{
 "generated_utc": "2026-09-12T23:26:35Z",
 "gfs_cycle_utc": "2026-09-12T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 463.5,
  "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_20260912_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260912_18Z.geojson.gz"
 },
 "counts": {
  "flights": 15,
  "members": 9,
  "rows": 64449
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 17:46:19",
   "seed_lat": 39.47917,
   "seed_lon": -7.66667,
   "seed_alt_m": 14590.0,
   "seed_age_h": 5.56,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 17:45:00",
    "lat": 43.70935,
    "lon": 12.342,
    "alt_m": 14044.2
   },
   "member_spread_deg": {
    "lat": 16.82,
    "lon": 71.04
   },
   "member_spread_now_deg": {
    "lat": 0.28,
    "lon": 1.08
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-30",
   "flight_id": "DG2GG-30_2026-08-07",
   "payload_type": "WSPR",
   "seed_time": "2026-09-05 04:41:00",
   "seed_lat": 86.0,
   "seed_lon": 110.20833,
   "seed_alt_m": 11660.0,
   "seed_age_h": 186.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-19 17:45:00",
    "lat": 69.74768,
    "lon": 3.34824,
    "alt_m": 11798.7
   },
   "member_spread_deg": {
    "lat": 22.51,
    "lon": 351.73
   },
   "member_spread_now_deg": {
    "lat": 17.96,
    "lon": 218.59
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 17:27:00",
   "seed_lat": 30.79167,
   "seed_lon": -37.04167,
   "seed_alt_m": 13760.0,
   "seed_age_h": 5.88,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": 47.47137,
    "lon": 40.52199,
    "alt_m": 13436.1
   },
   "member_spread_deg": {
    "lat": 22.64,
    "lon": 82.04
   },
   "member_spread_now_deg": {
    "lat": 0.73,
    "lon": 0.95
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 18:01:00",
   "seed_lat": 42.83333,
   "seed_lon": -53.66667,
   "seed_alt_m": 13540.0,
   "seed_age_h": 5.32,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": 47.97905,
    "lon": 67.18094,
    "alt_m": 13299.9
   },
   "member_spread_deg": {
    "lat": 23.57,
    "lon": 103.33
   },
   "member_spread_now_deg": {
    "lat": 1.09,
    "lon": 4.4
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DN3LEO-13",
   "flight_id": "DN3LEO-13_2026-04-12",
   "payload_type": "WSPR",
   "seed_time": "2026-08-31 09:53:00",
   "seed_lat": 62.54167,
   "seed_lon": 91.41667,
   "seed_alt_m": 11930.0,
   "seed_age_h": 301.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": 66.67832,
    "lon": -70.35009,
    "alt_m": 11627.8
   },
   "member_spread_deg": {
    "lat": 21.99,
    "lon": 255.32
   },
   "member_spread_now_deg": {
    "lat": 34.93,
    "lon": 310.24
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 177.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": 24.6758,
    "lon": -143.70398,
    "alt_m": 14390.7
   },
   "member_spread_deg": {
    "lat": 40.57,
    "lon": 307.44
   },
   "member_spread_now_deg": {
    "lat": 38.78,
    "lon": 191.22
   },
   "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": 65.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": 24.39115,
    "lon": -83.96469,
    "alt_m": 12765.7
   },
   "member_spread_deg": {
    "lat": 43.74,
    "lon": 208.81
   },
   "member_spread_now_deg": {
    "lat": 18.98,
    "lon": 78.37
   },
   "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": 231.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": 26.70246,
    "lon": 177.47345,
    "alt_m": 12867.0
   },
   "member_spread_deg": {
    "lat": 17.41,
    "lon": 348.64
   },
   "member_spread_now_deg": {
    "lat": 26.28,
    "lon": 298.11
   },
   "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": 17.25,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": 50.65051,
    "lon": -10.511,
    "alt_m": 12788.8
   },
   "member_spread_deg": {
    "lat": 25.41,
    "lon": 167.29
   },
   "member_spread_now_deg": {
    "lat": 3.19,
    "lon": 4.34
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 13:46:00",
   "seed_lat": 39.72917,
   "seed_lon": 7.875,
   "seed_alt_m": 12800.0,
   "seed_age_h": 9.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 17:45:00",
    "lat": 42.45288,
    "lon": -179.33264,
    "alt_m": 12902.0
   },
   "member_spread_deg": {
    "lat": 11.22,
    "lon": 356.95
   },
   "member_spread_now_deg": {
    "lat": 0.81,
    "lon": 3.02
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 22:55:45",
   "seed_lat": 68.20828,
   "seed_lon": -134.20831,
   "seed_alt_m": 12930.0,
   "seed_age_h": 0.4,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 23:00:00",
    "lat": 67.04079,
    "lon": 116.56969,
    "alt_m": 13249.5
   },
   "member_spread_deg": {
    "lat": 18.4,
    "lon": 98.55
   },
   "member_spread_now_deg": {
    "lat": 0.04,
    "lon": 0.37
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 21:46:00",
   "seed_lat": 34.33333,
   "seed_lon": -133.79167,
   "seed_alt_m": 16160.0,
   "seed_age_h": 1.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-19 21:15:00",
    "lat": 63.09236,
    "lon": 25.23633,
    "alt_m": 15456.4
   },
   "member_spread_deg": {
    "lat": 54.96,
    "lon": 121.86
   },
   "member_spread_now_deg": {
    "lat": 1.26,
    "lon": 1.45
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 13:51:00",
   "seed_lat": 44.95833,
   "seed_lon": 27.79167,
   "seed_alt_m": 13240.0,
   "seed_age_h": 9.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 17:45:00",
    "lat": 50.80327,
    "lon": -133.58788,
    "alt_m": 12932.0
   },
   "member_spread_deg": {
    "lat": 21.05,
    "lon": 316.84
   },
   "member_spread_now_deg": {
    "lat": 3.55,
    "lon": 1.55
   },
   "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": 97.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": 42.20154,
    "lon": -173.92404,
    "alt_m": 13178.2
   },
   "member_spread_deg": {
    "lat": 30.89,
    "lon": 351.89
   },
   "member_spread_now_deg": {
    "lat": 25.89,
    "lon": 65.76
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 09:06:00",
   "seed_lat": -19.02083,
   "seed_lon": 87.91667,
   "seed_alt_m": 15680.0,
   "seed_age_h": 14.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-19 17:30:00",
    "lat": -30.22879,
    "lon": -159.6249,
    "alt_m": 15296.9
   },
   "member_spread_deg": {
    "lat": 33.63,
    "lon": 318.47
   },
   "member_spread_now_deg": {
    "lat": 1.41,
    "lon": 9.22
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}