Weather Instruments
P 611-614
We need data
to forecast the weather
Temperature
 Air pressure
 Humidity
 Type of clouds
 Level of precipitation
 Wind direction and speed

Instruments used
to gather the data
Lower Atmospheric Conditions
Temperature


Thermometer
• Uses a liquid either mercury or alcohol
sealed in a glass tube

Electrical thermometer
• As temp rises the electrical current
increases
• A thermistor responds very quickly and is
used where temps change quickly
Air pressure
Barometer
 Aneroid (pictured)
 Mercury

fronts are usually
indicated by a drop
in air pressure
Wind Speed and direction

Anemometer


Wind speed
Wind vane

Wind direction
Rainfall

Rain gauge
Measuring Upper
Atmospheric Conditions
Doppler image
of a hurricane
Radar
Stands for radio
detection and ranging
 Uses reflected radio
waves
Doppler radar


Can indicate precise
location, intensity of
precip and extent of a
storm
Shows wind patterns

Towards or away
from the radar
Radiosonde



An instrument
package that is
carried by a heliumfilled balloon
Radio sends info to
ground
Determines direction
and speed of high
altitude winds
Skew-T





Shows a vertical
slice of the
atmosphere
Temperature on right
Dew point on left
Air pressure
Wind speed and
direction
Weather Satellites
Can measure
 visible
 Infrared
 Ocean conditions


temperature and
flow of ocean
currents and
height of ocean
waves
Computers



Solve
mathematical
equations that
describe the
behavior of the
atmosphere
Can store weather
data
Can store weather
records
This info is
reported from stations
WMO World Meteorological
Organization
 10,000 land based stations and
hundreds of ship-based stations
 Weather satellites
 GOES Global Orbiting Earth Satellite

Data from stations is compiled
and analyzed to forecast
In the past this was done by hand
 Now much is done by computer
 But, different programs work better
for different locations and types of
weather
 Often two or three computer models
are consulted to make one forecast

Weather Station Symbols


Temperature is
upper left corner
Barometric (air)
pressure is upper
right
Air pressure


represents the last
three digits of the
observed pressure
reading in
millibars (mb)
Like on previous
labs
Dew point



Dew Point is lower left
corner
When the air
temperature and the
dew point are the
same the air is
saturated
Relative humidity can
be inferred


High if temp and dp are
close
Low if large difference
between dp and temp
Relative Humidity
can be inferred
When the air and dew point
temperatures are very close, this
indicates that the air has a high
relative humidity.
 The opposite is true when there is a
large difference between air and
dew point temperatures, which
points to air with a low relative
humidity.

Wind Speed and Direction

Wind stick points
in the direction
"from" which the
wind is blowing



Which direction is
the wind from?
Wind Speed



May be measured
in mph, km/hr or
knots
The more barbs
the windier it is
Each long barb is
approx 10 knots

Cloud Cover
Precipitation Symbols
Worksheets
Surface Weather Map
 Study the tables and the station
model
 Use the info to answer the questions
Transparency worksheets
 Study the tables and the station
model
 Use the info to answer the questions
Dry Line


Note the sharp
difference in dew
points
The line that
separates dry air
from moist air
Isobars


Lines that connect
points with equal
air pressure
Drawn at 4 mb
(millibar) intervals

Pressure and
Wind Relationships





Draw isobars
Use pencil
CI = 4
Mark high and
low pressure
Answer the
questions
Methods of Forecasting
 Persistence
 Trend
 Analog
Persistence

Persistence—
based on
continuity of a
weather pattern—if
it is raining now it
will probably be
raining tomorrow
Trend

Trend—based on
the movement or
trend of the
weather system
Ex. Cold front
moving E at 20
Km/hr will affect
weather 80 KM
away in 4 hours
Analog

compares present
weather (cloud
cover, wind,
temperature,
humidity, etc) with
weather conditions
produced by same
features in the
past
Others
 Climatology—data
accumulated through
many years


4th of July is usually hot
and dry
Numerical Weather
Prediction—uses
programs built by
meteorologists

Not exact
Meteorologists
What high school courses are
necessary to prepare for a
career in meteorology?
 Because meteorology is a science, a
good background in mathematics
and the sciences is mandatory.
Knowledge of physics and
chemistry is helpful toward a
career in the atmospheric sciences.
OU is the Best
for Meteorology
Weather Station Symbols


Temperature is
upper left corner
Barometric (air)
pressure is upper
right
Lab

Do isotherms in red (every 2)


Do lightly in pencil first
Do isobars in blue (Every4)

Do lightly in pencil first
Winds
Three causes of motion(recap)
1. Warm air rises and cool air sinks because
of density

This is called a convection current
2.pressure differences in the atmosphere
that are a result of temperature
differences

Wind is horizontal air movement
3. The deflection of objects to the right in
the northern hemisphere—called the
Coriolis Effect

Due to rotation of the earth
Winds blow from
high to low pressure.
Highs and Lows?



