{
 "generated_utc": "2026-09-13T17:26:58Z",
 "gfs_cycle_utc": "2026-09-13T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 481.5,
  "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_20260913_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260913_12Z.geojson.gz"
 },
 "counts": {
  "flights": 16,
  "members": 9,
  "rows": 69858
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 16:54:18",
   "seed_lat": 34.125,
   "seed_lon": -14.16667,
   "seed_alt_m": 14570.0,
   "seed_age_h": 0.43,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 17:00:00",
    "lat": 39.2487,
    "lon": 12.9885,
    "alt_m": 14087.8
   },
   "member_spread_deg": {
    "lat": 7.87,
    "lon": 100.14
   },
   "member_spread_now_deg": {
    "lat": 0.03,
    "lon": 0.1
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 04:41:00",
   "seed_lat": 86.0,
   "seed_lon": 110.20833,
   "seed_alt_m": 11660.0,
   "seed_age_h": 204.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-20 11:45:00",
    "lat": 84.99992,
    "lon": -62.24804,
    "alt_m": 11792.5
   },
   "member_spread_deg": {
    "lat": 33.27,
    "lon": 322.13
   },
   "member_spread_now_deg": {
    "lat": 13.8,
    "lon": 295.16
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 16:02:00",
   "seed_lat": 24.125,
   "seed_lon": -26.54167,
   "seed_alt_m": 13470.0,
   "seed_age_h": 1.3,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 15:30:00",
    "lat": 34.03596,
    "lon": -41.2238,
    "alt_m": 13462.6
   },
   "member_spread_deg": {
    "lat": 20.99,
    "lon": 85.49
   },
   "member_spread_now_deg": {
    "lat": 0.33,
    "lon": 0.42
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 16:21:00",
   "seed_lat": 56.14583,
   "seed_lon": -9.83333,
   "seed_alt_m": 13500.0,
   "seed_age_h": 0.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 15:45:00",
    "lat": 47.70304,
    "lon": 104.40643,
    "alt_m": 13340.0
   },
   "member_spread_deg": {
    "lat": 11.98,
    "lon": 53.08
   },
   "member_spread_now_deg": {
    "lat": 0.06,
    "lon": 1.59
   },
   "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": 319.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-20 11:30:00",
    "lat": 77.76144,
    "lon": -71.30462,
    "alt_m": 11626.3
   },
   "member_spread_deg": {
    "lat": 37.34,
    "lon": 333.71
   },
   "member_spread_now_deg": {
    "lat": 41.89,
    "lon": 317.6
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DO3GU-47",
   "flight_id": "DO3GU-47_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 13:31:52",
   "seed_lat": 46.04167,
   "seed_lon": 61.70833,
   "seed_alt_m": 13960.0,
   "seed_age_h": 195.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-20 11:30:00",
    "lat": 16.33321,
    "lon": -169.88857,
    "alt_m": 14550.2
   },
   "member_spread_deg": {
    "lat": 36.24,
    "lon": 326.87
   },
   "member_spread_now_deg": {
    "lat": 38.38,
    "lon": 159.73
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "I1RFQ",
   "flight_id": "I1RFQ_2026-09-06",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 05:25:00",
   "seed_lat": 48.52083,
   "seed_lon": 159.54167,
   "seed_alt_m": 12130.0,
   "seed_age_h": 83.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-20 11:30:00",
    "lat": 25.39142,
    "lon": -85.06869,
    "alt_m": 12694.7
   },
   "member_spread_deg": {
    "lat": 37.06,
    "lon": 236.78
   },
   "member_spread_now_deg": {
    "lat": 8.68,
    "lon": 106.83
   },
   "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": 249.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 11:30:00",
    "lat": 10.16998,
    "lon": 162.36635,
    "alt_m": 12907.8
   },
   "member_spread_deg": {
