{
 "generated_utc": "2026-09-18T11:26:30Z",
 "gfs_cycle_utc": "2026-09-18T06:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 472.0,
  "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_06Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260918_06Z.geojson.gz"
 },
 "counts": {
  "flights": 14,
  "members": 9,
  "rows": 61281
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 10:52:18",
   "seed_lat": 40.3125,
   "seed_lon": 17.58333,
   "seed_alt_m": 14100.0,
   "seed_age_h": 0.46,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 10:45:00",
    "lat": 43.09496,
    "lon": 84.50178,
    "alt_m": 13843.1
   },
   "member_spread_deg": {
    "lat": 10.43,
    "lon": 248.96
   },
   "member_spread_now_deg": {
    "lat": 0.15,
    "lon": 0.16
   },
   "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": 16.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": 65.48734,
    "lon": 143.93155,
    "alt_m": 12131.6
   },
   "member_spread_deg": {
    "lat": 27.7,
    "lon": 332.14
   },
   "member_spread_now_deg": {
    "lat": 1.2,
    "lon": 1.65
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 10:32:00",
   "seed_lat": 33.52083,
   "seed_lon": 15.58333,
   "seed_alt_m": 13500.0,
   "seed_age_h": 0.8,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 10:00:00",
    "lat": 37.11342,
    "lon": -134.00137,
    "alt_m": 13481.1
   },
   "member_spread_deg": {
    "lat": 20.19,
    "lon": 335.48
   },
   "member_spread_now_deg": {
    "lat": 0.32,
    "lon": 0.28
   },
   "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": 27.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": 62.44398,
    "lon": -143.64494,
    "alt_m": 13103.1
   },
   "member_spread_deg": {
    "lat": 34.94,
    "lon": 27.28
   },
   "member_spread_now_deg": {
    "lat": 16.83,
    "lon": 5.18
   },
   "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": 309.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": -7.50329,
    "lon": 148.52895,
    "alt_m": 14603.0
   },
   "member_spread_deg": {
    "lat": 85.88,
    "lon": 290.4
   },
   "member_spread_now_deg": {
    "lat": 54.27,
    "lon": 332.7
   },
   "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": 197.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": 24.68898,
    "lon": 16.69306,
    "alt_m": 12737.4
   },
   "member_spread_deg": {
    "lat": 57.13,
    "lon": 252.3
   },
   "member_spread_now_deg": {
    "lat": 31.43,
    "lon": 175.71
   },
   "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": 149.25,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": 46.53471,
    "lon": 92.11626,
    "alt_m": 12586.3
   },
   "member_spread_deg": {
    "lat": 35.08,
    "lon": 239.05
   },
   "member_spread_now_deg": {
    "lat": 18.96,
    "lon": 89.01
   },
   "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": 118.32,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": 41.34737,
    "lon": 7.78565,
    "alt_m": 12906.1
   },
   "member_spread_deg": {
    "lat": 39.05,
    "lon": 166.16
   },
   "member_spread_now_deg": {
    "lat": 8.31,
    "lon": 349.67
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 42.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": 66.71553,
    "lon": -99.09804,
    "alt_m": 13020.8
   },
   "member_spread_deg": {
    "lat": 14.14,
    "lon": 106.98
   },
   "member_spread_now_deg": {
    "lat": 3.68,
    "lon": 56.49
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "NQ1W-6",
   "flight_id": "NQ1W-6_2026-09-11",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 10:51:00",
   "seed_lat": 31.33333,
   "seed_lon": 32.70833,
   "seed_alt_m": 13260.0,
   "seed_age_h": 0.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 10:45:00",
    "lat": 28.87064,
    "lon": 165.75982,
    "alt_m": 13349.7
   },
   "member_spread_deg": {
    "lat": 46.03,
    "lon": 331.88
   },
   "member_spread_now_deg": {
    "lat": 0.11,
    "lon": 0.11
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 10:51:00",
   "seed_lat": 58.52083,
   "seed_lon": -4.58333,
   "seed_alt_m": 15260.0,
   "seed_age_h": 0.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 10:45:00",
    "lat": 47.94244,
    "lon": 103.02658,
    "alt_m": 15399.5
   },
   "member_spread_deg": {
    "lat": 9.68,
    "lon": 54.61
   },
   "member_spread_now_deg": {
    "lat": 0.05,
    "lon": 0.43
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-18 05:31:00",
   "seed_lat": 49.22917,
   "seed_lon": 158.25,
   "seed_alt_m": 13130.0,
   "seed_age_h": 5.82,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": 69.89034,
    "lon": 75.76393,
    "alt_m": 12394.5
   },
   "member_spread_deg": {
    "lat": 36.45,
    "lon": 105.64
   },
   "member_spread_now_deg": {
    "lat": 0.55,
    "lon": 2.4
   },
   "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": 229.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 05:30:00",
    "lat": 40.53567,
    "lon": -77.9697,
    "alt_m": 13107.3
   },
   "member_spread_deg": {
    "lat": 38.5,
    "lon": 307.67
   },
   "member_spread_now_deg": {
    "lat": 39.07,
    "lon": 244.05
   },
   "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 05:11:00",
   "seed_lat": -37.10417,
   "seed_lon": 130.04167,
   "seed_alt_m": 15380.0,
   "seed_age_h": 6.15,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-25 05:45:00",
    "lat": -8.11484,
    "lon": 165.73109,
    "alt_m": 15732.5
   },
   "member_spread_deg": {
    "lat": 28.62,
    "lon": 343.93
   },
   "member_spread_now_deg": {
    "lat": 0.78,
    "lon": 4.07
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}