{
 "generated_utc": "2026-09-03T17:25:58Z",
 "gfs_cycle_utc": "2026-09-03T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 405.5,
  "output_interval_min": 30,
  "integration_step_s": 900,
  "wind_field_interval_h": 3
 },
 "staleness": {
  "fresh_seed_max_h": 24.0,
  "served_until_h": 336.0,
  "track_max_age_h": 72.0,
  "region_spread_deg": 60.0,
  "note": "A trajectory is served for 336 h after the last real fix and then the flight disappears. That matches the archive's own bridging limit: 23% of flights go quiet for over a week and are then heard again, so a shorter window drops balloons that are still flying. Past dead_reckoned flights the balloon has not been heard from since seed_time, so its present position is a prediction too -- the silent period is reconstructed from GFS analyses of weather that has already happened, which is why wind_source distinguishes analysis from forecast. Use display_as, not seed_age_h, to decide how to draw a flight: 'track' means the members still agree and a line is meaningful, 'region' means draw the member envelope instead because the nominal member is no better than any other."
 },
 "members": {
  "offsets_m": [
   -2000,
   -1500,
   -1000,
   -500,
   0,
   500,
   1000,
   1500,
   2000
  ],
  "nominal_offset_m": 0,
  "note": "Each member is seeded at the last observed altitude plus its offset and then conserves the density it started with. The ladder is a sensitivity fan, not a probability distribution: adjacent members diverge by roughly 1,200 km over seven days. levels_spanned reports how many GFS levels the fan actually straddles, usually 2 or 3."
 },
 "files": {
  "trajectories_csv_gz": "PBA_forecast_20260903_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260903_12Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 71595
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 16:13:40",
   "seed_lat": -64.54167,
   "seed_lon": -17.12499,
   "seed_alt_m": 11900.0,
   "seed_age_h": 145.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 11:45:00",
    "lat": -72.23398,
    "lon": 149.09976,
    "alt_m": 12345.5
   },
   "member_spread_deg": {
    "lat": 25.74,
    "lon": 323.83
   },
   "member_spread_now_deg": {
    "lat": 22.19,
    "lon": 237.91
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 00:05:48",
   "seed_lat": 32.64583,
   "seed_lon": -134.625,
   "seed_alt_m": 14550.0,
   "seed_age_h": 17.24,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:30:00",
    "lat": 32.83622,
    "lon": -24.51362,
    "alt_m": 14543.9
   },
   "member_spread_deg": {
    "lat": 26.08,
    "lon": 173.15
   },
   "member_spread_now_deg": {
    "lat": 1.09,
    "lon": 4.88
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-25 21:29:00",
   "seed_lat": 33.10417,
   "seed_lon": -84.75,
   "seed_alt_m": 13050.0,
   "seed_age_h": 211.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:30:00",
    "lat": -0.44874,
    "lon": -89.13738,
    "alt_m": 13157.1
   },
   "member_spread_deg": {
    "lat": 32.21,
    "lon": 111.15
   },
   "member_spread_now_deg": {
    "lat": 19.79,
    "lon": 42.36
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 09:41:00",
   "seed_lat": 81.97917,
   "seed_lon": 46.75,
   "seed_alt_m": 11960.0,
   "seed_age_h": 7.65,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 11:45:00",
    "lat": 79.10145,
    "lon": 143.45133,
    "alt_m": 11725.0
   },
   "member_spread_deg": {
    "lat": 18.93,
    "lon": 195.84
   },
   "member_spread_now_deg": {
    "lat": 0.94,
    "lon": 13.07
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 07:32:00",
   "seed_lat": 49.60417,
   "seed_lon": 103.20833,
   "seed_alt_m": 13010.0,
   "seed_age_h": 9.8,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:30:00",
    "lat": 31.32064,
    "lon": -58.25561,
    "alt_m": 13520.5
   },
   "member_spread_deg": {
    "lat": 23.2,
    "lon": 65.67
   },
   "member_spread_now_deg": {
    "lat": 4.13,
    "lon": 2.55
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:53:00",
   "seed_lat": 62.54167,
   "seed_lon": 91.41667,
   "seed_alt_m": 11930.0,
   "seed_age_h": 79.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 11:30:00",
    "lat": 58.43315,
    "lon": 148.72641,
    "alt_m": 11667.4
   },
   "member_spread_deg": {
    "lat": 22.49,
    "lon": 316.25
   },
   "member_spread_now_deg": {
    "lat": 29.84,
    "lon": 92.97
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-24 14:13:00",
   "seed_lat": 65.52083,
   "seed_lon": 37.33333,
   "seed_alt_m": 12490.0,
   "seed_age_h": 243.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:45:00",
