{
 "generated_utc": "2026-09-02T23:25:46Z",
 "gfs_cycle_utc": "2026-09-02T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 387.5,
  "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_20260902_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260902_18Z.geojson.gz"
 },
 "counts": {
  "flights": 16,
  "members": 9,
  "rows": 66366
 },
 "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": 127.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 17:45:00",
    "lat": -50.12061,
    "lon": 179.61665,
    "alt_m": 12156.3
   },
   "member_spread_deg": {
    "lat": 26.23,
    "lon": 356.3
   },
   "member_spread_now_deg": {
    "lat": 7.4,
    "lon": 346.8
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 22:39:48",
   "seed_lat": 33.25,
   "seed_lon": -135.41667,
   "seed_alt_m": 14520.0,
   "seed_age_h": 0.67,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 22:45:00",
    "lat": 33.9919,
    "lon": -13.6181,
    "alt_m": 14564.2
   },
   "member_spread_deg": {
    "lat": 15.12,
    "lon": 108.06
   },
   "member_spread_now_deg": {
    "lat": 0.09,
    "lon": 0.12
   },
   "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": 193.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 17:30:00",
    "lat": 29.56397,
    "lon": -103.94971,
    "alt_m": 13195.1
   },
   "member_spread_deg": {
    "lat": 29.12,
    "lon": 81.35
   },
   "member_spread_now_deg": {
    "lat": 14.73,
    "lon": 36.3
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 15:26:00",
   "seed_lat": 77.3125,
   "seed_lon": 23.41667,
   "seed_alt_m": 11990.0,
   "seed_age_h": 7.9,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 17:30:00",
    "lat": 72.95409,
    "lon": 51.05675,
    "alt_m": 11947.5
   },
   "member_spread_deg": {
    "lat": 25.07,
    "lon": 195.84
   },
   "member_spread_now_deg": {
    "lat": 1.67,
    "lon": 11.77
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 07:37:00",
   "seed_lat": 46.54167,
   "seed_lon": 66.41667,
   "seed_alt_m": 13020.0,
   "seed_age_h": 15.72,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 17:30:00",
    "lat": 50.78933,
    "lon": -107.31696,
    "alt_m": 13054.6
   },
   "member_spread_deg": {
    "lat": 21.99,
    "lon": 52.97
   },
   "member_spread_now_deg": {
    "lat": 0.49,
    "lon": 4.09
   },
   "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": 61.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 17:30:00",
    "lat": 63.13647,
    "lon": -41.62501,
    "alt_m": 11674.5
   },
   "member_spread_deg": {
    "lat": 20.14,
    "lon": 339.26
   },
   "member_spread_now_deg": {
    "lat": 25.75,
    "lon": 92.63
   },
   "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": 225.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 17:45:00",
    "lat": 59.47776,
    "lon": -87.97002,
    "alt_m": 12674.2
   },
   "member_spread_deg": {
    "lat": 18.42,
    "lon": 316.02
   },
   "member_spread_now_deg": {
    "lat": 31.37,
    "lon": 286.3
   },
   "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": 208.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 17:30:00",
    "lat": 37.86459,
    "lon": -173.50081,
    "alt_m": 13868.2
   },
   "member_spread_deg": {
    "lat": 45.23,
    "lon": 309.81
   },
   "member_spread_now_deg": {
    "lat": 17.01,
    "lon": 191.6
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 07:19:00",
   "seed_lat": 32.375,
   "seed_lon": 112.58333,
   "seed_alt_m": 12680.0,
   "seed_age_h": 16.02,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 17:45:00",
    "lat": 33.45042,
    "lon": 142.76688,
    "alt_m": 12883.8
   },
   "member_spread_deg": {
    "lat": 51.56,
    "lon": 281.61
   },
   "member_spread_now_deg": {
    "lat": 5.17,
    "lon": 12.1
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 21:50:00",
   "seed_lat": 26.54167,
   "seed_lon": -59.625,
   "seed_alt_m": 13060.0,
   "seed_age_h": 1.5,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 21:15:00",
    "lat": 37.37296,
    "lon": 39.34103,
    "alt_m": 12755.6
   },
   "member_spread_deg": {
    "lat": 20.14,
    "lon": 98.09
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.04
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 04:26:00",
   "seed_lat": 66.25,
   "seed_lon": 146.66667,
   "seed_alt_m": 12460.0,
   "seed_age_h": 18.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 17:30:00",
    "lat": 59.15816,
    "lon": -46.47831,
    "alt_m": 11847.3
   },
   "member_spread_deg": {
    "lat": 18.09,
    "lon": 128.87
   },
   "member_spread_now_deg": {
    "lat": 7.48,
    "lon": 6.69
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 19:20:45",
   "seed_lat": 61.74995,
   "seed_lon": -37.41665,
   "seed_alt_m": 13030.0,
   "seed_age_h": 3.99,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 18:45:00",
    "lat": 47.08469,
    "lon": 54.52076,
    "alt_m": 13324.3
   },
   "member_spread_deg": {
    "lat": 15.23,
    "lon": 57.53
   },
   "member_spread_now_deg": {
    "lat": 0.47,
    "lon": 0.26
   },
   "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": 175.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 17:45:00",
    "lat": 42.90253,
    "lon": 19.28482,
    "alt_m": 13232.7
   },
   "member_spread_deg": {
    "lat": 31.93,
    "lon": 73.99
   },
   "member_spread_now_deg": {
    "lat": 13.11,
    "lon": 58.94
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 22:18:00",
   "seed_lat": 41.97917,
   "seed_lon": 151.45833,
   "seed_alt_m": 16000.0,
   "seed_age_h": 1.03,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-09 21:45:00",
    "lat": 34.79938,
    "lon": -172.1502,
    "alt_m": 16162.1
   },
   "member_spread_deg": {
    "lat": 16.65,
    "lon": 93.62
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.87
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 21:11:00",
   "seed_lat": 48.72917,
   "seed_lon": -161.66667,
   "seed_alt_m": 13620.0,
   "seed_age_h": 2.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 20:45:00",
    "lat": 52.8279,
    "lon": 24.32522,
    "alt_m": 13360.6
   },
   "member_spread_deg": {
    "lat": 31.83,
    "lon": 154.95
   },
   "member_spread_now_deg": {
    "lat": 0.66,
    "lon": 0.89
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 17:41:00",
   "seed_lat": -22.60417,
   "seed_lon": -26.08333,
   "seed_alt_m": 15680.0,
   "seed_age_h": 5.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-09 17:45:00",
    "lat": -25.90056,
    "lon": 29.58726,
    "alt_m": 15687.4
   },
   "member_spread_deg": {
    "lat": 23.82,
    "lon": 17.15
   },
   "member_spread_now_deg": {
    "lat": 0.49,
    "lon": 0.8
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}