{
 "generated_utc": "2026-09-17T17:26:23Z",
 "gfs_cycle_utc": "2026-09-17T12:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 454.0,
  "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_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260917_12Z.geojson.gz"
 },
 "counts": {
  "flights": 14,
  "members": 9,
  "rows": 58905
 },
 "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": 1.36,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 15:30:00",
    "lat": 43.37508,
    "lon": 78.82975,
    "alt_m": 13803.8
   },
   "member_spread_deg": {
    "lat": 9.66,
    "lon": 267.26
   },
   "member_spread_now_deg": {
    "lat": 0.42,
    "lon": 0.35
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-17 16:36:00",
   "seed_lat": 56.47917,
   "seed_lon": -66.54167,
   "seed_alt_m": 11980.0,
   "seed_age_h": 0.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-24 16:30:00",
    "lat": 54.36873,
    "lon": 30.4809,
    "alt_m": 12173.9
   },
   "member_spread_deg": {
    "lat": 6.78,
    "lon": 8.94
   },
   "member_spread_now_deg": {
    "lat": 0.02,
    "lon": 0.06
   },
   "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": 1.47,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 15:15:00",
    "lat": 53.84455,
    "lon": -161.91287,
    "alt_m": 13029.0
   },
   "member_spread_deg": {
    "lat": 12.45,
    "lon": 320.19
   },
   "member_spread_now_deg": {
    "lat": 0.17,
    "lon": 0.33
   },
   "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": 9.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 11:30:00",
    "lat": 56.42359,
    "lon": -165.60171,
    "alt_m": 13051.6
   },
   "member_spread_deg": {
    "lat": 28.94,
    "lon": 344.72
   },
   "member_spread_now_deg": {
    "lat": 6.36,
    "lon": 2.33
   },
   "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": 291.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-24 11:30:00",
    "lat": 6.44373,
    "lon": 128.75503,
    "alt_m": 14629.8
   },
   "member_spread_deg": {
    "lat": 63.2,
    "lon": 286.86
   },
   "member_spread_now_deg": {
    "lat": 55.24,
    "lon": 320.63
   },
   "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": 179.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-24 11:30:00",
    "lat": 22.14562,
    "lon": 18.04553,
    "alt_m": 12775.9
   },
   "member_spread_deg": {
    "lat": 47.04,
    "lon": 276.21
   },
   "member_spread_now_deg": {
    "lat": 38.86,
    "lon": 191.08
   },
   "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": 131.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 11:30:00",
    "lat": 51.49115,
    "lon": 72.84029,
    "alt_m": 12688.5
   },
   "member_spread_deg": {
    "lat": 36.95,
    "lon": 151.93
   },
   "member_spread_now_deg": {
    "lat": 19.86,
    "lon": 57.92
   },
   "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": 100.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 11:30:00",
    "lat": 59.88418,
    "lon": -7.32524,
    "alt_m": 12881.3
   },
   "member_spread_deg": {
    "lat": 21.51,
    "lon": 180.42
   },
   "member_spread_now_deg": {
    "lat": 11.64,
    "lon": 24.17
   },
   "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": 24.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 11:30:00",
    "lat": 64.40536,
    "lon": -94.104,
    "alt_m": 12950.1
   },
   "member_spread_deg": {
    "lat": 23.99,
    "lon": 116.81
   },
   "member_spread_now_deg": {
    "lat": 1.51,
    "lon": 8.53
   },
   "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": 4.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 12:00:00",
    "lat": 31.52037,
    "lon": -141.14434,
    "alt_m": 13405.5
   },
   "member_spread_deg": {
    "lat": 29.23,
    "lon": 334.6
   },
   "member_spread_now_deg": {
    "lat": 0.13,
    "lon": 0.62
   },
   "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": 1.07,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 15:45:00",
    "lat": 52.97973,
    "lon": 81.22326,
    "alt_m": 15516.2
   },
   "member_spread_deg": {
    "lat": 35.64,
    "lon": 73.28
   },
   "member_spread_now_deg": {
    "lat": 0.18,
    "lon": 1.08
   },
   "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": 9.9,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 11:30:00",
    "lat": 71.63044,
    "lon": 60.35958,
    "alt_m": 12821.0
   },
   "member_spread_deg": {
    "lat": 28.75,
    "lon": 118.34
   },
   "member_spread_now_deg": {
    "lat": 0.79,
    "lon": 1.1
   },
   "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": 211.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 11:30:00",
    "lat": 42.43116,
    "lon": -81.53439,
    "alt_m": 13160.5
   },
   "member_spread_deg": {
    "lat": 42.18,
    "lon": 297.39
   },
   "member_spread_now_deg": {
    "lat": 36.54,
    "lon": 260.92
   },
   "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": 8.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-24 11:45:00",
    "lat": -14.58443,
    "lon": 174.98424,
    "alt_m": 15695.9
   },
   "member_spread_deg": {
    "lat": 24.77,
    "lon": 333.12
   },
   "member_spread_now_deg": {
    "lat": 5.85,
    "lon": 6.24
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}