Download Activity C: INTERPRETING SURFACE WEATHER MAPS

Activity C:
INTERPRETING SURFACE WEATHER MAPS
Educational Outcomes:
What is the weather now? What is the weather going to be in the next few hours? 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 too! for depicting weather conditions over
broad areas.
Decode the symbols appearing on a surface weather map and describe weather conditions
at various locations on the map.
Identify fronts appearing on the map, the weather differences likely to be occurring on
either side of a front, and the motions of fronts.
Describe general relationships between wind patterns and the high and low air pressure
centers shown on weather maps.
Investigations:
1. Examine the surface weather map presented in Figure 1 of the narrative section of this
guide. The weather map symbols shown are those commonly seen on television and in
newspapers- The H's and L's identify centers of relatively high or low air pressure
compared to their surroundings. Moving outward horizontally from the I_ located in lower
Michigan, air pressure [(tV/trc't/x'v > (ili-creases)]. Moving outward horizontally from the H
positioned in Texas, air pressure [(i/HTt'i;vr.v > (ffarreases)].
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, humidify, and density. Because air
masses of different densities do not readily mix. the boundaries separating air masses tend
to remain distinct. These boundaries, 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 pan of
Figure !, is signified by spike symbols which are pointing in the direction toward which
the cold front is moving. The leading edge of advancing warm air is a warm front and is
signified by semi-circles on ihe side of the front's movement. The front in the
Southeastern US is a |(cold) (warm)] front. According to (he map, persons living in South
Carolina can expect {(colder) (warmer)} weather otter the front passes.
;cipitation is depicted on maps by a variety of symbols including dots or periods for
tin} (snow)], stars or asterisks for \(rain} (snow)], horizontal lines for
_, and t
4. Some weather maps display weather conditions at individual weather stations by the use
of a station model. In the model, weather is plotted in, on, and around a circle
representing the station. The following plotted station model shows where and how
various weather elements are reported:
75
023
a. Temperature (at the ''1 1 o'clock" position): __ _°F.
b. Dewpoint (at the ''8 o'clock'' position): _
°F.
c. Wind direction is shown by the "arrow" shaft drawn into the circle representing the
station. Unless otherwise noted, north is to the top on the map and east is to the right.
Wind is always named for the direction from which it blows. In the above depiction,
the wind direction is __ __
.
d. Wind speed is rounded off to the nearest 5 knots (1 knot equals 1 .2 miles per hour)
and is symbolized by "feathers" drawn on the clockwise side of the wind-direction
shaft. A full feather represents 10 knots and half feathers indicate 5 knots. A
pennant indicates 50 knots and a circle drawn around the station circle signifies calm
conditions. In this case, the reported wind speed is __ knots.
e. Air pressure (adjusted to sea-level) is reported as a coded number to the nearest tenth
of a millibar (mb). To decipher the plotted pressure value (reported at the "1 o'clock''
position), first place a decimal point between the second and third number from the
left. Then add a "9" or "10" to the left so that the resulting number falls within the
range of air pressures that could occur at sea level (usually between 960 mb and 1050
nib). For example, a plotted value of 126 represents 1012.6 mb and 863 denotes
986.3 mb. The air pressure reported above is _
mb.
f. Sky coverage (total amount of cloud cover) is reported inside the station circle. An
empty circle indicates no cloud, a half-shaded circle means five-tenths of the sky
y is
cloud-covered, and a fully shaded circle stands for a completely overcast sky. Th
reported cloud cover is
__
.
g. Current weather is plotted at the "9 o'clock" position using a variety of symbols
representing the particular weather conditions. The reported current weather is
,t map time the conditions in Little Rock, Arkansas were: temperature
ewpoint
F. air pressure
_ millibars, cloud coverage _ _
degrees
and
7. Examine the current DataStreme Atmosphere surface weather map given to you. The dat.
of the map given to you is _
. Describe the weather conditions
reported at the station nearest where you live. How do these compare to the conditions al
surrounding stations?
