ERA5-derived South Asian monsoon low-pressure system catalogue, v5.4.2 (1940–2025)

ERA5-derived South Asian monsoon low-pressure-system v5.4.2 recall-first core catalogue containing 2,980 low-pressure systems (including tropical cyclones) and 368,925 hourly track positions. The dataset covers 1940 to the end of 2025 at hourly resolution. 

Tracks can be explored using the online atlas here: https://kieranmrhunt.github.io/monsoon-low-atlas/

Brief methodology

1. A detector identified candidate South Asian low-pressure-system centres from hourly ERA5 vorticity and supporting pressure, wind, precipitation, humidity and temperature fields.
2. The candidate collection was linked through time. Families were stitched and then resolved into distinct physical-event identities. These are identified with track_id.
3. Published centre geometry was projected onto an hourly path satisfying a mamximum speed, minimum smoothness, and criteria.
4. ERA5 variables were then resampled at each centre. Short missing sections were interpolated, subject to length and continuity thresholds.
5. Final tracks must last at least 30 hours, with at least 12 observed positions and 3 positions satisfying the frozen strength criteria. Final intensity was computed from the resampled final centre variables.

Identity and interpretation

track_id identifies one hourly-complete physical event and should be used for grouping, counting, plotting, matching and climatology. event_id and continuity_parent_track_id are identical aliases in v5.4.2.

Unsuffixed physics fields are sampled at the final published hourly centre. Fields ending _detectedcentre use values at the original detector centre and are blank for posterior/interpolated rows. IMD-equivalent category codes range from 0 (unclassified) to 7 (super cyclonic storm). The positions, intensities and category labels are derived from ERA5 and are not official IMD classifications.

Column guide

Event identity

• track_id (int64; identifier) — Hourly-complete strength-qualified physical-event identifier; use for grouping, counts, plotting, matching and climatology.
• continuity_parent_track_id (int64; identifier) — Alias of track_id in v5.4.2; retained for compatibility with earlier development releases.
• continuity_segment_number (int64; count) — Physical-continuity segment number within the pre-segmentation parent track.
• continuity_publication_split_count (int64; count) — Number of publication-continuity splits recorded for the parent track.
• event_id (int64; identifier) — Alias of track_id in v5.4.2.

Time

• time (timestamp[ns]; UTC) — Valid time of the published centre in UTC.
• frame (int64; hours since 1940-01-01 00:00 UTC) — Integer UTC hour index counted from 1940-01-01 00:00 UTC.
• year (int64; count) — UTC calendar year of time.
• month (int64; count) — UTC calendar month number of time (1–12).
• day (int64; count) — UTC day of month of time.
• hour (int64; count) — UTC hour of day of time (0–23).

