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Weather Maps– We use weather maps to give us a pictorial

view of the weather when dealing with large amounts of data.

– We typically report:» Temperature» Sea Level Pressure» Moisture» Winds (Speed and Direction)» Cloud Cover» Precipitation

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Surface Station Model

A station model is a pictorial way of representing the weather data recorded at a specific site.

T

T d

V is W x

P re s s

P re c ip .

d d

ffA simplified station model

This represents the typicaldata reported at a station.

Some stations may reportmore or less.

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Surface Station Model

T

T d

V is W x

P re s s

P re c ip .

d d

ff A simplified station model

T = Temperature (Fahrenheit)Td = Dew Point TemperatureVis. = Visibility (miles)Wx = Present WeatherPress = Sea Level PressurePrecip. = Precipitation amount

(Liquid Equiv. In inches)dd = Wind Direction (degrees)ff = Wind Speed (knots)

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Surface Station Model

A station model EXAMPLE

Temperature = 90 FDew Point = 68 FVisibility = 10 MilesPresent Weather = Rain ShowerPress = 1001.0 mbPrecipitation = 0.05 inchesWind Direction = North -- 00 DegreesWind Speed = 24 knotsCloud cover = 9/10 Clouds

9 0

6 8

0 1 0

.0 51 0

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Surface Closeup

At Oklahoma City (OKC)Temperature = 82 F Pressure 1001.0 mbDew Point = 64 F Weather = Partly CloudyWinds = Southeast at 3-7 knots.

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Surface Station Model

Comments on reporting pressure– The pressure is reported in millibars (tens,

units, and tenths -- the leading 9 or 10 is omitted) reduced to seal level.

Examples

1014.7 mb

986.3 mb

147

863

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Surface Station Model

Comments on reporting wind– The direction is reported, in degrees, from

where the wind comes from.

Examples

North Wind East Wind

SouthwestWind

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Surface Station Model Comments on reporting wind

– The speed is indicated by the barbs or pennants attached to the “arrow”.– Half barb represents 3-7 knots– Full barb represents 8-12 knots– Pennant represents 50 knots

Examples

Calm 13 - 17 Knots 58 - 62 Knots

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Surface Maps -- Pressure Systems

Low Pressure– Typical Weather:

» Cloudy» Windy» Warmer» Precipitation

– Flow around a low is cyclonic (counterclockwise in the Northern Hemisphere)

– Stronger pressure gradient» Pressure changes more rapidly over a given

distance.

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Surface Maps -- Pressure Systems

High Pressure– Typical Weather:

» Clear» Light Winds» Cooler» Dry

– Flow around a low is anticyclonic (clockwise in the Northern Hemisphere)

– Weaker pressure gradient» Pressure changes less rapidly over a given

distance.

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Surface Analysis

Warm Front– Long periods of clouds, winds, and

precipitation– Warm, moist air after frontal passage– Occasionally produces severe weather– Denoted by a red line with red half-circles

that point toward cold air.

Fronts: Boundaries between large regions of air(air masses) with differing temperature, humidity,or both.

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Surface Analysis

Cold Front– Shorter periods of clouds, winds, and

precipitation– Cold, dry air after frontal passage– Often produces severe weather in spring– Denoted by a blue line with blue triangles

that point toward warm air.

Fronts: Boundaries between large regions of air(air masses) with differing temperature, humidity,or both.

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Surface Analysis -- 12 Jan 98

High Pressure

Low Pressure Rain

Fog

Warm Front

Cold FrontSnow

Isobars: Lines of Constant Pressure

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Surface Analysis -- 20 Aug 98

Image from: The Weather Channel

Low Pressure

Isobars: Lines of Constant Pressure

Cold Front

High Pressure

TropicalDepression

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Upper Air Station Model A station model is a pictorial way of

representing the weather data recorded at a specific site.

T

D D

Z

d d

ffA simplified station model

This represents the typicaldata reported at a station.

Some stations may reportmore or less.

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Upper Air Station Model

T

D D

Z

d d

ff A simplified station model

T = Temperature (Celsius)DD = Dew Point DepressionZ = Height of the constant pressure surfacedd = Wind Direction (degrees)ff = Wind Speed (knots)

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Upper Air Station Model

A station model EXAMPLE

Temperature = -21 CDew Point Depression = 10 CHeight = 5460 mWind Direction = North -- 00 DegreesWind Speed = 50 knots -2 1

1 0

5 4 6

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Upper Air Station Model

Height of pressure surfaces– 850 mb

» 1100 - 1800 m» Recorded as 100 - 800 with the leading “1”

omitted

– 700 mb» 2700 - 3500 m» Recorded as 700 - 500 with the leading “2” or

“3” omitted

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Upper Air Station Model

Height of pressure surfaces– 500 mb

» 4700 - 6000 m» Recorded as 470 - 600 with the trailing “0”

omitted

– 250 mb» 9000 - 11000 m» Recorded as 900 - 1110 with the trailing “0”

omitted

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250 mb

Upper Air