National Hurricane Center products — a plain-language guide

NHC publishes a dozen+ different products for each active storm. Some are written for the public; others are written for meteorologists. Here's what each one is, when it's issued, and how to read it.

Public Advisory (TCP)

The main product for the general public. Plain-language summary of where the storm is, where it's going, and what to expect.

Issued: Every 6 hours (5 AM, 11 AM, 5 PM, 11 PM EDT). Every 3 hours when watches or warnings are in effect.

What's in it: Current position and intensity, movement, forecast track, watches/warnings, expected storm surge and rainfall, time of next advisory.

Forecast Discussion (TCD)

The meteorologist's reasoning. If the Public Advisory is the "what," the Discussion is the "why." Written by the forecaster on duty in technical but readable language.

Issued: Alongside each Public Advisory.

What's in it: Discussion of model agreement/disagreement, key uncertainties, why the forecast track and intensity were chosen, comparisons to similar past storms.

Forecast/Advisory (TCM)

The technical advisory. Same forecast as the public advisory but in a structured, machine-readable format.

Issued: Alongside the Public Advisory.

What's in it: Latitude/longitude positions, wind radii (34/50/64 kt) for every forecast hour, intensity forecast, sea condition warnings. This is the product that downstream tools (including ours) parse to render forecast cones and wind field plots.

Tropical Cyclone Update

Mid-cycle bulletins. Short updates issued between regular advisories when conditions change rapidly or new significant information is available.

Issued: As needed.

What's in it: Updated position, new watches/warnings, rapid intensification, eyewall replacement cycles, landfall confirmation.

Wind Speed Probabilities

Quantitative likelihood of wind speeds at specific locations. If you've ever wondered "what's the chance my city sees 39 mph or 58 mph or 74 mph winds?", this product answers that.

Issued: Every 6 hours with the Public Advisory.

What's in it: For 100+ named locations, the percentage probability of experiencing TS-force (39+), 50-kt (58+), and hurricane-force (74+) winds within each forecast time frame.

Graphics products

NHC publishes a suite of imagery products that go beyond the text bulletins:

• 5-day cone of uncertainty — the iconic forecast track graphic with the spreading "cone" of where the center could go.
• Wind probability maps — color-coded probability of wind impact across the region.
• Storm surge maps — forecast inundation depth above ground level.
• Earliest reasonable arrival time — when tropical-storm-force winds could first reach a location.

Tropical Weather Outlook (TWO)

For systems that aren't storms yet. The TWO covers areas of disturbed weather NHC is monitoring and gives a development probability over the next 48 hours and 7 days.

Issued: 4 times daily during hurricane season (2 AM, 8 AM, 2 PM, 8 PM EDT).

What's in it: Plain-language description of each tropical disturbance, location, environmental conditions, and the chance of development. Disturbances that get a number (90-99) are called "invests" and are being formally monitored.