{
 "generated_utc": "2026-08-11T23:27:11Z",
 "gfs_cycle_utc": "2026-08-11T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 490.0,
  "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_20260811_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260811_18Z.geojson.gz"
 },
 "counts": {
  "flights": 26,
  "members": 9,
  "rows": 116694
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 22:53:40",
   "seed_lat": -55.0,
   "seed_lon": -116.45832,
   "seed_alt_m": 12390.0,
   "seed_age_h": 0.44,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-18 23:00:00",
    "lat": -54.60712,
    "lon": -164.38729,
    "alt_m": 12544.8
   },
   "member_spread_deg": {
    "lat": 25.95,
    "lon": 329.44
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS53",
   "flight_id": "BSS53_2026-03-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 20:01:18",
   "seed_lat": 57.52083,
   "seed_lon": -17.58333,
   "seed_alt_m": 12640.0,
   "seed_age_h": 3.31,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 19:30:00",
    "lat": 57.96482,
    "lon": 174.34081,
    "alt_m": 12473.5
   },
   "member_spread_deg": {
    "lat": 6.04,
    "lon": 119.96
   },
   "member_spread_now_deg": {
    "lat": 1.22,
    "lon": 1.04
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 04:17:39",
   "seed_lat": 47.60417,
   "seed_lon": 117.45833,
   "seed_alt_m": 14140.0,
   "seed_age_h": 19.04,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": 42.79214,
    "lon": -152.63903,
    "alt_m": 14236.4
   },
   "member_spread_deg": {
    "lat": 21.24,
    "lon": 331.74
   },
   "member_spread_now_deg": {
    "lat": 3.4,
    "lon": 11.15
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 17:54:00",
   "seed_lat": 45.0,
   "seed_lon": -19.5,
   "seed_alt_m": 12870.0,
   "seed_age_h": 5.43,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 41.69346,
    "lon": 112.51605,
    "alt_m": 12640.0
   },
   "member_spread_deg": {
    "lat": 8.01,
    "lon": 69.68
   },
   "member_spread_now_deg": {
    "lat": 0.56,
    "lon": 0.84
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-27",
   "flight_id": "DG2GG-27_2026-07-04",
   "payload_type": "WSPR",
   "seed_time": "2026-08-10 00:18:00",
   "seed_lat": 17.10417,
   "seed_lon": -113.33333,
   "seed_alt_m": 14010.0,
   "seed_age_h": 47.03,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": -5.07104,
    "lon": -111.93352,
    "alt_m": 14113.4
   },
   "member_spread_deg": {
    "lat": 57.95,
    "lon": 76.25
   },
   "member_spread_now_deg": {
    "lat": 14.82,
    "lon": 22.6
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-29",
   "flight_id": "DG2GG-29_2026-07-28",
   "payload_type": "WSPR",
   "seed_time": "2026-08-04 04:57:00",
   "seed_lat": 46.91667,
   "seed_lon": 165.25,
   "seed_alt_m": 13380.0,
   "seed_age_h": 186.38,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 37.60357,
    "lon": 17.21947,
    "alt_m": 13312.9
   },
   "member_spread_deg": {
    "lat": 73.89,
    "lon": 256.69
   },
   "member_spread_now_deg": {
    "lat": 64.86,
    "lon": 252.31
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 21:01:00",
   "seed_lat": 56.625,
   "seed_lon": 144.79167,
   "seed_alt_m": 12760.0,
   "seed_age_h": 2.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 20:30:00",
    "lat": 54.67823,
    "lon": -39.84908,
    "alt_m": 12617.0
   },
   "member_spread_deg": {
    "lat": 18.66,
    "lon": 100.84
   },
   "member_spread_now_deg": {
    "lat": 0.16,
    "lon": 0.61
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DL0MZ-493",
   "flight_id": "DL0MZ-493_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-07-29 07:36:01",
   "seed_lat": 64.20833,
   "seed_lon": 58.16667,
   "seed_alt_m": 12170.0,
   "seed_age_h": 327.73,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 81.24601,
    "lon": 161.88953,
    "alt_m": 11585.8
   },
   "member_spread_deg": {
    "lat": 47.55,
    "lon": 326.78
   },
   "member_spread_now_deg": {
    "lat": 22.32,
    "lon": 277.54
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DL0MZ-493e",
   "flight_id": "DL0MZ-493e_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-07-29 07:27:02",