Published-centre geometry

• lon (double; degrees_east) — Longitude of the final published centre.
• lat (double; degrees_north) — Latitude of the final published centre.
• lon_detected (double; degrees_east) — Longitude of the original observed detector centre; null on posterior/interpolated rows.
• lat_detected (double; degrees_north) — Latitude of the original observed detector centre; null on posterior/interpolated rows.
• lon_smooth (double; degrees_east) — Longitude of the final publication-constrained hourly centre; identical to lon in this release.
• lat_smooth (double; degrees_north) — Latitude of the final publication-constrained hourly centre; identical to lat in this release.
• centre_score (double; 1) — Composite recall-first detector score sampled at the original candidate centre.
• centre_residual_km (double; km) — Distance between an observed detector centre and its final published centre; null for non-observed rows.
• position_source (large_string; category or text) — Whether the published centre is an observed detector fix or a supported posterior/interpolated position.
• position_sigma_km (double; km) — Estimated one-sigma horizontal position uncertainty used by the linker.
• centre_sigma_major_km (double; km) — Major-axis one-sigma centre uncertainty derived from half the object major axis, with the detector floor applied.
• centre_sigma_minor_km (double; km) — Minor-axis one-sigma centre uncertainty derived from half the object minor axis, with the detector floor applied.
• lon_grid_peak (double; degrees_east) — Longitude of the native-grid vorticity maximum underlying the detector object centre.
• lat_grid_peak (double; degrees_north) — Latitude of the native-grid vorticity maximum underlying the detector object centre.
• centre_centroid_lon (double; degrees_east) — Longitude of the vorticity-weighted object centroid used in detector-centre construction.
• centre_centroid_lat (double; degrees_north) — Latitude of the vorticity-weighted object centroid used in detector-centre construction.
• centre_method (large_string; category or text) — Method used to choose the original detector centre; v5.3 uses connected_vorticity_object.
• centre_inside_object (double; 1) — 1 when the constructed detector centre lies inside the connected object; otherwise 0.
• centre_snapped_to_object (double; 1) — 1 when a centre outside the object was moved to its nearest object grid cell; otherwise 0.
• centre_peak_to_centroid_km (double; km) — Distance between the object's vorticity peak and weighted centroid.
• centre_uncertainty_orientation_deg (double; degrees) — Orientation of the detector-centre uncertainty ellipse.
• lon_smooth_global_v54 (double; degrees_east) — Longitude of the globally smoothed centre before final publication-constraint projection.
• lat_smooth_global_v54 (double; degrees_north) — Latitude of the globally smoothed centre before final publication-constraint projection.
• geometry_method (large_string; category or text) — Method used to project the hourly path within publication speed and observed-residual bounds.
• geometry_speed_cap_ms (double; m s^-1) — Maximum hourly translation speed allowed by the publication geometry projection.
• geometry_acceleration_cap_kmh_per_h (double; km h^-1 h^-1) — Optional maximum hourly change in translation speed; null because acceleration was diagnostic-only in this release.
• geometry_maximum_observed_residual_km (double; km) — Maximum allowed distance between a final published centre and its observed detector centre.
• geometry_projection_adjusted (bool; boolean) — 1 when final projection moved this row from its globally smoothed centre; otherwise 0.
• geometry_projection_iterations (int32; count) — Number of constraint-projection iterations used for this event's final geometry.

Track linking and continuity

• association_kind (large_string; category or text) — Linker origin of the row, such as tentative_birth, transition or gap_posterior.
• association_cost (double; 1) — Cost assigned by the linker to the selected observation transition or birth; smaller is preferred.
• association_margin (double; 1) — Cost advantage of the selected link over its best competing assignment; larger means less ambiguity.
• association_probability (double; 1) — Probability-like confidence derived from the association margin.
• association_residual_km (double; km) — Distance between the linked observation and the track prediction used by the association step.
• association_gate_km (double; km) — Maximum association distance allowed for the row by the adaptive linker gate.
• posterior_gap_hours (double; hours) — Length of the candidate-free gap represented by a posterior/interpolated row; zero on observations.
• posterior_fraction (double; 1) — Fraction of this event's published rows that are posterior/interpolated; repeated on every event row.
• track_duration_hours (double; hours) — Inclusive number of hourly positions in the physical event; repeated on every event row.
• track_observed_support_hours (double; hours) — Number of observed detector positions in the event; repeated on every event row.
• track_mature_support_hours (double; hours) — Number of observed positions passing the mature-detection rule; repeated on every event row.
• track_occupancy_fraction (double; 1) — Observed positions divided by inclusive event duration; repeated on every event row.
• track_u_ms (double; m s^-1) — Eastward component of translation velocity along the final published hourly path.
• track_v_ms (double; m s^-1) — Northward component of translation velocity along the final published hourly path.
• lps53_member_tracklets (large_string; category or text) — Semicolon-separated v5.3 linker tracklets contributing observed positions to this event.
• track_n_observations (int64; count) — Number of observed detector positions in the event.
• track_elapsed_span_hours (double; hours) — Elapsed hours between the first and last event positions, excluding the inclusive endpoint.
• track_max_gap_hours (double; hours) — Largest time step between successive observed positions before hourly completion.
• track_max_missing_run_hours (double; hours) — Largest consecutive run of non-observed hourly positions in the event.
• track_start_frame (int64; hours since 1940-01-01 00:00 UTC) — Frame value at the first position of the event.
• track_end_frame (int64; hours since 1940-01-01 00:00 UTC) — Frame value at the last position of the event.
• track_member_tracklets (large_string; category or text) — Linker tracklet membership retained from the stitched-track workflow.
• track_stitch_count (int64; count) — Number of tracklet-to-tracklet stitches contributing to the linked event.
• track_duplicate_component_size (int64; count) — Number of linked tracks in the duplicate-resolution component containing this event.
• association_tracklet_id (double; identifier) — Linker tracklet identifier associated with this observed row.
• track_speed_ms (double; m s^-1) — Magnitude of the event translation vector along the final published path.

