{
 "generated_utc": "2026-09-01T23:25:20Z",
 "gfs_cycle_utc": "2026-09-01T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 363.5,
  "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_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260901_18Z.geojson.gz"
 },
 "counts": {
  "flights": 16,
  "members": 9,
  "rows": 65736
 },
 "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": 103.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-08 17:45:00",
    "lat": -58.88963,
    "lon": -24.83362,
    "alt_m": 12199.0
   },
   "member_spread_deg": {
    "lat": 19.4,
    "lon": 173.25
   },
   "member_spread_now_deg": {
    "lat": 15.66,
    "lon": 318.75
   },
   "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": 24.26,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-08 17:30:00",
    "lat": 30.70835,
    "lon": -69.74457,
    "alt_m": 14565.7
   },
   "member_spread_deg": {
    "lat": 16.43,
    "lon": 51.33
   },
   "member_spread_now_deg": {
    "lat": 15.15,
    "lon": 17.34
   },
   "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": 169.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 17:30:00",
    "lat": 22.50547,
    "lon": -87.5106,
    "alt_m": 13177.5
   },
   "member_spread_deg": {
    "lat": 24.07,
    "lon": 51.94
   },
   "member_spread_now_deg": {
    "lat": 17.24,
    "lon": 24.01
   },
   "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": 8.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-08 17:30:00",
    "lat": 72.24987,
    "lon": -56.1584,
    "alt_m": 11779.7
   },
   "member_spread_deg": {
    "lat": 13.35,
    "lon": 148.4
   },
   "member_spread_now_deg": {
    "lat": 2.76,
    "lon": 4.04
   },
   "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": 55.55,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 17:45:00",
    "lat": 43.06692,
    "lon": -118.30365,
    "alt_m": 13236.1
   },
   "member_spread_deg": {
    "lat": 29.42,
    "lon": 58.57
   },
   "member_spread_now_deg": {
    "lat": 1.95,
    "lon": 10.59
   },
   "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": 37.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-08 17:30:00",
    "lat": 59.03827,
    "lon": 151.19776,
    "alt_m": 11731.2
   },
   "member_spread_deg": {
    "lat": 22.97,
    "lon": 280.08
   },
   "member_spread_now_deg": {
    "lat": 9.16,
    "lon": 81.49
   },
   "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": 201.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 17:45:00",
    "lat": 60.43796,
    "lon": -124.83479,
    "alt_m": 13028.1
   },
   "member_spread_deg": {
    "lat": 27.59,
    "lon": 306.92
   },
   "member_spread_now_deg": {
    "lat": 19.12,
    "lon": 286.87
   },
   "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": 184.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 17:30:00",
    "lat": 44.19336,
    "lon": 167.21836,
    "alt_m": 13850.1
   },
   "member_spread_deg": {
    "lat": 45.16,
    "lon": 264.54
   },
   "member_spread_now_deg": {
    "lat": 28.79,
    "lon": 224.87
   },
   "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": 14.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 17:45:00",
    "lat": 30.58116,
    "lon": 164.98488,
    "alt_m": 12847.8
   },
   "member_spread_deg": {
    "lat": 45.32,
    "lon": 324.2
   },
   "member_spread_now_deg": {
    "lat": 3.75,
    "lon": 5.1
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 21:10:00",
   "seed_lat": 31.29167,
   "seed_lon": -62.75,
   "seed_alt_m": 13100.0,
   "seed_age_h": 2.17,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 20:45:00",
    "lat": 33.37573,
    "lon": 0.64442,
    "alt_m": 13036.1
   },
   "member_spread_deg": {
    "lat": 9.8,
    "lon": 47.77
   },
   "member_spread_now_deg": {
    "lat": 0.34,
    "lon": 0.31
   },
   "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": 60.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-08 17:45:00",
    "lat": 80.96586,
    "lon": -143.78461,
    "alt_m": 11973.9
   },
   "member_spread_deg": {
    "lat": 40.39,
    "lon": 139.59
   },
   "member_spread_now_deg": {
    "lat": 10.42,
    "lon": 30.33
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 19:45:45",
   "seed_lat": 66.64578,
   "seed_lon": -43.24998,
   "seed_alt_m": 12960.0,
   "seed_age_h": 3.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 19:15:00",
    "lat": 48.85389,
    "lon": 45.84595,
    "alt_m": 13167.3
   },
   "member_spread_deg": {
    "lat": 22.53,
    "lon": 31.14
   },
   "member_spread_now_deg": {
    "lat": 1.12,
    "lon": 0.62
   },
   "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": 151.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 17:45:00",
    "lat": 42.98706,
    "lon": -21.57338,
    "alt_m": 13583.3
   },
   "member_spread_deg": {
    "lat": 21.39,
    "lon": 60.99
   },
   "member_spread_now_deg": {
    "lat": 27.77,
    "lon": 43.9
   },
   "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 08:28:00",
   "seed_lat": 40.875,
   "seed_lon": 114.45833,
   "seed_alt_m": 16040.0,
   "seed_age_h": 14.87,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-08 17:30:00",
    "lat": 52.02227,
    "lon": -89.71361,
    "alt_m": 15678.2
   },
   "member_spread_deg": {
    "lat": 21.62,
    "lon": 124.88
   },
   "member_spread_now_deg": {
    "lat": 5.39,
    "lon": 18.45
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 22:36:00",
   "seed_lat": 38.64583,
   "seed_lon": -154.375,
   "seed_alt_m": 13660.0,
   "seed_age_h": 0.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-08 22:30:00",
    "lat": 53.67038,
    "lon": 18.00875,
    "alt_m": 13184.2
   },
   "member_spread_deg": {
    "lat": 28.75,
    "lon": 196.99
   },
   "member_spread_now_deg": {
    "lat": 0.16,
    "lon": 0.27
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-01 18:26:00",
   "seed_lat": -21.41667,
   "seed_lon": -36.70833,
   "seed_alt_m": 15750.0,
   "seed_age_h": 4.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-08 18:00:00",
    "lat": -31.10396,
    "lon": 33.067,
    "alt_m": 15483.2
   },
   "member_spread_deg": {
    "lat": 31.11,
    "lon": 52.53
   },
   "member_spread_now_deg": {
    "lat": 1.51,
    "lon": 1.64
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}