{
 "generated_utc": "2026-08-18T17:25:42Z",
 "gfs_cycle_utc": "2026-08-18T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 371.5,
  "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_20260818_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260818_12Z.geojson.gz"
 },
 "counts": {
  "flights": 20,
  "members": 9,
  "rows": 73665
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 03:23:40",
   "seed_lat": -65.0625,
   "seed_lon": 148.75001,
   "seed_alt_m": 12420.0,
   "seed_age_h": 13.94,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:30:00",
    "lat": -53.91564,
    "lon": 115.45222,
    "alt_m": 12187.7
   },
   "member_spread_deg": {
    "lat": 21.15,
    "lon": 340.75
   },
   "member_spread_now_deg": {
    "lat": 0.4,
    "lon": 5.09
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS53",
   "flight_id": "BSS53_2026-03-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 09:11:17",
   "seed_lat": 62.02083,
   "seed_lon": 145.375,
   "seed_alt_m": 12430.0,
   "seed_age_h": 8.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": 68.48084,
    "lon": 155.4496,
    "alt_m": 12149.7
   },
   "member_spread_deg": {
    "lat": 32.5,
    "lon": 295.47
   },
   "member_spread_now_deg": {
    "lat": 1.84,
    "lon": 2.11
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 03:48:18",
   "seed_lat": 43.79167,
   "seed_lon": -166.58333,
   "seed_alt_m": 14200.0,
   "seed_age_h": 13.53,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": 52.81678,
    "lon": -79.08825,
    "alt_m": 13779.9
   },
   "member_spread_deg": {
    "lat": 39.82,
    "lon": 134.32
   },
   "member_spread_now_deg": {
    "lat": 3.47,
    "lon": 9.35
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-23",
   "flight_id": "DG2GG-23_2026-05-23",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 09:19:00",
   "seed_lat": 47.58333,
   "seed_lon": 106.54167,
   "seed_alt_m": 12620.0,
   "seed_age_h": 8.02,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": 39.54226,
    "lon": -132.94912,
    "alt_m": 12834.6
   },
   "member_spread_deg": {
    "lat": 13.93,
    "lon": 7.15
   },
   "member_spread_now_deg": {
    "lat": 1.39,
    "lon": 2.43
   },
   "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": 209.03,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": -5.41933,
    "lon": -65.51465,
    "alt_m": 14074.7
   },
   "member_spread_deg": {
    "lat": 74.1,
    "lon": 184.07
   },
   "member_spread_now_deg": {
    "lat": 39.46,
    "lon": 87.34
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 15:31:00",
   "seed_lat": 53.35417,
   "seed_lon": -50.25,
   "seed_alt_m": 12500.0,
   "seed_age_h": 1.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 15:00:00",
    "lat": 53.11421,
    "lon": 158.94851,
    "alt_m": 12587.5
   },
   "member_spread_deg": {
    "lat": 9.25,
    "lon": 84.22
   },
   "member_spread_now_deg": {
    "lat": 0.6,
    "lon": 1.5
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 11:07:00",
   "seed_lat": 46.0,
   "seed_lon": 78.58333,
   "seed_alt_m": 13100.0,
   "seed_age_h": 6.22,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:30:00",
    "lat": 42.09386,
    "lon": -152.90447,
    "alt_m": 13238.1
   },
   "member_spread_deg": {
    "lat": 27.44,
    "lon": 61.85
   },
   "member_spread_now_deg": {
    "lat": 0.33,
    "lon": 1.97
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 16:38:00",
   "seed_lat": 81.58333,
   "seed_lon": 14.95833,
   "seed_alt_m": 11970.0,
   "seed_age_h": 0.7,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 16:15:00",
    "lat": 82.07245,
    "lon": -117.53324,
    "alt_m": 11789.9
   },
   "member_spread_deg": {
    "lat": 11.95,
    "lon": 288.31
   },
   "member_spread_now_deg": {
    "lat": 0.02,
    "lon": 0.35
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "EI6BFW-18",
   "flight_id": "EI6BFW-18_2026-07-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 16:53:00",
   "seed_lat": 63.66667,
   "seed_lon": -39.125,
   "seed_alt_m": 12660.0,
   "seed_age_h": 0.45,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 17:00:00",
    "lat": 55.78158,
    "lon": 77.52883,
    "alt_m": 12466.2
   },
   "member_spread_deg": {
    "lat": 19.87,
    "lon": 74.51
   },
   "member_spread_now_deg": {
    "lat": 0.13,
    "lon": 0.11
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "K5NOT-11",
   "flight_id": "K5NOT-11_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-15 20:50:37",
   "seed_lat": 40.97911,
   "seed_lon": -75.41666,
   "seed_alt_m": 13300.0,
   "seed_age_h": 68.49,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": 38.19903,
    "lon": -93.59518,
    "alt_m": 13340.2
   },
   "member_spread_deg": {
    "lat": 29.93,
    "lon": 111.66
   },
   "member_spread_now_deg": {
    "lat": 18.63,
    "lon": 35.06
