{
 "generated_utc": "2026-08-31T23:25:04Z",
 "gfs_cycle_utc": "2026-08-31T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 339.5,
  "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_20260831_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260831_18Z.geojson.gz"
 },
 "counts": {
  "flights": 17,
  "members": 9,
  "rows": 65061
 },
 "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": 79.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": -71.96095,
    "lon": 45.17303,
    "alt_m": 11989.9
   },
   "member_spread_deg": {
    "lat": 22.86,
    "lon": 143.92
   },
   "member_spread_now_deg": {
    "lat": 8.18,
    "lon": 107.57
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 22:06:18",
   "seed_lat": 53.0625,
   "seed_lon": 171.66667,
   "seed_alt_m": 13850.0,
   "seed_age_h": 1.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 21:30:00",
    "lat": 41.04566,
    "lon": -27.44475,
    "alt_m": 14530.1
   },
   "member_spread_deg": {
    "lat": 17.59,
    "lon": 60.62
   },
   "member_spread_now_deg": {
    "lat": 0.67,
    "lon": 0.8
   },
   "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": 145.85,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 17:30:00",
    "lat": 24.48832,
    "lon": -101.2871,
    "alt_m": 13034.9
   },
   "member_spread_deg": {
    "lat": 16.8,
    "lon": 78.17
   },
   "member_spread_now_deg": {
    "lat": 13.85,
    "lon": 30.62
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 16:11:00",
   "seed_lat": 61.0,
   "seed_lon": -15.16667,
   "seed_alt_m": 12030.0,
   "seed_age_h": 7.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": 70.08487,
    "lon": -57.29733,
    "alt_m": 11977.5
   },
   "member_spread_deg": {
    "lat": 22.73,
    "lon": 156.19
   },
   "member_spread_now_deg": {
    "lat": 2.86,
    "lon": 6.0
   },
   "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": 31.55,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": 66.64205,
    "lon": -124.94883,
    "alt_m": 12760.7
   },
   "member_spread_deg": {
    "lat": 24.26,
    "lon": 334.48
   },
   "member_spread_now_deg": {
    "lat": 5.64,
    "lon": 4.87
   },
   "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": 13.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 17:30:00",
    "lat": 53.41863,
    "lon": 124.08601,
    "alt_m": 12057.5
   },
   "member_spread_deg": {
    "lat": 26.84,
    "lon": 296.95
   },
   "member_spread_now_deg": {
    "lat": 3.98,
    "lon": 6.26
   },
   "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": 177.12,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": 64.13664,
    "lon": -158.58011,
    "alt_m": 12328.4
   },
   "member_spread_deg": {
    "lat": 31.04,
    "lon": 260.52
   },
   "member_spread_now_deg": {
    "lat": 16.5,
    "lon": 316.37
   },
   "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": 160.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 17:30:00",
    "lat": 60.38674,
    "lon": 70.67218,
    "alt_m": 13484.3
   },
   "member_spread_deg": {
    "lat": 52.83,
    "lon": 287.84
   },
   "member_spread_now_deg": {
    "lat": 34.84,
    "lon": 223.15
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KC7RW-3",
   "flight_id": "KC7RW-3_2026-08-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 08:49:00",
   "seed_lat": 35.0,
   "seed_lon": 106.08333,
   "seed_alt_m": 12580.0,
   "seed_age_h": 14.52,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": 23.91465,
    "lon": 140.53658,
    "alt_m": 12690.2
   },
   "member_spread_deg": {
    "lat": 53.7,
    "lon": 268.23
   },
   "member_spread_now_deg": {
    "lat": 0.67,
    "lon": 1.15
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 22:00:00",
   "seed_lat": 38.02083,
   "seed_lon": -70.91667,
   "seed_alt_m": 13060.0,
   "seed_age_h": 1.33,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 21:30:00",
    "lat": 39.74964,
    "lon": -6.39146,
    "alt_m": 13045.3
   },
   "member_spread_deg": {
    "lat": 15.72,
    "lon": 50.92
   },
   "member_spread_now_deg": {
    "lat": 0.22,
    "lon": 0.51
   },
   "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": 36.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": 72.96224,
    "lon": -93.52463,
    "alt_m": 12020.6
   },
   "member_spread_deg": {
    "lat": 18.63,
    "lon": 157.7
   },
   "member_spread_now_deg": {
    "lat": 6.33,
    "lon": 14.51
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 19:35:45",
   "seed_lat": 76.52078,
   "seed_lon": -54.12498,
   "seed_alt_m": 12900.0,
   "seed_age_h": 3.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 19:00:00",
    "lat": 51.16409,
    "lon": 36.9474,
    "alt_m": 13100.8
   },
   "member_spread_deg": {
    "lat": 18.54,
    "lon": 38.59
   },
   "member_spread_now_deg": {
    "lat": 1.94,
    "lon": 2.23
   },
   "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": 127.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": 36.84357,
    "lon": -35.32997,
    "alt_m": 13633.9
   },
   "member_spread_deg": {
    "lat": 19.01,
    "lon": 37.78
   },
   "member_spread_now_deg": {
    "lat": 15.17,
    "lon": 335.35
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:43:00",
   "seed_lat": 46.16667,
   "seed_lon": 91.54167,
   "seed_alt_m": 15960.0,
   "seed_age_h": 13.62,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": 21.39629,
    "lon": -165.30148,
    "alt_m": 16340.5
   },
   "member_spread_deg": {
    "lat": 38.13,
    "lon": 331.55
   },
   "member_spread_now_deg": {
    "lat": 6.34,
    "lon": 11.25
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 22:16:00",
   "seed_lat": 44.64583,
   "seed_lon": -150.54167,
   "seed_alt_m": 13690.0,
   "seed_age_h": 1.07,
   "float_reliable": false,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 22:15:00",
    "lat": 50.28367,
    "lon": -56.75955,
    "alt_m": 13175.3
   },
   "member_spread_deg": {
    "lat": 30.32,
    "lon": 125.66
   },
   "member_spread_now_deg": {
    "lat": 0.21,
    "lon": 0.07
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 10:15:23",
   "seed_lat": 49.31245,
   "seed_lon": 84.79169,
   "seed_alt_m": 13240.0,
   "seed_age_h": 13.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-07 17:45:00",
    "lat": 61.35768,
    "lon": -85.74118,
    "alt_m": 13242.3
   },
   "member_spread_deg": {
    "lat": 28.35,
    "lon": 338.35
   },
   "member_spread_now_deg": {
    "lat": 3.46,
    "lon": 1.99
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 20:01:00",
   "seed_lat": -20.58333,
   "seed_lon": -53.125,
   "seed_alt_m": 15810.0,
   "seed_age_h": 3.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-07 19:30:00",
    "lat": -21.89102,
    "lon": 16.83164,
    "alt_m": 15713.2
   },
   "member_spread_deg": {
    "lat": 31.25,
    "lon": 70.97
   },
   "member_spread_now_deg": {
    "lat": 1.16,
    "lon": 1.23
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}