8. Describe the general pattern of weather conditions across the country at map time.
OOZ
Fronts at OOZ
02 OCT 2004
NATIONAL 2 KM BASE REFLECT 0,00 DEG
Blue - Isobars (4 mb)
MONITORING THE WEATHER 3
9) Using the map in Figure 1 and the color codings
above the symbols, trace over the map symbols
with the correct colors and shade in the precipitation
areas. Then, plot the information on the station models.
STATION MODEL NUMBER:
1) Cloudy. Rain shower, Temp: 45°, Dew point: 44°, Wind: 330° at 1 Omph, Press: 1002.0mb
2) Pt. Cloudy, Temp: 65°, Dew point: 54°, Wind: 130° at ISmph, Press: 1000.0mb
3) Mo. Cloudy, Temp: 48°, Dew point: 40°, Wind: 270° at lOmph, Press: 1008.0mb
4) Sunny, Temp: 60 , Dew point: 40°, Wind: 210° at lOmph, Press: 1015.0mb
5) Mo. Sunny, Temp: 75°, Dew point: 25°, Wind: 100° at 20mph, Press: 1022.0mb
6) Pt. Cloudy, Temp: 65°, Dew point: 54°, Wind: 350° at 15mph, Press: 1030.0mb
7) Cloudy, Snow shower, Temp: 25°, Dew point: 24°, Wind: 330° at 25mph, Press: 995.0mb
8) Pt. Cloudy, Temp: 35°, Dew point: 32°, Wind: 100° at lOmph, Press: 1000.0mb
9) Mo. Cloudy, Temp: 33°, Dew point: 28°, Wind: 280° at 20mph, Press: 1010.0mb
Weather Map Symbols
CLOUD SYMBOLS
FOUR BASIC FORMS
( CIRRUS
u
r*
?O,000 It. to ten milei high.
Feathery curves, ma/es tails.
CUMULUS Q
2.5OO (eel to one mila high.
Heaped up. Fairer weather.
STRATUS Sea level to 2,000 led high.
Layered, misty, thm, loglike.
Sample Station Plot
~~~"~~
Wind' /
\ 1
\J
^<
/
57 \ 107
NIMBUS - Rain clouds lower
In tho sky and (dining with a
Stratus or * Cumukis rnaw.
wealher
> *f ( ) _§\
56 ^
TYPICAL. COM8INATSONS
CIRROSTRATUS
*CIRROCUMULUS - ^
ALTOSTRATUS - £
ALTOCUMULUS £
CUMULONIMBUS
S
STRATOCUMULUS - ~^~
NIMBOSTRATUS - &
/
DewPoint(F)
35t?
\
\
\
\
Pressure trend (mb)Sky cover
NOTE: Multiple rain or snow symbols indicate intensity,
i.e. light (2 symbols), moderate (3 symbols), heavy (4
symbols)
Wind
Sky Cover
O clear
O Calm
9m
Sea-lsvel pressure'
1-2 knots (I -2 mph)
Fronts apd Radar
cold front
,,
blue
warm front "*
C^scaltered
' 3-7-knots(3-Smph)
stationary front ^TLlTe
d>m
\
occluded front ^j rp ie
9 4/8
'N
8-l2knots(9-]4mph)
13-17knots(15-20mph)
Selected
Weather Symbols
.
.srt&n
V Rain Shower
JK'1
P-^ct
Thunderstorm
Drizzle
trough °T"j ""i™
SnOW (see note belov,)
*
» 5/8
® broken
GrfAS\
^
]8-22knots(21-25mph)
squall line
*
V Snow Shower
^
23-27 knots (26-3 1 mph)
dryline
Jf^^n
C^O Freezing Rain
Red
^\ 28-33 knots (32-35 mph)
O7/8
Smoke
^^ Freezing Drizzle
^\ 33-37 knots (36-41 mph)
W\ 38-42 knots (42-45 mph)
•overcast
\\\\\
~
S Dust or Sand
~Fog
" Blowing Snow
^Haze"" "
43-46 knots (46-52 mph)
^ 47-52 knots (53-61 mph)
G$ obscured
^1 53-57 knots (62-66 mph)