *[ Note: When winds of 50 knots or higher are reported, a pennant is used on the station's wind shaft to signify a 50-knot increment in speed. Also, the altitudes of the constant-pressure surfaces on upper air charts are given in coded values (as is the case with the air pressures on surface maps). On 500-mb maps, the height is plotted in tens of meters. Decoding requires adding a 0 to the plotted number. That is, a plotted 500-mb height value of 556 is actually 5560 m. Contour lines are labelled on the map with the full height value.]

  3. The following is an excerpt from a rawinsonde text report for the same time as the Image 2, 500-mb map (DataStreme Homepage: "Upper Air Data - Text"). Using the values reported at the 500-mb level, plot an upper air station model for 500 mb using the station circle to the right of the data table. Round temperature and dewpoint to the nearest whole degree. (Mid-way values are rounded up if positive and down if negative.) Wind speed is rounded to the nearest 5 knots. Be sure your plotted height value is the coded number, that is, in tens of meters.

    Date:       0000Z 31 OCT 2001
    -----------------------------------------------
    LEVL  PRES  HGHT  TMPC   DEWP  RELH   DIR  SPED 
           mb     m     C      C     %    deg   knt 
    -----------------------------------------------           Station
     SFC  1027    14  15.0    7.0    59   110     6  
       1  1000   243  14.6    3.6    48   105     8
       9   850  1605  10.6  -14.4    16    95     6              O
      17   700  3200   3.0  -28.0     8   115    16 
      28   500  5840 -14.5  -47.5     4   190    12 
      33   400  7490 -26.3  -56.3     4   280    19 

    Compare your station model plot to the 500-mb map. The station you have plotted is
    [(Albuquerque, NM) (Charleston, SC)].

  4. The 500-mb heights (heights above sea level where the air pressure is 500 mb) are analyzed by drawing contour lines connecting equal values of altitude. To better visualize the contour pattern, highlight the 5760-m contour by tracing over it. [The 5760-m contour crosses from southern California to the Atlantic Ocean over New Jersey.] The overall contour pattern shows:

  5. Compare the winds and contours in the Gulf coast area to those in New England. Generally, wind speeds on the 500-mb map are faster where the height contour lines are [(closer together) (farther apart)]. This relationship between the spacing of contours and wind speeds at 500 mb is [(similar to) (the opposite of)] the relationship between spacing of isobars and wind speeds on surface weather maps.

  6. On Northern Hemisphere surface maps, the wind circulation about Lows is counterclockwise and [(inward ) (outward)] while that about Highs is clockwise and [(inward ) (outward)]. This across-isobar flow is due to the presence of friction near the Earth's surface. At 500 mb, above the influence of surface friction, wind directions are generally [("parallel to the contours") (across the contours toward lower heights)].

  7. Compare the 500-mb temperatures and heights across the northern US with those across the southern US. The temperatures at 500 mb above the northern states are [(colder) (warmer)] than those over the southern states and the heights of the 500-mb surface are [(higher) (lower)] over the North. Recalling the Activity 5B pressure blocks, the atmospheric column associated with lower heights of pressure levels would be [(colder) (warmer)] than the column with higher heights.

  8. Image 3 is the 500-mb map for 12Z 25 OCT 2001, the map depicting the 500-mb atmospheric conditions at the same time as the Image 1 surface map of Activity A this week. You will recall that there was a strong, 975-mb surface Low centered over Lake Superior at that time. The 500-mb pattern shown here for that same time has a closed 5280-m contour around Lake Superior. The Lake Superior area 500-mb station heights inside that contour are [(higher) (lower)] than those at surrounding stations. The overall 500-mb contour pattern is one of a [(trough) (ridge)] over the east-central US associated with the surface storm system.

    A comparison of the Image 2, 31 OCT, and the Image 3, 31 OCT, 500-mb maps, shows the higher wind speeds to be present at the 500-mb level on [(25) (31)] OCT. The contours [(were) (were not)] more closely spaced where those higher wind speeds occurred.

Compare the Image 2 and 3 maps of this portion of the activity to the 500-mb map in the printed portion of the Activity on page 8B-2. These maps show a variety of mid-tropospheric flow patterns. Image 2, showing the 00Z 31 OCT 2001 flow with small north-south excursions and moderate wind speeds, is probably the more typical 500-mb pattern while the others were associated with well-developed storm systems. Dramatic weather situations are certainly more memorable, but fortunately not more frequent!


You or your students can make a height-contour analysis by printing an unanalyzed 500-mb map ("500 mb - Data") from the DataStreme Homepage. You can then compare the hand-analyzed pattern to the computer-analyzed map with contours. Also, compare upper-air maps to the weather conditions you experience locally.


Faxing Instructions:

After completing this week's applications, fax the following pages to your LIT mentor by Monday, 5 November 2001:

  1. Chapter 8 Progress Response Form from the Part B: Applications binder, Week 8, or the DataStreme Homepage Progress Response Form
  2. 8A and 8B Activity Response Form

Return to DataStreme Homepage

URL: datastreme/learn/b_act.html
©Copyright, 2001, American Meteorological Society