Aviation Weather Services

Figure 13-10. Surface analysis chart. Wind speed Total sky cover Wind direction Temperature Sea level pressure Present weather Pressure change in past 3 hours 34 147 Dew point ** 28 / Pressure tendency 32 1. Total sky cover: Overcast 2. Temperature/dew point: 34 °F/32 °F 3. Wind: From the northwest at 20 knots (relative to true north) Examples of Wind Speed and Direction Plots Calm NE/5 kts SW/10 kts N/15 kts W/50 kts S/60 kts 4. Present weather: Continuous light snow 5. Sea level pressure: 1014.7 millibars (mb) Note: Pressure is always shown in 3 digits to the nearest tenth of a millibar. For 1,000 mb or greater, prefix a “10” to the 3 digits For less than 1,000 mb, prefix a “9” to the 3 digits 6. Pressure change in past 3 hours: Increased steadily or unsteadily by 2.8 mb Figure 13-11. Sample station model and weather chart symbols. 13-14