   "seed_lat": 64.15625,
   "seed_lon": 58.08889,
   "seed_alt_m": 12170.0,
   "seed_age_h": 327.88,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 33.71582,
    "lon": -4.26785,
    "alt_m": 12579.0
   },
   "member_spread_deg": {
    "lat": 53.93,
    "lon": 172.03
   },
   "member_spread_now_deg": {
    "lat": 31.53,
    "lon": 125.6
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 16:33:00",
   "seed_lat": 63.0,
   "seed_lon": 3.91667,
   "seed_alt_m": 12360.0,
   "seed_age_h": 6.78,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 60.93121,
    "lon": -87.92927,
    "alt_m": 11940.7
   },
   "member_spread_deg": {
    "lat": 15.18,
    "lon": 257.88
   },
   "member_spread_now_deg": {
    "lat": 3.77,
    "lon": 2.66
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 22:53:00",
   "seed_lat": 74.35417,
   "seed_lon": -139.375,
   "seed_alt_m": 12610.0,
   "seed_age_h": 0.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 23:00:00",
    "lat": 66.01756,
    "lon": -32.31245,
    "alt_m": 12445.2
   },
   "member_spread_deg": {
    "lat": 26.18,
    "lon": 66.26
   },
   "member_spread_now_deg": {
    "lat": 0.08,
    "lon": 0.55
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "K5NOT-11",
   "flight_id": "K5NOT-11_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-10 03:45:37",
   "seed_lat": 33.04161,
   "seed_lon": 175.83333,
   "seed_alt_m": 13420.0,
   "seed_age_h": 43.57,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": 22.63345,
    "lon": -64.73462,
    "alt_m": 13534.5
   },
   "member_spread_deg": {
    "lat": 39.48,
    "lon": 285.18
   },
   "member_spread_now_deg": {
    "lat": 24.8,
    "lon": 35.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 20:47:18",
   "seed_lat": 53.9375,
   "seed_lon": -18.83333,
   "seed_alt_m": 13480.0,
   "seed_age_h": 2.55,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 20:15:00",
    "lat": 61.59238,
    "lon": 156.0542,
    "alt_m": 13274.0
   },
   "member_spread_deg": {
    "lat": 15.44,
    "lon": 355.21
   },
   "member_spread_now_deg": {
    "lat": 0.64,
    "lon": 0.75
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC5TRB-1",
   "flight_id": "KC5TRB-1_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 16:35:43",
   "seed_lat": 64.79161,
   "seed_lon": -4.79163,
   "seed_alt_m": 12660.0,
   "seed_age_h": 6.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 61.35277,
    "lon": 87.54991,
    "alt_m": 12646.3
   },
   "member_spread_deg": {
    "lat": 7.51,
    "lon": 237.81
   },
   "member_spread_now_deg": {
    "lat": 2.53,
    "lon": 6.87
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 18:12:30",
   "seed_lat": 38.97917,
   "seed_lon": -11.0,
   "seed_alt_m": 13112.0,
   "seed_age_h": 5.13,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": 47.15281,
    "lon": 132.98523,
    "alt_m": 12933.5
   },
   "member_spread_deg": {
    "lat": 4.25,
    "lon": 82.92
   },
   "member_spread_now_deg": {
    "lat": 0.25,
    "lon": 1.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 21:06:00",
   "seed_lat": 54.45833,
   "seed_lon": -78.16667,
   "seed_alt_m": 12100.0,
   "seed_age_h": 2.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-18 20:30:00",
    "lat": 73.08611,
    "lon": -71.59836,
    "alt_m": 12008.6
   },
   "member_spread_deg": {
    "lat": 8.06,
    "lon": 188.82
   },
   "member_spread_now_deg": {
    "lat": 0.3,
    "lon": 0.07
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE9DAB-11",
   "flight_id": "KE9DAB-11_2026-07-29",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 10:51:00",
   "seed_lat": 50.22917,
   "seed_lon": 92.08333,
   "seed_alt_m": 12160.0,
   "seed_age_h": 12.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": 31.92506,
    "lon": -120.5108,
    "alt_m": 12474.2
   },
   "member_spread_deg": {
    "lat": 18.79,
    "lon": 307.9
   },
   "member_spread_now_deg": {
    "lat": 3.77,
    "lon": 2.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI1TEN-1",
   "flight_id": "KI1TEN-1_2026-07-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-01 22:55:27",
   "seed_lat": 23.95828,
   "seed_lon": -104.12496,
   "seed_alt_m": 12380.0,
