{
 "generated_utc": "2026-08-21T17:26:55Z",
 "gfs_cycle_utc": "2026-08-21T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 443.5,
  "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_20260821_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260821_12Z.geojson.gz"
 },
 "counts": {
  "flights": 21,
  "members": 9,
  "rows": 85149
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 16:33:40",
   "seed_lat": -54.3125,
   "seed_lon": -4.04165,
   "seed_alt_m": 12300.0,
   "seed_age_h": 0.77,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 16:30:00",
    "lat": -42.13795,
    "lon": -139.45228,
    "alt_m": 12230.5
   },
   "member_spread_deg": {
    "lat": 44.39,
    "lon": 255.15
   },
   "member_spread_now_deg": {
    "lat": 0.09,
    "lon": 0.96
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS53",
   "flight_id": "BSS53_2026-03-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 16:33:48",
   "seed_lat": 74.22917,
   "seed_lon": -144.95833,
   "seed_alt_m": 12310.0,
   "seed_age_h": 0.77,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 16:30:00",
    "lat": 72.47128,
    "lon": -34.65551,
    "alt_m": 12235.6
   },
   "member_spread_deg": {
    "lat": 24.3,
    "lon": 114.1
   },
   "member_spread_now_deg": {
    "lat": 0.15,
    "lon": 0.81
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 16:31:18",
   "seed_lat": 55.14583,
   "seed_lon": -120.16667,
   "seed_alt_m": 14020.0,
   "seed_age_h": 0.81,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 16:30:00",
    "lat": 43.94823,
    "lon": 54.57657,
    "alt_m": 14103.8
   },
   "member_spread_deg": {
    "lat": 30.53,
    "lon": 206.46
   },
   "member_spread_now_deg": {
    "lat": 0.07,
    "lon": 0.35
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 03:24:00",
   "seed_lat": 55.64583,
   "seed_lon": -168.45833,
   "seed_alt_m": 12690.0,
   "seed_age_h": 13.93,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 11:30:00",
    "lat": 53.3591,
    "lon": -55.60181,
    "alt_m": 12682.5
   },
   "member_spread_deg": {
    "lat": 21.15,
    "lon": 41.63
   },
   "member_spread_now_deg": {
    "lat": 5.93,
    "lon": 0.87
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-27",
   "flight_id": "DG2GG-27_2026-07-04",
   "payload_type": "WSPR",
   "seed_time": "2026-08-10 00:18:00",
   "seed_lat": 17.10417,
   "seed_lon": -113.33333,
   "seed_alt_m": 14010.0,
   "seed_age_h": 281.03,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": -2.60466,
    "lon": -36.9636,
    "alt_m": 14056.1
   },
   "member_spread_deg": {
    "lat": 48.75,
    "lon": 172.77
   },
   "member_spread_now_deg": {
    "lat": 48.3,
    "lon": 113.01
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 16:01:00",
   "seed_lat": 54.91667,
   "seed_lon": 15.08333,
   "seed_alt_m": 12380.0,
   "seed_age_h": 25.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 11:30:00",
    "lat": 51.05374,
    "lon": -118.84253,
    "alt_m": 12421.6
   },
   "member_spread_deg": {
    "lat": 21.79,
    "lon": 66.68
   },
   "member_spread_now_deg": {
    "lat": 6.82,
    "lon": 10.25
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 06:09:30",
   "seed_lat": 45.72917,
   "seed_lon": 146.75,
   "seed_alt_m": 13135.0,
   "seed_age_h": 11.18,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": 47.43331,
    "lon": -70.43996,
    "alt_m": 13102.6
   },
   "member_spread_deg": {
    "lat": 16.75,
    "lon": 38.64
   },
   "member_spread_now_deg": {
    "lat": 3.11,
    "lon": 1.91
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 07:38:00",
   "seed_lat": 71.3125,
   "seed_lon": 136.125,
   "seed_alt_m": 11880.0,
   "seed_age_h": 9.7,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": 82.45398,
    "lon": 96.01548,
    "alt_m": 11368.5
   },
   "member_spread_deg": {
    "lat": 25.02,
    "lon": 266.95
   },
   "member_spread_now_deg": {
    "lat": 0.72,
    "lon": 0.73
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 16:13:00",
   "seed_lat": 50.58333,
   "seed_lon": -7.08333,
   "seed_alt_m": 12590.0,
   "seed_age_h": 1.12,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 15:45:00",
    "lat": 75.13755,
    "lon": 112.20814,
    "alt_m": 12452.5
   },
   "member_spread_deg": {
    "lat": 10.91,
    "lon": 74.84
   },
   "member_spread_now_deg": {
    "lat": 0.33,
    "lon": 0.75
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "K5NOT-11",
   "flight_id": "K5NOT-11_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-15 20:50:37",
   "seed_lat": 40.97911,
   "seed_lon": -75.41666,
   "seed_alt_m": 13300.0,
   "seed_age_h": 140.49,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": 22.54698,
    "lon": -72.48527,
    "alt_m": 13367.7
   },
   "member_spread_deg": {
    "lat": 28.15,
    "lon": 235.55
   },
   "member_spread_now_deg": {
    "lat": 32.0,
    "lon": 49.44
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 13:04:33",
