How we track the Atlantic hurricane season

What the dashboard shows, where the numbers come from, how current they are, and what they can’t tell you.

The short answer

The Atlantic hurricane season runs from 1 June to 30 November. The dashboard shows how the current season compares with an average year and with the official outlooks, the track of every storm, and how storm energy has varied over 175 years of records. All storm data comes from the US National Hurricane Center (NHC).

How we know

The season under way. While storms are active, NHC posts its operational best tracks: the storm’s position, strongest sustained wind and pressure every six hours. We download them every night. They are preliminary: after the season, NHC’s specialists review every storm with all the data from aircraft, satellites, ships and land stations, and sometimes change a storm’s peak strength or add a storm they missed.

The record since 1851. The reviewed tracks go into HURDAT2, NHC’s archive of every Atlantic storm since 1851, published once a year a few months after the season ends. When HURDAT2 covers a season, it replaces the preliminary tracks on this page. The oldest decades were rebuilt from ship logs, coastal stations and newspapers; before satellites (from the mid-1960s), storms that stayed at sea were often missed, so early seasons look calmer than they were.

Counting storms. A named storm reached at least 39 mph (34 knots) while tropical or subtropical; a hurricane 74 mph (64 knots); a major hurricane 111 mph (96 knots), Category 3 or above on the Saffir-Simpson scale. Winds after a storm has turned into an ordinary (post-tropical) low do not count.

Storm energy. Accumulated cyclone energy (ACE) adds up the square of each storm’s wind every six hours while it is at least a tropical storm. Because the wind is squared, a long-lived major hurricane counts far more than several short, weak storms. NOAA uses ACE to classify seasons: above 126.1 is above normal, below 73.0 below normal.

An average season is the mean of 1991–2020: 14.4 named storms, 7.2 hurricanes, 3.2 major hurricanes and ACE of about 123. Our own calculation from HURDAT2 gives the same values Colorado State University publishes. The headline compares this season with the average season by the same date, because most storm energy comes between mid-August and mid-October.

Outlooks. NOAA’s Climate Prediction Center issues an outlook in May and updates it in August, giving ranges it expects with a 70% chance. Colorado State University issues single-number forecasts from April to August. We read the latest of each from their pages.

How current each part is

• This season’s storms: NHC updates the operational tracks while storms are active; we download them every night.
• Past seasons: HURDAT2 is published once a year, a few months after the season ends; the latest covers seasons through 2025.
• Outlooks: as issued by NOAA and CSU, April to August.

What the dashboard can’t tell you

It is not a warning service. If a storm is approaching, follow the National Hurricane Center, your national weather service and local officials.

The Saffir-Simpson category describes wind only. Storm surge and rain flooding cause most hurricane deaths, and a slow, weak storm can flood a region as badly as a major hurricane. The “closest major hurricanes” list measures distance to a storm’s centre; damaging winds, rain and surge can reach far beyond it, so it is not a risk assessment.

One season says little about climate change. Seasons swing with El Niño, which usually suppresses Atlantic storms, and La Niña, which usually favours them. The IPCC finds that the share of the strongest storms and their rainfall are rising with warming, while long-term trends in the number of storms are uncertain.

Further reading

• NOAA NHC, HURDAT2: the best-track archive used by this dashboard. nhc.noaa.gov/data/hurdat
• Landsea & Franklin (2013), Monthly Weather Review: how uncertain the Atlantic hurricane database is, and the HURDAT2 format. doi.org/10.1175/MWR-D-12-00254.1
• Vecchi et al. (2021), Nature Communications: changes in Atlantic major hurricane frequency since the late 19th century, after correcting for missed storms. doi.org/10.1038/s41467-021-24268-5
• IPCC (2021), Sixth Assessment Report, Working Group I, Summary for Policymakers, statements A.3.4 and B.2.4 on tropical cyclones. ipcc.ch/report/ar6/wg1
• NOAA CPC: how seasons are classified with ACE. cpc.ncep.noaa.gov
• NOAA NHC: the Saffir-Simpson Hurricane Wind Scale. nhc.noaa.gov/aboutsshws.php

Credits

The storm data is the work of the National Hurricane Center’s hurricane specialists, the aircraft crews of NOAA and the US Air Force Reserve, satellite analysts, ship observers and the reanalysis teams who rebuilt the early record. Outlooks are by NOAA’s Climate Prediction Center and the Colorado State University Tropical Weather and Climate Research team. We only download and present their public data.