{
 "generated_utc": "2026-09-04T05:25:57Z",
 "gfs_cycle_utc": "2026-09-04T00:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 417.5,
  "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_00Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260904_00Z.geojson.gz"
 },
 "counts": {
  "flights": 16,
  "members": 9,
  "rows": 69525
 },
 "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": 157.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 23:45:00",
    "lat": -66.36107,
    "lon": -169.89035,
    "alt_m": 12180.9
   },
   "member_spread_deg": {
    "lat": 13.9,
    "lon": 338.9
   },
   "member_spread_now_deg": {
    "lat": 20.39,
    "lon": 124.14
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 01:01:18",
   "seed_lat": 31.04167,
   "seed_lon": -119.5,
   "seed_alt_m": 14530.0,
   "seed_age_h": 4.31,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 00:30:00",
    "lat": 42.47754,
    "lon": 5.88286,
    "alt_m": 14200.4
   },
   "member_spread_deg": {
    "lat": 19.36,
    "lon": 121.17
   },
   "member_spread_now_deg": {
    "lat": 0.34,
    "lon": 1.68
   },
   "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": 223.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:30:00",
    "lat": 4.68871,
    "lon": -100.35304,
    "alt_m": 13157.1
   },
   "member_spread_deg": {
    "lat": 35.22,
    "lon": 69.19
   },
   "member_spread_now_deg": {
    "lat": 22.32,
    "lon": 44.73
   },
   "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 04:41:00",
   "seed_lat": 84.29167,
   "seed_lon": 73.04167,
   "seed_alt_m": 11840.0,
   "seed_age_h": 0.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 04:45:00",
    "lat": 79.14242,
    "lon": -157.82727,
    "alt_m": 11987.1
   },
   "member_spread_deg": {
    "lat": 22.95,
    "lon": 285.36
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.81
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 03:52:00",
   "seed_lat": 54.04167,
   "seed_lon": 124.0,
   "seed_alt_m": 13320.0,
   "seed_age_h": 1.47,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 03:15:00",
    "lat": 57.25665,
    "lon": -28.24864,
    "alt_m": 12914.5
   },
   "member_spread_deg": {
    "lat": 25.88,
    "lon": 72.11
   },
   "member_spread_now_deg": {
    "lat": 0.1,
    "lon": 0.39
   },
   "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": 91.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-10 23:30:00",
    "lat": 55.19135,
    "lon": 153.45439,
    "alt_m": 11684.5
   },
   "member_spread_deg": {
    "lat": 29.56,
    "lon": 279.07
   },
   "member_spread_now_deg": {
    "lat": 29.41,
    "lon": 94.88
   },
   "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": 255.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:45:00",
    "lat": 54.49422,
    "lon": -105.83362,
    "alt_m": 12839.6
   },
   "member_spread_deg": {
    "lat": 33.2,
    "lon": 330.85
   },
   "member_spread_now_deg": {
    "lat": 23.16,
    "lon": 302.9
   },
   "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": 238.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:30:00",
    "lat": 46.42122,
    "lon": -153.90604,
    "alt_m": 13982.1
   },
   "member_spread_deg": {
    "lat": 34.39,
    "lon": 327.9
   },
   "member_spread_now_deg": {
    "lat": 31.75,
    "lon": 165.56
   },
   "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": 21.27,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:30:00",
    "lat": 30.26614,
    "lon": 126.38864,
    "alt_m": 12845.8
   },
   "member_spread_deg": {
    "lat": 14.28,
    "lon": 318.74
   },
   "member_spread_now_deg": {
    "lat": 3.48,
    "lon": 14.82
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 20:25:00",
   "seed_lat": 27.25,
   "seed_lon": -50.5,
   "seed_alt_m": 13080.0,
   "seed_age_h": 8.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:30:00",
    "lat": 45.52401,
    "lon": 79.01168,
    "alt_m": 12726.3
   },
   "member_spread_deg": {
    "lat": 25.34,
    "lon": 140.1
   },
   "member_spread_now_deg": {
    "lat": 0.85,
    "lon": 3.79
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 04:51:00",
   "seed_lat": 52.14583,
   "seed_lon": 165.70833,
   "seed_alt_m": 12060.0,
   "seed_age_h": 0.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-11 04:45:00",
    "lat": 74.8081,
    "lon": -33.12964,
    "alt_m": 12114.7
   },
   "member_spread_deg": {
    "lat": 22.94,
    "lon": 71.81
   },
   "member_spread_now_deg": {
    "lat": 0.06,
    "lon": 0.02
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 18:35:45",
   "seed_lat": 60.10411,
   "seed_lon": -25.83331,
   "seed_alt_m": 12960.0,
   "seed_age_h": 10.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:30:00",
    "lat": 48.04806,
    "lon": 136.42141,
    "alt_m": 13231.9
   },
   "member_spread_deg": {
    "lat": 11.89,
    "lon": 100.43
   },
   "member_spread_now_deg": {
    "lat": 1.59,
    "lon": 1.1
   },
   "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": 205.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:45:00",
    "lat": 50.4751,
    "lon": -20.30666,
    "alt_m": 13275.9
   },
   "member_spread_deg": {
    "lat": 40.11,
    "lon": 217.35
   },
   "member_spread_now_deg": {
    "lat": 10.91,
    "lon": 65.66
   },
   "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 03:51:00",
   "seed_lat": 39.39583,
   "seed_lon": -175.08333,
   "seed_alt_m": 16100.0,
   "seed_age_h": 1.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-11 03:15:00",
    "lat": 37.9532,
    "lon": -144.3194,
    "alt_m": 16280.3
   },
   "member_spread_deg": {
    "lat": 25.58,
    "lon": 106.45
   },
   "member_spread_now_deg": {
    "lat": 0.74,
    "lon": 1.04
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-04 01:01:00",
   "seed_lat": 44.22917,
   "seed_lon": -139.91667,
   "seed_alt_m": 13400.0,
   "seed_age_h": 4.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-11 00:30:00",
    "lat": 41.52261,
    "lon": 27.64225,
    "alt_m": 13284.0
   },
   "member_spread_deg": {
    "lat": 24.81,
    "lon": 77.05
   },
   "member_spread_now_deg": {
    "lat": 0.85,
    "lon": 1.02
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-03 16:01:00",
   "seed_lat": -25.04167,
   "seed_lon": -15.625,
   "seed_alt_m": 15540.0,
   "seed_age_h": 13.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-10 23:30:00",
    "lat": -18.77854,
    "lon": 50.72436,
    "alt_m": 15484.7
   },
   "member_spread_deg": {
    "lat": 31.09,
    "lon": 54.53
   },
   "member_spread_now_deg": {
    "lat": 5.64,
    "lon": 1.46
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}