Winds circle
Clockwise around
a high
Highs generally
mean cold dry air
that is sinking
High pressure
usually = fair
weather
Low Pressure Systems



Winds circle
counterclockwise
around a low
Warmer air rises
and cools and
forms clouds and
precipitation
Low pressure
usually = rainy
weather
Global Circulation Patterns

We are located
in the
Westerlies
section
 That means our
weather moves
from the west
coast to the
east coast


Overall movement
is west to east
Local wind
patterns can be
from any direction
Recognizing fronts
on a map





sharp temperature
changes over
relatively short
distances
changes in the
moisture content of
the air (dew point)
shifts in wind
direction
low pressure troughs
and pressure changes
clouds and
precipitation patterns
Types of fronts


Named for the
invader
Each type of front
has a typical
weather scenario
Cold Front





heavy cold air
displaces lighter warm
air, pushing it upward
Cumulus clouds form
and usually grow into
thunderstorms
Temperatures drop
anywhere from 5 to
15.
Winds become gusty
and erratic.
Rain, snow, sleet, and
hail can occur with a
cold front.
Warm Front




Warm fronts occur
when warm air
replaces cold air by
sliding over it.
Altocumulus clouds
form and may be
associated with rain,
snow, or sleet.
Temperatures may
warm slightly.
Winds are usually
gentle with this kind
of front.
Stationary Front

neither warm nor cold
air advances. The two
air masses reach a
stalemate.



That is what stationary
means - that neither
front is moving.
can last for days,
producing nothing but
Altocumulus clouds
Temperatures remain
stagnant and winds
are gentle to nil
Occluded Front



cold air is replacing
cool air or vice versa
at the surface, with
warm air above.
Both types of fronts
are usually associated
with rain or snow and
cumulus clouds.
Temperature
fluctuations are small
and winds are gentle.
Where are the fronts?
Stationary front
 Change in wind
direction
 Can dump heavy
rains
Warm Front

Marked
temperature
difference
Cold front

Cold temperatures
are moving in
Wind and Pressure
Relationship Lab
Remember Topographic Maps?
Same Concept—Different
Use

Isotherm=equal
temperature

Isobar=equal
barometric
pressure
contour interval (CI)
1.
The contour
intervals vary
2.
Isobars often have
an interval of 4
3.
Read the directions
or look at examples
to see the contour
level
Iso therm Equal temperature


If a station reports
the exact value the
line will go through
the station symbol
If it is not exactly
on the value it will
not
Points shown are reporting stations



Here, the stations
reported pressure and
temperature
The lines are drawn in
different colors to
help differentiate
them
There may be areas
that do not report or
have no station
The closer contour lines are to one
another, the higher the wind speed.

Where is
the wind
speed
high?
Where is it
low?
Inside a series of closed contours (the
contours make a circle) is a
Low pressure
High or
Describe the motion of the wind.
Wind Flow around Isobars

Winds flow
roughly
parallel to
the isobars,
as depicted
in the
schematic
below

Current Weather Conditions
Current
Weather Station Data

Source:University of Illinois

http://ww2010.at
mos.uiuc.edu/(Gh)
/home.rxml
Metars


In a small group try to figure out
what each set of numbers or letter
mean
TYPEIDTIMEWINDVISWXSKYT/TDALTREMARK
METAR KORD 041656Z 19020G26KT 6SM SHRA BKN070 12/08 A3016 RMK AO2
Understanding Metars
Activity



Brainstorm about
what the numbers
and letters may mean
Discuss as a class
Interpret metars and
decode them
Zulu Time



Used to be known
as Greenwich
Mean Time
Uses the military
clock of 24 hours
For numbers
above 13 subtract
12
Converting to KS
time
 For CST –6
 For CDT -5
Upper Air Data

Shows
Become a meteorologist

OU is the best