Contrail Forecast
Whether there will be chemtrails today depends on what is happening at 10,000 metres above your location — not at ground level. ChemTracker reads upper-atmosphere forecast data to predict when and where trail formationis likely, hours in advance. If today's upper air is cold and supersaturated, expect widespread persistent trails. If it's warm and dry aloft, trails will be short-lived or absent.
How the Contrail Forecast Works
A contrail forecast is fundamentally an upper-atmosphere weather forecast. ChemTracker pulls numerical weather prediction model data and applies the Schmidt-Appleman criterionacross the forecast period to determine when conditions will favor trail formation.
Step 1: Forecast Data Retrieval
ChemTracker retrieves hourly forecast outputs from weather models for the next 48 hours, focusing on upper-troposphere variables: temperature, specific humidity, and wind at 200, 250, and 300 hPa pressure levels — corresponding roughly to 11,000–13,000 metres, where most commercial aircraft cruise.
Step 2: Schmidt-Appleman Application
For each forecast time step and pressure level, the Schmidt-Appleman criterion is evaluated: is the temperature below the critical threshold G at which contrail formation is expected? This is calculated using standard commercial aircraft engine parameters (bypass ratio, fuel properties) to produce a representative threshold for typical air traffic.
Step 3: Persistence Assessment
Formation and persistence are separate questions. Where the criterion is met AND relative humidity over ice exceeds 100%, persistent (spreading) trails are predicted. Where the criterion is met but humidity is below 100% RHi, brief non-persistent trails are expected. This distinction is shown in the forecast output.
Step 4: Location-Specific Output
The forecast is calculated for your location (or any location you search) and presented as an hour-by-hour activity forecast: expected trail activity level (high, medium, low, or none), peak activity windows, and the specific atmospheric conditions driving the prediction.
What Drives Trail Activity on Any Given Day
Trail activity varies dramatically from day to day, and even hour to hour. The primary drivers are:
Upper-Troposphere Temperature
The colder the air at cruising altitude, the easier it is for contrails to form. Temperatures below −40°C are generally required. Winter months and high latitudes frequently see temperatures below −55°C at 250 hPa, creating very favorable conditions. Summer in tropical regions may bring temperatures above −35°C even at cruising altitude, suppressing trail formation.
Upper-Troposphere Humidity
Relative humidity with respect to ice (RHi) at cruising altitude governs whether trails persist. High RHi (>100%) means supersaturated conditions — trails grow and spread. Low RHi means trails evaporate quickly. Moisture at altitude comes from large-scale weather systems, particularly warm fronts and jet-stream disturbances, which explains why trail activity often precedes rainy weather by several hours.
Tropopause Height
When the tropopause is low (common in winter and during cold air outbreaks), aircraft spend more of their cruise at altitudes with the coldest, often most humid air. A low tropopause dramatically increases trail activity. A high summer tropopause can push cold enough air above typical cruise altitudes, reducing activity.
Air Traffic Volume
The number of aircraft in trail-forming conditions at any time is a product of both the atmospheric conditions and the flight schedule. Morning rush hours over Europe and North America (typically 06:00–10:00 UTC and 14:00–18:00 UTC) coincide with peak air traffic volume. Trail activity forecast accounts for both dimensions — conditions favorable and flights in those conditions. See current aircraft on the live trail activity page.
Seasonal Trail Patterns
Trail activity follows distinct seasonal patterns in mid-latitudes:
“The question 'will there be chemtrails today?' has a scientifically answerable component: are upper-atmosphere conditions favorable for persistent trail formation? ChemTracker gives you that answer for today and the next 48 hours.”
Frequently Asked Questions
Will there be chemtrails today?
Whether you will see persistent aircraft trails today depends on atmospheric conditions at cruising altitude above your location — primarily temperature and relative humidity at 200–300 hPa pressure levels. ChemTracker reads current weather model forecast data and tells you how likely trail formation is today, which hours are expected to see peak activity, and what conditions are forecast for the next 24–48 hours.
How is a contrail forecast different from a weather forecast?
A standard weather forecast focuses on surface conditions. A contrail forecast looks at conditions at 8–12 km altitude — the tropopause and upper troposphere. The key variables are temperature (must be below approximately −40°C), relative humidity with respect to ice (must exceed 100% for persistent trails), and wind shear. These upper-atmosphere conditions can be very different from what is happening on the ground.
How accurate is the contrail forecast?
Contrail prediction accuracy is ultimately limited by the resolution of weather model forecasts. At 6–12 hours ahead, the prediction is fairly reliable. Beyond 24 hours, uncertainty increases significantly — particularly for relative humidity at altitude, which is the hardest atmospheric variable to forecast accurately. ChemTracker expresses this as a probability range: high, medium, or low trail activity expected.
Why do some days have many more chemtrails than others?
Trail activity varies enormously based on upper-atmosphere conditions. Frontal systems often bring supersaturated air at cruising altitudes, leading to widespread persistent trail formation. High-pressure systems typically bring drier upper air, resulting in short-lived or absent trails. Seasonal patterns also play a role: winter generally produces more persistent trail activity in mid-latitudes because the tropopause is lower and upper air is colder.
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