    "lat": 23.93,
    "lon": 336.75
   },
   "member_spread_now_deg": {
    "lat": 26.83,
    "lon": 292.8
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 06:05:00",
   "seed_lat": 45.47917,
   "seed_lon": 159.375,
   "seed_alt_m": 12660.0,
   "seed_age_h": 35.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 11:30:00",
    "lat": 47.29773,
    "lon": -80.19753,
    "alt_m": 12465.4
   },
   "member_spread_deg": {
    "lat": 9.09,
    "lon": 145.65
   },
   "member_spread_now_deg": {
    "lat": 4.49,
    "lon": 11.9
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 13:01:00",
   "seed_lat": 42.0625,
   "seed_lon": 28.04167,
   "seed_alt_m": 12700.0,
   "seed_age_h": 4.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 12:30:00",
    "lat": 46.21668,
    "lon": -150.83688,
    "alt_m": 12673.2
   },
   "member_spread_deg": {
    "lat": 21.34,
    "lon": 90.74
   },
   "member_spread_now_deg": {
    "lat": 1.37,
    "lon": 1.48
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 16:55:45",
   "seed_lat": 66.08328,
   "seed_lon": -98.79165,
   "seed_alt_m": 12720.0,
   "seed_age_h": 0.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 17:00:00",
    "lat": 63.07137,
    "lon": 177.76244,
    "alt_m": 12969.6
   },
   "member_spread_deg": {
    "lat": 26.36,
    "lon": 355.64
   },
   "member_spread_now_deg": {
    "lat": 0.04,
    "lon": 0.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 14:41:00",
   "seed_lat": 41.4375,
   "seed_lon": -4.29167,
   "seed_alt_m": 13460.0,
   "seed_age_h": 2.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 14:15:00",
    "lat": 45.97415,
    "lon": 59.15253,
    "alt_m": 13116.8
   },
   "member_spread_deg": {
    "lat": 6.36,
    "lon": 75.28
   },
   "member_spread_now_deg": {
    "lat": 0.37,
    "lon": 0.22
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 16:51:00",
   "seed_lat": 38.8125,
   "seed_lon": -119.29167,
   "seed_alt_m": 16040.0,
   "seed_age_h": 0.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-20 16:15:00",
    "lat": 50.42677,
    "lon": 38.02309,
    "alt_m": 15821.7
   },
   "member_spread_deg": {
    "lat": 68.34,
    "lon": 135.73
   },
   "member_spread_now_deg": {
    "lat": 0.25,
    "lon": 0.53
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 13:51:00",
   "seed_lat": 44.95833,
   "seed_lon": 27.79167,
   "seed_alt_m": 13240.0,
   "seed_age_h": 27.48,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 11:45:00",
    "lat": 57.86266,
    "lon": -96.51184,
    "alt_m": 13000.3
   },
   "member_spread_deg": {
    "lat": 23.4,
    "lon": 60.91
   },
   "member_spread_now_deg": {
    "lat": 3.79,
    "lon": 16.33
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "W0RBO-12",
   "flight_id": "W0RBO-12_2026-05-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-08 21:35:23",
   "seed_lat": 52.33328,
   "seed_lon": -95.95831,
   "seed_alt_m": 12860.0,
   "seed_age_h": 115.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-20 11:30:00",
    "lat": 53.72835,
    "lon": -138.40557,
    "alt_m": 12976.6
   },
   "member_spread_deg": {
    "lat": 44.89,
    "lon": 294.31
   },
   "member_spread_now_deg": {
    "lat": 34.4,
    "lon": 42.98
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-13 09:36:00",
   "seed_lat": -14.16667,
   "seed_lon": 95.54167,
   "seed_alt_m": 15770.0,
   "seed_age_h": 7.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-20 11:30:00",
    "lat": -20.95014,
    "lon": 113.74862,
    "alt_m": 15695.8
   },
   "member_spread_deg": {
    "lat": 28.36,
    "lon": 63.52
   },
   "member_spread_now_deg": {
    "lat": 1.09,
    "lon": 4.52
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}