Storm CompareTropical cyclone comparator

Display data settings

Choose units, scales and the wind averaging-period conversion factors. Every change is saved automatically and applies to all comparison tabs.

Saved in this browser

Language

Choose the interface language. Your choice is saved in a browser cookie and applied on your next visits.

The page will reload to apply the new language. Your settings and selected storms are kept.

Measurement units

Source data: wind (kt), movement speed (kt or km/h), pressure (hPa), wind radii (nmile). Distance to land (DIST2LAND, LANDFALL) is originally in km; the page converts each field correctly.

Wind & pressure value source

Each IBTrACS point may hold data from several agencies. Choose how to pick one representative value for comparison.

Agency priority order

    Filter data points

    IBTrACS adds interpolated 3-hourly points, spur tracks, and provisional (PROVISIONAL) data that has not been post-analysed.

    System nature (NATURE)

    Only points of the selected types are shown. At least one type must be selected.

    Location, basin & storm name

    IBTrACS stores LAT/LON as decimals (longitude −180…180), 2-letter basin codes (BASIN, SUBBASIN) and upper-case storm names.

    In the Southern Hemisphere, IBTrACS SEASON runs from July of the previous year to June of the following year. Unnamed storms (NOT_NAMED) are shown as "Unnamed".

    Time & movement direction

    IBTrACS stores time in UTC (one point every 3 hours) and movement direction in degrees (0–360°).

    Intensity scale

    Beaufort uses the 10-minute mean wind; Saffir–Simpson uses the 1-minute mean wind.

    Wind averaging period

    Convert between 10-minute, 3-minute, 2-minute and 1-minute mean winds.

    Averaging period by forecasting agency (IBTrACS)
    AgencyCodeNative wind type

    Each data point is converted according to the agency that measured it, so comparing storms from several agencies stays fair.

    Conversion factor mode
    ConversionMultiplier (vs. 10-minute)
    1-min wind = 10-min wind ×
    3-min wind = 10-min wind ×
    2-min wind = 10-min wind ×
    iDefault factors follow the WMO / Harper et al. (2010) recommendation: 1-min wind ≈ 1.12 × 10-min wind at storm intensity. Ranges are determined by the value converted to 10 minutes. 1-min ↔ 2-min factors are derived via the 10-min reference.

    Wind radii, gusts & indices

    Each agency stores wind radii differently in IBTrACS. Gusts come from USA_GUST, BOM_GUST, REUNION_GUST.

    • USA (JTWC/NHC) · Réunion · BOMR34 · R50 · R64

      4 quadrants, 1-min wind (Réunion & BOM: 10-min)

      USA_R34_NE / SE / SW / NW
    • Tokyo (JMA)R30 · R50

      Major axis / minor axis + major axis direction, 10-min wind

      TOKYO_R30_LONG / SHORT / DIR
    • KMA (South Korea)R30 · R50

      Major axis / minor axis + major axis direction, 10-min wind

      KMA_R30_LONG / SHORT / DIR

    JMA/KMA R30 (10-min wind ≥ 30 kt) roughly equals JTWC R34 (1-min wind ≥ 34 kt) since 30 / 0.88 ≈ 34. But JMA/KMA R50 corresponds to about 57 kt 1-min wind, so it is usually smaller than JTWC R50. A value of 0 means no area reaches the threshold.

    ACE = sum of (wind in kt)² × 10⁻⁴ at 00/06/12/18 UTC points with wind ≥ 35 kt, ignoring extratropical (ET) and disturbance (DS) stages.

    Manage settings

    Settings are kept in localStorage and cookies, so they persist after the browser is closed.

    Guide & About

    Storm Compare · Tropical cyclone comparison tool

    1Introduction

    Storm Compare lets you place side by side the track, wind strength, pressure, ACE, movement speed and wind radii of many storms, based on IBTrACS data from meteorological agencies (JTWC, NHC, JMA, KMA, BOM, Réunion...).

    • 4working tabs
    • 10comparison modes
    • 12storms maximum
    • 1950data start year

    Fair comparison

    Converts units and wind averaging time according to the agency that measured them, so storms from many agencies can still be compared.

    Deep customization

    Choose data sources, agency priority order, point density, time zone, coordinate format, intensity scale and conversion factors.

    Visual on the map

    Tracks colored by level, wind radii, storm race animation over time and track overlay by origin.

    Share with one link

    The link contains settings, selected storms, comparison type, points, track segments and drawn areas. Whoever opens it sees exactly the same result.

    2Quick start

    1. Set units

      Open the tab Settings, choose the units for wind, pressure, distance and the intensity scale. You can skip this step if you use the defaults.

    2. Choose storms

      Open the tab Choose storms: choose the year, choose the ocean basin, and tick the storms to compare (maximum 12).

