{
 "generated_utc": "2026-09-12T17:26:26Z",
 "gfs_cycle_utc": "2026-09-12T12:00:00Z",
 "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_20260912_12Z.csv.gz",
  "trajectories_geojson_gz": "PBA_forecast_20260912_12Z.geojson.gz"
 },
 "counts": {
  "flights": 15,
  "members": 9,
  "rows": 63747
 },
 "flights": [
  {
   "callsign": "BSS54",
   "flight_id": "BSS54_2026-07-09",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 16:31:49",
   "seed_lat": 39.77083,
   "seed_lon": -7.625,
   "seed_alt_m": 14600.0,
   "seed_age_h": 0.8,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 16:00:00",
    "lat": 52.88032,
    "lon": 40.20863,
    "alt_m": 14015.0
   },
   "member_spread_deg": {
    "lat": 16.24,
    "lon": 68.89
   },
   "member_spread_now_deg": {
    "lat": 0.12,
    "lon": 0.15
   },
   "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": 180.65,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-19 11:45:00",
    "lat": 59.82703,
    "lon": -24.3626,
    "alt_m": 11755.2
   },
   "member_spread_deg": {
    "lat": 16.09,
    "lon": 345.28
   },
   "member_spread_now_deg": {
    "lat": 16.28,
    "lon": 213.41
   },
   "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 16:22:00",
   "seed_lat": 30.875,
   "seed_lon": -37.375,
   "seed_alt_m": 13770.0,
   "seed_age_h": 0.97,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 15:45:00",
    "lat": 38.87727,
    "lon": 62.31007,
    "alt_m": 13341.0
   },
   "member_spread_deg": {
    "lat": 19.52,
    "lon": 77.83
   },
   "member_spread_now_deg": {
    "lat": 0.14,
    "lon": 0.17
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "DG2GG-32",
   "flight_id": "DG2GG-32_2026-09-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 16:41:00",
   "seed_lat": 42.75,
   "seed_lon": -55.66667,
   "seed_alt_m": 13600.0,
   "seed_age_h": 0.65,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 16:45:00",
    "lat": 46.70709,
    "lon": 61.39634,
    "alt_m": 13449.1
   },
   "member_spread_deg": {
    "lat": 10.37,
    "lon": 47.43
   },
   "member_spread_now_deg": {
    "lat": 0.16,
    "lon": 0.45
   },
   "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": 295.45,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-19 11:30:00",
    "lat": 60.96865,
    "lon": -82.89662,
    "alt_m": 11625.4
   },
   "member_spread_deg": {
    "lat": 27.7,
    "lon": 266.44
   },
   "member_spread_now_deg": {
    "lat": 37.18,
    "lon": 315.89
   },
   "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": 171.8,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-19 11:30:00",
    "lat": 27.38573,
    "lon": -177.09266,
    "alt_m": 14580.5
   },
   "member_spread_deg": {
    "lat": 54.01,
    "lon": 345.24
   },
   "member_spread_now_deg": {
    "lat": 36.11,
    "lon": 201.07
   },
   "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": 59.92,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 3,
   "nominal_end": {
    "valid_time": "2026-09-19 11:30:00",
    "lat": 32.37017,
    "lon": -89.55536,
    "alt_m": 12603.7
   },
   "member_spread_deg": {
    "lat": 40.51,
    "lon": 202.42
   },
   "member_spread_now_deg": {
    "lat": 13.34,
    "lon": 69.79
   },
   "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": 225.27,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 11:30:00",
    "lat": 32.94273,
    "lon": -177.54875,
    "alt_m": 12889.1
   },
   "member_spread_deg": {
    "lat": 29.95,
    "lon": 301.77
   },
   "member_spread_now_deg": {
    "lat": 26.08,
    "lon": 302.4
   },
   "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": 11.25,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 11:30:00",
    "lat": 48.39559,
    "lon": -40.93813,
    "alt_m": 12726.6
   },
   "member_spread_deg": {
    "lat": 20.72,
    "lon": 162.83
   },
   "member_spread_now_deg": {
    "lat": 0.96,
    "lon": 358.99
   },
   "display_as": "region",
   "display_reason": "member_spread"
  },
  {
   "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": 3.57,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 13:15:00",
    "lat": 44.00761,
    "lon": -178.03735,
    "alt_m": 12785.5
   },
   "member_spread_deg": {
    "lat": 9.08,
    "lon": 350.34
   },
   "member_spread_now_deg": {
    "lat": 0.83,
    "lon": 0.96
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "KI6DS-11",
   "flight_id": "KI6DS-11_2026-02-03",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 03:55:45",
   "seed_lat": 60.18745,
   "seed_lon": -174.66665,
   "seed_alt_m": 13120.0,
   "seed_age_h": 13.41,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 11:30:00",
    "lat": 79.27543,
    "lon": 54.16438,
    "alt_m": 13116.7
   },
   "member_spread_deg": {
    "lat": 15.83,
    "lon": 147.71
   },
   "member_spread_now_deg": {
    "lat": 2.6,
    "lon": 11.64
   },
   "display_as": "track",
   "display_reason": "fresh"
  },
  {
   "callsign": "SP2ROC-41",
   "flight_id": "SP2ROC-41_2026-01-25",
   "payload_type": "WSPR",
   "seed_time": "2026-09-12 01:21:00",
   "seed_lat": 23.89583,
   "seed_lon": -142.91667,
   "seed_alt_m": 16440.0,
   "seed_age_h": 15.98,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 11:45:00",
    "lat": 47.14429,
    "lon": 8.66536,
    "alt_m": 16042.2
   },
   "member_spread_deg": {
    "lat": 44.99,
    "lon": 150.96
   },
   "member_spread_now_deg": {
    "lat": 11.67,
    "lon": 14.39
   },
   "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": 3.48,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 13:15:00",
    "lat": 57.03077,
    "lon": -140.45681,
    "alt_m": 12840.0
   },
   "member_spread_deg": {
    "lat": 26.91,
    "lon": 16.74
   },
   "member_spread_now_deg": {
    "lat": 1.37,
    "lon": 1.12
   },
   "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": 91.74,
   "float_reliable": true,
   "dead_reckoned": true,
   "levels_spanned": 2,
   "nominal_end": {
    "valid_time": "2026-09-19 11:30:00",
    "lat": 43.47614,
    "lon": 178.09039,
    "alt_m": 13276.8
   },
   "member_spread_deg": {
    "lat": 32.3,
    "lon": 341.48
   },
   "member_spread_now_deg": {
    "lat": 21.83,
    "lon": 71.96
   },
   "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": 8.23,
   "float_reliable": true,
   "dead_reckoned": false,
   "levels_spanned": 1,
   "nominal_end": {
    "valid_time": "2026-09-19 11:30:00",
    "lat": -27.97466,
    "lon": -149.65346,
    "alt_m": 15342.2
   },
   "member_spread_deg": {
    "lat": 30.51,
    "lon": 312.66
   },
   "member_spread_now_deg": {
    "lat": 0.87,
    "lon": 5.49
   },
   "display_as": "track",
   "display_reason": "fresh"
  }
 ]
}