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC3LBR-449",
   "flight_id": "KC3LBR-449_2026-07-06",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 16:57:03",
   "seed_lat": 73.58333,
   "seed_lon": 46.16667,
   "seed_alt_m": 13220.0,
   "seed_age_h": 0.38,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 17:00:00",
    "lat": 62.64785,
    "lon": -171.64426,
    "alt_m": 13054.1
   },
   "member_spread_deg": {
    "lat": 18.81,
    "lon": 355.39
   },
   "member_spread_now_deg": {
    "lat": 0.06,
    "lon": 0.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KC5TRB-1",
   "flight_id": "KC5TRB-1_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-12 11:40:43",
   "seed_lat": 57.39578,
   "seed_lon": 26.00003,
   "seed_alt_m": 12570.0,
   "seed_age_h": 149.66,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": 72.46516,
    "lon": 98.69749,
    "alt_m": 12502.3
   },
   "member_spread_deg": {
    "lat": 39.4,
    "lon": 274.58
   },
   "member_spread_now_deg": {
    "lat": 28.63,
    "lon": 259.57
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 07:45:00",
   "seed_lat": 46.41667,
   "seed_lon": 126.45833,
   "seed_alt_m": 12790.0,
   "seed_age_h": 9.58,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": 31.32445,
    "lon": -131.6945,
    "alt_m": 12960.9
   },
   "member_spread_deg": {
    "lat": 25.69,
    "lon": 64.46
   },
   "member_spread_now_deg": {
    "lat": 7.71,
    "lon": 3.86
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 15:31:00",
   "seed_lat": 78.41667,
   "seed_lon": -23.41667,
   "seed_alt_m": 12200.0,
   "seed_age_h": 1.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 15:00:00",
    "lat": 87.50431,
    "lon": -49.92194,
    "alt_m": 11903.7
   },
   "member_spread_deg": {
    "lat": 20.94,
    "lon": 341.43
   },
   "member_spread_now_deg": {
    "lat": 0.03,
    "lon": 2.24
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE9DAB-11",
   "flight_id": "KE9DAB-11_2026-07-29",
   "payload_type": "WSPR",
   "seed_time": "2026-08-13 21:11:00",
   "seed_lat": 63.66667,
   "seed_lon": 161.54167,
   "seed_alt_m": 10970.0,
   "seed_age_h": 116.15,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": 46.38673,
    "lon": 103.89067,
    "alt_m": 11033.3
   },
   "member_spread_deg": {
    "lat": 38.46,
    "lon": 215.34
   },
   "member_spread_now_deg": {
    "lat": 22.36,
    "lon": 65.72
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 09:30:45",
   "seed_lat": 61.39578,
   "seed_lon": 117.75002,
   "seed_alt_m": 13060.0,
   "seed_age_h": 7.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:30:00",
    "lat": 69.40539,
    "lon": -77.09137,
    "alt_m": 13001.5
   },
   "member_spread_deg": {
    "lat": 38.97,
    "lon": 317.04
   },
   "member_spread_now_deg": {
    "lat": 0.72,
    "lon": 2.5
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 08:51:00",
   "seed_lat": 9.625,
   "seed_lon": 112.125,
   "seed_alt_m": 16560.0,
   "seed_age_h": 8.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": 11.27864,
    "lon": -3.64784,
    "alt_m": 16498.9
   },
   "member_spread_deg": {
    "lat": 27.58,
    "lon": 157.57
   },
   "member_spread_now_deg": {
    "lat": 4.02,
    "lon": 1.73
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-08-18 03:06:00",
   "seed_lat": 40.5,
   "seed_lon": -167.125,
   "seed_alt_m": 13500.0,
   "seed_age_h": 14.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-08-25 11:30:00",
    "lat": 28.81427,
    "lon": -20.79477,
    "alt_m": 13672.9
   },
   "member_spread_deg": {
    "lat": 28.42,
    "lon": 124.86
   },
   "member_spread_now_deg": {
    "lat": 1.23,
    "lon": 7.66
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6SRC-37",
   "flight_id": "ZS6SRC-37_2026-07-31",
   "payload_type": "WSPR",
   "seed_time": "2026-08-17 20:59:00",
   "seed_lat": -20.58333,
   "seed_lon": -72.33333,
   "seed_alt_m": 12210.0,
   "seed_age_h": 20.35,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-08-25 11:30:00",
    "lat": -25.30208,
    "lon": 176.55886,
    "alt_m": 12099.7
   },
   "member_spread_deg": {
    "lat": 21.14,
    "lon": 356.03
   },
   "member_spread_now_deg": {
    "lat": 16.5,
    "lon": 21.09
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6SRC-39",
   "flight_id": "ZS6SRC-39_2026-08-05",
   "payload_type": "WSPR",
   "seed_time": "2026-08-12 06:21:00",
   "seed_lat": -22.16667,
   "seed_lon": 146.45833,
   "seed_alt_m": 15900.0,
   "seed_age_h": 154.98,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-08-25 11:45:00",
    "lat": -15.28695,
    "lon": -22.97614,
    "alt_m": 15937.3
   },
   "member_spread_deg": {
    "lat": 33.36,
    "lon": 258.02
   },
   "member_spread_now_deg": {
    "lat": 14.85,
    "lon": 143.53
   },
   "display_as": "region",
   "display_reason": "member_spread"
  }
 ]
}