    3. View on map

      Click View on map to go to the tab Display, choose a comparison mode and work directly on the tracks if the mode requires it.

    4. Read the results and share

      Click View comparison to go to the tab Compare see the detailed table, then use the button Share to send the link.

    3Settings tab

    All changes are saved automatically in the browser and apply to every tab. The Live preview box on the right shows the conversion result as you adjust.

    Measurement units
    Wind strength (kt, km/h, m/s, mph), movement speed (km/h, kt, mph), pressure (hPa, mb, kPa, Pa, mmHg, inHg, atm), length and wind radii (nmile, km, mile). Distance to land is originally in km and is converted correctly.
    Source of wind and pressure values
    Each point may contain data from several agencies (WMO, USA, Tokyo, KMA...). Choose how to take one representative value, set the agency priority order and turn on automatic fallback to the next agency when the main source is missing.
    Filter data points
    Choose the point density (IBTrACS has extra 3-hour interpolated points), track type, whether to include provisional data (PROVISIONAL), and the system nature to display (at least one type must be selected).
    Position, basin, storm name
    Coordinate format, precision, longitude range, how the basin is displayed, storm name, name letter case and how the storm season is computed (Southern Hemisphere from July to June).
    Time and direction of movement
    Displayed time zone, time format, date format and how the movement direction is shown.
    Intensity scale
    Beaufort (10-min mean wind) or Saffir–Simpson (1-min mean wind).
    Wind averaging period
    Switch between 10, 3, 2 and 1-minute wind. The default factors follow the WMO recommendation (Harper et al., 2010): 1-min wind is roughly 1.12 times 10-min wind. Each point is converted according to the agency that measured it; you can set factors by value range and sync with the intensity scale.
    Wind radii and gusts
    Choose the radius thresholds (R34, R50, R64 of USA, Réunion, BOM; R30, R50 of JMA and KMA), the providing agency, the display style and whether to show gusts. Gusts only change units, with no time conversion.
    ACE index
    Choose the source for computing ACE. The formula is in the Glossary section.
    Missing values, number format
    Choose how cells with missing data are displayed and the number format style.
    Manage settings
    Export or import settings as JSON, or reset everything to defaults. Settings live in localStorage and cookies, so they persist after you close the browser.

    4Select storms tab

    1. Choose year

      Use the arrows or the year list. In the Southern Hemisphere, the year is the storm season (July of the previous year to June of the following year).

    2. Choose ocean

      The number next to each basin is the number of storms in that year.

    3. Choose storms

      Tick to add to the list. Search by name or SID, change the search scope and sort order. Selected storms are kept when you change year, ocean or keyword.

    Selected storms

    Up to 12 storms, each with its own color shared by charts and the map. You can remove them one by one or Deselect all. The button Compare and View on map quickly switch to the corresponding tab.

    Displayed weather agencies

    Choose the data source (position, wind, pressure, wind radii) to draw the tracks. Choose several agencies (maximum 4) to compare tracks between agencies. Only agencies with data are available.

    5Display tab

    Track map of the selected storms and the place to work in the comparison modes.

    • Comparison mode: click Choose mode to change among the 10 modes. The instructions for the current mode appear right below.
    • Map and display layers: change the map background, turn layers on or off in Display options.
    • Legend: levels by scale, the color of each agency and wind radii (click a point on the track to see).
    • Play bar: drag the slider or click Play, choose the time sync point and play speed.
    • Displayed tracks: the list of tracks being drawn, with counts.

    6Compare tab

    Display Detailed comparison table according to the mode you chose. All figures use the units, scales and averaging time set in the Settings tab.

    • Click the mode name button at the top of the table to change mode without going back to the Display tab.
    • The point, segment, lifecycle and area modes show detailed results: first point, last point, strongest point, weakest point and the metrics for each storm or each agency.
    • Compare by wind category: separate statistics for each selected level, including distance, time, maximum wind, minimum pressure, and the number of times a level is reached or returned to. Applies to the range being compared.
    • The overlay, landfall and between-agency modes have extra charts and tables.

    710 comparison modes

    1

    Compare whole track

    Entire track

    Default mode, no map interaction needed. Compares overall metrics for the whole storm lifetime: maximum wind, minimum pressure, ACE, movement speed, wind radii.

    2

    Custom point comparison

    Click 1 point per track

    Click a point on each storm track (each agency is handled separately). There are quick-select buttons: strongest wind, lowest pressure, largest wind radius. Turn on time sync so agencies of the same storm pick the same time. Multi-point mode lets you click several points, click again to remove, and name each point.

    3

    Track segment comparison

    Click 2 points per track

    Click 2 points; the segment between them is highlighted in red; click a third time to choose again. You can auto-match the length so later tracks need only 1 point. Multi-segment mode lets you create several overlapping segments, each with its own color and name.

