Weather Theory: Pressure, Stability, Moisture, and Clouds
- Episode: core-11
- Version: 0.2.12
- Source verification: FAA and federal-science links, exact locators, show-note mappings, and source-tagged spoken passages are complete; source-relevance review is complete for version 0.2.12 as of September 1, 2026.
In this episode
- Distinguish station pressure, normalized sea-level pressure, altimeter setting, and standard-atmosphere references before connecting pressure, temperature, and density with atmospheric motion.
- Follow a rising parcel through lower pressure, expansion, cooling, stability, saturation, and cloud formation.
- Carry invisible water vapor through dew point, saturation, condensation on nuclei, droplets or ice crystals, and the light scattering that makes a cloud visible.
- Read layered and vertically developing clouds as evidence about stability, lift, ceiling, visibility, and precipitation.
- Carry the physical model into later VFR weather reports, forecasts, charts, and go/no-go or continue/divert decisions, then continue to Episode 12 for hazard application.
Study materials and visual aids
- PHAK pressure reference and altitude relationship — Figure 12-6 and the surrounding text show the standard sea-level pressure reference and explain why pressure decreases with altitude.
- PHAK temperature, dew point, and approximate cloud-base example — Figure 12-20 and the worked example show saturation and the simplified temperature-dew point convergence model.
- PHAK basic cloud families and vertical development — Figure 12-22 organizes low, middle, high, and vertically developing clouds.
Fact-check and source material
| Topic | Source type | Authoritative source | Locator | Verified |
|---|---|---|---|---|
| ACS weather-theory scope | FAA regulatory standard | Private Pilot ACS — Atmospheric composition, stability, and wind | PA.I.C.K3-K3b, printed p. 3 | 2026-08-28 |
| ACS moisture, clouds, risk, and correlation | FAA regulatory standard | Private Pilot ACS — Weather conditions, risk management, and skills | PA.I.C.K3c-K3l, R1-R2, and S1-S3, printed p. 4 | 2026-08-28 |
| Purpose of weather theory | FAA guidance | PHAK Chapter 12 — Introduction | Introduction, p. 12-1 | 2026-08-28 |
| Atmosphere, water vapor, and troposphere | FAA guidance | PHAK Chapter 12 — Atmosphere and composition | Atmosphere and Composition of the Atmosphere, p. 12-2 | 2026-08-28 |
| Air parcel and troposphere depth | FAA guidance | Aviation Weather Handbook — Air parcel and troposphere | Air Parcel and Troposphere, p. 4-3 | 2026-08-31 |
| Standard-atmosphere reference | FAA guidance | Aviation Weather Handbook — Standard atmosphere | The Standard Atmosphere, p. 4-5 | 2026-08-31 |
| Heating, density, and pressure | FAA guidance | PHAK Chapter 12 — Atmospheric circulation and pressure | Atmospheric Circulation and Atmospheric Pressure, p. 12-3 | 2026-08-28 |
| Radiation, conduction, convection, and advection | FAA guidance | Aviation Weather Handbook — Heat-transfer modes | Heat Transfer, Radiation, Conduction, and Convection, pp. 5-4 to 5-7 | 2026-08-31 |
| Horizontal temperature transport by wind | FAA guidance | Aviation Weather Handbook — Temperature advection | Wind Effects on Stability, p. 13-8 | 2026-08-31 |
| Pressure measurement and altitude | FAA guidance | PHAK pressure reference and altitude relationship | Measurement of Atmospheric Pressure and Altitude and Atmospheric Pressure, p. 12-5 | 2026-08-28 |
| Pressure units and station pressure | FAA guidance | Aviation Weather Handbook — Pressure units and station pressure | Atmospheric Pressure Units and Station Pressure, p. 8-3 | 2026-08-31 |
| Sea-level pressure comparison | FAA guidance | Aviation Weather Handbook — Sea level pressure | Sea Level Pressure, p. 8-6 | 2026-08-31 |
