{
 "generated_utc": "2026-08-30T23:26:48Z",
 "gfs_cycle_utc": "2026-08-30T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 476.5,
  "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_20260830_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260830_18Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 67806
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 16:13:40",
   "seed_lat": -64.54167,
   "seed_lon": -17.12499,
   "seed_alt_m": 11900.0,
   "seed_age_h": 55.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-06 17:45:00",
    "lat": -79.64883,
    "lon": 10.92591,
    "alt_m": 12138.3
   },
   "member_spread_deg": {
    "lat": 25.5,
    "lon": 118.6
   },
   "member_spread_now_deg": {
    "lat": 17.73,
    "lon": 47.52
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 22:57:18",
   "seed_lat": 44.25,
   "seed_lon": 140.08333,
   "seed_alt_m": 14000.0,
   "seed_age_h": 0.38,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-06 23:00:00",
    "lat": 40.71586,
    "lon": -75.73729,
    "alt_m": 14077.1
   },
   "member_spread_deg": {
    "lat": 12.39,
    "lon": 87.09
   },
   "member_spread_now_deg": {
    "lat": 0.12,
    "lon": 0.82
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-25 21:29:00",
   "seed_lat": 33.10417,
   "seed_lon": -84.75,
   "seed_alt_m": 13050.0,
   "seed_age_h": 121.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 17:30:00",
    "lat": 24.00565,
    "lon": -91.24153,
    "alt_m": 13125.2
   },
   "member_spread_deg": {
    "lat": 18.43,
    "lon": 82.47
   },
   "member_spread_now_deg": {
    "lat": 13.68,
    "lon": 21.14
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 17:11:00",
   "seed_lat": 62.79167,
   "seed_lon": -38.45833,
   "seed_alt_m": 12130.0,
   "seed_age_h": 6.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-06 17:45:00",
    "lat": 67.40697,
    "lon": -176.76278,
    "alt_m": 11946.6
   },
   "member_spread_deg": {
    "lat": 32.37,
    "lon": 124.99
   },
   "member_spread_now_deg": {
    "lat": 1.3,
    "lon": 0.61
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 15:47:00",
   "seed_lat": 50.16667,
   "seed_lon": 16.875,
   "seed_alt_m": 13220.0,
   "seed_age_h": 7.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 17:45:00",
    "lat": 52.85446,
    "lon": -142.25921,
    "alt_m": 13011.9
   },
   "member_spread_deg": {
    "lat": 20.18,
    "lon": 315.93
   },
   "member_spread_now_deg": {
    "lat": 3.14,
    "lon": 3.38
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-29 12:08:00",
   "seed_lat": 67.39583,
   "seed_lon": 49.5,
   "seed_alt_m": 12030.0,
   "seed_age_h": 35.2,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-06 17:45:00",
    "lat": 75.41971,
    "lon": 125.05802,
    "alt_m": 11711.1
   },
   "member_spread_deg": {
    "lat": 47.25,
    "lon": 298.68
   },
   "member_spread_now_deg": {
    "lat": 5.09,
    "lon": 22.2
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-24 14:13:00",
   "seed_lat": 65.52083,
   "seed_lon": 37.33333,
   "seed_alt_m": 12490.0,
   "seed_age_h": 153.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 17:45:00",
    "lat": 61.96232,
    "lon": -128.68434,
    "alt_m": 12651.4
   },
   "member_spread_deg": {
    "lat": 32.1,
    "lon": 179.29
   },
   "member_spread_now_deg": {
    "lat": 24.5,
    "lon": 296.52
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-25 06:33:48",
   "seed_lat": 61.6875,
   "seed_lon": -165.70833,
   "seed_alt_m": 13200.0,
   "seed_age_h": 136.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 17:30:00",
    "lat": 42.32463,
    "lon": 75.42649,
    "alt_m": 13611.1
   },
   "member_spread_deg": {
    "lat": 40.59,
    "lon": 232.42
   },
   "member_spread_now_deg": {
    "lat": 34.28,
    "lon": 204.99
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 06:59:00",
   "seed_lat": 44.97917,
   "seed_lon": 85.83333,
   "seed_alt_m": 12490.0,
