{
 "generated_utc": "2026-09-02T17:25:44Z",
 "gfs_cycle_utc": "2026-09-02T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 381.5,
  "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_20260902_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260902_12Z.geojson.gz"
 },
 "counts": {
  "flights": 16,
  "members": 9,
  "rows": 66429
 },
 "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": 121.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 11:45:00",
    "lat": -45.65514,
    "lon": 166.98003,
    "alt_m": 12191.1
   },
   "member_spread_deg": {
    "lat": 25.47,
    "lon": 91.53
   },
   "member_spread_now_deg": {
    "lat": 12.44,
    "lon": 288.25
   },
   "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": 42.26,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-09 11:30:00",
    "lat": 48.54044,
    "lon": -8.71658,
    "alt_m": 14142.2
   },
   "member_spread_deg": {
    "lat": 26.4,
    "lon": 56.17
   },
   "member_spread_now_deg": {
    "lat": 13.8,
    "lon": 14.34
   },
   "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": 187.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:30:00",
    "lat": 13.43518,
    "lon": -88.12995,
    "alt_m": 13150.0
   },
   "member_spread_deg": {
    "lat": 30.78,
    "lon": 77.56
   },
   "member_spread_now_deg": {
    "lat": 14.8,
    "lon": 32.18
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 15:26:00",
   "seed_lat": 77.3125,
   "seed_lon": 23.41667,
   "seed_alt_m": 11990.0,
   "seed_age_h": 1.9,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 15:00:00",
    "lat": 67.80339,
    "lon": 62.34566,
    "alt_m": 11879.8
   },
   "member_spread_deg": {
    "lat": 23.7,
    "lon": 182.89
   },
   "member_spread_now_deg": {
    "lat": 0.66,
    "lon": 2.46
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 07:37:00",
   "seed_lat": 46.54167,
   "seed_lon": 66.41667,
   "seed_alt_m": 13020.0,
   "seed_age_h": 9.72,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:30:00",
    "lat": 45.09551,
    "lon": -111.31052,
    "alt_m": 13155.1
   },
   "member_spread_deg": {
    "lat": 17.31,
    "lon": 42.92
   },
   "member_spread_now_deg": {
    "lat": 0.22,
    "lon": 2.61
   },
   "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": 55.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-09 11:30:00",
    "lat": 63.1856,
    "lon": 162.63918,
    "alt_m": 11712.9
   },
   "member_spread_deg": {
    "lat": 13.06,
    "lon": 340.09
   },
   "member_spread_now_deg": {
    "lat": 23.25,
    "lon": 94.35
   },
   "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": 219.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:45:00",
    "lat": 62.95164,
    "lon": -102.48126,
    "alt_m": 12786.9
   },
   "member_spread_deg": {
    "lat": 24.92,
    "lon": 269.63
   },
   "member_spread_now_deg": {
    "lat": 28.74,
    "lon": 285.61
   },
   "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": 202.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:30:00",
    "lat": 22.31603,
    "lon": 168.74513,
    "alt_m": 14086.6
   },
   "member_spread_deg": {
    "lat": 63.53,
    "lon": 322.3
   },
   "member_spread_now_deg": {
    "lat": 20.14,
    "lon": 193.96
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 07:19:00",
   "seed_lat": 32.375,
   "seed_lon": 112.58333,
   "seed_alt_m": 12680.0,
   "seed_age_h": 10.02,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:45:00",
    "lat": 24.85999,
    "lon": 138.12268,
    "alt_m": 12852.4
   },
   "member_spread_deg": {
    "lat": 41.79,
    "lon": 298.75
   },
   "member_spread_now_deg": {
    "lat": 3.25,
    "lon": 5.1
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 16:40:00",
   "seed_lat": 26.54167,
   "seed_lon": -60.08333,
   "seed_alt_m": 13120.0,
   "seed_age_h": 0.67,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 16:15:00",
    "lat": 34.58569,
    "lon": 23.59684,
    "alt_m": 12793.1
   },
   "member_spread_deg": {
    "lat": 16.91,
    "lon": 88.23
   },
   "member_spread_now_deg": {
    "lat": 0.04,
    "lon": 0.03
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 04:26:00",
   "seed_lat": 66.25,
   "seed_lon": 146.66667,
   "seed_alt_m": 12460.0,
   "seed_age_h": 12.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:30:00",
    "lat": 60.7093,
    "lon": -51.02754,
    "alt_m": 11814.3
   },
   "member_spread_deg": {
    "lat": 19.7,
    "lon": 87.47
   },
   "member_spread_now_deg": {
    "lat": 5.95,
    "lon": 3.39
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 16:55:45",
   "seed_lat": 62.16661,
   "seed_lon": -38.16665,
   "seed_alt_m": 13000.0,
   "seed_age_h": 0.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 17:00:00",
    "lat": 50.93164,
    "lon": 61.88406,
    "alt_m": 13160.2
   },
   "member_spread_deg": {
    "lat": 12.53,
    "lon": 57.7
   },
   "member_spread_now_deg": {
    "lat": 0.04,
    "lon": 0.12
   },
   "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": 169.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:45:00",
    "lat": 43.62356,
    "lon": -26.68,
    "alt_m": 13502.9
   },
   "member_spread_deg": {
    "lat": 29.6,
    "lon": 82.2
   },
   "member_spread_now_deg": {
    "lat": 16.23,
    "lon": 55.92
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 23:21:00",
   "seed_lat": 40.39583,
   "seed_lon": 126.58333,
   "seed_alt_m": 16040.0,
   "seed_age_h": 17.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-09 11:45:00",
    "lat": 42.46514,
    "lon": -172.23395,
    "alt_m": 16044.8
   },
   "member_spread_deg": {
    "lat": 37.65,
    "lon": 144.33
   },
   "member_spread_now_deg": {
    "lat": 2.64,
    "lon": 24.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 02:36:00",
   "seed_lat": 39.8125,
   "seed_lon": -156.66667,
   "seed_alt_m": 13650.0,
   "seed_age_h": 14.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-09 11:30:00",
    "lat": 50.32519,
    "lon": 16.39828,
    "alt_m": 13273.3
   },
   "member_spread_deg": {
    "lat": 26.98,
    "lon": 89.58
   },
   "member_spread_now_deg": {
    "lat": 3.89,
    "lon": 2.55
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-02 10:56:00",
   "seed_lat": -21.5,
   "seed_lon": -29.875,
   "seed_alt_m": 15710.0,
   "seed_age_h": 6.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-09 11:30:00",
    "lat": -36.13798,
    "lon": 33.68751,
    "alt_m": 15358.5
   },
   "member_spread_deg": {
    "lat": 27.21,
    "lon": 31.39
   },
   "member_spread_now_deg": {
    "lat": 0.46,
    "lon": 1.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}