   "seed_age_h": 240.41,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 7.37444,
    "lon": -104.92328,
    "alt_m": 12391.2
   },
   "member_spread_deg": {
    "lat": 49.11,
    "lon": 126.39
   },
   "member_spread_now_deg": {
    "lat": 18.82,
    "lon": 46.86
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 06:35:45",
   "seed_lat": 54.72911,
   "seed_lon": 24.66669,
   "seed_alt_m": 13360.0,
   "seed_age_h": 16.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 63.6418,
    "lon": 144.2205,
    "alt_m": 13028.3
   },
   "member_spread_deg": {
    "lat": 24.66,
    "lon": 313.31
   },
   "member_spread_now_deg": {
    "lat": 5.4,
    "lon": 4.83
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 21:48:00",
   "seed_lat": 33.10417,
   "seed_lon": 178.79167,
   "seed_alt_m": 16270.0,
   "seed_age_h": 1.53,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-18 21:15:00",
    "lat": 5.9854,
    "lon": 95.53474,
    "alt_m": 16392.2
   },
   "member_spread_deg": {
    "lat": 45.41,
    "lon": 355.42
   },
   "member_spread_now_deg": {
    "lat": 0.46,
    "lon": 0.58
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP6MPL-34",
   "flight_id": "SP6MPL-34_2025-12-03",
   "payload_type": "WSPR",
   "seed_time": "2026-07-31 18:52:00",
   "seed_lat": 74.5625,
   "seed_lon": -160.0,
   "seed_alt_m": 12890.0,
   "seed_age_h": 268.47,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": 63.79917,
    "lon": -30.24262,
    "alt_m": 12935.4
   },
   "member_spread_deg": {
    "lat": 20.81,
    "lon": 272.43
   },
   "member_spread_now_deg": {
    "lat": 16.0,
    "lon": 334.85
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "SP6MPL-9",
   "flight_id": "SP6MPL-9_2026-08-02",
   "payload_type": "APRS",
   "seed_time": "2026-08-04 04:05:45",
   "seed_lat": 45.52942,
   "seed_lon": 75.286,
   "seed_alt_m": 12836.0,
   "seed_age_h": 187.24,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 58.79419,
    "lon": 144.93684,
    "alt_m": 12493.3
   },
   "member_spread_deg": {
    "lat": 27.44,
    "lon": 309.59
   },
   "member_spread_now_deg": {
    "lat": 29.44,
    "lon": 324.19
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 00:51:00",
   "seed_lat": 49.16667,
   "seed_lon": 117.375,
   "seed_alt_m": 13220.0,
   "seed_age_h": 22.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": 27.56799,
    "lon": 174.17872,
    "alt_m": 13512.8
   },
   "member_spread_deg": {
    "lat": 23.9,
    "lon": 346.75
   },
   "member_spread_now_deg": {
    "lat": 6.72,
    "lon": 10.65
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 06:40:23",
   "seed_lat": 52.79161,
   "seed_lon": 83.50002,
   "seed_alt_m": 13540.0,
   "seed_age_h": 16.66,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": 54.57313,
    "lon": -162.19854,
    "alt_m": 12981.6
   },
   "member_spread_deg": {
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   },
   "member_spread_now_deg": {
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   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6SRC-37",
   "flight_id": "ZS6SRC-37_2026-07-15",
   "payload_type": "WSPR",
   "seed_time": "2026-07-31 04:34:00",
   "seed_lat": -23.70833,
   "seed_lon": 149.29167,
   "seed_alt_m": 12380.0,
   "seed_age_h": 282.77,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-18 17:30:00",
    "lat": 0.55998,
    "lon": 26.64117,
    "alt_m": 12690.9
   },
   "member_spread_deg": {
    "lat": 34.87,
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   },
   "member_spread_now_deg": {
    "lat": 24.66,
    "lon": 349.18
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6SRC-39",
   "flight_id": "ZS6SRC-39_2026-08-05",
   "payload_type": "WSPR",
   "seed_time": "2026-08-11 06:46:00",
   "seed_lat": -17.70833,
   "seed_lon": 133.83333,
   "seed_alt_m": 15910.0,
   "seed_age_h": 16.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-18 17:45:00",
    "lat": -20.06942,
    "lon": 96.76409,
    "alt_m": 15810.2
   },
   "member_spread_deg": {
    "lat": 18.39,
    "lon": 99.83
   },
   "member_spread_now_deg": {
    "lat": 5.84,
    "lon": 6.43
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}