{
 "generated_utc": "2026-09-11T23:26:20Z",
 "gfs_cycle_utc": "2026-09-11T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 439.5,
  "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_20260911_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260911_18Z.geojson.gz"
 },
 "counts": {
  "flights": 15,
  "members": 9,
  "rows": 61776
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 15:35:48",
   "seed_lat": 41.47917,
   "seed_lon": -16.95833,
   "seed_alt_m": 14600.0,
   "seed_age_h": 7.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 17:30:00",
    "lat": 39.60846,
    "lon": 8.90571,
    "alt_m": 13993.0
   },
   "member_spread_deg": {
    "lat": 19.07,
    "lon": 94.63
   },
   "member_spread_now_deg": {
    "lat": 2.81,
    "lon": 2.3
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 04:41:00",
   "seed_lat": 86.0,
   "seed_lon": 110.20833,
   "seed_alt_m": 11660.0,
   "seed_age_h": 162.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-18 17:45:00",
    "lat": 66.56649,
    "lon": -43.49267,
    "alt_m": 11652.9
   },
   "member_spread_deg": {
    "lat": 26.74,
    "lon": 351.8
   },
   "member_spread_now_deg": {
    "lat": 11.13,
    "lon": 189.24
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 19:02:00",
   "seed_lat": 29.3125,
   "seed_lon": -43.54167,
   "seed_alt_m": 13720.0,
   "seed_age_h": 4.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 18:30:00",
    "lat": 40.99008,
    "lon": -30.36122,
    "alt_m": 13553.4
   },
   "member_spread_deg": {
    "lat": 25.44,
    "lon": 94.34
   },
   "member_spread_now_deg": {
    "lat": 0.3,
    "lon": 0.96
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 21:31:00",
   "seed_lat": 51.52083,
   "seed_lon": -83.75,
   "seed_alt_m": 13270.0,
   "seed_age_h": 1.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 21:00:00",
    "lat": 38.19371,
    "lon": 53.00053,
    "alt_m": 13444.2
   },
   "member_spread_deg": {
    "lat": 26.53,
    "lon": 142.19
   },
   "member_spread_now_deg": {
    "lat": 0.09,
    "lon": 1.92
   },
   "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": 277.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-18 17:30:00",
    "lat": 57.79361,
    "lon": -95.65329,
    "alt_m": 11930.8
   },
   "member_spread_deg": {
    "lat": 47.78,
    "lon": 221.73
   },
   "member_spread_now_deg": {
    "lat": 45.95,
    "lon": 320.69
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DO3GU-47",
   "flight_id": "DO3GU-47_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 13:31:52",
   "seed_lat": 46.04167,
   "seed_lon": 61.70833,
   "seed_alt_m": 13960.0,
   "seed_age_h": 153.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-18 17:30:00",
    "lat": 20.28998,
    "lon": -168.90279,
    "alt_m": 14565.7
   },
   "member_spread_deg": {
    "lat": 30.34,
    "lon": 348.32
   },
   "member_spread_now_deg": {
    "lat": 28.6,
    "lon": 236.61
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "I1RFQ",
   "flight_id": "I1RFQ_2026-09-06",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 05:25:00",
   "seed_lat": 48.52083,
   "seed_lon": 159.54167,
   "seed_alt_m": 12130.0,
   "seed_age_h": 41.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-18 17:30:00",
    "lat": 26.89851,
    "lon": -84.30263,
    "alt_m": 12547.3
   },
   "member_spread_deg": {
    "lat": 31.85,
    "lon": 166.6
   },
   "member_spread_now_deg": {
    "lat": 5.95,
    "lon": 37.88
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 207.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 17:30:00",
    "lat": 28.50325,
    "lon": 176.7344,
    "alt_m": 12864.5
   },
   "member_spread_deg": {
    "lat": 23.66,
    "lon": 339.11
   },
   "member_spread_now_deg": {
    "lat": 19.17,
    "lon": 316.32
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 09:35:00",
   "seed_lat": 40.4375,
   "seed_lon": 108.79167,
   "seed_alt_m": 12700.0,
   "seed_age_h": 13.75,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 17:30:00",
    "lat": 47.73553,
    "lon": -82.63615,
    "alt_m": 12729.7
   },
   "member_spread_deg": {
    "lat": 9.3,
    "lon": 151.79
   },
   "member_spread_now_deg": {
    "lat": 0.81,
    "lon": 6.31
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 12:36:00",
   "seed_lat": 55.875,
   "seed_lon": -6.45833,
   "seed_alt_m": 12800.0,
   "seed_age_h": 10.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 17:30:00",
    "lat": 43.42649,
    "lon": 164.81821,
    "alt_m": 12978.2
   },
   "member_spread_deg": {
    "lat": 7.18,
    "lon": 319.16
   },
   "member_spread_now_deg": {
    "lat": 9.37,
    "lon": 1.5
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 22:55:45",
   "seed_lat": 57.43745,
   "seed_lon": 178.08335,
   "seed_alt_m": 13120.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 23:00:00",
    "lat": 65.81087,
    "lon": 75.15039,
    "alt_m": 13308.7
   },
   "member_spread_deg": {
    "lat": 13.67,
    "lon": 57.98
   },
   "member_spread_now_deg": {
    "lat": 0.06,
    "lon": 0.22
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 22:46:00",
   "seed_lat": 22.89583,
   "seed_lon": -143.83333,
   "seed_alt_m": 16440.0,
   "seed_age_h": 0.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 22:15:00",
    "lat": 52.10345,
    "lon": 4.2261,
    "alt_m": 15716.5
   },
   "member_spread_deg": {
    "lat": 41.86,
    "lon": 152.84
   },
   "member_spread_now_deg": {
    "lat": 0.18,
    "lon": 0.5
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 15:46:00",
   "seed_lat": 38.6875,
   "seed_lon": 9.54167,
   "seed_alt_m": 13310.0,
   "seed_age_h": 7.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 17:45:00",
    "lat": 43.5534,
    "lon": -158.0585,
    "alt_m": 13095.7
   },
   "member_spread_deg": {
    "lat": 22.09,
    "lon": 20.95
   },
   "member_spread_now_deg": {
    "lat": 1.03,
    "lon": 2.23
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-08 21:35:23",
   "seed_lat": 52.33328,
   "seed_lon": -95.95831,
   "seed_alt_m": 12860.0,
   "seed_age_h": 73.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 17:30:00",
    "lat": 46.59257,
    "lon": 162.76103,
    "alt_m": 13205.5
   },
   "member_spread_deg": {
    "lat": 24.75,
    "lon": 275.07
   },
   "member_spread_now_deg": {
    "lat": 10.21,
    "lon": 82.01
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-11 10:51:00",
   "seed_lat": -21.66667,
   "seed_lon": 67.0,
   "seed_alt_m": 15600.0,
   "seed_age_h": 12.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-18 17:45:00",
    "lat": -26.26348,
    "lon": -171.91075,
    "alt_m": 15541.7
   },
   "member_spread_deg": {
    "lat": 17.35,
    "lon": 342.57
   },
   "member_spread_now_deg": {
    "lat": 3.3,
    "lon": 13.8
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}