Candidate-detector diagnostics

• candidate_quality (double; 1) — Detector candidate-quality score combining centre score, pressure deficit, smoothed vorticity and heat-low penalty.
• heat_low_score (double; 1) — Heat-low likeness score from location, dryness, precipitation, vertical vorticity and lower-tropospheric warmth; larger is more heat-low-like.
• candidate_id (double; identifier) — Detector candidate identifier within its source processing block; null on non-observed rows.
• steering_u_ms (double; m s^-1) — Eastward component of the blended 850/700/500-hPa environmental-steering vector.
• steering_v_ms (double; m s^-1) — Northward component of the blended 850/700/500-hPa environmental-steering vector.
• candidate_uid (large_string; identifier) — Stable identifier of the original detector candidate; null on non-observed rows.
• object_id_frame (double; hours since 1940-01-01 00:00 UTC) — Identifier of the connected-vorticity subobject within this detector time frame.
• steering_is_missing (double; 1) — 1 when no valid multi-level environmental-steering vector could be calculated; otherwise 0.
• steering_spread_ms (double; m s^-1) — Weighted root-mean-square spread of valid environmental-steering vectors across levels.
• reject_reason (large_string; category or text) — Detector or linker rejection reason retained for audit; normally empty in the published core.
• candidate_rank_frame (double; hours since 1940-01-01 00:00 UTC) — Rank of this candidate's object score within the UTC detector frame; 1 is highest.
• candidate_tile (large_string; identifier) — Spatial detector-tile identifier used by the optional diversity safety cap.
• candidate_tile_rank (double; count) — Rank of this candidate within candidate_tile by object score.
• candidate_count_pre_domain (double; count) — Number of raw detector objects before the South Asian candidate-domain filter.
• candidate_count_pre_cap (double; count) — Number of candidates after domain filtering and before emergency safety caps.
• candidate_count_post_cap (double; count) — Number of candidates retained after emergency safety caps.
• object_n_gridcells (double; count) — Number of native ERA5 grid cells in the connected-vorticity subobject.
• object_area_km2 (double; km^2) — Area of the connected-vorticity subobject using latitude-dependent grid-cell areas.
• object_equivalent_radius_km (double; km) — Radius of a circle with area object_area_km2.
• object_peak_vort_band (double; 10^-5 s^-1) — Maximum band-limited dynamical vorticity inside the object.
• object_mean_vort_band (double; 10^-5 s^-1) — Area-weighted mean band-limited dynamical vorticity inside the object.
• object_integrated_vort_km2 (double; 10^-5 s^-1 km^2) — Area integral of band-limited vorticity above the object threshold.
• object_score_max (double; 1) — Maximum composite detector score inside the object.
• object_threshold_vort_band (double; 10^-5 s^-1) — Band-limited vorticity floor used to define the connected object.
• object_peak_count (double; count) — Number of separated vorticity peaks retained within the parent connected object.
• object_peak_number (double; count) — One-based number of this subobject's peak within the parent connected object.
• object_eccentricity (double; 1) — Eccentricity of the weighted object ellipse (0 circular; values nearer 1 more elongated).
• object_major_axis_km (double; km) — Major-axis length of the vorticity-weighted object ellipse.
• object_minor_axis_km (double; km) — Minor-axis length of the vorticity-weighted object ellipse.
• object_orientation_deg (double; degrees) — Orientation of the vorticity-weighted object major axis.
• object_centroid_lon (double; degrees_east) — Longitude of the vorticity-weighted connected-object centroid.
• object_centroid_lat (double; degrees_north) — Latitude of the vorticity-weighted connected-object centroid.
• object_peak_lon (double; degrees_east) — Parabolically refined longitude of the subobject vorticity peak.
• object_peak_lat (double; degrees_north) — Parabolically refined latitude of the subobject vorticity peak.
• object_bbox_lon_min (double; degrees_east) — Western edge of the object's native-grid bounding box.
• object_bbox_lon_max (double; degrees_east) — Eastern edge of the object's native-grid bounding box.
• object_bbox_lat_min (double; degrees_north) — Southern edge of the object's native-grid bounding box.