   "seed_age_h": 16.35,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 17:30:00",
    "lat": 17.82534,
    "lon": 157.49542,
    "alt_m": 12824.1
   },
   "member_spread_deg": {
    "lat": 29.24,
    "lon": 351.28
   },
   "member_spread_now_deg": {
    "lat": 1.97,
    "lon": 3.44
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 22:45:00",
   "seed_lat": 44.6875,
   "seed_lon": -100.41667,
   "seed_alt_m": 12810.0,
   "seed_age_h": 0.58,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 22:15:00",
    "lat": 30.45552,
    "lon": -17.69915,
    "alt_m": 12966.4
   },
   "member_spread_deg": {
    "lat": 29.94,
    "lon": 82.13
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.38
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 11:11:00",
   "seed_lat": 53.6875,
   "seed_lon": 74.70833,
   "seed_alt_m": 12000.0,
   "seed_age_h": 12.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-06 17:45:00",
    "lat": 61.31842,
    "lon": -138.77361,
    "alt_m": 12160.6
   },
   "member_spread_deg": {
    "lat": 13.33,
    "lon": 351.29
   },
   "member_spread_now_deg": {
    "lat": 3.8,
    "lon": 0.94
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 21:45:45",
   "seed_lat": 81.47911,
   "seed_lon": -97.12498,
   "seed_alt_m": 12900.0,
   "seed_age_h": 1.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 21:15:00",
    "lat": 53.24895,
    "lon": 30.11742,
    "alt_m": 13052.0
   },
   "member_spread_deg": {
    "lat": 13.27,
    "lon": 60.59
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 5.26
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KJ4AWK-1",
   "flight_id": "KJ4AWK-1_2026-08-22",
   "payload_type": "APRS",
   "seed_time": "2026-08-26 15:51:36",
   "seed_lat": 41.62025,
   "seed_lon": 25.112,
   "seed_alt_m": 13223.0,
   "seed_age_h": 103.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 17:45:00",
    "lat": 47.14016,
    "lon": -121.62749,
    "alt_m": 13043.9
   },
   "member_spread_deg": {
    "lat": 21.88,
    "lon": 135.14
   },
   "member_spread_now_deg": {
    "lat": 7.16,
    "lon": 26.81
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 12:33:00",
   "seed_lat": 43.375,
   "seed_lon": 58.79167,
   "seed_alt_m": 15960.0,
   "seed_age_h": 10.78,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-06 17:30:00",
    "lat": 65.32694,
    "lon": -108.57267,
    "alt_m": 15317.2
   },
   "member_spread_deg": {
    "lat": 34.39,
    "lon": 337.99
   },
   "member_spread_now_deg": {
    "lat": 2.53,
    "lon": 15.93
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 22:01:00",
   "seed_lat": 51.66667,
   "seed_lon": 170.79167,
   "seed_alt_m": 13220.0,
   "seed_age_h": 1.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-06 21:30:00",
    "lat": 40.4322,
    "lon": -84.86219,
    "alt_m": 13629.2
   },
   "member_spread_deg": {
    "lat": 25.2,
    "lon": 342.92
   },
   "member_spread_now_deg": {
    "lat": 0.79,
    "lon": 0.99
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6SRC-37",
   "flight_id": "ZS6SRC-37_2026-07-31",
   "payload_type": "WSPR",
   "seed_time": "2026-08-17 20:59:00",
   "seed_lat": -20.58333,
   "seed_lon": -72.33333,
   "seed_alt_m": 12210.0,
   "seed_age_h": 314.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-06 17:30:00",
    "lat": -26.24129,
    "lon": -88.70125,
    "alt_m": 12003.8
   },
   "member_spread_deg": {
    "lat": 15.92,
    "lon": 244.79
   },
   "member_spread_now_deg": {
    "lat": 25.57,
    "lon": 115.84
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-30 20:26:00",
   "seed_lat": -18.0,
   "seed_lon": -59.16667,
   "seed_alt_m": 15810.0,
   "seed_age_h": 2.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-06 20:00:00",
    "lat": -9.7354,
    "lon": -62.02282,
    "alt_m": 15716.1
   },
   "member_spread_deg": {
    "lat": 10.45,
    "lon": 40.02
   },
   "member_spread_now_deg": {
    "lat": 1.28,
    "lon": 0.56
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}