Pressure Tendency 3HR Change
Calculate signed observed three-hour pressure tendency with bracketed piecewise-linear samples at report time; no unobserved extrapolation or synoptic symbol/weather inference.
Description
Pressure tendency measures pressure change over a fixed reporting interval.
Pressure tendency measures pressure change over a fixed reporting interval. Irregular observations can bracket its endpoints without being sampled exactly at those times.1
Calculate signed observed three-hour pressure tendency with bracketed piecewise-linear samples at report time; no unobserved extrapolation or synoptic symbol/weather inference.
When to use Pressure Tendency 3HR Change
Use this tool to calculate signed observed three-hour pressure tendency with bracketed piecewise-linear samples at report time; no unobserved extrapolation or synoptic symbol/weather inference.
Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.
How to use Pressure Tendency 3HR Change 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 observationHours, observedPressuresHpa, reportHour using the field table and calculation rules, then run the tool.
- Read observedThreeHourPressureChangeHpa, bracketStartPressureHpa, bracketEndPressureHpa. 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 |
|---|---|---|---|
| observationHours | Observation hours | list of number | Required |
| observedPressuresHpa | Observed pressures hPa | list of number | Required |
| reportHour | Report hour | number | Required |
Provide increasing observation hours and aligned positive pressures in hPa. Linearly interpolate both requested endpoints within observed coverage; subtract the earlier pressure from the later pressure.
three-hour tendency = pressure(report hour) − pressure(report hour − 3) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| observedThreeHourPressureChangeHpa | Observed three hour pressure change hPa | number |
| bracketStartPressureHpa | Bracket start pressure hPa | number |
| bracketEndPressureHpa | Bracket end pressure hPa | number |
{
"input": {
"observationHours": [
0,
1,
3,
4
],
"observedPressuresHpa": [
1000,
1001,
1003,
1000
],
"reportHour": 4
},
"output": {
"observedThreeHourPressureChangeHpa": -1,
"bracketStartPressureHpa": 1001,
"bracketEndPressureHpa": 1000
}
}Limitations and assumptions
Extrapolation is rejected. The signed change does not identify a synoptic tendency symbol or forecast weather.
Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Cold Front Passing Temp Drop Rate: Audit observed interval cooling rates over irregular hours while preserving warming sign; temperature change alone does not establish a cold-front passage or weather hazard. For a complementary task, use Pressure Gradient Force per Mass: Convert measured three-dimensional Cartesian pressure gradient to signed per-mass acceleration; no Coriolis balance, coordinates or hydrostatic-gravity cancellation inferred.
References
-
Pressure Tendency 3HR Change — tool.io
Similar or alternative tools
- Cold Front Passing Temp Drop Rate
Audit observed interval cooling rates over irregular hours while preserving warming sign; temperature change alone does not establish a cold-front passage or weather hazard.
- Pressure Gradient Force per Mass
Convert measured three-dimensional Cartesian pressure gradient to signed per-mass acceleration; no Coriolis balance, coordinates or hydrostatic-gravity cancellation inferred.