{
 "generated_utc": "2026-09-01T17:25:21Z",
 "gfs_cycle_utc": "2026-09-01T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 357.5,
  "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_20260901_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260901_12Z.geojson.gz"
 },
 "counts": {
  "flights": 16,
  "members": 9,
  "rows": 64674
 },
 "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": 97.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-08 11:45:00",
    "lat": -52.22854,
    "lon": 87.83298,
    "alt_m": 12126.2
   },
   "member_spread_deg": {
    "lat": 18.6,
    "lon": 152.46
   },
   "member_spread_now_deg": {
    "lat": 15.89,
    "lon": 125.37
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 23:04:18",
   "seed_lat": 53.97917,
   "seed_lon": 172.375,
   "seed_alt_m": 13860.0,
   "seed_age_h": 18.26,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-08 11:30:00",
    "lat": 28.53843,
    "lon": -71.35769,
    "alt_m": 14497.2
   },
   "member_spread_deg": {
    "lat": 17.12,
    "lon": 57.82
   },
   "member_spread_now_deg": {
    "lat": 10.0,
    "lon": 20.55
   },
   "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": 163.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 11:30:00",
    "lat": 27.69677,
    "lon": -82.55333,
    "alt_m": 13197.0
   },
   "member_spread_deg": {
    "lat": 42.93,
    "lon": 89.47
   },
   "member_spread_now_deg": {
    "lat": 16.95,
    "lon": 25.0
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 15:06:00",
   "seed_lat": 68.20833,
   "seed_lon": 3.5,
   "seed_alt_m": 12060.0,
   "seed_age_h": 2.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-08 14:30:00",
    "lat": 74.82388,
    "lon": 53.63864,
    "alt_m": 11855.1
   },
   "member_spread_deg": {
    "lat": 26.95,
    "lon": 184.85
   },
   "member_spread_now_deg": {
    "lat": 0.68,
    "lon": 0.97
   },
   "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": 49.55,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 11:45:00",
    "lat": 66.42876,
    "lon": -114.70889,
    "alt_m": 13078.6
   },
   "member_spread_deg": {
    "lat": 33.38,
    "lon": 67.19
   },
   "member_spread_now_deg": {
    "lat": 2.6,
    "lon": 8.67
   },
   "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": 31.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-08 11:30:00",
    "lat": 55.83407,
    "lon": 146.96769,
    "alt_m": 11787.0
   },
   "member_spread_deg": {
    "lat": 27.01,
    "lon": 322.02
   },
   "member_spread_now_deg": {
    "lat": 8.24,
    "lon": 61.46
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 195.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 11:45:00",
    "lat": 56.30847,
    "lon": -115.587,
    "alt_m": 13003.2
   },
   "member_spread_deg": {
    "lat": 22.87,
    "lon": 271.04
   },
   "member_spread_now_deg": {
    "lat": 15.46,
    "lon": 290.7
   },
   "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": 178.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 11:30:00",
    "lat": 49.02159,
    "lon": 144.92632,
    "alt_m": 13200.7
   },
   "member_spread_deg": {
    "lat": 36.33,
    "lon": 256.46
   },
   "member_spread_now_deg": {
    "lat": 33.08,
    "lon": 223.11
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 08:21:30",
   "seed_lat": 31.8125,
   "seed_lon": 109.91667,
   "seed_alt_m": 12640.0,
   "seed_age_h": 8.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 11:45:00",
    "lat": 36.92419,
    "lon": 151.83355,
    "alt_m": 12823.1
   },
   "member_spread_deg": {
    "lat": 36.43,
    "lon": 315.52
   },
   "member_spread_now_deg": {
    "lat": 1.75,
    "lon": 2.43
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 16:30:00",
   "seed_lat": 31.75,
   "seed_lon": -63.625,
   "seed_alt_m": 13080.0,
   "seed_age_h": 0.83,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 16:00:00",
    "lat": 29.19723,
    "lon": -13.08431,
    "alt_m": 12996.6
   },
   "member_spread_deg": {
    "lat": 10.41,
    "lon": 41.25
   },
   "member_spread_now_deg": {
    "lat": 0.07,
    "lon": 0.23
   },
   "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": 54.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-08 11:45:00",
    "lat": 72.22844,
    "lon": -162.94732,
    "alt_m": 12121.7
   },
   "member_spread_deg": {
    "lat": 23.21,
    "lon": 156.69
   },
   "member_spread_now_deg": {
    "lat": 8.22,
    "lon": 34.69
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 16:55:45",
   "seed_lat": 67.68745,
   "seed_lon": -44.33331,
   "seed_alt_m": 13000.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 17:00:00",
    "lat": 62.23301,
    "lon": 53.53904,
    "alt_m": 13114.2
   },
   "member_spread_deg": {
    "lat": 31.9,
    "lon": 235.29
   },
   "member_spread_now_deg": {
    "lat": 0.19,
    "lon": 0.04
   },
   "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": 145.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 11:45:00",
    "lat": 49.01747,
    "lon": 6.47724,
    "alt_m": 13344.4
   },
   "member_spread_deg": {
    "lat": 17.54,
    "lon": 67.59
   },
   "member_spread_now_deg": {
    "lat": 25.31,
    "lon": 335.67
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 08:28:00",
   "seed_lat": 40.875,
   "seed_lon": 114.45833,
   "seed_alt_m": 16040.0,
   "seed_age_h": 8.87,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-08 11:30:00",
    "lat": 58.05074,
    "lon": -98.69156,
    "alt_m": 15519.8
   },
   "member_spread_deg": {
    "lat": 26.27,
    "lon": 138.07
   },
   "member_spread_now_deg": {
    "lat": 1.67,
    "lon": 10.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 02:21:00",
   "seed_lat": 41.58333,
   "seed_lon": -150.16667,
   "seed_alt_m": 13610.0,
   "seed_age_h": 14.98,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 11:45:00",
    "lat": 49.95677,
    "lon": -36.24956,
    "alt_m": 13478.8
   },
   "member_spread_deg": {
    "lat": 37.31,
    "lon": 114.1
   },
   "member_spread_now_deg": {
    "lat": 1.61,
    "lon": 5.09
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 16:06:00",
   "seed_lat": -21.4375,
   "seed_lon": -38.5,
   "seed_alt_m": 15770.0,
   "seed_age_h": 1.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-08 15:30:00",
    "lat": -22.70757,
    "lon": 26.45323,
    "alt_m": 15749.1
   },
   "member_spread_deg": {
    "lat": 33.73,
    "lon": 45.26
   },
   "member_spread_now_deg": {
    "lat": 0.06,
    "lon": 0.3
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}