Weather Map Analysis
Lab 7
Can include:
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Frontal lines
Barometric pressure
Isolines
Temperature
Frontal zones
Frontal air
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This is a surface weather chart. A weather map describing the state of the
atmosphere over a large area at a given moment.
Synoptic Map: map that shows weather conditions for a specific time.
Weather Map Analysis:
Simplified Surface Station Model
Data are always plotted in the same position around the station
symbol for consistent reading.
Barometric Pressure
•
NORMAL AIR PRESSURE: 950 – 1050 mb
1. insert decimal point – over 1 number from the
right to the left
2. replace the missing beginning number with a 9
or 10 :
a. The barometric pressure has to fall within the normal
range (for our purposes)
– EXAMPLE: 130 = 1013.0 mb
Wind Direction
• Measured by where wind is coming FROM
• Will also determine the temperatures and
moisture content of the air mass
• Pressure Gradient Force
Isolines
• Isolines (lines of constant value) generally
used to show spatial patterns of specific
variables:
1. Isotherms: temperature
2. Isodrosotherms: dew point
•
Typically drawn at 5° intervals
3. Isobars : barometric pressure
•
Typically drawn at 4-mb intervals
Streamlines:
used to show
wind flow
patterns
• Drawn parallel
to wind barbs
• Begin at an
upwind
location
• End with an
arrow where
wind shifts
abruptly
Tips:
1.Look for “corridors”
2.Draw streamlines from
the ‘tail’ to/towards the
‘head.’
Air Masses
• large body of air with relatively uniform temperature &
moisture characteristics
• Form over large land or water surfaces
• Take on the temperature & moisture characteristics of
the surfaces over which they formed.
Classification depends on:
1.Latitude – determines temperature characteristic (upper-case letter_
2.Nature of the surface – determines the moisture characteristic (lowercase letter)
They are identified by two-letter codes
Ex:
cP
Types of Air Masses
mE
cT
maritime equatorial
continental tropical
mT
cP
maritime tropical
continental polar
mP
cA
maritime polar
continental arctic
Is there a type of air mass missing from this list?
Fronts
• boundary between two unlike air masses
Identified by:
1.Sharp temperature gradient
2.Sharp moisture gradient
3.Sharp change in wind direction
(in a clockwise direction)
Types of Fronts
1. Cold – cold air advances on warm air
• Known to move more quickly
• Vertical cloud formation
2. Warm – warm air advances on cold air
• Clouds form ahead of the front
3. Stationary – neither air mass advances; air
flow parallel to the boundary
4. Occluded – cold front overtakes
warm front
Easterly
L
Winds from the North = COLD
Winds from the South ==
WARM
Winds from the East = COOL
SouthSoutheasterly
NorthNorthwesterly
Cold front: triangles extend into the warm air
Warm front: semicircles extend into the cold air.
• High pressure systems are characteristic of
clear skies
• Low Pressure systems are characteristic of
precipitation and clouds
• Pressure changes with
temperature
• Air flows from areas of higher
pressure to areas of lower
pressure
• source for most winds is solar
radiation (unequal heating of
Earth’s surface)
•High Pressure = high barometric
pressure. Air is dense
•Low Pressure = low barometric
pressure. Air is light.
Cold (dense) = HIGH
PRESSURE
Warm (less dense) =
LOW PRESSURE
Coriollis Effect
• http://en.wikipedia.org/wiki/Coriolis_effect