{
 "generated_utc": "2026-09-15T23:26:44Z",
 "gfs_cycle_utc": "2026-09-15T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 465.5,
  "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_20260915_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260915_18Z.geojson.gz"
 },
 "counts": {
  "flights": 15,
  "members": 9,
  "rows": 63540
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 16:29:48",
   "seed_lat": 36.5625,
   "seed_lon": -13.75,
   "seed_alt_m": 14440.0,
   "seed_age_h": 6.84,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:30:00",
    "lat": 45.16456,
    "lon": 65.41283,
    "alt_m": 13913.9
   },
   "member_spread_deg": {
    "lat": 15.22,
    "lon": 145.67
   },
   "member_spread_now_deg": {
    "lat": 0.73,
    "lon": 3.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 21:36:00",
   "seed_lat": 70.64583,
   "seed_lon": -130.0,
   "seed_alt_m": 11940.0,
   "seed_age_h": 1.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-22 21:30:00",
    "lat": 66.34691,
    "lon": 54.35758,
    "alt_m": 12273.0
   },
   "member_spread_deg": {
    "lat": 29.83,
    "lon": 63.15
   },
   "member_spread_now_deg": {
    "lat": 0.39,
    "lon": 0.82
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 16:52:00",
   "seed_lat": 26.5,
   "seed_lon": -31.95833,
   "seed_alt_m": 13460.0,
   "seed_age_h": 6.47,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:45:00",
    "lat": 25.79191,
    "lon": -2.73224,
    "alt_m": 13593.4
   },
   "member_spread_deg": {
    "lat": 23.65,
    "lon": 131.46
   },
   "member_spread_now_deg": {
    "lat": 1.73,
    "lon": 2.08
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 12:21:00",
   "seed_lat": 43.20833,
   "seed_lon": -2.25,
   "seed_alt_m": 13820.0,
   "seed_age_h": 10.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 17:45:00",
    "lat": 46.97823,
    "lon": 124.12624,
    "alt_m": 13169.0
   },
   "member_spread_deg": {
    "lat": 16.87,
    "lon": 119.03
   },
   "member_spread_now_deg": {
    "lat": 3.69,
    "lon": 8.61
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "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": 249.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 17:30:00",
    "lat": 4.18056,
    "lon": -163.21527,
    "alt_m": 14601.6
   },
   "member_spread_deg": {
    "lat": 55.56,
    "lon": 323.29
   },
   "member_spread_now_deg": {
    "lat": 35.45,
    "lon": 141.36
   },
   "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": 137.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-22 17:30:00",
    "lat": 14.83841,
    "lon": -52.37905,
    "alt_m": 12779.8
   },
   "member_spread_deg": {
    "lat": 35.38,
    "lon": 198.8
   },
   "member_spread_now_deg": {
    "lat": 27.9,
    "lon": 172.88
   },
   "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": 303.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:30:00",
    "lat": 30.65371,
    "lon": -131.00105,
    "alt_m": 12815.2
   },
   "member_spread_deg": {
    "lat": 30.55,
    "lon": 295.84
   },
   "member_spread_now_deg": {
    "lat": 23.31,
    "lon": 288.33
   },
   "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": 89.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:30:00",
    "lat": 56.93504,
    "lon": 59.11109,
    "alt_m": 12632.0
   },
   "member_spread_deg": {
    "lat": 22.1,
    "lon": 159.11
   },
   "member_spread_now_deg": {
    "lat": 10.68,
    "lon": 25.52
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "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": 58.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:30:00",
    "lat": 46.3369,
    "lon": -45.14359,
    "alt_m": 12693.4
   },
   "member_spread_deg": {
    "lat": 41.54,
    "lon": 122.6
   },
   "member_spread_now_deg": {
    "lat": 10.64,
    "lon": 14.23
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 19:15:45",
   "seed_lat": 70.16661,
   "seed_lon": -57.16665,
   "seed_alt_m": 12720.0,
   "seed_age_h": 4.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 18:45:00",
    "lat": 43.82337,
    "lon": -169.75412,
    "alt_m": 13285.2
   },
   "member_spread_deg": {
    "lat": 34.11,
    "lon": 252.65
   },
   "member_spread_now_deg": {
    "lat": 0.24,
    "lon": 2.72
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 15:16:00",
   "seed_lat": 31.60417,
   "seed_lon": -7.08333,
   "seed_alt_m": 13380.0,
   "seed_age_h": 8.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:45:00",
    "lat": 44.6226,
    "lon": 128.13449,
    "alt_m": 12871.7
   },
   "member_spread_deg": {
    "lat": 5.79,
    "lon": 38.25
   },
   "member_spread_now_deg": {
    "lat": 0.86,
    "lon": 1.34
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 20:38:00",
   "seed_lat": 48.54167,
   "seed_lon": -74.83333,
   "seed_alt_m": 15900.0,
   "seed_age_h": 2.7,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 20:15:00",
    "lat": 60.04273,
    "lon": 54.30928,
    "alt_m": 15461.3
   },
   "member_spread_deg": {
    "lat": 40.0,
    "lon": 69.75
   },
   "member_spread_now_deg": {
    "lat": 0.36,
    "lon": 2.27
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 05:26:00",
   "seed_lat": 49.72917,
   "seed_lon": 93.75,
   "seed_alt_m": 13210.0,
   "seed_age_h": 17.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:30:00",
    "lat": 64.48069,
    "lon": -8.37075,
    "alt_m": 12627.3
   },
   "member_spread_deg": {
    "lat": 33.74,
    "lon": 130.88
   },
   "member_spread_now_deg": {
    "lat": 0.96,
    "lon": 8.8
   },
   "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": 169.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-22 17:30:00",
    "lat": 42.81574,
    "lon": -105.85288,
    "alt_m": 13164.3
   },
   "member_spread_deg": {
    "lat": 39.32,
    "lon": 340.14
   },
   "member_spread_now_deg": {
    "lat": 33.8,
    "lon": 108.94
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-15 09:51:00",
   "seed_lat": -14.79167,
   "seed_lon": 93.66667,
   "seed_alt_m": 15780.0,
   "seed_age_h": 13.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-22 17:45:00",
    "lat": -22.49149,
    "lon": -124.38961,
    "alt_m": 15536.4
   },
   "member_spread_deg": {
    "lat": 21.59,
    "lon": 350.41
   },
   "member_spread_now_deg": {
    "lat": 1.17,
    "lon": 4.97
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}