{
 "generated_utc": "2026-09-19T23:26:06Z",
 "gfs_cycle_utc": "2026-09-19T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 428.0,
  "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_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260919_18Z.geojson.gz"
 },
 "counts": {
  "flights": 13,
  "members": 9,
  "rows": 55935
 },
 "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": 31.95,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 17:30:00",
    "lat": 45.66319,
    "lon": 152.35641,
    "alt_m": 13728.8
   },
   "member_spread_deg": {
    "lat": 14.99,
    "lon": 339.98
   },
   "member_spread_now_deg": {
    "lat": 2.24,
    "lon": 11.3
   },
   "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": 8.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-26 17:45:00",
    "lat": 50.90066,
    "lon": 19.73287,
    "alt_m": 12298.7
   },
   "member_spread_deg": {
    "lat": 8.96,
    "lon": 4.87
   },
   "member_spread_now_deg": {
    "lat": 0.37,
    "lon": 1.18
   },
   "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": 10.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 17:30:00",
    "lat": 51.34531,
    "lon": 172.55374,
    "alt_m": 12699.4
   },
   "member_spread_deg": {
    "lat": 13.0,
    "lon": 349.38
   },
   "member_spread_now_deg": {
    "lat": 1.78,
    "lon": 2.61
   },
   "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": 63.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 17:30:00",
    "lat": 66.93476,
    "lon": -158.69195,
    "alt_m": 12862.2
   },
   "member_spread_deg": {
    "lat": 39.63,
    "lon": 354.35
   },
   "member_spread_now_deg": {
    "lat": 16.0,
    "lon": 16.98
   },
   "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": 233.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-26 17:30:00",
    "lat": 20.56928,
    "lon": 36.25579,
    "alt_m": 12715.9
   },
   "member_spread_deg": {
    "lat": 53.94,
    "lon": 274.0
   },
   "member_spread_now_deg": {
    "lat": 38.77,
    "lon": 218.37
   },
   "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": 185.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 17:30:00",
    "lat": 45.40549,
    "lon": 83.94356,
    "alt_m": 12369.0
   },
   "member_spread_deg": {
    "lat": 34.36,
    "lon": 252.14
   },
   "member_spread_now_deg": {
    "lat": 23.91,
    "lon": 159.46
   },
   "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": 154.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 17:30:00",
    "lat": 43.21135,
    "lon": 42.06827,
    "alt_m": 12938.4
   },
   "member_spread_deg": {
    "lat": 35.9,
    "lon": 168.77
   },
   "member_spread_now_deg": {
    "lat": 21.55,
    "lon": 40.08
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 22:55:45",
   "seed_lat": 73.83328,
   "seed_lon": 162.29169,
   "seed_alt_m": 12870.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 23:00:00",
    "lat": 51.37675,
    "lon": -31.70139,
    "alt_m": 12972.5
   },
   "member_spread_deg": {
    "lat": 25.66,
    "lon": 63.71
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.53
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 12.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 17:45:00",
    "lat": 25.24467,
    "lon": -179.71663,
    "alt_m": 13269.8
   },
   "member_spread_deg": {
    "lat": 27.19,
    "lon": 358.7
   },
   "member_spread_now_deg": {
    "lat": 2.96,
    "lon": 5.6
   },
   "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": 10.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 17:45:00",
    "lat": 46.90252,
    "lon": 135.29445,
    "alt_m": 15239.6
   },
   "member_spread_deg": {
    "lat": 4.39,
    "lon": 21.18
   },
   "member_spread_now_deg": {
    "lat": 0.8,
    "lon": 5.86
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-19 22:51:00",
   "seed_lat": 57.10417,
   "seed_lon": -127.375,
   "seed_alt_m": 12870.0,
   "seed_age_h": 0.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 22:15:00",
    "lat": 49.94945,
    "lon": 133.62092,
    "alt_m": 12669.1
   },
   "member_spread_deg": {
    "lat": 19.7,
    "lon": 123.78
   },
   "member_spread_now_deg": {
    "lat": 0.16,
    "lon": 0.37
   },
   "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": 265.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-26 17:30:00",
    "lat": 54.88334,
    "lon": -6.66089,
    "alt_m": 12923.2
   },
   "member_spread_deg": {
    "lat": 41.25,
    "lon": 289.59
   },
   "member_spread_now_deg": {
    "lat": 44.58,
    "lon": 332.96
   },
   "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 22:06:00",
   "seed_lat": -16.10417,
   "seed_lon": 152.625,
   "seed_alt_m": 15850.0,
   "seed_age_h": 1.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-26 21:30:00",
    "lat": -21.92969,
    "lon": -164.4301,
    "alt_m": 15651.9
   },
   "member_spread_deg": {
    "lat": 15.09,
    "lon": 342.73
   },
   "member_spread_now_deg": {
    "lat": 0.09,
    "lon": 0.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}