Answers to Weather Map Questions

Answers to Weather Map Questions
Answers to Weather Map 1 questions
1. Were temperatures above or below freezing in your locality on the evening of Sept 27? They
were at 13o , above zero. Are they likely to drop below freezing during the night in any part of
southern Canada? North of Lake Superior, above the number 1024 is a weather station with a
temperature of 1. There is a good chance that it will drop below freezing.
2. What are the characteristic temperatures in maritime polar air? They are cool temperatures
from 1-20 Celsius. What are the characteristic temperatures in maritime arctic air? They are
cold, from about -2 to 5 Celsius. Suggest one reason for the very high temperatures in the
southwestern United States. There is a high pressure centre around Utah, Colorado and New
Mexico. Can you find a pattern relating wind direction and the isobars? Winds tend to flow
from high pressure centres to adjacent low pressure centres. What difference can you find
between the patterns around a high and low? In general, winds tend to move in directions that
are clockwise around a high pressure centre and in directions that are counterclockwise around
a low pressure centre.
Answers to Weather Map 2 questions
1. Is the wind bringing colder or warmer temperatures to your locality?
2. What temperature change has occurred during the last 12 hours at Schefferville? Schefferville
went from 10 to 1 Celsius. What temperature change has occurred during the last 12 hours at
Kenora? It rose from 4 to 7 Celsius. What would cause these changes? A cold front moved past
Schefferville from West to East. A warm front moved in past Kenora from West to East.
3. What is the most northerly latitude at which rain is falling? About 55o What is the most
southerly latitude at which snow is falling? 35o
4. Note fog or mist forms when the temperature and dew point are very close. Locate a station in
Alberta where the temperature and dew point are equal. Close to Fort McMurray the temp is 1
and the dew point is 1 and it seems to be snowing. Why is this? If air is at the dew point,
moisture begins to come out as rain or snow.
Answers to Weather Map 3 questions
1. Do the high and low centres move? Yes. Mark the highest pressure on Map 1 and then on
Map 3. This is the centre with a pressure greater than 1024, north of Alberta. In what direction
is it moving? South south east. How fast is it going? It travelled about 700 km in 24 h so its
speed is 700 km/24 h = 29 km/h. How far is Churchill from Baker Lake? 500 km. How far is
Winnipeg from Regina? 600 km.
2. Track the low pressure centre near Ungava Bay on Map 1 to Map 3. How fast is it moving? The
low pressure centre near Ungava Bay moved 800 km in 24 h so its speed was 800 km/24 h = 33
km/h. In what direction is it moving? It moved in a north north easterly direction.
3. What was the pressure change on the west side of the high centre on Map 3? The pressure on
the west side dropped. What was the pressure change on the east side of the high centre on
Map 3? The pressure on the east side rose. Do these pressure changes agree with the motion
of the high? Yes because the high is moving south south eastward.
4. In general do you find cloudy or clear skies in low pressure areas? In low pressure centres the
skies are usually clouded over or mostly cloudy. In high pressure areas what occurs? In high
Answers to Weather Map Questions
pressure centres the skies are mostly clear or just fractionally clouded. What are the skies like
in precipitation areas? Skies are overcast (full clouds) in precipitation areas.
5. What happened to the temperature and dew point at Lake Charles (in Louisiana) when the cold
front passed east of the station? (Compare Map 1 and Map 3) The temperature dropped from
27 to 21 and the dew point dropped from 24 to 18. What happened to the wind at this
station? The wind was at 5 knots from the south east and changed to 5 knots from the north
north east.
6. What changes occurred at The Pas in the preceding 24 hours? The Temperature dropped from 8
to 2 Celsius. The west wind at 5 knots changed to a north wind at 15 knots. The sky went from
clear to 1/8 th cloud cover. The pressure went from 100.8 to 102.3 because of the heavier cool
air. Why? A cold front pushed south past The Pas.
Answers to Weather Map 4 questions
1. What cloud type do you find in precipitation areas (low, middle or high cloud)? Mostly low
clouds of the stratus type with a few stratocumulus.
2. What type of cloud is associated with the showery weather in the southeastern United States?
Stratus clouds.
3. What clouds are giving the isolated areas of light snow? Stratus and Stratocumulus clouds.
4. How far has the precipitation area in eastern BC in Map 3 moved in the last 12 hours? 800 km
Where would you expect to find this rain area in 12 hours from now? In Manitoba
5. Where will the high pressure centre now over Manitoba likely be found in 12 hours? 500 km
south and east. Where will it likely be in 24 hours? 1000 km south east
6. On both this chart and the previous one, the temperature of Jasper is 3 or 4 degrees lower than
the nearby Prince George. What is a likely cause of this difference? Jasper was behind a cold
front of artic continental air while Prince George was in maritime artic air which was warmer.
Answers to Weather Map 5 questions
1. How many stations are reporting fog or mist on this weather chart? One station, San Francisco.
How many stations reported fog on the previous map? Six locations. Account for this difference.
Map 4 was done for 7:00 AM when the cool air is close to dew point and thus forms fog.
2. Again note the association of precipitation areas and pressure systems. Where do you find most
of the precipitation? Most of the precipitation is associated with low pressure centres.
3. Note at least 3 weather changes which have occurred at Nitchequon in the past 12 hours. The
dew point has dropped, the SSE wind of 25 knots has changed to a west wind of 10 knots, the
rain showers there have stopped, the air pressure has risen and there are 7/8 now as compared
to full clouds before. What caused these changes? A cold front has moved east over
Nitchequon and lifted warm air (an occluded front) and replaced the former warmer air. The
cold dry air has lowered the dew point and increased the air pressure because it is denser.
4. Did the high pressure system move as you expected? The high pressure centre moved more
east than south. Where would you predict it to be 12 hours from now? At Chapais Quebec.
See Map 6 for isobars and green shading for precipitation.
Answers to Weather Map Questions
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