{
 "generated_utc": "2026-09-06T17:26:54Z",
 "gfs_cycle_utc": "2026-09-06T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 477.5,
  "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_20260906_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260906_12Z.geojson.gz"
 },
 "counts": {
  "flights": 18,
  "members": 9,
  "rows": 84753
 },
 "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": 217.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-13 11:45:00",
    "lat": -80.03548,
    "lon": -144.06144,
    "alt_m": 12224.1
   },
   "member_spread_deg": {
    "lat": 24.65,
    "lon": 256.46
   },
   "member_spread_now_deg": {
    "lat": 22.38,
    "lon": 77.72
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 16:43:34",
   "seed_lat": 31.85417,
   "seed_lon": -78.41667,
   "seed_alt_m": 14575.0,
   "seed_age_h": 0.61,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 16:15:00",
    "lat": 40.37309,
    "lon": 3.55868,
    "alt_m": 14438.2
   },
   "member_spread_deg": {
    "lat": 20.61,
    "lon": 45.05
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.1
   },
   "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": 283.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 5.72157,
    "lon": -39.60718,
    "alt_m": 13189.8
   },
   "member_spread_deg": {
    "lat": 32.14,
    "lon": 111.08
   },
   "member_spread_now_deg": {
    "lat": 17.03,
    "lon": 57.35
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 04:41:00",
   "seed_lat": 86.0,
   "seed_lon": 110.20833,
   "seed_alt_m": 11660.0,
   "seed_age_h": 36.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-13 11:45:00",
    "lat": 87.37654,
    "lon": 109.57042,
    "alt_m": 11545.2
   },
   "member_spread_deg": {
    "lat": 9.48,
    "lon": 180.49
   },
   "member_spread_now_deg": {
    "lat": 1.28,
    "lon": 34.91
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 02:37:00",
   "seed_lat": 50.3125,
   "seed_lon": -174.08333,
   "seed_alt_m": 13010.0,
   "seed_age_h": 14.72,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 34.64076,
    "lon": -86.52706,
    "alt_m": 13645.9
   },
   "member_spread_deg": {
    "lat": 18.09,
    "lon": 128.29
   },
   "member_spread_now_deg": {
    "lat": 14.32,
    "lon": 7.79
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 07:36:00",
   "seed_lat": 43.02083,
   "seed_lon": 80.875,
   "seed_alt_m": 13360.0,
   "seed_age_h": 9.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 32.18385,
    "lon": 178.27181,
    "alt_m": 13567.1
   },
   "member_spread_deg": {
    "lat": 28.42,
    "lon": 356.81
   },
   "member_spread_now_deg": {
    "lat": 0.66,
    "lon": 3.01
   },
   "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": 151.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 61.43615,
    "lon": 158.74662,
    "alt_m": 11887.1
   },
   "member_spread_deg": {
    "lat": 48.53,
    "lon": 347.36
   },
   "member_spread_now_deg": {
    "lat": 19.04,
    "lon": 319.13
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DO3GU-47",
   "flight_id": "DO3GU-47_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 13:31:52",
   "seed_lat": 46.04167,
   "seed_lon": 61.70833,
   "seed_alt_m": 13960.0,
   "seed_age_h": 27.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 33.99733,
    "lon": 179.33797,
    "alt_m": 14213.7
   },
   "member_spread_deg": {
    "lat": 29.19,
    "lon": 359.85
   },
   "member_spread_now_deg": {
    "lat": 1.87,
    "lon": 11.11
   },
   "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": 315.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:45:00",
    "lat": 39.89076,
    "lon": -143.22811,
    "alt_m": 13054.3
   },
   "member_spread_deg": {
    "lat": 27.59,
    "lon": 312.43
   },
   "member_spread_now_deg": {
    "lat": 26.59,
    "lon": 226.01
   },
   "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": 298.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 29.40313,
    "lon": 143.53974,
    "alt_m": 14324.6
   },
   "member_spread_deg": {
    "lat": 48.87,
    "lon": 315.76
   },
   "member_spread_now_deg": {
    "lat": 38.78,
    "lon": 264.56
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 08:04:00",
   "seed_lat": 37.27083,
   "seed_lon": 133.375,
   "seed_alt_m": 12750.0,
   "seed_age_h": 81.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 31.39097,
    "lon": 156.48811,
    "alt_m": 12932.8
   },
   "member_spread_deg": {
    "lat": 62.29,
    "lon": 316.78
   },
   "member_spread_now_deg": {
    "lat": 22.63,
    "lon": 344.43
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 16:55:00",
   "seed_lat": 28.70833,
   "seed_lon": -4.5,
   "seed_alt_m": 13010.0,
   "seed_age_h": 0.42,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 17:00:00",
    "lat": 47.46848,
    "lon": 149.56955,
    "alt_m": 12601.2
   },
   "member_spread_deg": {
    "lat": 15.86,
    "lon": 322.64
   },
   "member_spread_now_deg": {
    "lat": 0.21,
    "lon": 0.14
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 02:01:00",
   "seed_lat": 62.91667,
   "seed_lon": -150.16667,
   "seed_alt_m": 12300.0,
   "seed_age_h": 15.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 73.55726,
    "lon": 107.31671,
    "alt_m": 12402.3
   },
   "member_spread_deg": {
    "lat": 35.76,
    "lon": 114.55
   },
   "member_spread_now_deg": {
    "lat": 2.33,
    "lon": 22.44
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 15:25:45",
   "seed_lat": 57.95828,
   "seed_lon": 16.20835,
   "seed_alt_m": 13120.0,
   "seed_age_h": 25.9,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 64.78539,
    "lon": -130.78122,
    "alt_m": 13086.6
   },
   "member_spread_deg": {
    "lat": 13.47,
    "lon": 236.49
   },
   "member_spread_now_deg": {
    "lat": 1.52,
    "lon": 2.52
   },
   "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": 265.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:45:00",
    "lat": 38.47229,
    "lon": -5.91123,
    "alt_m": 13400.6
   },
   "member_spread_deg": {
    "lat": 37.95,
    "lon": 270.73
   },
   "member_spread_now_deg": {
    "lat": 16.73,
    "lon": 102.9
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 03:03:00",
   "seed_lat": 28.04167,
   "seed_lon": -162.5,
   "seed_alt_m": 16300.0,
   "seed_age_h": 14.28,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 11:30:00",
    "lat": 22.80945,
    "lon": -163.9927,
    "alt_m": 16489.3
   },
   "member_spread_deg": {
    "lat": 20.24,
    "lon": 339.01
   },
   "member_spread_now_deg": {
    "lat": 1.94,
    "lon": 10.37
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 16:46:00",
   "seed_lat": 39.0625,
   "seed_lon": -73.66667,
   "seed_alt_m": 13200.0,
   "seed_age_h": 0.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 16:15:00",
    "lat": 49.86552,
    "lon": 94.52472,
    "alt_m": 13262.1
   },
   "member_spread_deg": {
    "lat": 25.22,
    "lon": 103.33
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.32
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-06 14:41:00",
   "seed_lat": -26.25,
   "seed_lon": 20.70833,
   "seed_alt_m": 15570.0,
   "seed_age_h": 2.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-13 14:15:00",
    "lat": -25.33516,
    "lon": 95.11362,
    "alt_m": 15613.3
   },
   "member_spread_deg": {
    "lat": 21.73,
    "lon": 144.49
   },
   "member_spread_now_deg": {
    "lat": 0.21,
    "lon": 0.39
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}