{
 "generated_utc": "2026-09-17T23:26:26Z",
 "gfs_cycle_utc": "2026-09-17T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 460.0,
  "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_20260917_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260917_18Z.geojson.gz"
 },
 "counts": {
  "flights": 14,
  "members": 9,
  "rows": 59904
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 15:58:18",
   "seed_lat": 37.4375,
   "seed_lon": 9.0,
   "seed_alt_m": 14120.0,
   "seed_age_h": 7.36,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": 44.1652,
    "lon": 75.11073,
    "alt_m": 13812.7
   },
   "member_spread_deg": {
    "lat": 16.29,
    "lon": 282.7
   },
   "member_spread_now_deg": {
    "lat": 1.93,
    "lon": 0.77
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 18:31:00",
   "seed_lat": 56.47917,
   "seed_lon": -63.58333,
   "seed_alt_m": 11970.0,
   "seed_age_h": 4.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-24 18:00:00",
    "lat": 56.46798,
    "lon": 35.61047,
    "alt_m": 12041.4
   },
   "member_spread_deg": {
    "lat": 17.27,
    "lon": 104.52
   },
   "member_spread_now_deg": {
    "lat": 0.37,
    "lon": 0.82
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 15:52:00",
   "seed_lat": 29.04167,
   "seed_lon": -2.91667,
   "seed_alt_m": 13510.0,
   "seed_age_h": 7.47,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:45:00",
    "lat": 60.51236,
    "lon": -159.79928,
    "alt_m": 13033.0
   },
   "member_spread_deg": {
    "lat": 27.33,
    "lon": 339.14
   },
   "member_spread_now_deg": {
    "lat": 0.6,
    "lon": 2.29
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 08:01:00",
   "seed_lat": 45.77083,
   "seed_lon": 25.5,
   "seed_alt_m": 13600.0,
   "seed_age_h": 15.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": 53.55253,
    "lon": -163.97659,
    "alt_m": 12953.1
   },
   "member_spread_deg": {
    "lat": 28.21,
    "lon": 39.93
   },
   "member_spread_now_deg": {
    "lat": 11.06,
    "lon": 4.16
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 297.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": -5.64886,
    "lon": 134.14199,
    "alt_m": 14611.1
   },
   "member_spread_deg": {
    "lat": 76.58,
    "lon": 286.75
   },
   "member_spread_now_deg": {
    "lat": 58.53,
    "lon": 322.67
   },
   "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": 185.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": 24.93352,
    "lon": -1.15497,
    "alt_m": 12718.6
   },
   "member_spread_deg": {
    "lat": 57.19,
    "lon": 301.45
   },
   "member_spread_now_deg": {
    "lat": 35.72,
    "lon": 191.73
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 06:05:00",
   "seed_lat": 45.47917,
   "seed_lon": 159.375,
   "seed_alt_m": 12660.0,
   "seed_age_h": 137.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": 55.67932,
    "lon": 78.741,
    "alt_m": 12638.8
   },
   "member_spread_deg": {
    "lat": 29.72,
    "lon": 148.27
   },
   "member_spread_now_deg": {
    "lat": 17.48,
    "lon": 69.64
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 13:01:00",
   "seed_lat": 42.0625,
   "seed_lon": 28.04167,
   "seed_alt_m": 12700.0,
   "seed_age_h": 106.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": 42.46576,
    "lon": -33.37064,
    "alt_m": 12771.0
   },
   "member_spread_deg": {
    "lat": 26.74,
    "lon": 179.68
   },
   "member_spread_now_deg": {
    "lat": 9.93,
    "lon": 26.56
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-16 16:35:45",
   "seed_lat": 76.41661,
   "seed_lon": -30.16665,
   "seed_alt_m": 12780.0,
   "seed_age_h": 30.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": 65.50977,
    "lon": -82.40413,
    "alt_m": 12931.4
   },
   "member_spread_deg": {
    "lat": 16.71,
    "lon": 90.99
   },
   "member_spread_now_deg": {
    "lat": 1.57,
    "lon": 10.39
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 12:36:00",
   "seed_lat": 32.77083,
   "seed_lon": 17.25,
   "seed_alt_m": 13360.0,
   "seed_age_h": 10.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": 31.45762,
    "lon": -157.46066,
    "alt_m": 13442.4
   },
   "member_spread_deg": {
    "lat": 32.51,
    "lon": 58.12
   },
   "member_spread_now_deg": {
    "lat": 0.6,
    "lon": 1.09
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 16:16:00",
   "seed_lat": 57.83333,
   "seed_lon": -23.25,
   "seed_alt_m": 15460.0,
   "seed_age_h": 7.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:45:00",
    "lat": 55.89119,
    "lon": 78.54271,
    "alt_m": 15516.8
   },
   "member_spread_deg": {
    "lat": 36.03,
    "lon": 81.03
   },
   "member_spread_now_deg": {
    "lat": 2.35,
    "lon": 6.29
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 22:01:00",
   "seed_lat": 47.52083,
   "seed_lon": 149.625,
   "seed_alt_m": 13150.0,
   "seed_age_h": 1.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 22:00:00",
    "lat": 70.36802,
    "lon": 63.8403,
    "alt_m": 12814.0
   },
   "member_spread_deg": {
    "lat": 32.08,
    "lon": 166.07
   },
   "member_spread_now_deg": {
    "lat": 0.23,
    "lon": 0.51
   },
   "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": 217.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:30:00",
    "lat": 46.61305,
    "lon": -84.59759,
    "alt_m": 13084.1
   },
   "member_spread_deg": {
    "lat": 38.96,
    "lon": 313.9
   },
   "member_spread_now_deg": {
    "lat": 37.59,
    "lon": 253.52
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 08:41:00",
   "seed_lat": -26.77083,
   "seed_lon": 106.04167,
   "seed_alt_m": 15520.0,
   "seed_age_h": 14.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 17:45:00",
    "lat": -15.24985,
    "lon": 174.88513,
    "alt_m": 15699.6
   },
   "member_spread_deg": {
    "lat": 26.97,
    "lon": 327.47
   },
   "member_spread_now_deg": {
    "lat": 7.43,
    "lon": 15.48
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}