| MSL and AGL altitude | FAA guidance | FAA Pilot/Controller Glossary — Altitude reference | Term ALTITUDE, including MSL Altitude and AGL Altitude | 2026-08-30 |
| Airport elevation | FAA guidance | FAA Pilot/Controller Glossary — Airport elevation | Term AIRPORT ELEVATION | 2026-08-30 |
| Local altimeter setting | FAA guidance | Aviation Weather Handbook — Altimeter setting | Altimeter Setting, p. 8-12 | 2026-08-31 |
| Pressure altitude | FAA guidance | Aviation Weather Handbook — Pressure altitude | Pressure Altitude, p. 8-13 | 2026-08-31 |
| Density altitude | FAA guidance | Aviation Weather Handbook — Density altitude | Density Altitude, p. 8-14 | 2026-08-31 |
| METAR cloud heights and altimeter group | FAA guidance | Aviation Weather Handbook — METAR cloud heights and altimeter group | Sky Condition and Altimeter Group, p. 24-18 | 2026-08-31 |
| METAR sea-level-pressure remark | FAA guidance | Aviation Weather Handbook — METAR sea-level-pressure remark | Sea Level Pressure remark, p. 24-24 | 2026-08-31 |
| ASOS and AWOS observations | FAA guidance | AIM — ASOS and AWOS observations | Para. 7-1-29 | 2026-08-31 |
| ATIS weather content | FAA guidance | FAA Air Traffic Control — ATIS weather content | Para. 2-9-3 | 2026-08-31 |
| Altimeter-setting issuance | FAA guidance | FAA Air Traffic Control — Altimeter-setting issuance | Paras. 2-7-1 to 2-7-2 | 2026-08-31 |
| Pressure patterns and vertical motion | FAA guidance | PHAK Chapter 12 — Wind, currents, highs, and lows | Wind and Currents and Wind Patterns, p. 12-7 | 2026-08-28 |
| Stability and adiabatic temperature change | FAA guidance | PHAK Chapter 12 — Atmospheric stability | Atmospheric Stability, printed p. 12-12 | 2026-08-28 |
| Parcel-versus-environment stability comparison | FAA guidance | Aviation Weather Handbook — Parcel comparison for stability | Using a Parcel as a Tool to Evaluate Stability, p. 13-2 | 2026-08-31 |
| Convection | FAA guidance | Aviation Weather Handbook — Convection | Convection, p. 13-11 | 2026-08-31 |
| Parcel lapse, moisture, and inversion | FAA guidance | PHAK Chapter 12 — Adiabatic process, moisture, and inversion | Adiabatic Process, Moisture and Temperature, Relative Humidity, and Inversion, p. 12-13 | 2026-08-28 |
| Dew point and saturation paths | FAA guidance | PHAK temperature, dew point, and approximate cloud-base example | Temperature/Dew Point Relationship and Methods by Which Air Reaches Saturation, p. 12-14 | 2026-08-28 |
| Dew-point definition | Federal science guidance | National Weather Service Glossary — Dew Point | Term Dew Point | 2026-08-31 |
| Cloud formation and low clouds | FAA guidance | PHAK Chapter 12 — Cloud formation and low clouds | Clouds and low-cloud classification, p. 12-15 | 2026-08-28 |
| Cloud particles and light scattering | Federal science guidance | NOAA NESDIS — Cloud droplets, ice crystals, and light | The Short Answer | 2026-08-31 |
| Cloud families and vertical growth | FAA guidance | PHAK basic cloud families and vertical development | Basic Cloud Types and Clouds with Vertical Development, p. 12-16 | 2026-08-28 |
| Cloud-name classifications | FAA guidance | PHAK Chapter 12 — Cloud-name classifications | Cloud classifications, p. 12-17 | 2026-08-31 |
| Ceiling, visibility, and precipitation | FAA guidance | PHAK Chapter 12 — Ceiling, visibility, and precipitation | Ceiling, Visibility, and Precipitation, p. 12-17 | 2026-08-28 |
Correction status
Corrections and source updates are recorded in the episode production log before a revised version is published. Submit a source correction through the repository issue form or email [email protected]. Do not send credentials, private documents, or personal flight information.