{
 "generated_utc": "2026-09-03T23:25:57Z",
 "gfs_cycle_utc": "2026-09-03T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 411.5,
  "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_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260903_18Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 72090
 },
 "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": 151.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 17:45:00",
    "lat": -61.36523,
    "lon": -175.75519,
    "alt_m": 12127.4
   },
   "member_spread_deg": {
    "lat": 22.43,
    "lon": 355.08
   },
   "member_spread_now_deg": {
    "lat": 21.24,
    "lon": 229.97
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 22:57:18",
   "seed_lat": 30.58333,
   "seed_lon": -121.0,
   "seed_alt_m": 14540.0,
   "seed_age_h": 0.38,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:00:00",
    "lat": 37.26978,
    "lon": -15.06545,
    "alt_m": 14694.1
   },
   "member_spread_deg": {
    "lat": 24.39,
    "lon": 109.81
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.16
   },
   "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": 217.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 17:30:00",
    "lat": 16.74507,
    "lon": -84.06656,
    "alt_m": 13197.5
   },
   "member_spread_deg": {
    "lat": 18.8,
    "lon": 114.95
   },
   "member_spread_now_deg": {
    "lat": 21.49,
    "lon": 43.52
   },
   "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": 13.65,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 17:45:00",
    "lat": 64.27697,
    "lon": 116.2366,
    "alt_m": 12126.2
   },
   "member_spread_deg": {
    "lat": 20.67,
    "lon": 336.17
   },
   "member_spread_now_deg": {
    "lat": 2.83,
    "lon": 17.44
   },
   "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": 15.8,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 17:30:00",
    "lat": 37.76982,
    "lon": -47.98326,
    "alt_m": 13242.9
   },
   "member_spread_deg": {
    "lat": 27.09,
    "lon": 102.7
   },
   "member_spread_now_deg": {
    "lat": 4.19,
    "lon": 5.61
   },
   "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": 85.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 17:30:00",
    "lat": 59.66036,
    "lon": 154.18942,
    "alt_m": 11660.0
   },
   "member_spread_deg": {
    "lat": 16.92,
    "lon": 292.28
   },
   "member_spread_now_deg": {
    "lat": 30.35,
    "lon": 92.53
   },
   "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": 249.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 17:45:00",
    "lat": 54.10364,
    "lon": -81.32778,
    "alt_m": 12713.3
   },
   "member_spread_deg": {
    "lat": 30.12,
    "lon": 245.82
   },
   "member_spread_now_deg": {
    "lat": 26.92,
    "lon": 305.92
   },
   "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": 232.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 17:30:00",
    "lat": 48.71112,
    "lon": -167.77655,
    "alt_m": 13775.7
   },
   "member_spread_deg": {
    "lat": 32.04,
    "lon": 331.82
   },
   "member_spread_now_deg": {
    "lat": 27.21,
    "lon": 166.26
   },
   "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": 15.27,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 17:30:00",
    "lat": 9.70538,
    "lon": 136.43784,
    "alt_m": 12848.1
   },
   "member_spread_deg": {
    "lat": 38.77,
    "lon": 294.81
   },
   "member_spread_now_deg": {
    "lat": 2.75,
    "lon": 14.47
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 20:25:00",
   "seed_lat": 27.25,
   "seed_lon": -50.5,
   "seed_alt_m": 13080.0,
   "seed_age_h": 2.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 20:00:00",
    "lat": 37.68312,
    "lon": 46.82131,
    "alt_m": 12737.2
   },
   "member_spread_deg": {
    "lat": 17.02,
    "lon": 123.07
   },
   "member_spread_now_deg": {
    "lat": 0.63,
    "lon": 0.77
   },
   "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": 17.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 17:45:00",
    "lat": 55.07938,
    "lon": -4.28014,
    "alt_m": 12256.9
   },
   "member_spread_deg": {
    "lat": 29.39,
    "lon": 127.1
   },
   "member_spread_now_deg": {
    "lat": 3.43,
    "lon": 7.44
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 18:35:45",
   "seed_lat": 60.10411,
   "seed_lon": -25.83331,
   "seed_alt_m": 12960.0,
   "seed_age_h": 4.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 18:00:00",
    "lat": 46.63335,
    "lon": 116.07314,
    "alt_m": 13449.7
   },
   "member_spread_deg": {
    "lat": 25.26,
    "lon": 85.58
   },
   "member_spread_now_deg": {
    "lat": 0.7,
    "lon": 0.18
   },
   "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": 199.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 17:45:00",
    "lat": 40.6684,
    "lon": -38.27053,
    "alt_m": 13441.9
   },
   "member_spread_deg": {
    "lat": 27.78,
    "lon": 209.5
   },
   "member_spread_now_deg": {
    "lat": 11.6,
    "lon": 57.9
   },
   "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 22:23:00",
   "seed_lat": 39.3125,
   "seed_lon": 179.33333,
   "seed_alt_m": 16040.0,
   "seed_age_h": 0.95,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-10 22:00:00",
    "lat": 48.08952,
    "lon": -154.63273,
    "alt_m": 16043.3
   },
   "member_spread_deg": {
    "lat": 14.51,
    "lon": 82.62
   },
   "member_spread_now_deg": {
    "lat": 0.47,
    "lon": 359.88
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 22:26:00",
   "seed_lat": 45.8125,
   "seed_lon": -141.375,
   "seed_alt_m": 13420.0,
   "seed_age_h": 0.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 22:00:00",
    "lat": 44.72134,
    "lon": 25.53684,
    "alt_m": 13272.0
   },
   "member_spread_deg": {
    "lat": 23.07,
    "lon": 133.43
   },
   "member_spread_now_deg": {
    "lat": 0.19,
    "lon": 0.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 22:55:23",
   "seed_lat": 47.99995,
   "seed_lon": -171.37498,
   "seed_alt_m": 13240.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:00:00",
    "lat": 47.73158,
    "lon": -66.23784,
    "alt_m": 13085.3
   },
   "member_spread_deg": {
    "lat": 48.0,
    "lon": 120.11
   },
   "member_spread_now_deg": {
    "lat": 0.43,
    "lon": 0.08
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 7.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 17:30:00",
    "lat": -16.60915,
    "lon": 34.03328,
    "alt_m": 15623.8
   },
   "member_spread_deg": {
    "lat": 20.93,
    "lon": 27.79
   },
   "member_spread_now_deg": {
    "lat": 2.97,
    "lon": 0.61
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}