   "seed_lat": 67.29167,
   "seed_lon": 108.45833,
   "seed_alt_m": 13250.0,
   "seed_age_h": 4.26,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 12:30:00",
    "lat": 81.09628,
    "lon": 0.6873,
    "alt_m": 12983.7
   },
   "member_spread_deg": {
    "lat": 36.16,
    "lon": 178.67
   },
   "member_spread_now_deg": {
    "lat": 0.47,
    "lon": 1.23
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC5TRB-1",
   "flight_id": "KC5TRB-1_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-12 11:40:43",
   "seed_lat": 57.39578,
   "seed_lon": 26.00003,
   "seed_alt_m": 12570.0,
   "seed_age_h": 221.66,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": 61.87776,
    "lon": 110.71971,
    "alt_m": 12617.5
   },
   "member_spread_deg": {
    "lat": 35.78,
    "lon": 323.57
   },
   "member_spread_now_deg": {
    "lat": 26.32,
    "lon": 325.48
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 05:25:00",
   "seed_lat": 48.27083,
   "seed_lon": 176.70833,
   "seed_alt_m": 13020.0,
   "seed_age_h": 11.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 11:30:00",
    "lat": 40.11153,
    "lon": -60.49773,
    "alt_m": 13133.9
   },
   "member_spread_deg": {
    "lat": 23.46,
    "lon": 113.51
   },
   "member_spread_now_deg": {
    "lat": 2.49,
    "lon": 359.65
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-20 10:01:00",
   "seed_lat": 85.25,
   "seed_lon": 45.875,
   "seed_alt_m": 11960.0,
   "seed_age_h": 31.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 11:30:00",
    "lat": 79.92468,
    "lon": 83.25572,
    "alt_m": 11663.1
   },
   "member_spread_deg": {
    "lat": 27.83,
    "lon": 345.22
   },
   "member_spread_now_deg": {
    "lat": 9.18,
    "lon": 24.78
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE9DAB-11",
   "flight_id": "KE9DAB-11_2026-07-29",
   "payload_type": "WSPR",
   "seed_time": "2026-08-13 21:11:00",
   "seed_lat": 63.66667,
   "seed_lon": 161.54167,
   "seed_alt_m": 10970.0,
   "seed_age_h": 188.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": 26.01691,
    "lon": -37.32453,
    "alt_m": 11220.5
   },
   "member_spread_deg": {
    "lat": 26.83,
    "lon": 348.27
   },
   "member_spread_now_deg": {
    "lat": 20.58,
    "lon": 100.67
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 04:30:45",
   "seed_lat": 68.79161,
   "seed_lon": 179.37502,
   "seed_alt_m": 12870.0,
   "seed_age_h": 12.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 11:30:00",
    "lat": 74.79328,
    "lon": -165.63227,
    "alt_m": 12763.0
   },
   "member_spread_deg": {
    "lat": 15.15,
    "lon": 339.32
   },
   "member_spread_now_deg": {
    "lat": 2.18,
    "lon": 2.1
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 12:21:00",
   "seed_lat": 12.97917,
   "seed_lon": 50.95833,
   "seed_alt_m": 16600.0,
   "seed_age_h": 4.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": 28.368,
    "lon": -16.48484,
    "alt_m": 16326.1
   },
   "member_spread_deg": {
    "lat": 11.3,
    "lon": 20.33
   },
   "member_spread_now_deg": {
    "lat": 0.37,
    "lon": 0.96
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 15:21:00",
   "seed_lat": 49.3125,
   "seed_lon": -125.33333,
   "seed_alt_m": 13320.0,
   "seed_age_h": 1.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-28 14:45:00",
    "lat": 49.30675,
    "lon": 78.73934,
    "alt_m": 13114.0
   },
   "member_spread_deg": {
    "lat": 25.81,
    "lon": 218.66
   },
   "member_spread_now_deg": {
    "lat": 0.92,
    "lon": 0.57
   },
   "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": 92.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-28 11:30:00",
    "lat": -28.09946,
    "lon": -105.91319,
    "alt_m": 12115.3
   },
   "member_spread_deg": {
    "lat": 13.43,
    "lon": 157.52
   },
   "member_spread_now_deg": {
    "lat": 29.22,
    "lon": 122.3
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6SRC-39",
   "flight_id": "ZS6SRC-39_2026-08-05",
   "payload_type": "WSPR",
   "seed_time": "2026-08-12 06:21:00",
   "seed_lat": -22.16667,
   "seed_lon": 146.45833,
   "seed_alt_m": 15900.0,
   "seed_age_h": 226.98,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": -30.83645,
    "lon": 115.19123,
    "alt_m": 15674.0
   },
   "member_spread_deg": {
    "lat": 51.35,
    "lon": 261.76
   },
   "member_spread_now_deg": {
    "lat": 18.65,
    "lon": 176.74
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-21 10:16:00",
   "seed_lat": -20.72917,
   "seed_lon": 71.95833,
   "seed_alt_m": 15680.0,
   "seed_age_h": 7.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-28 11:45:00",
    "lat": -28.78181,
    "lon": -88.12879,
    "alt_m": 15162.8
   },
   "member_spread_deg": {
    "lat": 22.76,
    "lon": 328.83
   },
   "member_spread_now_deg": {
    "lat": 0.9,
    "lon": 4.43
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}