CWS 2A - 1
SURFACE WEATHER MAPS
Do Now:
1. Print this file.
2. Print the Monday Current Weather Studies Image 1 File.
3. When available, answer the two "Concept of the Day" questions in the Tuesday,
1 February 2011 Daily Summary File.
To Complete Investigation:
1. Read Chapter 2 in the DataStreme Atmosphere textbook and respond to the Chapter
Progress Questions in the DataStreme Atmosphere Study Guide Investigations binder.
2. Complete the introductory portion of Investigation 2A in the Weather Studies
Investigations Manual, which ends when you reach the statement, "As directed by your
course instructor, complete this investigation by either: ---." [Do not complete the
Applications portion of the Investigation.]
3. Go to the Monday - CWS A (Current Weather Studies A) link on the course website to
complete this investigation.
After completing the introductory portion of Investigation 2A in the Investigations Manual,
use the WeatherCycler provided in the Study Guide to answer the following questions.
1. Some weather maps display weather conditions at individual weather stations by the use
of a station model. The WeatherCycler displays station models of wind speed and
direction and cloud cover. Explanations of station model symbols are presented to the
lower left on the WeatherCycler. Move the slide so that the H is centered in the large
window. Stations under the influence of a high-pressure system are generally [(clear or
partly cloudy)(mostly cloudy or overcast)].
2. Next, position the slide all the way into the chart with the L showing in the window.
Stations under the influence of a low-pressure system are generally [(clear or partly
cloudy)(mostly cloudy or overcast)]. With the insert in this position, imagine yourself at
the weather station represented by the circle directly above the green pointer (B). At that
location, the cloud cover is ________, and the wind is from the ______ at ______ knots.
(1 knot equals 1.2 statute or land miles per hour)
The Monday Daily Weather Summary for 31 January 2011 describes the current and recent
weather across the United States. A frontal system stretched across much of the U.S. North
of the front, cold air covered the north-central and northeastern portions of the country while
warmer air was confined to the southern Gulf States and the western states beyond the Rocky
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Mountains. Two main precipitation areas were located in the Southeast and the northern
plains.
3. Image 1 is the surface weather map ("Isobars, Fronts, Radar & Data") for 12Z 31 JAN
2011, Monday morning (7 AM EST, 6 AM CST, 5 AM MST, 4 AM PST) for the
contiguous U.S. The Image 1 map shows selected weather data plotted about circles that
represent the location of stations using the coded surface station model. Observe the
station model for St. Louis along the Missouri-Illinois border. The station model shows a
temperature of [(42)(30)(25)] degrees F, and a dewpoint of 22 degrees F.
4. The winds at St. Louis were generally from the [(northwest)(northeast)(southeast)
(southwest)] at about 10 knots (one long "feather" on the shaft).
5. The coded pressure value was plotted as "236", meaning the actual atmospheric pressure
corrected to sea level was [(23.6)(236.0)(1023.6)(1236.0)] mb.
6. The sky cover (designated by the amount of shading inside the station circle) indicated
[(clear)(partly cloudy)(overcast)] conditions existed over St. Louis at map time.
7. Wind speeds across the map showed a variety of station model notations for different
speeds. Rapid City, SD had two long feathers for 20 knots, Las Vegas, NV, had one long
and one short for 15 kts while San Antonio, TX, Albany, NY, and Billings, MT all had
one short feather for 5 kts. Fresno, in central California and Miami, FL both had a circle
around the station circle to denote a wind speed reported as [(calm)(25 knots)(50 knots)].
8. At the "9 o'clock" position alongside the station circle, a weather symbol may be plotted
to show present weather conditions. Detroit, MI shows two stars or asterisks that signify
[(light rain)(light snow)(haze)(fog)] was occurring. For a listing of the frequently
occurring present weather symbols, see the User's Guide linked from the course website
or go to http://www.hpc.ncep.noaa.gov/html/stationplot.shtml.
9. Oklahoma City, OK, had a figure 8 on its side to denote haze while several stations
across the map, such as Wichita, KS, had two parallel horizontal lines indicating
[(light rain)(light snow)(haze)(fog)] was occurring. Little Rock, AK, showed two
commas for a report of drizzle.
The surface weather map additionally shows the position of high-pressure centers and lowpressure centers with fronts as analyzed by meteorologists at NOAA's National Centers for
Environmental Prediction. Colored shadings further denote where the national network of
weather radars detected precipitation. Radar reflectivities are related to precipitation
intensities according to the color scale along the left margin of the map area. (Generally, the
greater the reflectivity, the greater the intensity of precipitation.)
10. The coded station pressure reports were used to draw a computer analysis of the pressure
pattern in a manner similar to the one you did in Current Weather Study 1A. A number
of Ls along the frontal system identified localized centers of relatively low pressure while
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a broad area of relatively [(low)(high)] pressure was centered north of Lake Huron in the
Province of Ontario, Canada.
11. The wind directions at the stations to the southern side of the high pressure center from
New England around to Minnesota were generally [(counterclockwise and inward)
(clockwise and outward)], consistent with the hand-twist model of a High.
12. The bold line with alternating blue triangles and red semicircles on opposite sides
extending much of the way from the Atlantic Ocean across the south-central states and
northwestward along the Rocky Mountains is a(n) [(cold)(warm)(stationary)] front.
13. The short portion of the frontal system from the L in northeastern Texas southwestward
to San Antonio displayed two consecutive triangles (blue on-screen) that marked that
portion as a [(cold)(warm)(stationary)] front. This area of the front was the leading edge
of slightly cooler and drier air that was advancing southeastward.
14. Although not shown on this map, if the bold line had shown consecutive solid half-circles
(red) as a part of the frontal system, it would have been designated a
[(cold)(warm)(stationary)] front.
Additionally, dashed orange lines on the map signify low-pressure troughs, extensions of
lower pressure, which may be used on maps to mark the positions of dissipated or
forming fronts. The abundance of Hs and Ls over the western U.S. is the result of
localized areas of relatively high or low pressure, respectively, where the corrections of
pressure readings to sea level altitude can vary somewhat. Finally, the orange line in
southern Texas with open half circles on one side designates a dry line. Dry lines are
boundaries between humid and dry air masses caused by density differences primarily
due to water vapor content and may become the focus of thunderstorm formation.
15. The area of relatively intense precipitation over the southeastern part of the country,
shown in brighter greens and some reds, occurs mainly [(north)(south)] of the frontal
boundary in this case.
For more practice on deciphering station models and map symbols, go to
http://profhorn.aos.wisc.edu/wxwise/AckermanKnox/chap1/decoding_surface.html.
Displaying a sequence of recent surface weather maps ending with the current map in your
classroom can show the movement of "weather makers" (high and low pressure centers and
fronts) and the changes in atmospheric conditions at your location over time resulting from
their movements. Practice looking for connections between weather changes depicted on the
map sequence and predict local weather for the next half day or so.
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You can also observe how station model conditions change as weather systems pass across a
region by going to the NWS Surface Analysis link on the course website under Surface. The
link takes you to the NWS' Hydrometeorological Prediction Center site. Scrolling down
allows you to "Create a Surface Analysis Loop" for various regions. Selecting the United
States choice, then clicking "Display Loop" will show an animation of the latest day's series
of 3-hourly station models along with fronts and Highs and Lows.
Place the answers to Current Weather Studies activities 2A and 2B on the CWS Answer
Form (provided from the DataStreme Atmosphere website on Wednesdays).
Return to DataStreme Atmosphere website
©Copyright 2011, American Meteorological Society