{
 "generated_utc": "2026-09-04T23:26:22Z",
 "gfs_cycle_utc": "2026-09-04T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 435.5,
  "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_20260904_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260904_18Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 75051
 },
 "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": 175.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 17:45:00",
    "lat": -54.34498,
    "lon": -114.46283,
    "alt_m": 12193.8
   },
   "member_spread_deg": {
    "lat": 31.9,
    "lon": 278.92
   },
   "member_spread_now_deg": {
    "lat": 25.68,
    "lon": 26.59
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 22:46:17",
   "seed_lat": 39.8125,
   "seed_lon": -103.58333,
   "seed_alt_m": 14570.0,
   "seed_age_h": 0.56,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 22:45:00",
    "lat": 42.92231,
    "lon": -14.97047,
    "alt_m": 14633.6
   },
   "member_spread_deg": {
    "lat": 26.82,
    "lon": 112.28
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.24
   },
   "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": 241.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:30:00",
    "lat": -3.66314,
    "lon": -102.85275,
    "alt_m": 13167.6
   },
   "member_spread_deg": {
    "lat": 23.43,
    "lon": 66.66
   },
   "member_spread_now_deg": {
    "lat": 21.04,
    "lon": 48.56
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 06:56:00",
   "seed_lat": 84.47917,
   "seed_lon": 75.83333,
   "seed_alt_m": 11790.0,
   "seed_age_h": 16.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 17:30:00",
    "lat": 80.06882,
    "lon": -148.52591,
    "alt_m": 11639.9
   },
   "member_spread_deg": {
    "lat": 26.65,
    "lon": 331.73
   },
   "member_spread_now_deg": {
    "lat": 6.91,
    "lon": 9.93
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 07:27:00",
   "seed_lat": 53.39583,
   "seed_lon": 126.70833,
   "seed_alt_m": 13200.0,
   "seed_age_h": 15.88,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:30:00",
    "lat": 23.01027,
    "lon": -60.83367,
    "alt_m": 13615.1
   },
   "member_spread_deg": {
    "lat": 39.32,
    "lon": 115.96
   },
   "member_spread_now_deg": {
    "lat": 3.59,
    "lon": 4.08
   },
   "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": 109.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 17:30:00",
    "lat": 70.74621,
    "lon": -127.39304,
    "alt_m": 11667.9
   },
   "member_spread_deg": {
    "lat": 25.11,
    "lon": 336.05
   },
   "member_spread_now_deg": {
    "lat": 30.04,
    "lon": 334.58
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DO3GU-47",
   "flight_id": "DO3GU-47_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 13:23:25",
   "seed_lat": 40.625,
   "seed_lon": 28.375,
   "seed_alt_m": 13960.0,
   "seed_age_h": 9.94,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-11 17:30:00",
    "lat": 56.82855,
    "lon": -95.59301,
    "alt_m": 13733.6
   },
   "member_spread_deg": {
    "lat": 27.52,
    "lon": 104.58
   },
   "member_spread_now_deg": {
    "lat": 1.53,
    "lon": 3.97
   },
   "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": 273.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:45:00",
    "lat": 48.25926,
    "lon": -30.99723,
    "alt_m": 13156.8
   },
   "member_spread_deg": {
    "lat": 25.87,
    "lon": 280.32
   },
   "member_spread_now_deg": {
    "lat": 24.58,
    "lon": 273.21
   },
   "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": 256.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:30:00",
    "lat": 52.45954,
    "lon": -113.26338,
    "alt_m": 13424.1
   },
   "member_spread_deg": {
    "lat": 33.15,
    "lon": 240.14
   },
   "member_spread_now_deg": {
    "lat": 37.2,
    "lon": 164.17
   },
   "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": 39.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:30:00",
    "lat": 7.79127,
    "lon": 127.864,
    "alt_m": 12855.6
   },
   "member_spread_deg": {
    "lat": 25.65,
    "lon": 300.29
   },
   "member_spread_now_deg": {
    "lat": 4.82,
    "lon": 349.35
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 19:05:00",
   "seed_lat": 25.79167,
   "seed_lon": -32.75,
   "seed_alt_m": 13040.0,
   "seed_age_h": 4.25,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 18:30:00",
    "lat": 44.31378,
    "lon": 71.89145,
    "alt_m": 12720.4
   },
   "member_spread_deg": {
    "lat": 18.25,
    "lon": 137.62
   },
   "member_spread_now_deg": {
    "lat": 0.56,
    "lon": 1.16
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 22:11:00",
   "seed_lat": 54.02083,
   "seed_lon": -177.91667,
   "seed_alt_m": 12060.0,
   "seed_age_h": 1.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 21:45:00",
    "lat": 54.59629,
    "lon": -19.16154,
    "alt_m": 12512.7
   },
   "member_spread_deg": {
    "lat": 19.56,
    "lon": 155.91
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.35
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 17:05:45",
   "seed_lat": 60.52078,
   "seed_lon": -5.12498,
   "seed_alt_m": 12960.0,
   "seed_age_h": 6.24,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:30:00",
    "lat": 55.38538,
    "lon": 160.70987,
    "alt_m": 13112.4
   },
   "member_spread_deg": {
    "lat": 16.55,
    "lon": 355.68
   },
   "member_spread_now_deg": {
    "lat": 0.41,
    "lon": 0.5
   },
   "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": 223.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:45:00",
    "lat": 27.46194,
    "lon": -28.09169,
    "alt_m": 13299.2
   },
   "member_spread_deg": {
    "lat": 23.12,
    "lon": 136.19
   },
   "member_spread_now_deg": {
    "lat": 17.01,
    "lon": 72.81
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 22:26:00",
   "seed_lat": 37.41667,
   "seed_lon": -163.66667,
   "seed_alt_m": 16100.0,
   "seed_age_h": 0.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-11 22:00:00",
    "lat": 32.97095,
    "lon": -136.17869,
    "alt_m": 16148.1
   },
   "member_spread_deg": {
    "lat": 15.75,
    "lon": 355.88
   },
   "member_spread_now_deg": {
    "lat": 0.67,
    "lon": 0.29
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 21:46:00",
   "seed_lat": 38.29167,
   "seed_lon": -122.29167,
   "seed_alt_m": 13180.0,
   "seed_age_h": 1.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 21:15:00",
    "lat": 45.80854,
    "lon": 59.42263,
    "alt_m": 13029.1
   },
   "member_spread_deg": {
    "lat": 16.06,
    "lon": 99.75
   },
   "member_spread_now_deg": {
    "lat": 0.63,
    "lon": 0.75
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 14:41:00",
   "seed_lat": -33.35417,
   "seed_lon": -2.91667,
   "seed_alt_m": 15420.0,
   "seed_age_h": 8.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 17:45:00",
    "lat": -26.6609,
    "lon": 63.52882,
    "alt_m": 15395.9
   },
   "member_spread_deg": {
    "lat": 15.17,
    "lon": 336.91
   },
   "member_spread_now_deg": {
    "lat": 3.14,
    "lon": 1.79
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}