• object_bbox_lat_max (double; degrees_north) — Northern edge of the object's native-grid bounding box.
• score_component_vort_centre (double; 1) — Vorticity contribution to the composite detector score at the original candidate centre.
• score_component_low_centre (double; 1) — Pressure-low contribution to the composite detector score at the original candidate centre.
• score_component_deep_centre (double; 1) — Deep-layer vorticity contribution to the composite detector score at the original candidate centre.
• score_component_moist_centre (double; 1) — Moisture contribution to the composite detector score at the original candidate centre.
• score_component_precip_centre (double; 1) — Precipitation contribution to the composite detector score at the original candidate centre.
• score_low_valid (double; 1) — 1 when the pressure-low detector-score component was based on valid data; otherwise 0.
• score_deep_valid (double; 1) — 1 when the deep-layer vorticity detector-score component was based on valid data; otherwise 0.
• score_moist_valid (double; 1) — 1 when the moisture detector-score component was based on valid data; otherwise 0.
• score_precip_valid (double; 1) — 1 when the precipitation detector-score component was based on valid data; otherwise 0.
• score_available_weight_fraction (double; 1) — Fraction of configured composite-score weight supported by valid input fields.
• score_optional_weight_renormalisation (double; 1) — Factor applied to renormalise available optional detector-score components.
• steering_valid_levels (double; count) — Number of pressure levels (850, 700 and 500 hPa) contributing to the blended steering vector.
• steering_valid_points (double; count) — Total valid annulus grid points contributing across all steering levels.
• steering_annulus_inner_km (double; km) — Inner radius of the environmental-steering sampling annulus.
• steering_annulus_outer_km (double; km) — Outer radius of the environmental-steering sampling annulus.
• steering_u_850_ms (double; m s^-1) — Eastward component of the robust environmental-steering vector at 850 hPa.
• steering_v_850_ms (double; m s^-1) — Northward component of the robust environmental-steering vector at 850 hPa.
• steering_spread_850_ms (double; m s^-1) — Root-mean-square vector spread of valid environmental-steering samples at 850 hPa.
• steering_n_850 (double; count) — Number of valid annulus grid points contributing to the 850-hPa steering vector.
• steering_u_700_ms (double; m s^-1) — Eastward component of the robust environmental-steering vector at 700 hPa.
• steering_v_700_ms (double; m s^-1) — Northward component of the robust environmental-steering vector at 700 hPa.
• steering_spread_700_ms (double; m s^-1) — Root-mean-square vector spread of valid environmental-steering samples at 700 hPa.
• steering_n_700 (double; count) — Number of valid annulus grid points contributing to the 700-hPa steering vector.
• steering_u_500_ms (double; m s^-1) — Eastward component of the robust environmental-steering vector at 500 hPa.
• steering_v_500_ms (double; m s^-1) — Northward component of the robust environmental-steering vector at 500 hPa.
• steering_spread_500_ms (double; m s^-1) — Root-mean-square vector spread of valid environmental-steering samples at 500 hPa.
• steering_n_500 (double; count) — Number of valid annulus grid points contributing to the 500-hPa steering vector.
• heat_low_feature_fraction (double; 1) — Fraction of non-location heat-low features available rather than filled with neutral evidence.
• passes_mature_physics (double; 1) — 1 when the original candidate passed the frozen mature detector-score, vorticity and pressure-deficit thresholds; otherwise 0.
• passes_legacy_emit_gate (double; 1) — 1 when the candidate would have passed the deprecated detector-stage emission gate; retained only for audit.
• retention_reason (large_string; category or text) — Reason the recall-first detector retained this candidate.
• candidate_quality_missing_components (double; count) — Number of missing inputs among the four candidate-quality components.
• candidate_diagnostics_available (bool; boolean) — True where full original-candidate diagnostics exist for this row.
• candidate_diagnostics_source (large_string; category or text) — Provenance tag explaining why candidate diagnostics are present or absent.
• steering_speed_ms (double; m s^-1) — Magnitude of the blended environmental-steering vector.

