{
 "generated_utc": "2026-09-09T23:26:40Z",
 "gfs_cycle_utc": "2026-09-09T18:00:00Z",
 "model": {
  "source": "NCEP GFS 0.50 degree",
  "vertical_coordinate": "constant density (isopycnic)",
  "horizon_hours": 457.5,
  "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_20260909_18Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260909_18Z.geojson.gz"
 },
 "counts": {
  "flights": 15,
  "members": 9,
  "rows": 61902
 },
 "flights": [
  {
   "callsign": "AG6NS-23",
   "flight_id": "AG6NS-23_2026-02-07",
   "payload_type": "WSPR",
   "seed_time": "2026-08-28 16:13:40",
   "seed_lat": -64.54167,
   "seed_lon": -17.12499,
   "seed_alt_m": 11900.0,
   "seed_age_h": 295.11,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-16 17:45:00",
    "lat": -64.95791,
    "lon": 64.02375,
    "alt_m": 12078.7
   },
   "member_spread_deg": {
    "lat": 13.79,
    "lon": 171.58
   },
   "member_spread_now_deg": {
    "lat": 22.14,
    "lon": 214.26
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 16:43:48",
   "seed_lat": 39.45833,
   "seed_lon": -15.41667,
   "seed_alt_m": 14620.0,
   "seed_age_h": 6.6,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 17:45:00",
    "lat": 55.33993,
    "lon": 10.77878,
    "alt_m": 13941.8
   },
   "member_spread_deg": {
    "lat": 26.75,
    "lon": 64.21
   },
   "member_spread_now_deg": {
    "lat": 1.2,
    "lon": 2.22
   },
   "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": 114.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-16 17:45:00",
    "lat": 76.47062,
    "lon": -111.51349,
    "alt_m": 11745.0
   },
   "member_spread_deg": {
    "lat": 26.9,
    "lon": 338.03
   },
   "member_spread_now_deg": {
    "lat": 25.41,
    "lon": 346.23
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "DG2GG-31",
   "flight_id": "DG2GG-31_2026-08-13",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 19:57:00",
   "seed_lat": 44.4375,
   "seed_lon": -63.625,
   "seed_alt_m": 13290.0,
   "seed_age_h": 3.38,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 19:30:00",
    "lat": 23.05509,
    "lon": -76.3158,
    "alt_m": 13688.9
   },
   "member_spread_deg": {
    "lat": 29.47,
    "lon": 170.12
   },
   "member_spread_now_deg": {
    "lat": 1.52,
    "lon": 1.39
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 21:51:00",
   "seed_lat": 53.27083,
   "seed_lon": -162.75,
   "seed_alt_m": 13690.0,
   "seed_age_h": 1.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 21:15:00",
    "lat": 39.99319,
    "lon": 36.12634,
    "alt_m": 13584.0
   },
   "member_spread_deg": {
    "lat": 22.4,
    "lon": 208.95
   },
   "member_spread_now_deg": {
    "lat": 0.27,
    "lon": 0.73
   },
   "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": 229.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-16 17:30:00",
    "lat": 47.54586,
    "lon": -108.1036,
    "alt_m": 12226.2
   },
   "member_spread_deg": {
    "lat": 37.11,
    "lon": 308.9
   },
   "member_spread_now_deg": {
    "lat": 43.04,
    "lon": 322.67
   },
   "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": 105.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-16 17:30:00",
    "lat": 36.80549,
    "lon": 155.05134,
    "alt_m": 14590.7
   },
   "member_spread_deg": {
    "lat": 40.86,
    "lon": 146.81
   },
   "member_spread_now_deg": {
    "lat": 22.86,
    "lon": 327.18
   },
   "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": 159.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 17:30:00",
    "lat": 19.14942,
    "lon": 161.34071,
    "alt_m": 12813.6
   },
   "member_spread_deg": {
    "lat": 25.97,
    "lon": 281.48
   },
   "member_spread_now_deg": {
    "lat": 17.07,
    "lon": 316.55
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "callsign": "KD7FXO-1",
   "flight_id": "KD7FXO-1_2026-08-02",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 14:15:00",
   "seed_lat": 37.16667,
   "seed_lon": 42.29167,
   "seed_alt_m": 12780.0,
   "seed_age_h": 9.08,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 17:45:00",
    "lat": 40.85486,
    "lon": -118.0488,
    "alt_m": 12896.5
   },
   "member_spread_deg": {
    "lat": 26.03,
    "lon": 240.72
   },
   "member_spread_now_deg": {
    "lat": 0.34,
    "lon": 2.91
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KE8RES-8",
   "flight_id": "KE8RES-8_2026-06-20",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 18:21:00",
   "seed_lat": 42.75,
   "seed_lon": -52.91667,
   "seed_alt_m": 12370.0,
   "seed_age_h": 4.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 17:45:00",
    "lat": 45.19726,
    "lon": 111.79567,
    "alt_m": 12873.6
   },
   "member_spread_deg": {
    "lat": 7.23,
    "lon": 88.47
   },
   "member_spread_now_deg": {
    "lat": 1.87,
    "lon": 0.42
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 09:35:45",
   "seed_lat": 59.81245,
   "seed_lon": 102.54169,
   "seed_alt_m": 13330.0,
   "seed_age_h": 13.74,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 17:30:00",
    "lat": 75.66786,
    "lon": -45.15001,
    "alt_m": 12594.5
   },
   "member_spread_deg": {
    "lat": 33.66,
    "lon": 73.02
   },
   "member_spread_now_deg": {
    "lat": 5.16,
    "lon": 2.86
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 22:43:30",
   "seed_lat": 35.875,
   "seed_lon": -154.04167,
   "seed_alt_m": 16440.0,
   "seed_age_h": 0.61,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 22:45:00",
    "lat": 29.56326,
    "lon": -145.22068,
    "alt_m": 16245.7
   },
   "member_spread_deg": {
    "lat": 28.73,
    "lon": 343.08
   },
   "member_spread_now_deg": {
    "lat": 0.15,
    "lon": 0.2
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "VE3VRO-36",
   "flight_id": "VE3VRO-36_2026-07-30",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 16:46:00",
   "seed_lat": 30.02083,
   "seed_lon": -7.54167,
   "seed_alt_m": 13420.0,
   "seed_age_h": 6.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 17:45:00",
    "lat": 38.09916,
    "lon": 127.34149,
    "alt_m": 13392.3
   },
   "member_spread_deg": {
    "lat": 15.52,
    "lon": 136.22
   },
   "member_spread_now_deg": {
    "lat": 0.97,
    "lon": 1.02
   },
   "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": 25.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-16 17:30:00",
    "lat": 42.51469,
    "lon": 69.30924,
    "alt_m": 13144.4
   },
   "member_spread_deg": {
    "lat": 34.89,
    "lon": 86.05
   },
   "member_spread_now_deg": {
    "lat": 5.21,
    "lon": 12.96
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "ZS6WBT-1",
   "flight_id": "ZS6WBT-1_2026-08-19",
   "payload_type": "WSPR",
   "seed_time": "2026-09-09 13:36:00",
   "seed_lat": -15.125,
   "seed_lon": 40.41667,
   "seed_alt_m": 15630.0,
   "seed_age_h": 9.73,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-16 17:30:00",
    "lat": -18.34021,
    "lon": 138.6285,
    "alt_m": 15677.9
   },
   "member_spread_deg": {
    "lat": 30.94,
    "lon": 308.73
   },
   "member_spread_now_deg": {
    "lat": 1.45,
    "lon": 6.67
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}