Concept/Process Exercise
Surface Weather Maps
(12 Points)

Educational Outcomes:

Weather is the state of the atmosphere at a particular time and place, mainly with respect to its impact upon life and human activity.  It is defined by the various weather elements including air temperature, humidity, cloudiness, precipitation, visibility, air pressure, and wind speed and direction.  The surface weather map is a useful tool for depicting weather conditions over broad areas.

After completing this activity, you should be able to:

Background Information

Before you begin this exercise, you will have had to attend the "Weather Basics" discussion and should have read Chapter 1 in the Online Weather Studies textbook (of if a different textbook is being used, the supplemental reading Weather Information in your reference manual following the Weather Basics lecture outline), Z-Time on Weather Maps, and  Reading the Surface Station Model and the assigned pages in the textbook on weather maps.  You will also need the following images which may be downloaded and printed.
 

Image 1
Image 2
Image 3
(print in landscape)
Image 4
(print in landscape)
Answer Sheet
Investigations:

Before you begin this section, download and print the answer sheet.  Unless told otherwise, put all your answers on this answer sheet.

1)    Examine the surface weather map presented in Image 1.  The weather symbols shown are those commonly seen on television and in newspaper.  The H's and L's identify centers of relatively high and low air pressure compared to their surroundings.  These pressure systems are commonly 500-1000 miles across.  The "H" positioned in Texas locates the center of a high pressure system; atmospheric pressure increases horizontally inward toward this "H" and decreases horizontally outward away from the "H".  Moving outward horizontally from the "L"  located in lower Michigan, air pressure   [    A) increases    B) decreases    ].

2)    The thick curved lines on the map are air mass boundaries.  In the atmosphere, broad expanses of air with generally uniform temperature, humidity, and density come in contact with other masses of air having different temperature, humidity, and density.  Because air masses of different densities do not readily mix, the boundaries separating air masses tend to remain distinct.  These boundaries, which are actually narrow zones of transition, called fronts, typically separate warm and cold air.  The leading edge of advancing cold air is a cold front and, as shown in the lower part of Image 1, is signified by triangle symbols which are pointing in the direction toward which the cold front is moving.  The leading edge of advancing warm air as it moves into a region of relatively cooler/colder air, is a warm front and is signified by semi-circles on the side of the front's forward movement.  (a) The front in the Southeastern U.S. is a  [    A) cold front   B) warm front   ].   (b) According to the map, persons living in South Carolina can expect     [    A) colder    B) warmer    ]   weather after the front passes.

3)    Precipitation is depicted on weather maps by a variety of symbols including dots or periods for rain, horizontal lines for fog,  and stars or asterisks for __________________ .

4)    Make certain you have read the supplemental reading Reading the Surface Station Model .  Refer to the model legend in Image 2 to interpret the following plotted data:

Questions 5-10 refer to the 00Z 08 FEB 2000 weather map (Image 3).

5)    Click onto Image 3 which is the 00Z 08 FEB 2000 surface weather map.  It depicted weather conditions across the country as a cooler continental polar air mass moved into central and eastern U.S.   Ohio is in the eastern time zone of the U.S. and is five time zones west of the Prime Meridian.  Weather observations for the entire map were taken at what local time and day (date) in Youngstown?
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6)    The wind directions at stations in the central U.S. and  Canada  region around the high pressure center centered in  Iowa generally showed the   (a) [   A) clockwise    B) counterclockwise   ]    and     (b) [  A) inward     B) outward  ]  circulation pattern typical of Northern Hemisphere high pressure systems.

7)    At map time, St. Louis, on the eastern border of Missouri along the Mississippi River, had winds from the  (a) ______________ at about 5 knots and the air pressure corrected to sea level was (b) __________________ mb.

8)    At  North Platte, in central Nebraska, the air pressure corrected to sea level was 1030.3 mb and at San Antonio, in south-central Texas, it was 1024.2 mb.   (a)  Which city,  [   A) North Platte    B) San Antonio   ],   was cooler?   The dewpoint is the temperature to which air must be cooled (at constant pressure) to achieve saturation (100% relative humidity).  The higher the dewpoint, the greater the concentration of water vapor in the air.  (b)  From the reported dewpoints, the air in    [   A) North Platte    B) San Antonio  ]   contained less water vapor.   This is consistent with the Canadian air mass that is affecting the north-central and north-eastern United States.

9)    The boundary of  continental polar air moving out of Canada is shown by a heavy line (blue if in color) with triangles stretching from northeastern U.S. to northern Oklahoma.  This line locates the position of a cold front.  Greensboro in north-central North Carolina could expect    [   A) cooler    B) warmer   ]   temperatures in the next day or so.

10)    Locate the "H" over Iowa.  Moving outward horizontally for several hundreds of miles from the "H", air pressure [   A) increases    B) decreases   ].   Hint: examine the pressure values displayed on the station models located progressively outward from the "H."
 

Questions 11-13 refer to the 20Z 27 OCT 1999 surface weather map (Image 4).

11)   Centered over the Dakotas is a low pressure center on the 20Z 27 OCT 1999 surface weather map (Image 4).  (a) Winds around this low pressure center are blowing in a   [  A) clockwise     B) counterclockwise  ]   manner.   (b) These winds are blowing   [  A) inward toward     B) outward from  ]   the center of the low pressure system.

12)   Extending toward the southeast from the "L" marking the center of the low pressure system over the Dakotas is a warm front.  This front is indicated by a line (red if in color) with semi-circles that point in the direction that relatively warmer air is moving into a region of relatively cooler air.  This front is moving toward the  [  A) north-northeast     B) south-southwest  ].

13)   Warm air can "hold" more water vapor than cold air.  The relative humidity is a ratio that compares the water vapor content of the air with the air's water vapor capacity and is given as a percentage.  A parcel of air with a relative humidity of 60% means that the parcel is "holding" 60% of the water vapor it could hold at that given temperature.  If the temperature and dew point are close together, the relative humidity is high.  If the temperature and dew point are far apart, the relative humidity is low; that is because the temperature of the air parcel must be cooled quite  a bit because it reach saturation (100% relative humidity).  (a)  Which location, Nagagami,  north-northeast of Lake Superior or Key West at the southwest tip of Florida, experienced the higher  relative humidity  [  A) Nagagami     B) Key West  ] ?   (b)  Which location is actually "holding the greater quantity of water vapor within the air [ A) Nagagami     B) Key West  ]?
 

After downloading and printing, please put your answers on the answer sheet and only turn this sheet in on the due date.  Late exercises will NOT be accepted.


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The exercise is based on material from the American Meteorological Society's DataStreme Project.

1 February 2002