ERA5 physics at the published centre

• max_vort_smoothed (double; 10^-5 s^-1) — Maximum spatially smoothed core relative vorticity inside the dynamical sampling radius sampled at the final published centre.
• mean_vort_500 (double; 10^-5 s^-1) — Mean 500-hPa relative vorticity inside the dynamical sampling radius sampled at the final published centre.
• precip_24hr (double; mm) — Area-mean trailing 24-hour ERA5 precipitation inside the precipitation sampling radius sampled at the final published centre.
• max_wind (double; m s^-1) — Maximum ERA5 10-m wind speed inside the wind sampling radius sampled at the final published centre.
• pressure_deficit_hpa (double; hPa) — Environmental-annulus MSLP 60th percentile minus the local MSLP minimum, floored at zero sampled at the final published centre.
• max_vort (double; 10^-5 s^-1) — Maximum core relative vorticity inside the dynamical sampling radius sampled at the final published centre.
• mean_vort (double; 10^-5 s^-1) — Mean core relative vorticity inside the dynamical sampling radius sampled at the final published centre.
• mean_vort_850 (double; 10^-5 s^-1) — Mean 850-hPa relative vorticity inside the dynamical sampling radius sampled at the final published centre.
• mean_vort_700 (double; 10^-5 s^-1) — Mean 700-hPa relative vorticity inside the dynamical sampling radius sampled at the final published centre.
• precip_1hr (double; mm) — Area-mean ERA5 precipitation during the valid hour inside the precipitation sampling radius sampled at the final published centre.
• mean_wind (double; m s^-1) — Mean ERA5 10-m wind speed inside the wind sampling radius sampled at the final published centre.
• min_mslp (double; hPa) — Minimum mean-sea-level pressure inside the inner pressure radius sampled at the final published centre.
• ring_mslp_p60 (double; hPa) — 60th percentile of mean-sea-level pressure in the environmental annulus sampled at the final published centre.
• q850_mean_gkg (double; g kg^-1) — Mean 850-hPa specific humidity inside the dynamical sampling radius sampled at the final published centre.
• rh850_mean_pct (double; %) — Mean 850-hPa relative humidity inside the dynamical sampling radius sampled at the final published centre.
• t850_mean_k (double; K) — Mean 850-hPa air temperature inside the dynamical sampling radius sampled at the final published centre.
• t850_inner_minus_annulus_k (double; K) — Mean inner-region 850-hPa temperature minus the environmental-annulus mean sampled at the final published centre.
• q700_mean_gkg (double; g kg^-1) — Mean 700-hPa specific humidity inside the dynamical sampling radius sampled at the final published centre.
• rh700_mean_pct (double; %) — Mean 700-hPa relative humidity inside the dynamical sampling radius sampled at the final published centre.
• t700_mean_k (double; K) — Mean 700-hPa air temperature inside the dynamical sampling radius sampled at the final published centre.
• t700_inner_minus_annulus_k (double; K) — Mean inner-region 700-hPa temperature minus the environmental-annulus mean sampled at the final published centre.
• q500_mean_gkg (double; g kg^-1) — Mean 500-hPa specific humidity inside the dynamical sampling radius sampled at the final published centre.
• rh500_mean_pct (double; %) — Mean 500-hPa relative humidity inside the dynamical sampling radius sampled at the final published centre.
• t500_mean_k (double; K) — Mean 500-hPa air temperature inside the dynamical sampling radius sampled at the final published centre.
• t500_inner_minus_annulus_k (double; K) — Mean inner-region 500-hPa temperature minus the environmental-annulus mean sampled at the final published centre.
• precip_24hr_valid_hours (double; hours) — Number of valid hourly precipitation inputs contributing to precip_24hr sampled at the final published centre.
• precip_history_complete (double; 1) — 1 when the full precipitation history required by the detector was available; otherwise 0.
• precip_used_in_score (double; 1) — 1 when precipitation contributed to the detector score; otherwise 0.
• surface_pressure_available (double; 1) — 1 when ERA5 surface pressure was directly available to the detector; otherwise 0.
• surface_pressure_estimate_available (double; 1) — 1 when a standard-atmosphere surface-pressure estimate was available; otherwise 0.
• estimated_pressure_used_for_level_validity (double; 1) — 1 when estimated surface pressure was used to decide pressure-level validity; otherwise 0.
• orography_used_for_mslp_score (double; 1) — 1 when the detector used orography to gate the MSLP score; otherwise 0.
• pressure_level_validity_source (large_string; category or text) — Method used to determine whether 850, 700 and 500 hPa fields were above ground and valid.
• orography_available (double; 1) — 1 when the detector had an orography value at the candidate centre; otherwise 0.
• land_fraction_available (double; 1) — 1 when the detector had a land-fraction value at the candidate centre; otherwise 0.
• surface_pressure_hpa (double; hPa) — ERA5 surface pressure at the original detector centre.
• surface_pressure_estimate_hpa (double; hPa) — Surface pressure estimated from MSLP and orography at the original detector centre.
• orography_m (double; m) — Surface elevation sampled at the final published centre.
• land_fraction (double; 1) — ERA5 land fraction, from 0 (water) to 1 (land) sampled at the final published centre.
• mean_vort_deep (double; 10^-5 s^-1) — Mean of published-centre relative vorticity at 850, 700 and 500 hPa.
• t850_minus_t500_k (double; K) — Published-centre 850-hPa temperature minus 500-hPa temperature.
• t700_minus_t500_k (double; K) — Published-centre 700-hPa temperature minus 500-hPa temperature.
• vort500_to_850_ratio (double; 1) — Published-centre mean 500-hPa vorticity divided by mean 850-hPa vorticity.
• vort_peak_lon (double; degrees_east) — Longitude of the local smoothed-vorticity maximum sampled at the final published centre.
• vort_peak_lat (double; degrees_north) — Latitude of the local smoothed-vorticity maximum sampled at the final published centre.
• vort_peak_distance_km (double; km) — Great-circle distance from the sampled centre to the local smoothed-vorticity maximum sampled at the final published centre.
• mslp_min_lon (double; degrees_east) — Longitude of the local mean-sea-level-pressure minimum sampled at the final published centre.
• mslp_min_lat (double; degrees_north) — Latitude of the local mean-sea-level-pressure minimum sampled at the final published centre.
• mslp_min_distance_km (double; hPa) — Great-circle distance from the sampled centre to the local MSLP minimum sampled at the final published centre.
• vort_mslp_extrema_separation_km (double; hPa) — Great-circle distance between the local vorticity maximum and MSLP minimum sampled at the final published centre.

