{
 "generated_utc": "2026-09-20T11:26:16Z",
 "gfs_cycle_utc": "2026-09-20T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 440.0,
  "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_20260920_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260920_06Z.geojson.gz"
 },
 "counts": {
  "flights": 13,
  "members": 9,
  "rows": 56079
 },
 "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": 43.95,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 05:30:00",
    "lat": 47.33995,
    "lon": -176.66608,
    "alt_m": 13663.6
   },
   "member_spread_deg": {
    "lat": 24.1,
    "lon": 347.43
   },
   "member_spread_now_deg": {
    "lat": 1.48,
    "lon": 16.73
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 10:36:00",
   "seed_lat": 63.22917,
   "seed_lon": 11.45833,
   "seed_alt_m": 11920.0,
   "seed_age_h": 0.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-27 10:30:00",
    "lat": 53.39732,
    "lon": 41.08262,
    "alt_m": 12562.9
   },
   "member_spread_deg": {
    "lat": 18.88,
    "lon": 15.0
   },
   "member_spread_now_deg": {
    "lat": 0.01,
    "lon": 0.19
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 09:02:00",
   "seed_lat": 41.70833,
   "seed_lon": 48.45833,
   "seed_alt_m": 13340.0,
   "seed_age_h": 2.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 08:30:00",
    "lat": 61.49202,
    "lon": -89.53649,
    "alt_m": 13124.5
   },
   "member_spread_deg": {
    "lat": 35.94,
    "lon": 43.55
   },
   "member_spread_now_deg": {
    "lat": 0.25,
    "lon": 0.4
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 09:36:00",
   "seed_lat": 46.47917,
   "seed_lon": 59.83333,
   "seed_alt_m": 13460.0,
   "seed_age_h": 1.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 09:00:00",
    "lat": 56.57587,
    "lon": -102.12278,
    "alt_m": 13162.5
   },
   "member_spread_deg": {
    "lat": 17.88,
    "lon": 53.29
   },
   "member_spread_now_deg": {
    "lat": 0.23,
    "lon": 0.34
   },
   "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": 245.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-27 05:30:00",
    "lat": 25.25572,
    "lon": -60.66986,
    "alt_m": 12743.2
   },
   "member_spread_deg": {
    "lat": 26.04,
    "lon": 232.72
   },
   "member_spread_now_deg": {
    "lat": 40.75,
    "lon": 235.44
   },
   "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": 197.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 05:30:00",
    "lat": 46.36667,
    "lon": 116.16583,
    "alt_m": 12542.4
   },
   "member_spread_deg": {
    "lat": 40.06,
    "lon": 249.01
   },
   "member_spread_now_deg": {
    "lat": 21.12,
    "lon": 167.85
   },
   "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": 166.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 05:30:00",
    "lat": 54.78686,
    "lon": 44.99576,
    "alt_m": 12727.4
   },
   "member_spread_deg": {
    "lat": 37.42,
    "lon": 144.02
   },
   "member_spread_now_deg": {
    "lat": 21.35,
    "lon": 39.6
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 04:20:45",
   "seed_lat": 71.68745,
   "seed_lon": 168.25002,
   "seed_alt_m": 12840.0,
   "seed_age_h": 6.99,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 05:45:00",
    "lat": 53.7306,
    "lon": -53.33019,
    "alt_m": 12821.5
   },
   "member_spread_deg": {
    "lat": 27.49,
    "lon": 69.06
   },
   "member_spread_now_deg": {
    "lat": 1.6,
    "lon": 3.86
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 07:41:00",
   "seed_lat": 37.85417,
   "seed_lon": 77.95833,
   "seed_alt_m": 13120.0,
   "seed_age_h": 3.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 07:15:00",
    "lat": 22.883,
    "lon": -166.85744,
    "alt_m": 13336.2
   },
   "member_spread_deg": {
    "lat": 34.35,
    "lon": 336.71
   },
   "member_spread_now_deg": {
    "lat": 0.64,
    "lon": 0.72
   },
   "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": 22.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 05:45:00",
    "lat": 50.19299,
    "lon": 160.63601,
    "alt_m": 15197.6
   },
   "member_spread_deg": {
    "lat": 5.19,
    "lon": 326.83
   },
   "member_spread_now_deg": {
    "lat": 1.27,
    "lon": 12.24
   },
   "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": 12.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 05:45:00",
    "lat": 52.10939,
    "lon": 152.74557,
    "alt_m": 12563.0
   },
   "member_spread_deg": {
    "lat": 19.24,
    "lon": 160.33
   },
   "member_spread_now_deg": {
    "lat": 3.28,
    "lon": 1.75
   },
   "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": 277.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 05:30:00",
    "lat": 53.26778,
    "lon": 2.44577,
    "alt_m": 12978.1
   },
   "member_spread_deg": {
    "lat": 45.08,
    "lon": 132.61
   },
   "member_spread_now_deg": {
    "lat": 50.2,
    "lon": 339.7
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 06:01:00",
   "seed_lat": -15.0,
   "seed_lon": 153.125,
   "seed_alt_m": 15910.0,
   "seed_age_h": 5.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-27 05:30:00",
    "lat": -20.71759,
    "lon": -165.45299,
    "alt_m": 15760.4
   },
   "member_spread_deg": {
    "lat": 15.75,
    "lon": 341.4
   },
   "member_spread_now_deg": {
    "lat": 0.71,
    "lon": 1.3
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}