{
 "generated_utc": "2026-09-17T11:26:10Z",
 "gfs_cycle_utc": "2026-09-17T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 448.0,
  "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_20260917_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260917_06Z.geojson.gz"
 },
 "counts": {
  "flights": 14,
  "members": 9,
  "rows": 58698
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-16 14:26:18",
   "seed_lat": 33.6875,
   "seed_lon": -3.33333,
   "seed_alt_m": 14260.0,
   "seed_age_h": 20.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 05:30:00",
    "lat": 45.49208,
    "lon": 113.82813,
    "alt_m": 13769.2
   },
   "member_spread_deg": {
    "lat": 16.51,
    "lon": 319.46
   },
   "member_spread_now_deg": {
    "lat": 4.23,
    "lon": 5.37
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-16 21:16:00",
   "seed_lat": 56.29167,
   "seed_lon": -98.04167,
   "seed_alt_m": 11980.0,
   "seed_age_h": 14.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-24 05:45:00",
    "lat": 56.03441,
    "lon": 35.82241,
    "alt_m": 12035.3
   },
   "member_spread_deg": {
    "lat": 22.46,
    "lon": 126.07
   },
   "member_spread_now_deg": {
    "lat": 1.24,
    "lon": 1.82
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 10:12:00",
   "seed_lat": 29.22917,
   "seed_lon": -8.875,
   "seed_alt_m": 13490.0,
   "seed_age_h": 1.13,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 10:15:00",
    "lat": 45.74721,
    "lon": 172.94793,
    "alt_m": 12896.5
   },
   "member_spread_deg": {
    "lat": 13.66,
    "lon": 341.35
   },
   "member_spread_now_deg": {
    "lat": 0.16,
    "lon": 0.45
   },
   "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": 3.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 07:30:00",
    "lat": 49.44579,
    "lon": -175.64197,
    "alt_m": 13007.1
   },
   "member_spread_deg": {
    "lat": 28.91,
    "lon": 347.26
   },
   "member_spread_now_deg": {
    "lat": 2.05,
    "lon": 0.45
   },
   "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": 285.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-24 05:30:00",
    "lat": -0.22781,
    "lon": 119.61848,
    "alt_m": 14622.4
   },
   "member_spread_deg": {
    "lat": 73.36,
    "lon": 277.6
   },
   "member_spread_now_deg": {
    "lat": 50.64,
    "lon": 325.16
   },
   "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": 173.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-24 05:30:00",
    "lat": 27.04527,
    "lon": -18.59221,
    "alt_m": 12719.3
   },
   "member_spread_deg": {
    "lat": 31.13,
    "lon": 275.16
   },
   "member_spread_now_deg": {
    "lat": 39.75,
    "lon": 187.54
   },
   "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": 125.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 05:30:00",
    "lat": 51.76763,
    "lon": 66.20322,
    "alt_m": 12640.7
   },
   "member_spread_deg": {
    "lat": 31.09,
    "lon": 189.1
   },
   "member_spread_now_deg": {
    "lat": 20.74,
    "lon": 48.54
   },
   "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": 94.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 05:30:00",
    "lat": 42.84066,
    "lon": -75.30497,
    "alt_m": 12787.9
   },
   "member_spread_deg": {
    "lat": 22.51,
    "lon": 165.64
   },
   "member_spread_now_deg": {
    "lat": 13.76,
    "lon": 24.95
   },
   "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": 18.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 05:30:00",
    "lat": 57.007,
    "lon": -106.68732,
    "alt_m": 13024.5
   },
   "member_spread_deg": {
    "lat": 23.98,
    "lon": 85.75
   },
   "member_spread_now_deg": {
    "lat": 1.21,
    "lon": 9.23
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 10:06:00",
   "seed_lat": 32.77083,
   "seed_lon": 15.75,
   "seed_alt_m": 13370.0,
   "seed_age_h": 1.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 09:30:00",
    "lat": 36.09973,
    "lon": -135.59016,
    "alt_m": 13302.4
   },
   "member_spread_deg": {
    "lat": 30.19,
    "lon": 343.77
   },
   "member_spread_now_deg": {
    "lat": 0.13,
    "lon": 0.18
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-16 18:11:00",
   "seed_lat": 54.0,
   "seed_lon": -52.45833,
   "seed_alt_m": 15660.0,
   "seed_age_h": 17.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-24 05:45:00",
    "lat": 53.3463,
    "lon": 77.76071,
    "alt_m": 15388.0
   },
   "member_spread_deg": {
    "lat": 39.72,
    "lon": 91.5
   },
   "member_spread_now_deg": {
    "lat": 3.69,
    "lon": 17.63
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 07:26:00",
   "seed_lat": 44.0625,
   "seed_lon": 137.0,
   "seed_alt_m": 13110.0,
   "seed_age_h": 3.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 07:00:00",
    "lat": 68.31554,
    "lon": 4.2689,
    "alt_m": 12747.4
   },
   "member_spread_deg": {
    "lat": 34.28,
    "lon": 148.08
   },
   "member_spread_now_deg": {
    "lat": 0.5,
    "lon": 0.29
   },
   "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": 205.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 05:30:00",
    "lat": 58.37474,
    "lon": -61.02592,
    "alt_m": 12811.4
   },
   "member_spread_deg": {
    "lat": 43.48,
    "lon": 323.37
   },
   "member_spread_now_deg": {
    "lat": 35.96,
    "lon": 268.66
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 08:41:00",
   "seed_lat": -26.77083,
   "seed_lon": 106.04167,
   "seed_alt_m": 15520.0,
   "seed_age_h": 2.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 08:15:00",
    "lat": -8.44048,
    "lon": 173.45516,
    "alt_m": 15764.7
   },
   "member_spread_deg": {
    "lat": 32.66,
    "lon": 338.61
   },
   "member_spread_now_deg": {
    "lat": 1.29,
    "lon": 1.53
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}