{
 "generated_utc": "2026-09-19T17:26:02Z",
 "gfs_cycle_utc": "2026-09-19T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 422.0,
  "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_20260919_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260919_12Z.geojson.gz"
 },
 "counts": {
  "flights": 13,
  "members": 9,
  "rows": 56448
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 15:23:18",
   "seed_lat": 40.79167,
   "seed_lon": 19.75,
   "seed_alt_m": 14090.0,
   "seed_age_h": 25.95,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 11:30:00",
    "lat": 46.04782,
    "lon": 145.24857,
    "alt_m": 13628.3
   },
   "member_spread_deg": {
    "lat": 17.16,
    "lon": 351.77
   },
   "member_spread_now_deg": {
    "lat": 2.3,
    "lon": 9.12
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 15:11:00",
   "seed_lat": 61.72917,
   "seed_lon": -8.66667,
   "seed_alt_m": 11860.0,
   "seed_age_h": 2.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-26 15:15:00",
    "lat": 53.00691,
    "lon": 20.33639,
    "alt_m": 12178.8
   },
   "member_spread_deg": {
    "lat": 12.65,
    "lon": 9.88
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.27
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 13:02:00",
   "seed_lat": 36.66667,
   "seed_lon": 33.58333,
   "seed_alt_m": 13440.0,
   "seed_age_h": 4.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 12:30:00",
    "lat": 59.06754,
    "lon": 177.31395,
    "alt_m": 12531.8
   },
   "member_spread_deg": {
    "lat": 29.46,
    "lon": 357.11
   },
   "member_spread_now_deg": {
    "lat": 0.81,
    "lon": 0.83
   },
   "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": 57.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 11:30:00",
    "lat": 50.06896,
    "lon": -111.95366,
    "alt_m": 13476.8
   },
   "member_spread_deg": {
    "lat": 39.3,
    "lon": 70.42
   },
   "member_spread_now_deg": {
    "lat": 14.7,
    "lon": 15.21
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 227.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-26 11:30:00",
    "lat": 25.73039,
    "lon": 32.35106,
    "alt_m": 12712.2
   },
   "member_spread_deg": {
    "lat": 28.47,
    "lon": 263.22
   },
   "member_spread_now_deg": {
    "lat": 39.82,
    "lon": 214.79
   },
   "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": 179.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 11:30:00",
    "lat": 46.0644,
    "lon": 111.49489,
    "alt_m": 12544.0
   },
   "member_spread_deg": {
    "lat": 30.25,
    "lon": 271.23
   },
   "member_spread_now_deg": {
    "lat": 24.15,
    "lon": 152.49
   },
   "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": 148.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 11:30:00",
    "lat": 46.12224,
    "lon": 33.25788,
    "alt_m": 12921.8
   },
   "member_spread_deg": {
    "lat": 37.5,
    "lon": 185.62
   },
   "member_spread_now_deg": {
    "lat": 19.18,
    "lon": 42.02
   },
   "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": 72.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 11:30:00",
    "lat": 57.56299,
    "lon": -46.57079,
    "alt_m": 13052.5
   },
   "member_spread_deg": {
    "lat": 23.21,
    "lon": 83.26
   },
   "member_spread_now_deg": {
    "lat": 13.78,
    "lon": 77.64
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 10:46:00",
   "seed_lat": 39.52083,
   "seed_lon": 54.625,
   "seed_alt_m": 13210.0,
   "seed_age_h": 6.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 11:45:00",
    "lat": 29.23493,
    "lon": -168.23562,
    "alt_m": 13298.7
   },
   "member_spread_deg": {
    "lat": 27.59,
    "lon": 352.4
   },
   "member_spread_now_deg": {
    "lat": 1.37,
    "lon": 3.95
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 13:15:00",
   "seed_lat": 61.22917,
   "seed_lon": 21.16667,
   "seed_alt_m": 15200.0,
   "seed_age_h": 4.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 12:45:00",
    "lat": 45.59834,
    "lon": 131.72147,
    "alt_m": 15289.5
   },
   "member_spread_deg": {
    "lat": 5.92,
    "lon": 8.89
   },
   "member_spread_now_deg": {
    "lat": 0.21,
    "lon": 2.07
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 01:41:00",
   "seed_lat": 48.39583,
   "seed_lon": -161.66667,
   "seed_alt_m": 12640.0,
   "seed_age_h": 15.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 11:45:00",
    "lat": 61.49788,
    "lon": 121.07542,
    "alt_m": 12448.8
   },
   "member_spread_deg": {
    "lat": 22.98,
    "lon": 104.64
   },
   "member_spread_now_deg": {
    "lat": 2.46,
    "lon": 7.93
   },
   "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": 259.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 11:30:00",
    "lat": 51.15106,
    "lon": -14.14933,
    "alt_m": 12989.8
   },
   "member_spread_deg": {
    "lat": 33.45,
    "lon": 276.86
   },
   "member_spread_now_deg": {
    "lat": 42.73,
    "lon": 318.63
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 06:26:00",
   "seed_lat": -23.83333,
   "seed_lon": 152.04167,
   "seed_alt_m": 15790.0,
   "seed_age_h": 10.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-26 11:30:00",
    "lat": -27.55431,
    "lon": -144.14702,
    "alt_m": 15570.6
   },
   "member_spread_deg": {
    "lat": 13.95,
    "lon": 338.44
   },
   "member_spread_now_deg": {
    "lat": 3.87,
    "lon": 2.77
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}