{
 "generated_utc": "2026-09-10T23:27:01Z",
 "gfs_cycle_utc": "2026-09-10T18:00:00Z",
 "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_20260910_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260910_18Z.geojson.gz"
 },
 "counts": {
  "flights": 16,
  "members": 9,
  "rows": 67833
 },
 "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": 319.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-17 17:45:00",
    "lat": -63.63586,
    "lon": 102.48138,
    "alt_m": 11967.6
   },
   "member_spread_deg": {
    "lat": 31.54,
    "lon": 284.07
   },
   "member_spread_now_deg": {
    "lat": 16.76,
    "lon": 320.58
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 17:05:17",
   "seed_lat": 35.33333,
   "seed_lon": -19.45833,
   "seed_alt_m": 14660.0,
   "seed_age_h": 6.25,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 44.38256,
    "lon": 14.79035,
    "alt_m": 14121.7
   },
   "member_spread_deg": {
    "lat": 26.74,
    "lon": 75.78
   },
   "member_spread_now_deg": {
    "lat": 1.33,
    "lon": 1.39
   },
   "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": 138.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-17 17:45:00",
    "lat": 79.70617,
    "lon": -115.28717,
    "alt_m": 11500.9
   },
   "member_spread_deg": {
    "lat": 24.11,
    "lon": 318.52
   },
   "member_spread_now_deg": {
    "lat": 21.74,
    "lon": 124.72
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 18:42:00",
   "seed_lat": 31.89583,
   "seed_lon": -51.625,
   "seed_alt_m": 13630.0,
   "seed_age_h": 4.63,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 18:15:00",
    "lat": 20.08052,
    "lon": -42.93391,
    "alt_m": 13799.5
   },
   "member_spread_deg": {
    "lat": 16.99,
    "lon": 71.06
   },
   "member_spread_now_deg": {
    "lat": 1.41,
    "lon": 2.25
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 21:01:00",
   "seed_lat": 45.875,
   "seed_lon": -130.79167,
   "seed_alt_m": 13480.0,
   "seed_age_h": 2.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 20:30:00",
    "lat": 38.15199,
    "lon": 10.88448,
    "alt_m": 13555.8
   },
   "member_spread_deg": {
    "lat": 30.0,
    "lon": 83.84
   },
   "member_spread_now_deg": {
    "lat": 0.61,
    "lon": 2.34
   },
   "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": 253.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 64.10504,
    "lon": -121.62919,
    "alt_m": 11840.4
   },
   "member_spread_deg": {
    "lat": 49.56,
    "lon": 299.28
   },
   "member_spread_now_deg": {
    "lat": 45.41,
    "lon": 322.14
   },
   "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": 129.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 34.27018,
    "lon": 146.59478,
    "alt_m": 14549.5
   },
   "member_spread_deg": {
    "lat": 28.35,
    "lon": 135.14
   },
   "member_spread_now_deg": {
    "lat": 31.81,
    "lon": 279.69
   },
   "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": 17.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 61.14211,
    "lon": -5.47683,
    "alt_m": 11791.1
   },
   "member_spread_deg": {
    "lat": 33.69,
    "lon": 167.12
   },
   "member_spread_now_deg": {
    "lat": 5.32,
    "lon": 23.41
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 183.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 27.10223,
    "lon": 156.32253,
    "alt_m": 12830.5
   },
   "member_spread_deg": {
    "lat": 32.63,
    "lon": 288.39
   },
   "member_spread_now_deg": {
    "lat": 8.7,
    "lon": 330.84
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 12:25:00",
   "seed_lat": 42.45833,
   "seed_lon": 73.66667,
   "seed_alt_m": 12750.0,
   "seed_age_h": 10.92,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 42.34437,
    "lon": -112.27506,
    "alt_m": 12676.7
   },
   "member_spread_deg": {
    "lat": 12.39,
    "lon": 116.85
   },
   "member_spread_now_deg": {
    "lat": 1.16,
    "lon": 8.31
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 17:16:00",
   "seed_lat": 51.1875,
   "seed_lon": -40.375,
   "seed_alt_m": 12600.0,
   "seed_age_h": 6.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 17:45:00",
    "lat": 53.34365,
    "lon": 141.16419,
    "alt_m": 12799.6
   },
   "member_spread_deg": {
    "lat": 15.77,
    "lon": 55.84
   },
   "member_spread_now_deg": {
    "lat": 0.56,
    "lon": 1.33
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 07:35:45",
   "seed_lat": 48.41661,
   "seed_lon": 121.04169,
   "seed_alt_m": 13390.0,
   "seed_age_h": 15.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 71.89556,
    "lon": 32.83584,
    "alt_m": 13346.8
   },
   "member_spread_deg": {
    "lat": 30.88,
    "lon": 98.92
   },
   "member_spread_now_deg": {
    "lat": 2.87,
    "lon": 5.78
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 22:51:00",
   "seed_lat": 23.91667,
   "seed_lon": -152.41667,
   "seed_alt_m": 16440.0,
   "seed_age_h": 0.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 22:45:00",
    "lat": 53.19094,
    "lon": -18.44376,
    "alt_m": 15836.2
   },
   "member_spread_deg": {
    "lat": 28.45,
    "lon": 164.95
   },
   "member_spread_now_deg": {
    "lat": 0.08,
    "lon": 0.36
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 16:31:00",
   "seed_lat": 31.3125,
   "seed_lon": 1.20833,
   "seed_alt_m": 13350.0,
   "seed_age_h": 6.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 42.85648,
    "lon": -173.9152,
    "alt_m": 13343.3
   },
   "member_spread_deg": {
    "lat": 12.2,
    "lon": 344.6
   },
   "member_spread_now_deg": {
    "lat": 1.11,
    "lon": 1.23
   },
   "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": 49.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": 45.13826,
    "lon": 88.23586,
    "alt_m": 13100.1
   },
   "member_spread_deg": {
    "lat": 32.7,
    "lon": 140.01
   },
   "member_spread_now_deg": {
    "lat": 6.31,
    "lon": 57.11
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-10 12:31:00",
   "seed_lat": -18.91667,
   "seed_lon": 54.125,
   "seed_alt_m": 15600.0,
   "seed_age_h": 10.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-17 17:30:00",
    "lat": -20.93093,
    "lon": 168.16414,
    "alt_m": 15555.2
   },
   "member_spread_deg": {
    "lat": 22.49,
    "lon": 328.66
   },
   "member_spread_now_deg": {
    "lat": 1.79,
    "lon": 10.81
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}