    4

    Lifecycle stage comparison

    Formation to dissipation

    Each track is split into 5 stages, colored right on the map. Adjust the “is a storm” threshold (1-min wind) and the margin considered “peak intensity”, then choose the stages to view in detail.

    5

    Area comparison

    Draw an area or upload GeoJSON

    Click the map to place vertices, click the first point again, double-click or press Enter to close the area. You can also upload a GeoJSON/JSON file, save the area to JSON and enable remembering the area in the browser.

    6

    Storm race over time

    Synchronize by time reference

    Use the play bar under the map: each storm appears at its position at the same time since the sync point, with the track traveled so far. Adjust the sync point and play speed.

    7

    Overlay tracks by origin

    Same coordinate origin, compare headings

    Shifts all tracks to a common origin (first point, the time it became a storm, or peak intensity) to compare shape and heading like a fan. Includes distance circles, time range and a tortuosity index.

    8

    Landfall and weakening

    Compare each time it moves inland

    Separates each time a storm moves inland using DIST2LAND, comparing intensity at landfall, time over land and weakening after 6, 12, 24 and 48 hours. The over-land segment is colored orange.

    9

    Comparison between agencies

    Deviation from the reference agency

    Choose a storm and a reference agency. The white dashed line on the map connects the reference agency position with the other agencies every 24 hours, showing the deviation between agencies.

    10

    Impact at a location

    Point + Open-Meteo data

    Choose a location to see Open-Meteo reanalysis observations there, compared with the time the storm passed.

    8Glossary

    IBTrACS
    International best track dataset that gathers storm data from many meteorological agencies, since 1950.
    SID
    Unique identifier of each storm in IBTrACS, used to find it exactly.
    Best track
    Track and intensity adjusted by the agency after the storm season. Recent storms may be provisional data (PROVISIONAL).
    ACE
    Accumulated cyclone energy: sum of (wind kt)² × 10⁻⁴ at 00/06/12/18 UTC points with wind of at least 35 kt, excluding extratropical (ET) and disturbance (DS) stages.
    R34 / R50 / R64
    Wind radii for 34, 50, 64 kt across 4 quadrants. JMA and KMA use R30/R50 along the major and minor axes.
    Wind averaging period
    Mean wind over 1, 2, 3 or 10 minutes. Each agency uses a different standard, so conversion is needed before comparing.
    DIST2LAND / LANDFALL
    Distance from the storm center to land (km). A value of 0 means the center is over land.
    TRACK_TYPE / NATURE
    Track type (main, spur branch) and nature of the system (tropical, extratropical, disturbance...).

    9Sharing & storage

    Share button

    Each section (Settings, Selected storms, Comparison type, Everything) has a Copy button and quick-share buttons for Facebook, Zalo, X and Telegram. The link Comparison type includes the points, track segments, drawn areas and display style as well.

    When opening a link

    The configuration is applied and saved in the recipient browser, and the page opens on the right tab automatically. The link can be very long if you draw many areas; in that case use Copy.

    Saved in the browser

    Settings, selected storms and comparison options are saved automatically. You can export settings and areas to a JSON file to reuse on another machine.

    Reset

    In the Settings tab, the section Manage settings has the button Reset everything. Each comparison mode also has its own button to reset points, segments or areas.

    10Quick actions

    • EnterClose the area being drawn in Area comparison mode
    • EscCancel drawing an area, close a dialog or menu
    • BackspaceDelete the last vertex while drawing an area
    • Double-clickClose the area at the point just clicked
    • Third clickChoose the track segment again from the start
    • Click the point againDeselect a point in multi-point mode

    11Frequently asked questions

    What is tropical cyclone comparison?

    It means placing the metrics of several storms side by side, such as wind speed, pressure, movement speed, ACE and wind radii, to see which storm was stronger, travelled farther or intensified faster.

    What comparison types are there?

    There are five types: the whole track, at a chosen point, a track segment between points A and B, by life-cycle stage, and by an area drawn on the map or loaded from GeoJSON.

    Can I change measurement units?

    Yes. Wind can be kt, km/h, m/s or mph; pressure hPa, mb, kPa, mmHg, inHg or atm; distance nmile, km or mile. You can also choose the wind averaging-period conversion factors.

    How do I share a comparison?

    Click the Share button at the top of the page to copy a link for the settings, the selected storms, the comparison type, or everything.

    Why are some agencies greyed out and unselectable?

    Only agencies with data for the selected storms are available. If an agency chip reports a data-loading error, select the storm again to retry.

    Why is my wind number different from the agency’s number?

    The page converts wind to the averaging time and units you set in the Settings tab. Check the conversion factors and the wind value source in use.