ERA5 physics at the original detected centre

• max_vort_detectedcentre (double; 10^-5 s^-1) — Maximum core relative vorticity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• mean_vort_detectedcentre (double; 10^-5 s^-1) — Mean core relative vorticity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• max_vort_smoothed_detectedcentre (double; 10^-5 s^-1) — Maximum spatially smoothed core relative vorticity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• mean_vort_850_detectedcentre (double; 10^-5 s^-1) — Mean 850-hPa relative vorticity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• mean_vort_700_detectedcentre (double; 10^-5 s^-1) — Mean 700-hPa relative vorticity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• mean_vort_500_detectedcentre (double; 10^-5 s^-1) — Mean 500-hPa relative vorticity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• precip_1hr_detectedcentre (double; mm) — Area-mean ERA5 precipitation during the valid hour inside the precipitation sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• precip_24hr_detectedcentre (double; mm) — Area-mean trailing 24-hour ERA5 precipitation inside the precipitation sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• max_wind_detectedcentre (double; m s^-1) — Maximum ERA5 10-m wind speed inside the wind sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• mean_wind_detectedcentre (double; m s^-1) — Mean ERA5 10-m wind speed inside the wind sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• min_mslp_detectedcentre (double; hPa) — Minimum mean-sea-level pressure inside the inner pressure radius sampled at the original detected centre; retained for comparison with the published-centre value.
• ring_mslp_p60_detectedcentre (double; hPa) — 60th percentile of mean-sea-level pressure in the environmental annulus sampled at the original detected centre; retained for comparison with the published-centre value.
• pressure_deficit_hpa_detectedcentre (double; hPa) — Environmental-annulus MSLP 60th percentile minus the local MSLP minimum, floored at zero sampled at the original detected centre; retained for comparison with the published-centre value.
• closed_isobars_2hpa_local_detectedcentre (double; count) — Integer pressure-depth proxy equal to floor(pressure deficit / 2 hPa) sampled at the original detected centre; retained for comparison with the published-centre value.
• orography_m_detectedcentre (double; m) — Surface elevation sampled at the original detected centre; retained for comparison with the published-centre value.
• land_fraction_detectedcentre (double; 1) — ERA5 land fraction, from 0 (water) to 1 (land) sampled at the original detected centre; retained for comparison with the published-centre value.
• q850_mean_gkg_detectedcentre (double; g kg^-1) — Mean 850-hPa specific humidity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• rh850_mean_pct_detectedcentre (double; %) — Mean 850-hPa relative humidity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• t850_mean_k_detectedcentre (double; K) — Mean 850-hPa air temperature inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• t850_inner_minus_annulus_k_detectedcentre (double; K) — Mean inner-region 850-hPa temperature minus the environmental-annulus mean sampled at the original detected centre; retained for comparison with the published-centre value.
• q700_mean_gkg_detectedcentre (double; g kg^-1) — Mean 700-hPa specific humidity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• rh700_mean_pct_detectedcentre (double; %) — Mean 700-hPa relative humidity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• t700_mean_k_detectedcentre (double; K) — Mean 700-hPa air temperature inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• t700_inner_minus_annulus_k_detectedcentre (double; K) — Mean inner-region 700-hPa temperature minus the environmental-annulus mean sampled at the original detected centre; retained for comparison with the published-centre value.
• q500_mean_gkg_detectedcentre (double; g kg^-1) — Mean 500-hPa specific humidity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• rh500_mean_pct_detectedcentre (double; %) — Mean 500-hPa relative humidity inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• t500_mean_k_detectedcentre (double; K) — Mean 500-hPa air temperature inside the dynamical sampling radius sampled at the original detected centre; retained for comparison with the published-centre value.
• t500_inner_minus_annulus_k_detectedcentre (double; K) — Mean inner-region 500-hPa temperature minus the environmental-annulus mean sampled at the original detected centre; retained for comparison with the published-centre value.
• precip_24hr_valid_hours_detectedcentre (double; hours) — Number of valid hourly precipitation inputs contributing to precip_24hr sampled at the original detected centre; retained for comparison with the published-centre value.
• imd_category_raw_detectedcentre (double; category code) — Instantaneous ERA5-derived IMD-equivalent numeric intensity code before persistence filtering sampled at the original detected centre; retained for comparison with the published-centre value.
• imd_label_raw_detectedcentre (large_string; category or text) — Text label for imd_category_raw sampled at the original detected centre; retained for comparison with the published-centre value.

