{
 "generated_utc": "2026-09-18T05:26:29Z",
 "gfs_cycle_utc": "2026-09-18T00:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 466.0,
  "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_20260918_00Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260918_00Z.geojson.gz"
 },
 "counts": {
  "flights": 14,
  "members": 9,
  "rows": 61020
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 15:58:18",
   "seed_lat": 37.4375,
   "seed_lon": 9.0,
   "seed_alt_m": 14120.0,
   "seed_age_h": 13.36,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 45.02652,
    "lon": 74.92771,
    "alt_m": 13817.0
   },
   "member_spread_deg": {
    "lat": 10.72,
    "lon": 318.94
   },
   "member_spread_now_deg": {
    "lat": 2.56,
    "lon": 2.32
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 18:31:00",
   "seed_lat": 56.47917,
   "seed_lon": -63.58333,
   "seed_alt_m": 11970.0,
   "seed_age_h": 10.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 55.3427,
    "lon": 127.00353,
    "alt_m": 12412.3
   },
   "member_spread_deg": {
    "lat": 19.5,
    "lon": 101.43
   },
   "member_spread_now_deg": {
    "lat": 0.7,
    "lon": 1.19
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 15:52:00",
   "seed_lat": 29.04167,
   "seed_lon": -2.91667,
   "seed_alt_m": 13510.0,
   "seed_age_h": 13.47,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:45:00",
    "lat": 50.05847,
    "lon": -143.22712,
    "alt_m": 13099.0
   },
   "member_spread_deg": {
    "lat": 17.16,
    "lon": 308.14
   },
   "member_spread_now_deg": {
    "lat": 1.14,
    "lon": 4.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 08:01:00",
   "seed_lat": 45.77083,
   "seed_lon": 25.5,
   "seed_alt_m": 13600.0,
   "seed_age_h": 21.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 53.02711,
    "lon": -145.77361,
    "alt_m": 13236.2
   },
   "member_spread_deg": {
    "lat": 36.04,
    "lon": 36.76
   },
   "member_spread_now_deg": {
    "lat": 14.57,
    "lon": 5.24
   },
   "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": 303.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": -2.90056,
    "lon": 134.76975,
    "alt_m": 14611.1
   },
   "member_spread_deg": {
    "lat": 63.99,
    "lon": 301.22
   },
   "member_spread_now_deg": {
    "lat": 58.56,
    "lon": 326.54
   },
   "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": 191.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 21.03466,
    "lon": 5.85673,
    "alt_m": 12759.0
   },
   "member_spread_deg": {
    "lat": 55.43,
    "lon": 268.57
   },
   "member_spread_now_deg": {
    "lat": 31.27,
    "lon": 186.77
   },
   "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": 143.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 45.43769,
    "lon": 81.11779,
    "alt_m": 12596.0
   },
   "member_spread_deg": {
    "lat": 40.98,
    "lon": 205.76
   },
   "member_spread_now_deg": {
    "lat": 17.63,
    "lon": 78.39
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 112.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 41.9897,
    "lon": -75.54461,
    "alt_m": 12671.5
   },
   "member_spread_deg": {
    "lat": 33.11,
    "lon": 193.38
   },
   "member_spread_now_deg": {
    "lat": 7.72,
    "lon": 34.13
   },
   "display_as": "region",
   "display_reason": "seed_age"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-16 16:35:45",
   "seed_lat": 76.41661,
   "seed_lon": -30.16665,
   "seed_alt_m": 12780.0,
   "seed_age_h": 36.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 63.51432,
    "lon": -89.49769,
    "alt_m": 12983.0
   },
   "member_spread_deg": {
    "lat": 19.82,
    "lon": 95.65
   },
   "member_spread_now_deg": {
    "lat": 3.08,
    "lon": 22.92
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 12:36:00",
   "seed_lat": 32.77083,
   "seed_lon": 17.25,
   "seed_alt_m": 13360.0,
   "seed_age_h": 16.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 32.55035,
    "lon": -159.86476,
    "alt_m": 13439.0
   },
   "member_spread_deg": {
    "lat": 24.16,
    "lon": 50.38
   },
   "member_spread_now_deg": {
    "lat": 1.39,
    "lon": 1.78
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 16:16:00",
   "seed_lat": 57.83333,
   "seed_lon": -23.25,
   "seed_alt_m": 15460.0,
   "seed_age_h": 13.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:45:00",
    "lat": 50.30918,
    "lon": 78.87807,
    "alt_m": 15502.6
   },
   "member_spread_deg": {
    "lat": 36.21,
    "lon": 95.45
   },
   "member_spread_now_deg": {
    "lat": 5.7,
    "lon": 9.3
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 04:26:00",
   "seed_lat": 49.125,
   "seed_lon": 156.70833,
   "seed_alt_m": 13120.0,
   "seed_age_h": 0.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 04:00:00",
    "lat": 74.80586,
    "lon": 65.09185,
    "alt_m": 12589.0
   },
   "member_spread_deg": {
    "lat": 31.64,
    "lon": 111.36
   },
   "member_spread_now_deg": {
    "lat": 0.07,
    "lon": 0.33
   },
   "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": 223.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 23:30:00",
    "lat": 40.66996,
    "lon": -81.79714,
    "alt_m": 13144.1
   },
   "member_spread_deg": {
    "lat": 36.32,
    "lon": 316.22
   },
   "member_spread_now_deg": {
    "lat": 38.26,
    "lon": 246.54
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 04:46:00",
   "seed_lat": -37.10417,
   "seed_lon": 129.45833,
   "seed_alt_m": 15380.0,
   "seed_age_h": 0.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 04:45:00",
    "lat": -11.87953,
    "lon": 168.54333,
    "alt_m": 15740.1
   },
   "member_spread_deg": {
    "lat": 25.13,
    "lon": 341.02
   },
   "member_spread_now_deg": {
    "lat": 0.09,
    "lon": 0.39
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}