Telltale

weather · sailing knowledge

About Telltale: evidence, weather and sailing records

A measurement, a forecast and a conclusion are three different things. We keep their sources and times attached.

By Telltale Team · Reviewed

Before you go

  1. Check the source and time on any number before you use it.
  2. Compare forecasts with stations for the hours that matter. Conditions
  3. Check a recording for gaps before trusting its summary.

Measured, predicted, decided

This is the one caveat that applies to every guide.

A forecast is not a measurement. A station reports one place at a known height and averaging time. A model predicts a grid cell for an hour, from a run made earlier. Your decision draws on both and is yours.

How Telltale shows weather

Each forecast keeps its model, run and valid time.

Conditions shows named model guidance beside the stations, with the model and run on every row. The nowcast nudges a model toward recent station readings nearby, and says so. A finer grid alone doesn’t prove skill.

Telltale Conditions with the Point Atkinson station open: an Observed row of hourly wind above rows for HRDPS, HRDPS West, HRRR and ECMWF, a spread row, and a note on which model has done best there lately.
In TelltaleMeasured against forecast, per station. Tap a station in Conditions to line up what it measured beside each model for the same hours, with the spread between the models and the one that has done best there lately. Open Point Atkinson

References 1 2

How Telltale treats a recording

Summaries are built from the readings, and the readings stay available.

Sensors have installation and calibration limits. Detected tacks, percent of polar and highlights interpret the readings; they don’t replace them. A missing reading stays missing.

The Performance tab of a Telltale session: upwind at 87 % of polar, reaching at 80 % and downwind at 81 %, with the minutes lost on each, and the three stretches that cost the most.
In TelltalePercent of polar, by kind of sailing. A session’s Performance tab says in one sentence where you were closest to your polar and where the time went, then breaks it down by upwind, reaching and downwind. Reviewing a sail

How these guides are written

Sources are listed, examples are real, and nothing is claimed without evidence.

Each guide lists its official references and a review date. Examples quote real station and model values frozen on the date shown, and the build checks every quoted number against that file. Screens are captures of the app itself. A general claim about forecast skill needs the owner’s approval and its evidence before it can appear here.

Sources and review

Official references checked on 2026-10-11. Product details and schedules change; the provider’s page is the current word.

Take it to the water

Check the stations before you leave, then record the sail for the debrief.

Open ConditionsRecord a sail