Physical support for completed gaps

• pre_physics_gap_track_id (int64; identifier) — Physical-segment identifier before unsupported physics gaps were removed and identities renumbered.
• physics_gap_segment_number (int32; count) — Zero-based supported physical segment number within pre_physics_gap_track_id.
• physics_gap_block_id (large_string; identifier) — Identifier of the candidate-free gap block containing this row; null on observed rows.
• physics_gap_supported (bool; boolean) — Whether the gap block satisfies the frozen physical-support contract.
• physics_gap_support_fraction (double; 1) — Fraction of hours in the gap block supported by nearby final-centre ERA5 extrema.
• physics_gap_required_support_fraction (double; 1) — Minimum supported-hour fraction required for a gap block of this duration.
• physics_gap_maximum_unsupported_run_hours (int16; hours) — Longest consecutive unsupported run found inside the gap block.
• physics_gap_maximum_allowed_unsupported_run_hours (double; hours) — Longest consecutive unsupported run permitted by the frozen gap contract.
• physics_gap_endpoint_path_speed_ms (double; m s^-1) — Maximum endpoint-interpolated translation speed used to assess a short gap.
• physics_gap_support_method (large_string; category or text) — Versioned name of the frozen gap-support decision method.
• physics_gap_support_basis (large_string; category or text) — Decision basis, such as observed, short_endpoint_interpolation or reanalysis_extremum.
• physics_gap_extremum_proximity_required (bool; boolean) — Whether the gap contract required a nearby vorticity or pressure extremum.
• physics_gap_minimum_vorticity (double; 10^-5 s^-1) — Minimum smoothed-vorticity threshold for extremum support.
• physics_gap_minimum_pressure_deficit_hpa (double; hPa) — Minimum pressure-deficit threshold for pressure-extremum support.
• physics_gap_maximum_vorticity_distance_km (double; km) — Maximum distance from the published centre to a supporting vorticity extremum.
• physics_gap_maximum_pressure_distance_km (double; km) — Maximum distance from the published centre to a supporting MSLP minimum.
• physics_gap_maximum_short_endpoint_speed_ms (double; m s^-1) — Maximum endpoint-interpolated speed allowed for automatic short-gap support.

