Why more data does not automatically mean better decisions
Contents
Use the links below to jump to any section:
- Why Weather Data Is a Decision Tool, Not a Truth
- The Three Types of Weather Information at Sea
- Onboard Observations – The Only Real-Time Truth
- Forecast Products – Models, Not Reality
- Synoptic Charts – The Big Picture Tool
- Text Forecasts, NAVTEX & SafetyNET
- GRIB Files & Digital Forecasts
- Weather Routing Services
- Conflicting Data – Which Source Do You Believe?
- Professional Use of Weather Information on the Bridge
1. Why Weather Data Is a Decision Tool, Not a Truth
All weather information at sea is interpretive.
It represents:
- models
- assumptions
- probabilities
No weather product tells you what will happen.
They tell you what is likely, possible, or unlikely.
Bridge officers who treat forecasts as facts lose flexibility when conditions diverge.
2. The Three Types of Weather Information at Sea
All onboard weather data falls into three categories:
- Observation – what is happening now
- Analysis – interpretation of recent data
- Forecast – projection of future conditions
Professional decision-making blends all three.
Using forecasts alone is operationally weak.
3. Onboard Observations – The Only Real-Time Truth
The ship itself is a weather station.
Onboard observations include:
- barometric pressure and trend
- wind speed and direction
- sea state and swell direction
- visibility and precipitation
Pressure trend is especially valuable.
A falling barometer often provides earlier warning than any forecast update.
Ignoring onboard observations is one of the most common weather-related errors.
4. Forecast Products – Models, Not Reality
Forecasts are generated by numerical models.
They rely on:
- initial data quality
- grid resolution
- physical assumptions
At sea, data density is low — which reduces accuracy.
Forecast confidence decreases with:
- time horizon
- distance from observation networks
- system complexity
Forecasts should guide attention, not replace judgement.
5. Synoptic Charts – The Big Picture Tool
Synoptic charts remain one of the most powerful tools onboard.
They show:
- pressure systems
- isobar spacing
- fronts and troughs
- system movement
Charts allow officers to:
- visualise evolution
- detect intensification
- anticipate changes before they occur
They explain why a forecast says what it says.
6. Text Forecasts, NAVTEX & SafetyNET
Text products provide:
- official warnings
- regional context
- consistency across fleets
NAVTEX and SafetyNET are reliable but:
- low resolution
- regionally broad
- slow to update
They are best used as baseline safety information, not fine-tuning tools.
7. GRIB Files & Digital Forecasts
GRIB files offer:
- high spatial resolution
- time-stepped forecasts
- visual overlays
They are powerful — and dangerous if misunderstood.
Risks include:
- false precision
- overconfidence in colour scales
- ignoring uncertainty
GRIBs are decision aids, not guarantees.
8. Weather Routing Services
Routing services optimise routes based on:
- forecast conditions
- vessel characteristics
- commercial priorities
They can:
- reduce fuel consumption
- avoid severe weather
- improve schedule reliability
They cannot:
- account for every local effect
- replace onboard judgement
- make decisions for the Master
Routing advice must always be validated onboard.
9. Conflicting Data – Which Source Do You Believe?
Conflicts are normal.
When data disagrees:
- trust onboard observations first
- assess pressure trends
- compare forecast evolution, not single outputs
- assume conditions may worsen
When in doubt, plan for the less favourable outcome.
Optimism bias is a known contributor to weather-related accidents.
10. Professional Use of Weather Information on the Bridge
Professional bridge teams:
- cross-check sources
- track trends, not snapshots
- reassess continuously
- discuss uncertainty openly
They understand that weather data does not remove risk.
It allows risk to be managed earlier.
Closing Perspective
Modern ships have access to more weather information than ever before.
Accidents still happen because information is mistaken for certainty.
Weather data does not make decisions safer by itself.
People do — when they understand what the data can and cannot tell them.
The bridge officer’s task is not to find the “right” forecast.
It is to recognise when reality is drifting away from expectation — and act while options still exist.
Tags
marine weather data · NAVTEX · GRIB · weather routing · bridge decision-making · maritime meteorology