Hazardous Weather Detection
How PlaneWX detects and assesses thunderstorms, icing, turbulence, and other hazardous conditions along your route.
Convective Watch
The Convective Watch section appears in your briefing whenever thunderstorm or convective activity is detected along your route. It combines data from three sources to build a comprehensive threat picture:
1. Numerical Weather Models
HRRR, GFS, and ECMWF model soundings are sampled at multiple points along your route to extract convective indices (CAPE, K-Index, Lifted Index). These indices measure the atmosphere's potential for thunderstorm development.
2. Weather Prediction Center (WPC)
WPC short-range and extended discussions are analyzed for convective language. PlaneWX classifies WPC text into 4 severity tiers using 80+ phrase patterns sourced from real aviation weather products.
3. TAF Convective Phrases
TAFs at departure, arrival, and en-route airports are scanned for convective weather codes (TS, TSRA, VCTS) and probability groups (PROB30, PROB40) containing thunderstorm activity.
Convective Indices Explained
In Enhanced View, the Convective Watch card displays three key atmospheric indices with gauge bars showing where each value falls within its range. Here's what they mean for your flight:
CAPE (Convective Available Potential Energy)
Measures how much energy is available to fuel thunderstorm updrafts. Higher CAPE means stronger potential storms. Measured in Joules per kilogram (J/kg).
0–500
Weak
Little convective potential
500–1,500
Moderate
Isolated storms possible
1,500–3,000
Strong
Organized storms likely
3,000+
Extreme
Severe storms possible
K-Index
A composite index measuring thunderstorm potential based on temperature lapse rate, moisture content, and dewpoint depression. Higher values indicate greater thunderstorm probability.
<20
Low
Thunderstorms unlikely
20–30
Moderate
Isolated possible
30–40
High
Scattered storms likely
40+
Very High
Numerous storms expected
Lifted Index (LI)
Measures atmospheric stability by comparing the temperature of a lifted air parcel to the environment at 500 mb (~18,000 ft). Negative values indicate instability. The more negative the value, the more unstable the atmosphere.
>0
Stable
No thunderstorm support
0 to −3
Marginally Unstable
Weak storms possible
−3 to −6
Unstable
Strong storms likely
<−6
Very Unstable
Severe storms possible
How PlaneWX uses these indices: No single index tells the full story. PlaneWX evaluates all three together across multiple sample points along your route and combines them with WPC discussions and TAF convective phrases to determine the overall threat level (Isolated, Scattered, or Widespread).
Multi-Model Icing Analysis
PlaneWX analyzes icing conditions using temperature, humidity, and cloud data from HRRR, GFS, and ECMWF models. The analysis considers your specific cruise altitude and route.
What's Assessed
- •Freezing level: Altitude where temperature drops below 0°C along your route
- •Icing layer: The altitude band where icing conditions exist (base to top)
- •Severity: None, Trace, Light, Moderate, or Severe based on humidity and temperature profiles
- •Phase exposure: Whether icing affects your climb, cruise, or descent
- •FIKI status: Whether your aircraft has Flight Into Known Icing equipment
Freezing level warning: If your cruise altitude is above the freezing level, an amber indicator appears in the Icing grid. This doesn't necessarily mean you'll encounter icing — it means you're flying in an altitude range where icing is possible if moisture is present.
Multi-Model Turbulence Analysis
PlaneWX combines two turbulence data sources into a single per-waypoint hybrid assessment:
GTGN Nowcast (near-term)
The FAA/NCAR Graphical Turbulence Guidance Nowcast provides EDR-based turbulence severity computed from actual aircraft sensor data, updated every 15 minutes. For departures within approximately 2 hours, GTGN is the primary turbulence source along your route.
NWP Models (all departures)
HRRR, GFS, and ECMWF model soundings provide wind shear and Richardson number analysis at 24 pressure levels. Thresholds are calibrated for light GA aircraft — roughly 40% lower than transport-category standards, because your SR22 feels the same air very differently than a 737.
Severity Scale
Why you may see SEVERE when other tools don't: PlaneWX uses GA-calibrated thresholds that are roughly 40% lower than the transport-category standards used by most aviation weather products. What shows as Moderate in a 737-calibrated tool can legitimately be Severe in a light GA aircraft at 3,400 lbs. The easy path would have been to display the same numbers every other tool shows — we chose not to, because those numbers aren't calibrated for the airplane you're flying.
For the full methodology including exposure time, severity smoothing, Richardson number analysis, mountain wave detection, and PIREP normalization, see the Turbulence Analysis help page.
AIRMETs & SIGMETs
PlaneWX automatically detects active weather advisories that intersect your route corridor and affect your cruise altitude. These are shown in the AIRMETs/SIGMETs section with their type, affected area, and valid time.
G-AIRMET Types
- SierraIFR conditions and mountain obscuration
- TangoModerate turbulence and sustained surface winds ≥30 kt
- ZuluModerate icing and freezing levels
SIGMETs
- •Convective SIGMETs: Severe thunderstorms, tornadoes, or embedded thunderstorms. Highest priority.
- •SIGMETs: Severe icing, severe or extreme turbulence, volcanic ash, sandstorms.
- •CWAs (Center Weather Advisories): Short-term hazards not covered by SIGMETs.
Impact on WX Score: Active SIGMETs along your route may result in an automatic NO-GO (0% score) during the pre-flight check within 12 hours of departure. G-AIRMETs result in point deductions proportional to their severity.