{
 "generated_utc": "2026-09-20T17:26:14Z",
 "gfs_cycle_utc": "2026-09-20T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 446.0,
  "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_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260920_12Z.geojson.gz"
 },
 "counts": {
  "flights": 13,
  "members": 9,
  "rows": 56925
 },
 "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": 49.95,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:30:00",
    "lat": 45.59973,
    "lon": 175.61018,
    "alt_m": 13744.3
   },
   "member_spread_deg": {
    "lat": 24.94,
    "lon": 278.6
   },
   "member_spread_now_deg": {
    "lat": 2.09,
    "lon": 20.13
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 13:41:00",
   "seed_lat": 63.45833,
   "seed_lon": 14.16667,
   "seed_alt_m": 11910.0,
   "seed_age_h": 3.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-27 13:15:00",
    "lat": 65.98935,
    "lon": 33.87059,
    "alt_m": 12483.7
   },
   "member_spread_deg": {
    "lat": 18.5,
    "lon": 26.81
   },
   "member_spread_now_deg": {
    "lat": 0.26,
    "lon": 0.37
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 11:32:00",
   "seed_lat": 42.29167,
   "seed_lon": 50.875,
   "seed_alt_m": 13270.0,
   "seed_age_h": 5.8,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:30:00",
    "lat": 43.74691,
    "lon": -90.30406,
    "alt_m": 13310.4
   },
   "member_spread_deg": {
    "lat": 20.72,
    "lon": 45.62
   },
   "member_spread_now_deg": {
    "lat": 0.45,
    "lon": 1.82
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 10:26:00",
   "seed_lat": 46.33333,
   "seed_lon": 60.45833,
   "seed_alt_m": 13460.0,
   "seed_age_h": 6.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:30:00",
    "lat": 59.60944,
    "lon": -83.85624,
    "alt_m": 13091.1
   },
   "member_spread_deg": {
    "lat": 14.21,
    "lon": 44.02
   },
   "member_spread_now_deg": {
    "lat": 1.33,
    "lon": 0.8
   },
   "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": 251.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-27 11:30:00",
    "lat": 22.90604,
    "lon": 11.945,
    "alt_m": 12743.4
   },
   "member_spread_deg": {
    "lat": 28.83,
    "lon": 217.86
   },
   "member_spread_now_deg": {
    "lat": 41.26,
    "lon": 243.23
   },
   "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": 203.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:30:00",
    "lat": 43.45095,
    "lon": 125.61682,
    "alt_m": 12541.3
   },
   "member_spread_deg": {
    "lat": 26.6,
    "lon": 260.1
   },
   "member_spread_now_deg": {
    "lat": 21.73,
    "lon": 171.61
   },
   "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": 172.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:30:00",
    "lat": 33.30142,
    "lon": 21.53623,
    "alt_m": 12877.4
   },
   "member_spread_deg": {
    "lat": 33.51,
    "lon": 212.61
   },
   "member_spread_now_deg": {
    "lat": 19.29,
    "lon": 39.17
   },
   "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": 12.99,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:45:00",
    "lat": 55.80729,
    "lon": -40.58487,
    "alt_m": 12655.0
   },
   "member_spread_deg": {
    "lat": 23.68,
    "lon": 86.67
   },
   "member_spread_now_deg": {
    "lat": 3.38,
    "lon": 359.55
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 9.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:45:00",
    "lat": 27.36312,
    "lon": -125.6909,
    "alt_m": 13299.0
   },
   "member_spread_deg": {
    "lat": 36.5,
    "lon": 326.38
   },
   "member_spread_now_deg": {
    "lat": 1.07,
    "lon": 2.48
   },
   "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": 28.08,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:45:00",
    "lat": 49.56925,
    "lon": 162.05082,
    "alt_m": 15179.6
   },
   "member_spread_deg": {
    "lat": 8.97,
    "lon": 335.02
   },
   "member_spread_now_deg": {
    "lat": 1.18,
    "lon": 14.66
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-20 16:01:00",
   "seed_lat": 54.25,
   "seed_lon": -105.41667,
   "seed_alt_m": 12950.0,
   "seed_age_h": 1.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 16:00:00",
    "lat": 57.59582,
    "lon": 155.08474,
    "alt_m": 12354.2
   },
   "member_spread_deg": {
    "lat": 29.19,
    "lon": 144.4
   },
   "member_spread_now_deg": {
    "lat": 0.33,
    "lon": 0.16
   },
   "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": 283.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-27 11:30:00",
    "lat": 27.53798,
    "lon": -28.22074,
    "alt_m": 13396.7
   },
   "member_spread_deg": {
    "lat": 54.33,
    "lon": 221.7
   },
   "member_spread_now_deg": {
    "lat": 50.44,
    "lon": 316.53
   },
   "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": 11.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-27 11:30:00",
    "lat": -24.6935,
    "lon": -153.29256,
    "alt_m": 15627.2
   },
   "member_spread_deg": {
    "lat": 14.45,
    "lon": 343.57
   },
   "member_spread_now_deg": {
    "lat": 1.29,
    "lon": 2.49
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}