    "lat": 43.21507,
    "lon": -51.0662,
    "alt_m": 12768.8
   },
   "member_spread_deg": {
    "lat": 19.11,
    "lon": 263.68
   },
   "member_spread_now_deg": {
    "lat": 29.76,
    "lon": 308.66
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-25 06:33:48",
   "seed_lat": 61.6875,
   "seed_lon": -165.70833,
   "seed_alt_m": 13200.0,
   "seed_age_h": 226.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:30:00",
    "lat": 52.02786,
    "lon": -162.78108,
    "alt_m": 13951.5
   },
   "member_spread_deg": {
    "lat": 29.24,
    "lon": 296.37
   },
   "member_spread_now_deg": {
    "lat": 23.01,
    "lon": 168.98
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 08:04:00",
   "seed_lat": 37.27083,
   "seed_lon": 133.375,
   "seed_alt_m": 12750.0,
   "seed_age_h": 9.27,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:30:00",
    "lat": 36.41537,
    "lon": 157.16682,
    "alt_m": 12910.8
   },
   "member_spread_deg": {
    "lat": 12.34,
    "lon": 316.27
   },
   "member_spread_now_deg": {
    "lat": 3.9,
    "lon": 9.31
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 14:10:00",
   "seed_lat": 27.39583,
   "seed_lon": -53.625,
   "seed_alt_m": 13120.0,
   "seed_age_h": 3.17,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 13:45:00",
    "lat": 36.12234,
    "lon": 44.74714,
    "alt_m": 12877.3
   },
   "member_spread_deg": {
    "lat": 21.65,
    "lon": 100.27
   },
   "member_spread_now_deg": {
    "lat": 0.32,
    "lon": 0.89
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 05:46:00",
   "seed_lat": 56.66667,
   "seed_lon": 150.91667,
   "seed_alt_m": 12260.0,
   "seed_age_h": 11.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 11:45:00",
    "lat": 58.28552,
    "lon": -26.74469,
    "alt_m": 12002.9
   },
   "member_spread_deg": {
    "lat": 17.51,
    "lon": 120.42
   },
   "member_spread_now_deg": {
    "lat": 3.18,
    "lon": 2.35
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 16:55:45",
   "seed_lat": 60.06245,
   "seed_lon": -26.99998,
   "seed_alt_m": 12900.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 17:00:00",
    "lat": 47.82849,
    "lon": 118.29516,
    "alt_m": 13303.4
   },
   "member_spread_deg": {
    "lat": 10.97,
    "lon": 71.47
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.01
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KJ4AWK-1",
   "flight_id": "KJ4AWK-1_2026-08-22",
   "payload_type": "APRS",
   "seed_time": "2026-08-26 15:51:36",
   "seed_lat": 41.62025,
   "seed_lon": 25.112,
   "seed_alt_m": 13223.0,
   "seed_age_h": 193.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:45:00",
    "lat": 27.10034,
    "lon": -7.04433,
    "alt_m": 13344.8
   },
   "member_spread_deg": {
    "lat": 38.42,
    "lon": 209.3
   },
   "member_spread_now_deg": {
    "lat": 13.39,
    "lon": 52.67
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 05:23:00",
   "seed_lat": 40.45833,
   "seed_lon": 159.66667,
   "seed_alt_m": 16100.0,
   "seed_age_h": 11.95,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-10 11:30:00",
    "lat": 15.58454,
    "lon": 148.94117,
    "alt_m": 16568.3
   },
   "member_spread_deg": {
    "lat": 34.39,
    "lon": 343.63
   },
   "member_spread_now_deg": {
    "lat": 1.83,
    "lon": 11.74
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 02:51:00",
   "seed_lat": 51.125,
   "seed_lon": -157.875,
   "seed_alt_m": 13550.0,
   "seed_age_h": 14.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:45:00",
    "lat": 32.44495,
    "lon": 8.07726,
    "alt_m": 13492.4
   },
   "member_spread_deg": {
    "lat": 24.61,
    "lon": 152.69
   },
   "member_spread_now_deg": {
    "lat": 5.11,
    "lon": 5.2
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 05:05:23",
   "seed_lat": 44.39578,
   "seed_lon": 161.87502,
   "seed_alt_m": 13300.0,
   "seed_age_h": 12.24,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 11:30:00",
    "lat": 25.13055,
    "lon": -67.16497,
    "alt_m": 14059.3
   },
   "member_spread_deg": {
    "lat": 37.19,
    "lon": 116.79
   },
   "member_spread_now_deg": {
    "lat": 1.12,
    "lon": 358.76
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 16:01:00",
   "seed_lat": -25.04167,
   "seed_lon": -15.625,
   "seed_alt_m": 15540.0,
   "seed_age_h": 1.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 15:30:00",
    "lat": -18.31423,
    "lon": 27.63843,
    "alt_m": 15627.5
   },
   "member_spread_deg": {
    "lat": 30.51,
    "lon": 27.18
   },
   "member_spread_now_deg": {
    "lat": 0.46,
    "lon": 0.2
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}