The most lethal hazard in tropical cyclones is the water, and it works differently from what most people picture.
The mechanism
Wind pushing seawater towards the shore.
Which raises water level above normal tide.
Interaction with tide
Surge arriving at high tide producing much worse flooding.
Which is why timing matters enormously.
Coastal shape
Shallow, gently sloping coasts amplifying surge.
Which is why identical storms produce different flooding.
Why evacuation orders exist
Surge zones defined by modelling rather than by distance from shore.
Why it kills more people than wind
Wind damages buildings; water moves them, and moving water carries enormous force at depths that seem survivable.
Which is why evacuation orders are based on surge zones rather than on wind categories.
A relatively weak storm over a shallow coastal shelf can produce worse flooding than a stronger one hitting a steep coast, and the category number alone does not convey that.
Surge mapping
Models producing zone maps used for evacuation planning.
Which are published in advance.
Freshwater flooding
Rainfall inland as a separate and substantial hazard.
Which affects areas far from the coast.
Evacuation timing
Roads becoming impassable before conditions look severe.
Knowing your zone
Local emergency management publishing maps.
Why evacuation orders follow zones rather than categories
Surge depends on storm size, forward speed, angle of approach, tide and the shape of the sea floor as much as on wind speed.
Which means the category number is a poor predictor of flooding.
Emergency managers work from surge models producing zone maps, and those zones are the basis of evacuation decisions rather than the headline category.
Vertical evacuation
Moving up within a building where leaving is impossible.
Which is a last resort with real limits.
Six inches of moving water
Enough to knock an adult down.
Which is the standard warning and is accurate.
Vehicles in floodwater
Floating in far less depth than people assume.
Preparing
Knowing your zone and your route before the season.
Why understanding the system matters
Weather warnings are the output of a large, expensive, internationally coordinated system that most people interact with only through an app icon. It is one of the clearest examples anywhere of publicly funded science producing something everyone uses daily without noticing.
The practical value of understanding it is in reading warnings correctly. A cone is not a map of the storm, a watch is not a warning, a hundred-year flood is not once a century, and a radar app is not a warning service. Each of those misunderstandings has cost lives, and each is corrected in a sentence.
Where the authoritative information is
National meteorological services issue the warnings, publish the forecasts, explain the products and archive the data, all freely. Local emergency management agencies publish evacuation zones, shelter locations and preparedness guidance specific to the hazards where you live.
Those two sources answer almost every question anyone has about weather risk, and both are considerably more reliable than aggregated coverage, which frequently reproduces the misunderstandings described above.
A general note
Warning terminology, alert thresholds and emergency procedures differ between countries and between agencies. Anything with safety consequences should be checked against the service responsible for the area you are actually in.
How the warning system is actually organised
National meteorological services observe, model and forecast; they issue watches, warnings and advisories against defined criteria; and local emergency management agencies decide what action to take in response, including evacuations, shelter openings and road closures.
Those are two different organisations with two different jobs, which is why a national forecast office issues a hurricane warning and a county decides who evacuates. Knowing which one to follow for which question saves a great deal of confusion during an event.
What is worth doing before a season starts
Find out which hazards actually affect where you live, check whether your address sits in a flood or surge zone, identify where you would shelter, confirm that emergency alerts are enabled on your phone, and know how you would get information if the power and the network both failed.
None of that takes long, all of it is free, and every element of it becomes considerably harder to arrange once a warning has been issued. Emergency managers say the same thing after every major event: the households that coped were the ones who had decided in advance.
Where the authoritative information is
National meteorological services issue the warnings, publish the forecasts, explain what each product means and archive the underlying data, all freely. Local emergency management agencies publish evacuation zones, shelter locations and preparedness guidance specific to the hazards where you actually live.
Between them those two sources answer almost every question anyone has about weather risk, and both are considerably more reliable than aggregated coverage, which routinely reproduces the misunderstandings that cause harm.
A general note
Warning terminology, alert thresholds and emergency procedures differ between countries and between agencies, and they are revised as understanding improves. Anything with safety consequences should be checked against the service responsible for the area you are in rather than against a general description.