How to Read a National Hurricane Center Forecast

During an active storm, your feed fills with maps. Most of them are screenshots of a single model run, stripped of context, reposted hours after they were superseded. Learning to read the official product directly takes about fifteen minutes and it is the difference between informed decisions and rumor-driven ones.

The source

The National Hurricane Center at nhc.noaa.gov is the authoritative source for Atlantic and eastern Pacific tropical systems. Your local National Weather Service office translates that into local impacts. Your county emergency management office issues evacuation orders. Those three sources cover everything you need.

Advisories: the update cycle

For an active system, the NHC issues a full advisory package every six hours (5 AM, 11 AM, 5 PM, 11 PM ET), with intermediate advisories every three hours when watches or warnings are in effect, and special advisories any time conditions change significantly.

Each package contains:

• Public Advisory — plain-language summary, current position, wind speed, movement, and hazards. Read this one.
• Forecast Advisory — technical coordinates and wind radii.
• Forecast Discussion — the forecaster explaining their reasoning, including where they are uncertain. This is the most valuable product for anyone who wants to understand what is actually going on, and it is written in readable prose.
• Wind Speed Probabilities — chance of specific wind thresholds at specific locations.

Always check the advisory number and timestamp on any image you see. A cone from advisory 14 circulating during advisory 22 is misinformation, even if it was accurate when it was made.

The cone of uncertainty

The cone shows the probable track of the storm's center, based on historical forecast error. The center stays within the cone roughly two-thirds of the time — which means one time in three, it does not.

Three things the cone does not show:

• The size of the storm. The cone's width is a measure of forecast error, not of the hurricane. Damaging winds and surge routinely extend far outside it.
• Intensity. The cone is drawn the same whether the storm is a tropical storm or a Category 5.
• Where impacts will occur. Being outside the cone is not safety. Rainfall and surge affect areas hundreds of miles from the center, especially to the right of the track.

The useful mental model: if you are anywhere near the cone, prepare as if you are in it.

Watches and warnings

• Tropical Storm Watch: sustained winds of 39-73 mph possible within 48 hours.
• Tropical Storm Warning: those winds expected within 36 hours.
• Hurricane Watch: sustained winds of 74 mph or greater possible within 48 hours. Begin final preparations.
• Hurricane Warning: hurricane conditions expected within 36 hours. Preparations should be complete; if you are evacuating, you may already be too late.
• Storm Surge Watch/Warning: issued separately because surge is a distinct hazard. A surge warning means life-threatening inundation is expected within 36 hours. This is the product that should drive evacuation decisions.

Note the asymmetry: watch means possible, warning means expected, and the lead times are shorter than most people assume. A hurricane warning is not the moment to start preparing.

Storm surge maps

The NHC's potential storm surge flooding map shows a reasonable worst case for inundation above ground level. It is color-coded by depth. If your address appears in a shaded area and an evacuation order is issued, leave — this is the map the order is based on.

Spaghetti models

Those tangles of colored lines are individual computer model tracks. They are useful for seeing the spread of possibilities, and dangerous when misread.

• Not all models are equal. The global models (often abbreviated GFS and ECMWF) and a handful of hurricane-specific models have far better track records than the many statistical and older dynamical models plotted alongside them.
• A single outlier line is not a forecast. People routinely panic over one model run showing a track nobody else supports.
• Model output changes every run. Human forecasters at the NHC blend models with observations and experience, which is why the official forecast usually outperforms any individual model.

Use spaghetti plots to gauge uncertainty — tightly clustered lines mean confidence, widely spread lines mean the forecast may shift substantially. Then act on the official forecast.

Rapid intensification

Defined as a 35 mph increase in sustained winds within 24 hours. It is difficult to forecast and has become more frequent. Practically, this means preparing for the higher end of the forecast intensity range, especially for storms crossing very warm water with low wind shear near landfall.

Terms worth knowing

• Sustained winds: a one-minute average at 33 feet above the surface. Gusts are higher, typically by 20-30%.
• Eyewall: the ring of intense thunderstorms around the eye, where the strongest winds occur.
• Right-front quadrant: relative to the storm's direction of motion, the area with the worst winds and surge, because the forward speed adds to the rotational wind.
• Wind shear: change in wind with height. High shear tears storms apart; low shear lets them strengthen.
• Extratropical transition: a storm losing tropical characteristics. It can still produce damaging wind and enormous rainfall — it is not a downgrade in the risk sense.

Getting alerts reliably

Enable Wireless Emergency Alerts on every phone. Keep a battery or hand-crank NOAA weather radio, which works when cell networks saturate or fail. Follow your county emergency management office directly — they issue the evacuation orders. And keep a paper copy of key phone numbers, because a dead phone should not cut you off entirely.

Track active systems on our hurricane dashboard, and check your readiness with the free checklist.