Polar Maritime Returning Polar Maritime Tropical Maritime Tropical Continental Polar Continental Arctic Maritime Air Masses

Norwegian Model

Passage of a warm front … Backs slowly Sharp veer Steady again Wind Dew point PressureTemperatureCloudVisibilityWeather Before On After Slow increase Sharper rise Steady Usually falls Usually steady Steady Little effect Fall in rain Milder than before Increases & Thick layers Thin layer cloud lowers as rain with some breaks approaches possible Good becoming Poor in rain Moderate or poor moderate Rain turning Short burst Damp, drizzly heavy of heavy rain

Passage of a cold front... Steady Sharp veer Steady (gusty) Wind Dew point PressureTemperatureCloudVisibilityWeather Before On After Steady Falling Fall continues for a bit Steady Pressure ‘kick’ Rises Mild usually Fall in rain Usually falls Thin low cloud Thick layers Convective cloud some breaks embedded Cb develops after a bit Moderate or Poor in rain Very good poor Light rain or Short burst Dry then showers drizzle of heavy rain

/30 Mean sea level pressure Last 3 figures of the MSL Pressure e.g = hPa Present weather Symbols Rain Drizzle Snow Showers Thunderstorm Fog Phenomena occurred in past hour. Visibility 01 to 50 add 00 for visibility in metres 56 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 feet 56 to 89 subtract 50 for height in thousands of feet Past weather Symbols as Present weather Period covered 0000,0600,1200,1800 last 6hrs 0300,0900,1500,2100 last 3hrs All other hours last hour Type of low cloud Dew point in tenths of a degree e.g = 4.5 C Screen temperature in tenths of a degree e.g = 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 of up or down. Decode over page Windspeed and direction Wind from direction of the shaft Triangle = 50 kts Full feather =10 kts Half feather = 5 kts Just shaft < 3kts The Station Circle

Observations , ,, 9

Tephigrams & Stability Any point on an ascent Absolutely Unstable Absolutely Stable Conditionally Unstable The position of the ELR gives the stability of the ascent at that point DALR > SALR > ELR ELR > DALR > SALR DALR > ELR > SALR