PolarMaritime

ReturningPolar Maritime

TropicalMaritime

TropicalContinental

PolarContinental

Arctic Maritime

Air Masses

Norwegian Model

Norwegian Model

Passage of a warm front …

Backs slowly Sharp veer Steady againBacks slowly Sharp veer Steady againWindWindDew pointDew pointPressurePressure

TemperatureTemperatureCloudCloud

VisibilityVisibility

WeatherWeather

BeforeBefore OnOn AfterAfter

Slow increase Sharper rise SteadySlow increase Sharper rise Steady

Usually falls Usually steady SteadyUsually falls Usually steady Steady

Little effect Fall Little effect Fall inin rain Milder than before rain Milder than beforeIncreases & Thick layers Thin layer cloudIncreases & Thick layers Thin layer cloudlowers as rain with some breakslowers as rain with some breaksapproaches possibleapproaches possible

Good becoming Poor in rain Moderate or poorGood becoming Poor in rain Moderate or poormoderatemoderate

Rain turning Short burst Damp, drizzlyRain turning Short burst Damp, drizzlyheavy of heavy rainheavy of heavy rain

Passage of a cold front ...Passage of a cold front ...

Steady Sharp veer Steady (gusty)Steady Sharp veer Steady (gusty)WindWindDew pointDew pointPressurePressure

TemperatureTemperatureCloudCloud

VisibilityVisibility

WeatherWeather

BeforeBefore OnOn AfterAfter

Steady Falling Fall continues for a bitSteady Falling Fall continues for a bit

Steady Pressure ‘kick’ RisesSteady Pressure ‘kick’ Rises

Mild usually Fall in rain Usually fallsMild usually Fall in rain Usually fallsThin low cloud Thick layers Convective cloudThin low cloud Thick layers Convective cloudsome breaks embedded Cb develops after a bit some breaks embedded Cb develops after a bit

Moderate or Poor in rain Very goodModerate or Poor in rain Very goodpoorpoor

Light rain or Short burst Dry then showersLight rain or Short burst Dry then showersdrizzle of heavy raindrizzle of heavy rain

167 181

64

045

10

1/30

Mean sea level pressureLast 3 figures of the MSL Pressure

e.g... 181 = 1018.1hPa

Present weatherSymbols

Rain

DrizzleSnow

Showers

Thunderstorm

Fog

Phenomena occurred in past hour.

Visibility01 to 50 add 00 for visibility in metres56 to 89 subtract 50 for visibility in km

Cloud amount and height ( Low, Medium and High)Amount of cloud in eighths /height of cloud in feet

01 to 50 add 00 for height in feet56 to 89 subtract 50 for height in thousands of feet

Past weatherSymbols as Present weather

Period covered0000,0600,1200,1800 last 6hrs0300,0900,1500,2100 last 3hrs

All other hours last hour

Type of low cloud

Dew point in tenths of a degreee.g.... 045 = 4.5 C

Screen temperature in tenths of a degreee.g... 167 = 16.7 C

Type of medium and high cloud.

Decode over page

Change in pressure (tendency)Difference in pressure from 3 hours

in tenths of hPa and direction ofup or down. Decode over page

Windspeed and directionWind from direction of the shaft

Triangle = 50 ktsFull feather =10 ktsHalf feather = 5 kts

Just shaft < 3kts

The Station Circle

Observations

012

65

9

724

11

11,4510

50 3500199711

11

30 159978

475

00706 20

,,9

Tephigrams & Stability

Any point on an ascent

AbsolutelyUnstable

AbsolutelyStable

ConditionallyUnstable

The position of the ELR gives the stability of the ascent at that point

DALR > SALR > ELR

ELR > DALR > SALR

DALR > ELR > SALR