{
 "generated_utc": "2026-08-31T17:27:18Z",
 "gfs_cycle_utc": "2026-08-31T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 494.5,
  "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_20260831_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260831_12Z.geojson.gz"
 },
 "counts": {
  "flights": 18,
  "members": 9,
  "rows": 72999
 },
 "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": 73.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": -44.09967,
    "lon": 60.01769,
    "alt_m": 12221.4
   },
   "member_spread_deg": {
    "lat": 23.98,
    "lon": 119.28
   },
   "member_spread_now_deg": {
    "lat": 9.59,
    "lon": 99.15
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 06:11:19",
   "seed_lat": 43.52083,
   "seed_lon": 154.41667,
   "seed_alt_m": 13960.0,
   "seed_age_h": 11.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 38.0475,
    "lon": -58.25054,
    "alt_m": 14196.3
   },
   "member_spread_deg": {
    "lat": 14.74,
    "lon": 52.46
   },
   "member_spread_now_deg": {
    "lat": 3.78,
    "lon": 3.29
   },
   "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": 139.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 11:30:00",
    "lat": 24.77956,
    "lon": -98.73801,
    "alt_m": 13148.7
   },
   "member_spread_deg": {
    "lat": 10.01,
    "lon": 65.06
   },
   "member_spread_now_deg": {
    "lat": 12.34,
    "lon": 29.71
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 12:21:00",
   "seed_lat": 60.375,
   "seed_lon": -19.29167,
   "seed_alt_m": 12020.0,
   "seed_age_h": 4.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 74.7816,
    "lon": -69.58053,
    "alt_m": 11852.8
   },
   "member_spread_deg": {
    "lat": 37.43,
    "lon": 308.17
   },
   "member_spread_now_deg": {
    "lat": 1.92,
    "lon": 3.54
   },
   "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": 25.55,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 61.67968,
    "lon": -135.55855,
    "alt_m": 13022.1
   },
   "member_spread_deg": {
    "lat": 20.89,
    "lon": 351.18
   },
   "member_spread_now_deg": {
    "lat": 6.74,
    "lon": 4.57
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:53:00",
   "seed_lat": 62.54167,
   "seed_lon": 91.41667,
   "seed_alt_m": 11930.0,
   "seed_age_h": 7.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 11:30:00",
    "lat": 59.56727,
    "lon": 134.30352,
    "alt_m": 12067.6
   },
   "member_spread_deg": {
    "lat": 26.8,
    "lon": 338.94
   },
   "member_spread_now_deg": {
    "lat": 2.58,
    "lon": 3.74
   },
   "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": 171.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 68.85474,
    "lon": -139.32152,
    "alt_m": 12540.1
   },
   "member_spread_deg": {
    "lat": 29.84,
    "lon": 228.24
   },
   "member_spread_now_deg": {
    "lat": 18.15,
    "lon": 316.01
   },
   "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": 154.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 11:30:00",
    "lat": 47.83388,
    "lon": 117.46607,
    "alt_m": 13531.6
   },
   "member_spread_deg": {
    "lat": 44.86,
    "lon": 251.77
   },
   "member_spread_now_deg": {
    "lat": 32.39,
    "lon": 221.71
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 08:49:00",
   "seed_lat": 35.0,
   "seed_lon": 106.08333,
   "seed_alt_m": 12580.0,
   "seed_age_h": 8.52,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 29.88002,
    "lon": 152.09609,
    "alt_m": 12811.6
   },
   "member_spread_deg": {
    "lat": 35.1,
    "lon": 282.79
   },
   "member_spread_now_deg": {
    "lat": 0.49,
    "lon": 0.63
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 15:55:00",
   "seed_lat": 41.0,
   "seed_lon": -75.95833,
   "seed_alt_m": 12980.0,
   "seed_age_h": 1.42,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 15:30:00",
    "lat": 36.6352,
    "lon": -3.3677,
    "alt_m": 12942.7
   },
   "member_spread_deg": {
    "lat": 13.75,
    "lon": 45.02
   },
   "member_spread_now_deg": {
    "lat": 0.53,
    "lon": 0.28
   },
   "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": 30.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 69.1134,
    "lon": -93.32517,
    "alt_m": 12081.1
   },
   "member_spread_deg": {
    "lat": 21.51,
    "lon": 345.42
   },
   "member_spread_now_deg": {
    "lat": 6.64,
    "lon": 4.87
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 15:45:45",
   "seed_lat": 77.99995,
   "seed_lon": -57.87498,
   "seed_alt_m": 12900.0,
   "seed_age_h": 1.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 15:15:00",
    "lat": 57.63887,
    "lon": 46.05963,
    "alt_m": 13026.6
   },
   "member_spread_deg": {
    "lat": 16.11,
    "lon": 61.93
   },
   "member_spread_now_deg": {
    "lat": 0.6,
    "lon": 1.54
   },
   "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": 121.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 45.90154,
    "lon": -19.69791,
    "alt_m": 13346.4
   },
   "member_spread_deg": {
    "lat": 15.17,
    "lon": 59.1
   },
   "member_spread_now_deg": {
    "lat": 11.54,
    "lon": 337.44
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:43:00",
   "seed_lat": 46.16667,
   "seed_lon": 91.54167,
   "seed_alt_m": 15960.0,
   "seed_age_h": 7.62,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 31.92763,
    "lon": 174.83108,
    "alt_m": 16264.1
   },
   "member_spread_deg": {
    "lat": 26.11,
    "lon": 350.45
   },
   "member_spread_now_deg": {
    "lat": 2.92,
    "lon": 7.73
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 04:16:00",
   "seed_lat": 57.25,
   "seed_lon": -179.33333,
   "seed_alt_m": 13330.0,
   "seed_age_h": 13.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 43.82155,
    "lon": -67.77571,
    "alt_m": 13122.9
   },
   "member_spread_deg": {
    "lat": 33.37,
    "lon": 152.51
   },
   "member_spread_now_deg": {
    "lat": 4.42,
    "lon": 4.64
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 10:15:23",
   "seed_lat": 49.31245,
   "seed_lon": 84.79169,
   "seed_alt_m": 13240.0,
   "seed_age_h": 7.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 11:45:00",
    "lat": 50.88759,
    "lon": -88.673,
    "alt_m": 13549.6
   },
   "member_spread_deg": {
    "lat": 51.09,
    "lon": 142.24
   },
   "member_spread_now_deg": {
    "lat": 1.73,
    "lon": 2.13
   },
   "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": 332.35,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 11:30:00",
    "lat": -30.40464,
    "lon": -46.16267,
    "alt_m": 12139.2
   },
   "member_spread_deg": {
    "lat": 38.78,
    "lon": 241.52
   },
   "member_spread_now_deg": {
    "lat": 28.35,
    "lon": 117.8
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 16:31:00",
   "seed_lat": -19.89583,
   "seed_lon": -55.20833,
   "seed_alt_m": 15870.0,
   "seed_age_h": 0.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 16:30:00",
    "lat": -30.28892,
    "lon": 23.15237,
    "alt_m": 15576.1
   },
   "member_spread_deg": {
    "lat": 34.17,
    "lon": 79.0
   },
   "member_spread_now_deg": {
    "lat": 0.29,
    "lon": 0.36
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}