Bora Katabatic Drainage Speed
Evaluate inviscid uniform katabatic parcel acceleration over supplied slope distance/density proxy; no friction, entrainment, sustained Bora wind prediction or safety assessment.
Description
Katabatic drainage accelerates a relatively cold parcel downslope under an idealized buoyancy contrast.
Katabatic drainage accelerates a relatively cold parcel downslope under an idealized buoyancy contrast. An inviscid constant-acceleration calculation omits drag and mixing.1
Evaluate inviscid uniform katabatic parcel acceleration over supplied slope distance/density proxy; no friction, entrainment, sustained Bora wind prediction or safety assessment.
When to use Bora Katabatic Drainage Speed
Use this tool to evaluate inviscid uniform katabatic parcel acceleration over supplied slope distance/density proxy; no friction, entrainment, sustained Bora wind prediction or safety assessment.
Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.
How to use Bora Katabatic Drainage Speed and understand its results
- Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.
- Enter coldLayerTemperatureK, ambientReferenceTemperatureK, downslopeTravelDistanceM, slopeAngleDegrees, gravityMPerSecondSquared, initialDownslopeSpeedMPerSecond using the field table and calculation rules, then run the tool.
- Read idealKatabaticAccelerationMPerSecond2, idealKatabaticEndpointSpeedMPerSecond. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| coldLayerTemperatureK | Cold layer temperature k | number | Required |
| ambientReferenceTemperatureK | Ambient reference temperature k | number | Required |
| downslopeTravelDistanceM | Downslope travel distance m | number | Required |
| slopeAngleDegrees | Slope angle degrees | number | Required |
| gravityMPerSecondSquared | Gravity m per second squared | number | Required |
| initialDownslopeSpeedMPerSecond | Initial downslope speed m per second | number | Required |
Use positive Kelvin temperatures with cold no warmer than ambient, positive gravity, nonnegative distance/speed and slope from 0° to 90°. Compute the uniform downslope acceleration and nonnegative endpoint speed.
a = g(Tambient−Tcold)/Tambient × sin(slope); endpoint speed = sqrt(initial speed² + 2a distance) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| idealKatabaticAccelerationMPerSecond2 | Ideal katabatic acceleration m per second2 | number |
| idealKatabaticEndpointSpeedMPerSecond | Ideal katabatic endpoint speed m per second | number |
{
"input": {
"coldLayerTemperatureK": 280,
"ambientReferenceTemperatureK": 300,
"downslopeTravelDistanceM": 1000,
"slopeAngleDegrees": 30,
"gravityMPerSecondSquared": 10,
"initialDownslopeSpeedMPerSecond": 0
},
"output": {
"idealKatabaticAccelerationMPerSecond2": 0.33333333333333326,
"idealKatabaticEndpointSpeedMPerSecond": 25.81988897471611
}
}Limitations and assumptions
Friction, entrainment and evolving temperature are excluded. The result does not predict sustained Bora winds.
Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Foehn Chinook Warming Rate: Model windward dry/saturated ascent then dry lee descent with supplied crest/LCL/lapse rates; explicit rainout/unsaturated descent idealization, not actual Chinook event or environmental profile fit. For a complementary task, use Gradient Wind Curvature Correction: Solve continuous geostrophic-limit normal branch of V²/(fR)+V=Vg with signed curvature, rejecting no-real anticyclonic balance; no anomalous branch, surface gusts or safe-flight inference.
References
-
Bora Katabatic Drainage Speed — tool.io
Similar or alternative tools
- Foehn Chinook Warming Rate
Model windward dry/saturated ascent then dry lee descent with supplied crest/LCL/lapse rates; explicit rainout/unsaturated descent idealization, not actual Chinook event or environmental profile fit.
- Gradient Wind Curvature Correction
Solve continuous geostrophic-limit normal branch of V²/(fR)+V=Vg with signed curvature, rejecting no-real anticyclonic balance; no anomalous branch, surface gusts or safe-flight inference.