Provenance, intensity and quality control

• life_stage (large_string; category or text) — Categorical life-cycle stage assigned to this hourly position.
• imd_category_pre_final_physics (double; category code) — ERA5-derived IMD-equivalent numeric intensity before final-centre physics was resampled; retained for audit.
• imd_label_pre_final_physics (large_string; category or text) — Text label for imd_category_pre_final_physics.
• imd_category_raw (double; category code) — Instantaneous ERA5-derived IMD-equivalent numeric intensity code before persistence filtering sampled at the final published centre.
• is_mature_detection (double; 1) — 1 when the original candidate passed mature physics and was not heat-low-like; otherwise 0.
• is_heat_low_like (double; 1) — 1 when heat_low_score reaches the frozen heat-low threshold; otherwise 0.
• is_seed_detection (double; 1) — 1 when the original candidate was retained as a permissive seed rather than a mature detection; otherwise 0.
• parent_object_id_frame (double; hours since 1940-01-01 00:00 UTC) — Identifier of the parent connected-vorticity object before multi-peak partitioning.
• source_file (large_string; identifier) — Source monthly candidate-cache file from which the observed row originated.
• source_row (double; count) — Zero-based row number in source_file used for provenance and joins.
• row_id (double; identifier) — Stable workflow row identifier used to join final-centre recomputation results back to the track table.
• genesis_frame (int64; hours since 1940-01-01 00:00 UTC) — Frame value at the first published position of the event.
• parallel_block_year (int64; calendar year) — Year block used by the parallel linking workflow.
• parallel_local_track_id (int64; identifier) — Track identifier local to parallel_block_year before global identity reconciliation.
• subgrid_dx_gridpoints (double; native grid cells) — Parabolic subgrid longitudinal offset from lon_grid_peak, in native grid cells.
• subgrid_dy_gridpoints (double; native grid cells) — Parabolic subgrid latitudinal offset from lat_grid_peak, in native grid cells.
• near_sri_lanka (double; 1) — 1 when the original candidate centre lies inside the detector's Sri Lanka audit box; otherwise 0.
• closed_isobars_2hpa_local (double; count) — Integer pressure-depth proxy equal to floor(pressure deficit / 2 hPa) sampled at the final published centre.
• imd_label_raw (large_string; category or text) — Text label for imd_category_raw sampled at the final published centre.
• detector_version (double; version) — Version string of the candidate detector that produced the observation.
• legacy_max_candidates_per_time (double; count) — Deprecated global per-time candidate cap recorded for audit; deliberately not used by v5.3.
• hard_candidate_safety_cap (double; count) — Emergency maximum candidate count permitted per frame after spatial-diversity selection.
• legacy_emit_reasons (large_string; category or text) — Semicolon-separated reasons for failing the deprecated emission gate, or pass.
• aux_fields_available (double; 1) — 1 when at least one auxiliary wind, moisture, humidity or temperature input was available; otherwise 0.
• valid_850_at_centre (double; 1) — 1 when 850-hPa input fields were directly valid at the detector centre; otherwise 0.
• valid_700_at_centre (double; 1) — 1 when 700-hPa input fields were directly valid at the detector centre; otherwise 0.
• valid_500_at_centre (double; 1) — 1 when 500-hPa input fields were directly valid at the detector centre; otherwise 0.
• estimated_valid_850_at_centre (double; 1) — Audit estimate of 850-hPa field validity from surface pressure.
• estimated_valid_700_at_centre (double; 1) — Audit estimate of 700-hPa field validity from surface pressure.
• estimated_valid_500_at_centre (double; 1) — Audit estimate of 500-hPa field validity from surface pressure.
• rh_deep_mean_pct (double; %) — Mean of published-centre relative humidity at 850, 700 and 500 hPa.
• q_deep_mean_gkg (double; g kg^-1) — Mean of published-centre specific humidity at 850, 700 and 500 hPa.
• t_inner_minus_annulus_deep_k (double; K) — Mean inner-minus-environment temperature contrast across 850, 700 and 500 hPa.
• physics_fields_finite_count (double; count) — Number of required ERA5 physics diagnostics that are finite sampled at the final published centre.
• physics_required_field_count (double; count) — Number of ERA5 physics diagnostics required by the completeness test sampled at the final published centre.
• physics_complete (bool; boolean) — True when every required ERA5 physics diagnostic is finite sampled at the final published centre.
• physics_source (large_string; category or text) — Provenance tag for the sampled ERA5 physics diagnostics sampled at the final published centre.
• imd_category (double; category code) — Final persistent ERA5-derived IMD-equivalent numeric intensity code; not an official IMD classification.
• imd_label (large_string; category or text) — Text label for imd_category.

Licence and source-data note

The catalogue files are released under CC BY 4.0. ERA5 source data remain subject to the Copernicus/ECMWF terms that apply to ERA5.