A rain-detail chart is a precipitation figure that keeps grain visible: the individual tipping-bucket increment, the hourly depth, and the daily (or storm) total. Those three numbers are not the same measurement repeated. A tip is a count event. An hourly total is a sum of tips (or of another sensor’s depth) over a clock hour. A daily total is a sum over a rain day whose reset may not be midnight. Confusing them is how a desert thunderstorm becomes “0.00 inches today” on one panel and a flood on another.
The historical TNET Weather page at /tws-raindetail.php was the Mesa station’s rain-detail chart. The recovered snapshot said the report had been taken offline due to errors; the original plots are not rehosted. This article replaces that dead panel with a reading and calibration guide. It does not publish current Mesa rainfall.
Historical context
Personal weather stations in the southwestern United States needed a rain page that could show a 20-minute convective burst without hiding it inside a monthly bar. Weather Display-style sites therefore offered a “rain detail” view: rate, tips or incremental depth, hour columns, and day/month/year running totals. Incoming links wanted that hydrologic grain, not a temperature dashboard.
The chart suite may include a rain PNG among other variables. NOAA-style daily tables print daily amounts in a climate-form layout. Doppler radar is a different evidence family: remotely sensed reflectivity, not a funnel. This URL is the gauge’s own multi-grain chart.
Tips are events; hours and days are sums
Most hobby and many professional automatic gauges are tipping buckets. A calibrated bucket fills and tips at a design depth—commonly 0.01 inch in U.S. consumer and NWS-adjacent gear, or 0.2 mm (sometimes 0.1 mm) in WMO-oriented millimetre hardware. Each tip is an observed increment at the resolution of the bucket, not a continuous intensity.
Hourly totals bin those increments (or a weighing-gauge depth) into clock hours. The hour boundary is a publishing choice. A storm that peaks at 14:59 and 15:01 is two hours on the chart and one storm in the air.
Daily totals depend on the rain-day reset. Midnight local, midnight UTC, and a 07:00 or 08:00 cooperative observation time are different hydrological days. Weather Display historically offered more than one running total (for example a 9 a.m. versus midnight reset). Those totals must not be averaged or substituted for each other.
Rate is depth per time, usually derived from recent tips. A one-tip hour in a 0.01-inch bucket is 0.01 in/h if you spread it over the hour, or a much higher instantaneous rate if the two tips that define the interval were 30 seconds apart. Rain-detail charts should say which rate definition they use. A spike that lasts one sample is a candidate for a funnel dump or a double-tip, not automatically “6 inches per hour of climate.”
WMO observing practice expresses precipitation as a vertical depth of water, in millimetres (equivalent to kg m⁻² for liquid water). Daily amounts are to be read to 0.2 mm, or 0.1 mm if feasible. Intensity is millimetres per hour. U.S. operational practice still reports inches and hundredths; an NWS 8-inch standard gauge is a different orifice than a small plastic backyard funnel. Conversion is exact in arithmetic (1 inch = 25.4 mm) and sloppy in software that applies 25 or 25.4 inconsistently, or that treats a 0.01-inch tip as 0.01 mm.
Funnel calibration is a geometric fact
A tipping bucket reports volume per tip. Depth is volume divided by orifice area. If you change the funnel diameter and keep the same bucket, you have changed the depth per tip. If you enter the wrong depth-per-tip in the logger, every hour and every day is scaled wrong by a constant. That error is silent on a pretty chart.
Calibration checks that belong on a rain-detail page:
- Orifice and bucket match the configured resolution. A millimetre bucket displayed in inches without conversion will under-report by a factor of about 25.
- Level and debris. A tilted gauge changes the effective catchment. A clogged funnel under-reports until a dump produces a single huge tip cluster.
- Undercatch in intense rain. During a high rate, water can be lost while the bucket is moving. WMO literature treats that as a known mechanism error of tipping buckets, not as a mystery storm. Desert convective bursts are exactly the intensity where this matters.
- Wind and siting. A gauge in a windy, unshielded exposure under-catches. A gauge under an eave over-catches drip. Neither is fixed by choosing a nicer color for the hourly bars.
A rain-detail chart that shows a one-sample spike of implausible depth should flag the sample. Smoothing it into the hourly bar hides the calibration problem.
Desert convective bursts
Mesa and the broader Phoenix area receive much of their annual rain in short, locally intense storms, especially in the North American monsoon season, rather than in long stratiform events. On a rain-detail chart that fact has a signature:
- Many hours at zero, then a cluster of tips inside one or two hours.
- Daily total dominated by a single hour.
- Monthly and yearly panels that look “dry” until that hour is included.
- Radar that lights up a cell the gauge never sees, or a gauge spike with no echo, if the cell missed the yard.
Those are observed hydrology at a point. Radar is areal and volumetric in a different sense; it does not replace the funnel. Point and radar disagree often at convective scale. That disagreement is a reason to keep both, labeled as different families, not a reason to average them into one “rain truth.”
A burst also stresses the bucket: splash-out, undercatch, and clog-then-dump. If the hourly bar is 0.80 inch and the daily total is 0.02 inch, you have a reset or a dual-total bug, not a meteorological paradox.
Inches versus millimetres
Pick one native unit for the logger and convert at the display edge.
| Display | Native 0.01 in tip | Native 0.2 mm tip | |---|---|---| | Inch chart | 0.01 per tip | about 0.0079 in per tip | | Millimetre chart | 0.254 mm per tip | 0.2 mm per tip |
If the chart axis says inches and the tips were millimetres, a monsoon hour will look like a trace. If the axis says millimetres and the tips were inches, a modest shower will look like a flood. Print the native resolution in the caption: “0.01 in tips, summed to local midnight.”
Trace amounts have a definition. WMO-oriented practice treats less than 0.1 mm (0.2 mm in some U.S. usage) as a trace. A backyard chart that prints 0.00 for a single tip has rounded the only information it had.
What rain-detail is not
It is not an NWS warning. Flash-flood and severe-thunderstorm products come from the National Weather Service and local emergency authorities.
It is not a climate normal. A wet hour does not update NCEI statistics.
It is not a statement that precipitation “kills” a satellite link. Atmospheric water—precipitable water, rain, and storm structure—is one of the weather evidence families a connection outlook may consider, as observations or model fields, not as a cartoon mechanism and not as a disclosed internal weight. For a dated, location-specific outlook see the Connection Outlook. For how those families are described without scoring formulas, see how the service works.
Practical checklist
- Tips, hourly sums, and daily sums are separate series with named resets.
- Depth per tip and orifice are documented.
- Units are inches or millimetres, stated once, converted with 25.4 mm per inch.
- Rate definition (interval used) is printed.
- Implausible single-sample spikes are flagged, not smoothed.
- Radar, if shown, is labeled as radar, not as the gauge.
- Missing hours are missing, not zeros (zeros dry the day).
Modern relevance
Multi-grain precipitation records are how you tell a clogged funnel from a dry climate, and a convective burst from a stratiform day. That distinction matters for hydrology and, conceptually, for any product that treats atmospheric water as evidence rather than as a slogan. The historical observations hub indexes the related station pages.
This URL does not restore the old Mesa rain report. It states how a rain-detail chart has to be built if the grain is going to remain scientific.
Sources
- World Meteorological Organization, Guide to Instruments and Methods of Observation (WMO-No. 8), precipitation measurement: community.wmo.int
- National Weather Service, official precipitation and flood products: weather.gov
- NOAA Physical Sciences Laboratory, example tipping-bucket documentation (0.01 in / 0.1 mm resolutions): psl.noaa.gov
- TNET, How the service works